GroupDIY

Project Specific Discussions => Dynamic Processors => Topic started by: jsteiger on March 26, 2015, 07:00:17 PM

Title: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 26, 2015, 07:00:17 PM
Since the kits have started shipping, it's time for the support thread!   :)

**This is a semi complicated build. It is very important to read completely thru the Assembly Aid before starting on anything. There are some points made in the doc that can save you much time and prevent crucial errors during the build.

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September 21st, 2015 Update:
All support docs for this project can be found on the recently added Support Docs (http://capi-gear.com/catalog/support_docs.php) page at www.capi-gear.com
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RV7 must be jumpered for an FC526 XFMR comp to work.
https://groupdiy.com/index.php?topic=59050.msg911575#msg911575
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Having trouble with the meter cal? Maybe this will help http://groupdiy.com/index.php?topic=59050.msg785426#msg785426

Some details can be found here http://capi-gear.com/catalog/product_info.php?cPath=22_117_190&products_id=432

(http://www.capi-gear.com/catalog/images/gallery/capi_temp/temp-FC526.jpg)

Cheers, Jeff
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:01:09 PM
building the do-hicky.  Please stand by. . .

Sorry everyone for the extended delays.  I know Jeff really wanted full documentation up for this project much sooner.

Let's get started.  The kit should arrive with the following component packages.

(http://studio939.zenfolio.com/img/s2/v71/p1285637303-4.jpg)

Begin by assembling the main PCB.  Locate the main PCB and the bag with main PCB components.

(http://studio939.zenfolio.com/img/s3/v44/p1285639472-4.jpg)

Locate the bag with knobs, switches, and hardware.

(http://studio939.zenfolio.com/img/s7/v157/p1285641175-4.jpg)

And retrieve the Milmax sockets for the 3 discrete op-amps.

(http://studio939.zenfolio.com/img/s4/v69/p1285643384-4.jpg)

Turn the board upside down and place all of these sockets from the back side.

(http://studio939.zenfolio.com/img/s2/v1/p1285643745-4.jpg)

Set soldering iron temperature a bit higher than normal because these pins take a bit to heat up.  I elevated one side of the PCB so the pins all end up resting consistently on one side before the solder cools.

(http://studio939.zenfolio.com/img/s9/v86/p1285646267-4.jpg)

Aim to have a nice fillet of solder flow onto the front side of the board so the pins have a strong mechanical connection.

(http://studio939.zenfolio.com/img/s7/v164/p1285648233-4.jpg)

Next, locate the Milmax pins from one of your un-assembled DOA kits and insert and remove it from each of the sockets.  When the sockets are new, they can be very stiff the first time a pin is inserted, so it is much easier to deal with them one at a time without critical components surrounding them.  This will make installing the DOA much easier when the compressor is fully assembled.

(http://studio939.zenfolio.com/img/s2/v73/p1285650137-4.jpg)

(http://studio939.zenfolio.com/img/s11/v30/p1285651415-4.jpg)

Use a multimeter to confirm all resistor values and sort them before installing.

(http://studio939.zenfolio.com/img/s8/v78/p1285654771-4.jpg)

I use a piece of regular white paper to lay out the components and cross-reference with the BOM file from the 1st post.

(http://studio939.zenfolio.com/img/s5/v116/p1337691342-6.jpg)

(http://studio939.zenfolio.com/img/s9/v86/p1285664627-6.jpg)

Carefully bend each resistor and place them into the PCB.

(http://studio939.zenfolio.com/img/s12/v170/p1285657587-4.jpg)

(http://studio939.zenfolio.com/img/s4/v67/p1285658103-4.jpg)

As a way of double checking my component placement and my parts sorting paper, I do not solder the resistors until all of them have been placed.  This way, if a mistake is made, it is very easy to correct.

(http://studio939.zenfolio.com/img/s4/v69/p1285678363-4.jpg)

Bend all of the leads outwards to secure them to the PCB and flip the board over.

(http://studio939.zenfolio.com/img/s9/v87/p1285681312-4.jpg)

Solder the resistors into place, and trim the leads tight to the PCB.

(http://studio939.zenfolio.com/img/s3/v26/p1285683601-4.jpg)

(http://studio939.zenfolio.com/img/s11/v36/p1285685897-4.jpg)

And, here is the main board with all of the resistors installed.

(http://studio939.zenfolio.com/img/s9/v90/p1285773775-4.jpg)

Next, locate the bag with the diodes and transistors.

(http://studio939.zenfolio.com/img/s3/v41/p1285740235-4.jpg)

Sort all of these components referencing the BOM.

(http://studio939.zenfolio.com/img/s7/v158/p1285777008-4.jpg)

Some of the markings are quite small, but it is important to accurately identify each one.

IN914 are marked:

91
4B

(http://studio939.zenfolio.com/img/s2/v61/p1285778149-4.jpg)

IN5243B Zener is marked

24
3B

(http://studio939.zenfolio.com/img/s11/v34/p1285778319-4.jpg)

BZX79C4V3 is marked:

9C
4V3

(http://studio939.zenfolio.com/img/s7/v153/p1285778461-4.jpg)

Diodes have polarity.  Make sure the end of the component that has the strip locates in the same direction as the silk-screened arrow on the PCB.

(http://studio939.zenfolio.com/img/s9/v88/p1285791367-4.jpg)

Place all of the diodes and double check that the polarity is correct on all of them before soldering.

(http://studio939.zenfolio.com/img/s12/v183/p1285792195-4.jpg)

(http://studio939.zenfolio.com/img/s11/v34/p1285796337-4.jpg)

Trim the leads flush to the PCB.

(http://studio939.zenfolio.com/img/s5/v127/p1285799189-4.jpg)

(http://studio939.zenfolio.com/img/s2/v61/p1285801949-4.jpg)

Next, install CR1 to complete the component bag.

(http://studio939.zenfolio.com/img/s5/v131/p1286008203-4.jpg)

Next, locate the bag containing the capacitors and sort them.

(http://studio939.zenfolio.com/img/s4/v9/p1286011849-4.jpg)

(http://studio939.zenfolio.com/img/s5/v118/p1337648901-6.jpg)

Start installing the capacitors on the "right" side of the sorting sheet until you reach the 6.8uF capacitors (C2, C3).

The tantalum capacitors have polarity.  Note the "+" marking screen printed on the body.

(http://studio939.zenfolio.com/img/s11/v36/p1286016221-4.jpg)

Make sure the correct leg is inserted into the pad with the "+" symbol screen printed on the PCB.

(http://studio939.zenfolio.com/img/s7/v166/p1286016471-4.jpg)

Here, we have all of the capacitors sorted on the "right" side of the sheet installed.

(http://studio939.zenfolio.com/img/s1/v5/p1286020237-4.jpg)


Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:01:24 PM
At this point, I jumped to the transistors, opamps, relays, and trimmers bag.  The only reason I did this is to populate the board components from "shortest to tallest".

(http://studio939.zenfolio.com/img/s3/v25/p1286189975-6.jpg)

The opamps can sometimes be tricky to orient correctly.  For the TL084, note the notch on one side of the housing.

(http://studio939.zenfolio.com/img/s12/v187/p1286191049-4.jpg)

This will orient to the notch indicated on the screen printing as well as the side with pin 1 (the square solder pad).

(http://studio939.zenfolio.com/img/s1/v20/p1286191386-4.jpg)

On the TL081, the circle on the housing indicates the pin 1 position.

(http://studio939.zenfolio.com/img/s9/v17/p1286194769-4.jpg)

Make sure the circle is positioned at the square solder lug on the PCB.

(http://studio939.zenfolio.com/img/s12/v176/p1286194964-4.jpg)

Here, both opamps are installed in the proper orientation.

(http://studio939.zenfolio.com/img/s9/v17/p1286196074-4.jpg)

Next, install the relays making sure the line mark on the component orients to the silk-screened line on the PCB.

(http://studio939.zenfolio.com/img/s3/v45/p1286197196-4.jpg)

The trimmer values can be confirmed with a multimeter by probing the outer leads.

(http://studio939.zenfolio.com/img/s9/v86/p1286200507-4.jpg)

Note, RV1 has the trimmer dial oriented towards the outside of the PCB.

(http://studio939.zenfolio.com/img/s11/v31/p1286199663-4.jpg)

After all the trimmers are installed, the board should look like this.

(http://studio939.zenfolio.com/img/s9/v88/p1286312741-4.jpg)

Backtrack now a little bit to the remaining electrolytic capacitors.  These parts have polarity, so it is important to get the + and - sides correct.  For the radial capacitors, the lead with the large stripe is "-".

(http://studio939.zenfolio.com/img/s3/v42/p1286314451-4.jpg)

Also, the longer lead corresponds to the "+" side.

(http://studio939.zenfolio.com/img/s1/v20/p1286314821-4.jpg)

Make sure these correspond to the silk screening on the PCB.  Also, the "+" solder pad is square.

(http://studio939.zenfolio.com/img/s3/v23/p1286315327-4.jpg)

C36 and C38 are bi-polar, so they do not have polarity even though the casing looks like a normal electrolytic capacitor.

(http://studio939.zenfolio.com/img/s11/v35/p1286315957-4.jpg)

These blue axial capacitors have an "arrow" line pointing towards the negative lead.

(http://studio939.zenfolio.com/img/s2/v59/p1286316382-4.jpg)

This is how they should orient on the PCB.  The arrows point towards the negative terminal.

(http://studio939.zenfolio.com/img/s7/v156/p1286316871-4.jpg)

For C13, the black stripe indicates the negative side, and it should orient like this.

(http://studio939.zenfolio.com/img/s6/v146/p1286343598-4.jpg)

And now, all of the capacitors are populated.

(http://studio939.zenfolio.com/img/s5/v124/p1286344325-4.jpg)

(http://studio939.zenfolio.com/img/s9/v16/p1286345749-4.jpg)

Next, bend a thick lead cut-off with a screwdriver.

(http://studio939.zenfolio.com/img/s5/v125/p1286347437-4.jpg)

And install for a ground test point.

(http://studio939.zenfolio.com/img/s7/v157/p1286347792-4.jpg)

(http://studio939.zenfolio.com/img/s11/v34/p1286348265-4.jpg)

In the knobs, switches, and hardware bag, locate the cable header and install.

(http://studio939.zenfolio.com/img/s12/v176/p1286348557-4.jpg)

(http://studio939.zenfolio.com/img/s5/v127/p1286349659-4.jpg)

(http://studio939.zenfolio.com/img/s1/v19/p1286349783-4.jpg)

It only goes in one way due to the plastic locating pins.

(http://studio939.zenfolio.com/img/s6/v135/p1286351559-4.jpg)

Next, locate the pots and grayhill switch.  The pots can be tested with a multimeter on the outer 2 pins just like the smaller trimmer pots installed earlier.

(http://studio939.zenfolio.com/img/s9/v16/p1286354328-6.jpg)

Be careful to solder the grayhill switch pins carefully and double check that there are no solder bridges between the pins as they are quite close together.

(http://studio939.zenfolio.com/img/s3/v40/p1286354963-4.jpg)

(http://studio939.zenfolio.com/img/s2/v60/p1286356567-4.jpg)

One last resistor to install.

(http://studio939.zenfolio.com/img/s8/v14/p1286362401-4.jpg)

Insert at this point and carefully solder

(http://studio939.zenfolio.com/img/s9/v16/p1286362805-4.jpg)

(http://studio939.zenfolio.com/img/s3/v41/p1286363684-4.jpg)


It is not explicitly stated that this project requires cleaning of the solder flux, but I personally like to keep my builds clean.  Please note, if you decide to clean the PCB of solder residue, go all the way and thoroughly clean it.  There is no half-way option.  It would just leave a sticky mess all over the board.  Use 90% isopropyl alcohol as 70% does not nearly work as well to dissolve the flux residue.  Mechanical scrubbing is necessary.  I use an old toothbrush.  If using a small plate of alcohol like I did here, you will need to change the solution because flux gets dissolved into it and after a while, more scrubbing with the same solution just spreads the muck around.

(http://studio939.zenfolio.com/img/s8/v80/p1286361409-4.jpg)

(http://studio939.zenfolio.com/img/s3/v39/p1286383715-4.jpg)

The result should be a nice, clean board with no residue.

(http://studio939.zenfolio.com/img/s9/v90/p1286385165-4.jpg)
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:01:40 PM
With the main PCB cleaned up, locat the mounting hardware for the transformer.

(http://studio939.zenfolio.com/img/s6/v147/p1286387487-4.jpg)

We need 2 long screws and 4 lock washers.

(http://studio939.zenfolio.com/img/s8/v14/p1286388426-4.jpg)

And of course a transformer.

(http://studio939.zenfolio.com/img/s4/v67/p1286388541-4.jpg)

We want to have lock washers directly contacting both sides of the PCB.  Start by inserting the screws directly into the top of the transformer.

(http://studio939.zenfolio.com/img/s11/v30/p1286388865-4.jpg)

Flip the assembly over, and place lock washers on the bottom side of the transformer.

(http://studio939.zenfolio.com/img/s4/v12/p1286389859-4.jpg)

Place the PCB on the transformer.

(http://studio939.zenfolio.com/img/s9/v86/p1286593931-4.jpg)

Place 2 lock washers on the back side of the PCB.

(http://studio939.zenfolio.com/img/s3/v44/p1286595185-4.jpg)

And install the nuts finger tight.

(http://studio939.zenfolio.com/img/s12/v186/p1286598846-4.jpg)

After aligning the transformer to the screen printing, snug down the screws from the top side with a screwdriver to lock it into position.

(http://studio939.zenfolio.com/img/s2/v52/p1286599707-4.jpg)

Carefully trim, tin, and install the transformer wire leads to the PCB.  Too long, and they look messy, too short, and well, they won't reach.  Cut a little bit at a time to get the correctly length a little bit at a time.

(http://studio939.zenfolio.com/img/s4/v12/p1286600919-4.jpg)

(http://studio939.zenfolio.com/img/s3/v45/p1286601487-4.jpg)

After tinning, solder the wires from the back side of the PCB.

(http://studio939.zenfolio.com/img/s6/v141/p1286602139-4.jpg)

Clean the solder flux from the new solder connections being careful to avoid spilling alcohol on the transformer.

(http://studio939.zenfolio.com/img/s3/v23/p1286638771-4.jpg)

(http://studio939.zenfolio.com/img/s7/v158/p1286640164-4.jpg)

The main PCB is now assembled.

(http://studio939.zenfolio.com/img/s6/v141/p1286641116-4.jpg)

(http://studio939.zenfolio.com/img/s7/v152/p1286642483-4.jpg)

(http://studio939.zenfolio.com/img/s7/v166/p1286643529-4.jpg)

(http://studio939.zenfolio.com/img/s6/v150/p1286644572-4.jpg)
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:01:56 PM
Next locate the meter PCB and the bag containing the components to populate it.

(http://studio939.zenfolio.com/img/s8/v83/p1455059357-4.jpg)

(http://studio939.zenfolio.com/img/s11/v27/p1455058287-4.jpg)

Carefully sort and identify all of the components and cross reference with the BOM document.

(http://studio939.zenfolio.com/img/s7/v154/p1455058935-6.jpg)

First, populate the resistors.

(http://studio939.zenfolio.com/img/s6/v134/p1455059703-4.jpg)

(http://studio939.zenfolio.com/img/s11/v29/p1455060431-4.jpg)

(http://studio939.zenfolio.com/img/s11/v27/p1455061325-4.jpg)

Next, locate the main PCB mounting hardware.  We will fit the PCB's to the L-bracket before soldering in the switches and LED's to the meter PCB.

(http://studio939.zenfolio.com/img/s8/v78/p1455060817-4.jpg)

Install the four flat head screws and standoffs to the L-bracket.

(http://studio939.zenfolio.com/img/s4/v66/p1455061817-4.jpg)

(http://studio939.zenfolio.com/img/s4/v12/p1455062143-4.jpg)

(http://studio939.zenfolio.com/img/s11/v33/p1455062356-4.jpg)

Set the L-bracket aside and locate this long standoff, nut, and lock washer.

(http://studio939.zenfolio.com/img/s11/v35/p1455062637-4.jpg)

Install the lock washer between the PCB and the long standoff.

(http://studio939.zenfolio.com/img/s6/v135/p1455062981-4.jpg)

And position the standoff here on the PCB.

(http://studio939.zenfolio.com/img/s6/v141/p1455063407-4.jpg)

Secure the standoff on the back side of the PCB with the nut.

(http://studio939.zenfolio.com/img/s11/v31/p1455063801-4.jpg)

Slide the main PCB into the L-bracket.

(http://studio939.zenfolio.com/img/s11/v36/p1455064281-4.jpg)

Confirm that all of the pots, switches, and trimmers are aligned with the L-bracket.

(http://studio939.zenfolio.com/img/s9/v18/p1455064567-6.jpg)

Center the main board on the L-bracket.

(http://studio939.zenfolio.com/img/s1/v48/p1455064793-4.jpg)

Attach the faceplate and install the rotary switch and pot knobs finger tight for fitting.

(http://studio939.zenfolio.com/img/s3/v8/p1455064997-4.jpg)

Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:02:12 PM
Next, locate the remaining 2 long standoffs for the meter board.

(http://studio939.zenfolio.com/img/s3/v8/p1455065146-4.jpg)

Install the first standoff making sure to use a lock washer.

(http://studio939.zenfolio.com/img/s4/v66/p1455065215-4.jpg)

And the second one in the same manner.

(http://studio939.zenfolio.com/img/s3/v40/p1455065386-4.jpg)

Next, secure the rear of the PCB with the remaining screws and split lock washers.

(http://studio939.zenfolio.com/img/s1/v49/p1455065531-4.jpg)

Next, locate these 3 toggle switches for the meter board.

(http://studio939.zenfolio.com/img/s1/v21/p1455066047-4.jpg)

And set them in place on the front side of the meter board.  For my installation, the switches held in place at this time via friction fit, so I will not solder them yet until I have the meter board secured in final position so all of the switches will be guaranteed to align perfectly.

(http://studio939.zenfolio.com/img/s7/v160/p1455066325-4.jpg)

Next, I begin placing the meter LED's making sure to heed the polarity of the LED's.  Note, the short solder pads correspond to the shorter lead on the LED units.  In this step, I deviated from the build documentation that recommends cutting the LED leads to length before placing on the board.  My main reason is I wanted to be extra careful not to make a mistake on the polarity of the LED's and I trust my finesse with wire cutters after soldering.

(http://studio939.zenfolio.com/img/s2/v61/p1455066605-4.jpg)

Placing all of the components first without trimming them to length allows me to visually confirm polarity with all of the LED's in position.

(http://studio939.zenfolio.com/img/s4/v67/p1455066833-4.jpg)

Next, place the meter board into final position and align all of the components to the front plate.

(http://studio939.zenfolio.com/img/s/v-2/p1455066980-4.jpg)

Locate the following hardware to secure the meter board.

(http://studio939.zenfolio.com/img/s/v-2/p1455067329-4.jpg)

(http://studio939.zenfolio.com/img/s/v-2/p1455067523-4.jpg)

Place a piece of console tape on the front plate to help hold the LED's in place for soldering.

(http://studio939.zenfolio.com/img/s/v-2/p1455067819-4.jpg)

And press all of the LED's firmly to the tape and re-verify polarity and colors.

(http://studio939.zenfolio.com/img/s/v-2/p1455068043-4.jpg)

With all of the LED's in final position and verified correctly oriented, solder the exposed pads.

(http://studio939.zenfolio.com/img/s3/v40/p1455068201-4.jpg)

Next, with the switches in final alignment against the front plate, we can solder them in place.

(http://studio939.zenfolio.com/img/s2/v59/p1455068503-4.jpg)

Carefully cut the excess LED leads at this time and visually confirm that the solder connections are clean and only touch the correct solder pads.

(http://studio939.zenfolio.com/img/s/v-2/p1455068861-4.jpg)

(http://studio939.zenfolio.com/img/s2/v50/p1455069189-4.jpg)

Next, remove the switch PCB from the main assembly, turn it over to the back side, and solder the remaining LED leads.

(http://studio939.zenfolio.com/img/s/v-2/p1455069330-4.jpg)

(http://studio939.zenfolio.com/img/s2/v59/p1455069557-4.jpg)

Carefully trim the back side LED leads in the same manner as the front and confirm there are no shorts beyond the designated pads for each connection.

(http://studio939.zenfolio.com/img/s3/v39/p1455069838-4.jpg)

With these components in place, now is a good time to clean the board with isopropyl alcohol.

(http://studio939.zenfolio.com/img/s/v-2/p1455070011-4.jpg)

Next, install the ceramic capacitors.

(http://studio939.zenfolio.com/img/s1/v46/p1619698238-4.jpg)

(http://studio939.zenfolio.com/img/s11/v32/p1851304939-4.jpg)

And the IC's making sure the notch in the chip corresponds to the notch in the silk screening on the PCB.

(http://studio939.zenfolio.com/img/s1/v6/p1809277854-4.jpg)

(http://studio939.zenfolio.com/img/s10/v100/p1702954545-4.jpg)

Next, populate the film capacitor.

(http://studio939.zenfolio.com/img/s4/v65/p1723886902-4.jpg)

Install the electrolytic capacitors making sure the confirm the correct polarity.  The longer lead is + and the printed white stripe on the can is -.

(http://studio939.zenfolio.com/img/s3/v43/p1705212492-4.jpg)

Populate the cable connector.

(http://studio939.zenfolio.com/img/s6/v134/p1740825029-4.jpg)

. . .and CR1 diode and Q1 transistor.

(http://studio939.zenfolio.com/img/s/v-2/p1737991982-4.jpg)

With that, the meter PCB is fully populated.

(http://studio939.zenfolio.com/img/s5/v124/p1725882566-4.jpg)

If you are opting to clean the boards, scrub the flux off with isopropyl alcohol.

(http://studio939.zenfolio.com/img/s2/v58/p1621852169-4.jpg)

(http://studio939.zenfolio.com/img/s11/v28/p1847748909-4.jpg)

Nice and clean.

(http://studio939.zenfolio.com/img/s9/v91/p1678294336-4.jpg)

Next, locate the ribbon cable.

(http://studio939.zenfolio.com/img/s2/v50/p1770087386-4.jpg)

And install one end to the meter PCB.  Note the location of the red wire in the ribbon cable.  This corresponds to pin 1.

(http://studio939.zenfolio.com/img/s7/v153/p1856103973-4.jpg)

Re-install the fully populated meter PCB.

(http://studio939.zenfolio.com/img/s2/v52/p1816320190-4.jpg)

And connect the other end of the ribbon cable to the main PCB.

(http://studio939.zenfolio.com/img/s2/v53/p1852261517-4.jpg)

With the electronic components fully populated and the PCB's cleaned, refer back to the sorting sheet where we placed the information for our F3 and F4 FET's.

(http://studio939.zenfolio.com/img/s9/v96/p1780314362-5.jpg)

Copy this information to the designated white areas on the main PCB with a permanent marker.

(http://studio939.zenfolio.com/img/s9/v89/p1718067769-4.jpg)

Use console tape placed on top of socket wrench to install the knob nuts. 

(http://studio939.zenfolio.com/img/s10/v107/p1657693938-4.jpg)

And set the knobs with an allen key.

(http://studio939.zenfolio.com/img/s12/v175/p1666805107-4.jpg)

(http://studio939.zenfolio.com/img/s1/v6/p1837533551-4.jpg)

Next, locate the colored inserts for the knobs. . .

(http://studio939.zenfolio.com/img/s1/v47/p1628935204-4.jpg)

. . . and install them into the knob centers.

(http://studio939.zenfolio.com/img/s2/v71/p1648372765-4.jpg)

With that, final assembly is complete.

(http://studio939.zenfolio.com/img/s/v-2/p1736176431-4.jpg)

Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:02:25 PM
Next, we will run through the initial verification steps outlined in the build guide.

First connect the ground lead of a multimeter to this lug.

(http://studio939.zenfolio.com/img/s10/v105/p1737621739-4.jpg)

And confirm that the resistance to the "-V" DOA sockets is more than 500 ohm.  This is confirm there are no direct shorts.  Mine registers 2.6K.

(http://studio939.zenfolio.com/img/s9/v95/p1690625052-6.jpg)

Next, connect a power supply to the unit.  Here, I am using my "plug in" adaptation of a JLM powerstation.

(http://studio939.zenfolio.com/img/s1/v47/p1830743503-4.jpg)

Apply power to the unit and confirm no smoke! 

Then, confirm the "V+" and "V-" sockets for the DOA's are correct.

(http://studio939.zenfolio.com/img/s/v-2/p1732187825-4.jpg)

(http://studio939.zenfolio.com/img/s12/v173/p1875272954-4.jpg)

On Jeff's recommendation based on field testing by various studios, I will be using GAR1731 op amps all around on this build.

(http://studio939.zenfolio.com/img/s/v-2/p1694940885-4.jpg)

Place the 3 opamps into their sockets.

(http://studio939.zenfolio.com/img/s6/v134/p1743747190-4.jpg)

And this completes the build phase of the compressor.

Humans Win!

(http://studio939.zenfolio.com/img/s11/v29/p1805547714-4.jpg)

(http://studio939.zenfolio.com/img/s1/v56/p1828305642-4.jpg)

(http://studio939.zenfolio.com/img/s10/v98/p1723640041-5.jpg)

(http://studio939.zenfolio.com/img/s12/v178/p1817051427-5.jpg)
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:02:41 PM
Reserved...
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:02:54 PM
Reserved...
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:03:07 PM
Reserved...
Title: Re: Coming soon...please don't reply yet!!
Post by: chunger on March 26, 2015, 07:03:21 PM
Reserved...
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Winetree on March 26, 2015, 11:45:15 PM
Sonically would there be a difference running
I.C. opamps in the Receiver and VVR Signal Preamp positions vs. discrete opamps?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 27, 2015, 10:07:53 AM
Sonically would there be a difference running
I.C. opamps in the Receiver and VVR Signal Preamp positions vs. discrete opamps?
Yes, they all add up and make a noticeable difference. While its not huge, it is definitely there. I'm very interested to see what you and Tony think. I imagine you guys will do some extensive listening  ;)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 30, 2015, 03:46:37 PM
I have just added the calibration doc to the first post of this thread.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: fragletrollet on March 31, 2015, 10:39:43 AM
so.... who won the compressor in the end?  8)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 31, 2015, 12:44:13 PM
so.... who won the compressor in the end?  8)
Lolo from RealGear. He's in Australia. He's having our buddy Joel Phillips from Nashville build it for him.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jswagler55 on April 01, 2015, 09:24:24 PM
I'm going through the build and on the Meter BOM it says that C1 is one of the 33μf, 35V Radial Capacitors. On the actual PCB it looks like C1 should be the .47μF, 63V Metallized Polyester Cap that is currently labeled C3 in the BOM.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 01, 2015, 09:55:40 PM
I'm going through the build and on the Meter BOM it says that C1 is one of the 33μf, 35V Radial Capacitors. On the actual PCB it looks like C1 should be the .47μF, 63V Metallized Polyester Cap that is currently labeled C3 in the BOM.
Good catch! There is always something. I have made the correction and uploaded the new file. Hopefully that was the only one  ;)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Winetree on April 02, 2015, 02:39:49 AM
Jeff,
I know the sockets are not included in the kit,
but would it be a good idea to socket the I.C.s and transistors or not?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 02, 2015, 09:48:47 AM
Jeff,
I know the sockets are not included in the kit,
but would it be a good idea to socket the I.C.s and transistors or not?
I thought about it but did not really see a need for it Robert.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 06, 2015, 08:44:41 PM
I just added another 50pc batch of these to the store.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: PeteJE on April 07, 2015, 12:56:34 PM
Can anybody comment on these sonically when it comes to clarity / transparency in a light ratio (2:1) on clean vocal?  As something more like a mastering touch on a vocal?  Hoping to get depth and clarity and fullness in a light mode without too much harmonic or fuzzy coloration.  Clearly these are fantastic for color and  crushing parallel compression hugeness (I listened to the drum examples on realgear online - awesome), but wonder about a less colored use.  For some reference have been using massey CT5 in plug in world and the JLM LA 500 in the analogue and have used just about all different models of the analogue classics over the years.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 07, 2015, 01:32:54 PM
Can anybody comment on these sonically when it comes to clarity / transparency in a light ratio (2:1) on clean vocal?  As something more like a mastering touch on a vocal?  Hoping to get depth and clarity and fullness in a light mode without too much harmonic or fuzzy coloration.  Clearly these are fantastic for color and  crushing parallel compression hugeness (I listened to the drum examples on realgear online - awesome), but wonder about a less colored use.  For some reference have been using massey CT5 in plug in world and the JLM LA 500 in the analogue and have used just about all different models of the analogue classics over the years.
Hi Pete, I would suggest posting over at RGO and tagging John Kennedy. He has one of the first 8 units that I built up. I know many folks are working on them but I don't think anyone has made it to the finish line yet. If John is not super busy, he may be able to post some clips. FYI, Rob Schnapf had a demo for a few weeks. He tried it on everything. I could probably get him to reply if you post your question on the FC526 thread at RGO.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: stribor1 on April 14, 2015, 08:28:15 AM
One unit up and running, did the 3x1731 myself, everything fired up right from the bench. Just finished the calibration, quick soundcheck, works great on drums!!! I'm ordering a second one.
Anyhow, any instructions on the THD N measurement? Don't have any analyzers just my DAW (Windows, Cubase, RME HDSPe AES32, Mytek 8x192)can someone recoment an plug-in or easy to use app?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 14, 2015, 10:38:40 AM
One unit up and running, did the 3x1731 myself, everything fired up right from the bench. Just finished the calibration, quick soundcheck, works great on drums!!! I'm ordering a second one.
Anyhow, any instructions on the THD N measurement? Don't have any analyzers just my DAW (Windows, Cubase, RME HDSPe AES32, Mytek 8x192)can someone recoment an plug-in or easy to use app?
I am far from a DAW guy but did some googling and found this for a Windows machine. I found the link in a SoundOnSound article http://www.sillanumsoft.org
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: PeteJE on April 16, 2015, 02:49:48 PM
On main PCB parts, can anyone id the two loose glass diodes on the BOM for me?  I id the 9 (on tape), the two small black are the FDH333 I believe, the two larger black are the 1N4004 I believe, but don't know what the two loose other ones are (look like the 9 on tape)....  thanks.  (chunger!! I'm scared without the pics, ha)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 16, 2015, 03:27:42 PM
On main PCB parts, can anyone id the two loose glass diodes on the BOM for me?  I id the 9 (on tape), the two small black are the FDH333 I believe, the two larger black are the 1N4004 I believe, but don't know what the two loose other ones are (look like the 9 on tape)....  thanks.  (chunger!! I'm scared without the pics, ha)
One will be the 13V zener. The markings on the side with be :
24
3B

The other will be the 4.3V zener and will be marked 4V3.

You will need some sort of magnification to read these labels.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: PeteJE on April 16, 2015, 03:33:13 PM
On main PCB parts, can anyone id the two loose glass diodes on the BOM for me?  I id the 9 (on tape), the two small black are the FDH333 I believe, the two larger black are the 1N4004 I believe, but don't know what the two loose other ones are (look like the 9 on tape)....  thanks.  (chunger!! I'm scared without the pics, ha)
One will be the 13V zener. The markings on the side with be :
24
3B

The other will be the 4.3V zener and will be marked 4V3.

You will need some sort of magnification to read these labels.

Thanks Jeff, I just got it - my table mag + glasses barely made it lolol......
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: JeromeMason on April 20, 2015, 06:25:50 PM
Having an issue here, when the comp is engaged getting a very thin sound, almost like a HPF as been rolled up to 400hz. Could this be in the Q-bias setup? I've always turned my trim pots CCW before I adjust, did you have this preset or anything?

Also, for most folks they'll be using their DAW's to monitor the levels being sent and monitored, I don't have any elaborate metering that will tell me dbu or vu, everything is just db that I can reference to -18dbfs. Is there some formula to be able to use so we can translate dbu into db? For instance, none of my metering will even go to +15.5dbu.

On THD+N I'm guessing the best way is to read the output with a spectrum analyzer and adjust until most of the noise is gone? That's how I did it but, maybe that's where this roll off is happening, maybe it's run too soft?

I think my problem is in the calibration, and my scope is being borrowed right now so I'm trying to do this in my DAW like a lot of folks will, it'll be good to go ahead and get this in the build thread.

Thanks!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: pachi2007 on April 20, 2015, 07:53:05 PM
http://www.cranesong.com/Volts%20to%20dBu%20to%20VU%20Comparison.pdf

You can send a tone from the secuencer and measure volts across pin 2 and 3.
I guess you can move the fader till you get the needed volts/dBu.

There´s a video at Hairball about calibrating very useful.

Also useful:

 http://www.sengpielaudio.com/calculator-db-volt.htm

Hope it helps

Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 20, 2015, 08:17:46 PM
First off, it would be helpful to know if the opamps are new builds and/or if they have been tested in something else. Starting up with 3 freshly built opamps in a freshly built FC526 is a definite no-no! So please, anyone posting for help, let us know those details first.

Having an issue here, when the comp is engaged getting a very thin sound, almost like a HPF as been rolled up to 400hz. Could this be in the Q-bias setup? I've always turned my trim pots CCW before I adjust, did you have this preset or anything?
None of the trim pots should be turned before it is specified in the calibration doc. They are all in their factory set position which is somewhere near 50%. Turning them all CCW is for sure not a good way to start especially if you look at step 14 of the calibration doc which states that the Q-Bias trimmer should be turned CW. I also have it bold and underlined in the doc.  ;)

I would recommend to turn GR off, monitor the output level, turn the Q-Bias trimmer CW until the level stops increasing. This will take the VVR FET out of its conductive range. At this point, measure the freq response to see if it is high passed still. If so, you have a problem with the audio path somewhere. We'll go down that path if and when we need to.

PSA, when adjusting the Q-Bias trimmer, turning it CW will let the signal level increase. Turning it CCW will essentially turn the signal level down. Kinda reacts like turning a volume knob, in a logical fashion. Hope that makes sense. It's opposite of an 1176 so keep that in mind, or just follow my calibration doc to the letter and you'll be fine.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 02, 2015, 03:52:56 AM
I just finished building my first FC526, my 7th kit from CAPI, thank you Jeff for such addicting products. 
When applying the 1khz sine wave and flipping the toggle to ACT I still get a .775 vac reading on my meter.
All 3 of the op amps are taken from existing working preamps.
I have check for solder bridges and didn't find any.
I would be grateful for any suggestions on where i should start trouble shooting.
Thanks,
Rob
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 02, 2015, 10:02:38 AM
Are you saying the hard bypass relays are not flipping?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 02, 2015, 09:48:29 PM
The switch seems to be working; when in the BYP position there is continuity between to outside 2 back pins and when it is in the ACT position there is no continuity. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 02, 2015, 09:52:24 PM
When in hard bypass the following gold fingers should be connected;

Finger #2 to #10

Finger #4 to #8

When in ACTive mode, there should be no continuity between the above gold fingers.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 02, 2015, 10:07:37 PM
Thanks for the quick response!!
There is continuity between the #2 to #10 fingers
and the #4 to #8 fingers in both BYPass and ACtive modes. 
Should I replace the switch?  I have another from a second FC526 kit that i haven't started yet.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 02, 2015, 10:18:21 PM
Thanks for the quick response!!
There is continuity between the #2 to #10 fingers
and the #4 to #8 fingers in both BYPass and ACtive modes. 
Should I replace the switch?  I have another from a second FC526 kit that i haven't started yet.
Hmm, I would check continuity on the switch pins before removing it. The chances of a bad switch are pretty slim.

What is your test jig apparatus? Did you have the 10R in between the #5 and #13 gold fingers?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 02, 2015, 11:01:22 PM
I do not have the 10R in between the # 5 & #13 fingers. 
I am using a Lindell 506 lunch box and the EXT test jig from you.
I pulled the 526 out of the jig to test the fingers.
I am using an Wavetek Meterman DMM to test with
The switch seems to be good.  I must have made a mistake somewhere.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 03, 2015, 12:27:11 AM
Install the 10R and try it again  ;)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 03, 2015, 02:27:04 AM
Adding the 10R resister didn't work   :(
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: JeromeMason on May 03, 2015, 05:50:49 AM
First off, it would be helpful to know if the opamps are new builds and/or if they have been tested in something else. Starting up with 3 freshly built opamps in a freshly built FC526 is a definite no-no! So please, anyone posting for help, let us know those details first.

Having an issue here, when the comp is engaged getting a very thin sound, almost like a HPF as been rolled up to 400hz. Could this be in the Q-bias setup? I've always turned my trim pots CCW before I adjust, did you have this preset or anything?
None of the trim pots should be turned before it is specified in the calibration doc. They are all in their factory set position which is somewhere near 50%. Turning them all CCW is for sure not a good way to start especially if you look at step 14 of the calibration doc which states that the Q-Bias trimmer should be turned CW. I also have it bold and underlined in the doc.  ;)

I would recommend to turn GR off, monitor the output level, turn the Q-Bias trimmer CW until the level stops increasing. This will take the VVR FET out of its conductive range. At this point, measure the freq response to see if it is high passed still. If so, you have a problem with the audio path somewhere. We'll go down that path if and when we need to.

PSA, when adjusting the Q-Bias trimmer, turning it CW will let the signal level increase. Turning it CCW will essentially turn the signal level down. Kinda reacts like turning a volume knob, in a logical fashion. Hope that makes sense. It's opposite of an 1176 so keep that in mind, or just follow my calibration doc to the letter and you'll be fine.

This is good info to have, some builds require that you zero out trimmers, yours did not State that that's my fault, but at least it's on record and No one else will make that mistake. As for the problem I was having I don't believe it was anything associated for The actual compressor, I believe my problem had to do with the routing in my interfaces D a W. The issue right now is the calibration. The compressor seems a bit off, the transients are not as transparent as I remember your kits Jeff. It also seems a little spongy and I'm certain it's in the calibration. The compressor still does have the effect of making the source seem larger and fuller. Once I've done the proper calibration with a reliable scope I will report back as I'm sure that's the issue.

Thanks for the help and response Jeff.

Jerome
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 03, 2015, 10:02:48 AM
Adding the 10R resister didn't work   :(
Can you post a pic of the relay area of the build?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 03, 2015, 10:28:07 AM
.....The issue right now is the calibration. The compressor seems a bit off, the transients are not as transparent as I remember your kits Jeff. It also seems a little spongy and I'm certain it's in the calibration.....
Well, "calibration" does encompass a few steps but to me the term (and the steps in the guide) mainly refer to the meter alignment.

There are 3 basic steps to the FC526 calibration and only the simplest two to carry out will effect the audio path and "sound" of the unit.

1. Q_Bias of the FET. Pretty simple and straight forward, Just make sure your FET is biased to be reducing the audio path by 0.5dB.

2. THD Null. Will also effect the audio path and sound of the module. Fairly easy to do.

3. Meter. This is the hardest and most finicky thing to adjust or calibrate but will not effect the sound or audio path of the module whatsoever.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 03, 2015, 05:32:44 PM
Adding the 10R resister didn't work   :(
Can you post a pic of the relay area of the build?

Here is a pic of the relay area.
Your support is greatly appreciated.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 03, 2015, 05:45:26 PM
Adding the 10R resister didn't work   :(
Can you post a pic of the relay area of the build?

Here is a pic of the relay area.
Your support is greatly appreciated.
The transistor by the relays is in backwards.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: rabe on May 03, 2015, 10:41:23 PM
Adding the 10R resister didn't work   :(
Can you post a pic of the relay area of the build?

Here is a pic of the relay area.
Your support is greatly appreciated.
The transistor by the relays is in backwards.

Thanks!! need to get my eye glass prescription checked :o
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: dandeurloo on May 05, 2015, 09:33:23 AM
This may help a few guys, maybe not.  Be sure to check you voltage at TP9.  It should be very close(.01%) to -10vdc if not exactly.  If it is off then you have a problem with the voltage and it will make it impossible to calibrate your comps.  It took me quite awhile to figure out (with the help of Jeff) that my rails on my 51x  PSU had been sagging to low causing the voltage into the modules to be to low to properly get my -10VDC causing meter calibration issues.  So, just be sure you have -10VDC there and save yourselves a lot of headache in case your PSU is drifting or sagging like mine was.

Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 14, 2015, 01:03:51 AM
I'm gonna bet this is inline with Dan's problem above:

Two FC526's with same status.
Meter alignment step 5) should be nothing but the green LED lit, I have -2 (3 yellow) lit, true for all but ABI ratio which is none lit.
TP9 -9.85VDC, op amps +/-15.2VDC,  connector +/-16VDC.
15 modules powered.
Remove 11 modules from load (3A PSU), no obvious VDC changes anywhere but meter then lights to -7 (all but 2 LED’s). 

Late, gotta stop for the night, assume PSU needs to be trimmed higher.  I thought +/-16VDC was the standard at the connector, but the first power check here looks for +/-16VDC at the op amp pins. 

Thoughts?

-----EDIT----

problem with the rack itself:
http://groupdiy.com/index.php?topic=59050.msg756890#msg756890
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 14, 2015, 11:08:59 AM
TP9 needs to be -10V give or take .05V. The precision shunt regulator will snap right to target when the supply voltage is correct. I have tested here and found that the supply to the card edge needs to be no less than +/-15.7V. Sounds like your findings are a little different?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 14, 2015, 11:24:49 AM
I have +/-16 at the card edge.   I'm 0.1V-0.15V lower than expected range at TP9. 

I don't know if it's a clue of not, but the load change affecting the (incorrect) meter lighting seems to indicate....something.  I ran out of time and did not re-run the meter alignment with lesser load, so can't speak to any further indications there.   Wondering if the PSU is on the verge of current limiting, shouldn't be.   Not sure what total load really is, not sure how PSU derates when turned up to +/-16V when A rating is for +/-15V.   I'll look at the load, and maybe try at +/-16.2ish if all else fails. 

They sound good!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 14, 2015, 12:19:03 PM
Well, I may look into changing the current limit R for the -10V rail. I thought I had it set for +/-15V at the card edge but recent tests tell me I must have changed it. That was done last fall so I don't recall. The meter comparator string is based on a 2.5V precision reference shunt so the V at the top of the meter R string should be a solid 2.5V. If that is varying for some odd reason, the meter will be very unpredictable. Both the 2.5V R string for the meter and the -10V rail draw very little current on their own.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: djroshi on May 15, 2015, 12:11:30 AM
I'm having issues with the meter LEDs not illuminating. Only the green one lights up. I've checked the orientation of the LEDs of course.

BTW I'm getting -9.88V at TP9.

Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 15, 2015, 12:19:09 AM
I'm having issues with the meter LEDs not illuminating. Only the green one lights up. I've checked the orientation of the LEDs of course.

BTW I'm getting -9.88V at TP9.
That is too low. What is the supply V at the gold finger side of the 1N4004 protection diodes?

The GR LED's are in a string from the green one down to the orange. If one of them is in backwards, that one and all that come after it will not illuminate.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: djroshi on May 15, 2015, 12:54:35 AM
That is too low. What is the supply V at the gold finger side of the 1N4004 protection diodes?

The GR LED's are in a string from the green one down to the orange. If one of them is in backwards, that one and all that come after it will not illuminate.

15.97V and -15.98V respectively.

The LEDs are installed correctly as far as I can tell, e.g. looking from the top in can see the green led cathode, the first yellow anode, the second yellow cathode, alternating as such all the way down to the last orange cathode. I have also checked with my DMM that e.g the green led anode lead is connected to the first yellow cathode lead, that the first yellow anode lead is connected to the second yellow cathode lead, etc right the way down to rule out any problematic solder joints.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: dandeurloo on May 15, 2015, 01:11:22 PM
Guys, I had + & - 15.9 volts in my PSU.  By the time it got into the unit it was down almost a volt and that threw everything off.  If you are building on a test PSU crank the voltage up to + & - 16.9 and see if that solves everything.  Once I did that I had a perfect -10VDC and everything was happy.  It took a ton of time and head scratching to get that figured out.  Hopefully this helps you guys and we can get Jeff some more info to work with.

BTW, I have been using mine on some vocal tracking session into my LA 2A.  They sound good!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: daveriot on May 15, 2015, 05:05:04 PM
any idea why r50 would smoke on an f526?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 15, 2015, 05:13:31 PM
any idea why r50 would smoke on an f526?

From value and position it would appear to be power isolation/filter to the preamp DOA, so probably a short around that DOA.   Just a guess.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 15, 2015, 08:18:44 PM
any idea why r50 would smoke on an f526?
As Doug mentioned, R50 is the damping R for the -V supply to opamp A3. That would indicate a serious problem or short on that opamp. What amp is in there?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 17, 2015, 06:19:34 PM
adjusted PSU to +/-16.14VDC, TP9 -9.93. Not there yet.
adjusted PSU to +/-16.27VDC, TP9 -9.98.  Looks good to go.

TP10 +2.487V, no probe = 2 yellow LED’s lit.
engage GR, TP10 +2.196V, 7dB actual reduction, meters 10dB reduction.

If I then adjust TP10 for +2.245V, disengage GR and remove probe I have only the green LED lit.  TP10 then +2.561V.
Readjust RV1 for +2.487 with no GR, two yellow LED’s again lit. 


Reran entire alignment, same result, only difference being Meter Step 7: TP10 +2.18V.


adjusted PSU to +/-16.37VDC (max), TP9 -9.98 (no change), metering no change.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 17, 2015, 07:14:47 PM
Doug, I am in the midst of collecting some benchmark test data from a finished unit here. I still have a bunch of stuff to measure and then put it in a useful format for everyone.

In the meantime, your issue sounds like something is not right with the comparator resistor string. Can you check for 2.5V DC at the precision shunt on the meter card? If that is correct at the shunt, something in the resistor string got swapped around.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 17, 2015, 08:11:38 PM
I recall measuring the sh*t out of every R as it went in there, especially R6-8 which with tolerances, can look like one another.  Build pic looks like the R string is correct, unless I'm missing something.  What do you see?

https://c4.staticflickr.com/8/7715/17610318049_0f74d64e0a_o.jpg (https://c4.staticflickr.com/8/7715/17610318049_0f74d64e0a_o.jpg)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 17, 2015, 08:48:27 PM
Yes from what I see those are correct. With the way the string is set up, only the green LED should fire with 2.487V present on TP10. That is interesting and at the moment, puzzling. I think the data I am collecting for the DCV's at the LM339 pins may help narrow down the issue.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 20, 2015, 03:47:45 PM
I built my first FC526 no issue. Just completed the second one and it will not power up. It is causing my Radial Workhorse Powerstrip to go into protect mode. I double checked diode/capacitor orientation/values and resistor values. I'm stumped. Here are a few pictures of the board.

(http://s8.postimg.org/mb57hvk9t/20150520_132347.jpg) (http://postimg.org/image/mb57hvk9t/)

(http://s8.postimg.org/a7zvub97l/20150520_132412.jpg) (http://postimg.org/image/a7zvub97l/)

Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 20, 2015, 03:53:06 PM
I built my first FC526 no issue. Just completed the second one and it will not power up. It is causing my Radial Workhorse Powerstrip to go into protect mode. I double checked diode/capacitor orientation/values and resistor values. I'm stumped. Here are a few pictures of the board.
The TL084 is in backwards.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 20, 2015, 05:45:41 PM
I built my first FC526 no issue. Just completed the second one and it will not power up. It is causing my Radial Workhorse Powerstrip to go into protect mode. I double checked diode/capacitor orientation/values and resistor values. I'm stumped. Here are a few pictures of the board.
The TL084 is in backwards.

Doh! Thanks,  I got it on correctly and it powered up. I'm trying to calibrate the metre now and I can only get 1.76v at TP10. Did I fry the TL084?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 20, 2015, 05:48:35 PM
Most likely, yes.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 20, 2015, 06:54:04 PM
Any reason I couldn't sub a TL074 in this application? That's what I have on hand. If not I'll have to bite the bullet and order parts. I really appreciate the help and quick response.

Thank you!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 20, 2015, 07:44:00 PM
Any reason I couldn't sub a TL074 in this application? That's what I have on hand.
It should be fine.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 21, 2015, 04:43:24 PM
Replaced the TL084. It's still won't trim up past 1.76v on TP10. what else should I be checking?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 04:58:37 PM
Replaced the TL084. It's still won't trim up past 1.76v on TP10. what else should I be checking?
What is your voltage at TP9? Should be -10V.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 21, 2015, 05:06:32 PM
TP9 is giving me -8.56
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 05:13:02 PM
TP9 is giving me -8.56
OK that is your issue for TP10. I am changing the kits and including a 750R for R41 on the main PCB. Right now its a 1k2. Swap that out if you have something close and then make sure you have -10V at TP9. That is a crucial measurement to take. If its not -10V, the Q-Bias and meter cal will never happen correctly.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 21, 2015, 07:27:56 PM
Can you check for 2.5V DC at the precision shunt on the meter card?

2.58VDC at the center pin of one, 2.6VDC on the other.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: tctonn on May 21, 2015, 09:00:30 PM
TP9 is giving me -8.56
OK that is your issue for TP10. I am changing the kits and including a 750R for R41 on the main PCB. Right now its a 1k2. Swap that out if you have something close and then make sure you have -10V at TP9. That is a crucial measurement to take. If its not -10V, the Q-Bias and meter cal will never happen correctly.

Hi Jeff,

I am putting together a pair of these now. Would you recommend making this swap at R41 on kits that I bought in your last batch of 50?

Also, should I be concerned that in my kits the 300k (R39, R40) and 1M (R37, R38) resistors are 5% rather than the 1% that is shown on the Rev A.2 PCB BOM?

Thanks as always for all your help with these.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 09:19:08 PM
Would you recommend making this swap at R41 on kits that I bought in your last batch of 50?
Absolutely yes, This will only make your life easier and the reference voltages will be solid if you slip in it another rack somewhere.

Quote
Also, should I be concerned that in my kits the 300k (R39, R40) and 1M (R37, R38) resistors are 5% rather than the 1% that is shown on the Rev A.2 PCB BOM?
No not at all. The parts are actually correct. I just need to update the BOM. The clerical part slipped thru the cracks on those  :-[
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 21, 2015, 09:43:33 PM
Paralleled an actual 2161R across the 1K2 to get about 771R at R41, no time to go further....
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 09:46:05 PM
Can you check for 2.5V DC at the precision shunt on the meter card?
2.58VDC at the center pin of one, 2.6VDC on the other......
This is a problem Doug. This should be between 2.497V and 2.503V. I have recently tested and verified that this voltage will be rock solid with a supply voltage ranging from 14.5V to 20V at the gold fingers. I would look at R14 on the meter PCB and make sure its 5k1.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 09:47:21 PM
Paralleled an actual 2161R across the 1K2 to get about 771R at R41, no time to go further....
This will also work a treat. I would call that being a tricky bastard!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 21, 2015, 09:59:05 PM
2.58VDC at the center pin of one, 2.6VDC on the other......
This is a problem Doug. This should be between 2.497V and 2.503V. I have recently tested and verified that this voltage will be rock solid with a supply voltage ranging from 14.5V to 20V at the gold fingers. I would look at R14 on the meter PCB and make sure its 5k1.

OK, ASAP.


Paralleled an actual 2161R across the 1K2 to get about 771R at R41, no time to go further....
This will also work a treat. I would call that being a tricky bastard!

I call it 'F pulling the boards out, take the shortest path'. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 10:07:03 PM
OK I apologize for this not being a better quality. I will put something more professional together when I have a minute. I am heading down to Nashville early tomorrow morning and have not packed anything yet!

In the attachment, you will see a chart of points to check the comparator string. The numbers are merely the junction of the resistor string, not component pin numbers. It starts with the 2.5V precision shunt so if that is off, the whole string will be wonky.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 21, 2015, 10:11:59 PM
BTW, by changing R41 to 750R, I have verified on multiple units here that the -10V rail stays rock solid from a supply voltage ranging from -14.5V to -20V. That is a supply voltage at the gold fingers coming to the card. The 2.5V rail is rock solid as well from the same voltage range.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: dandeurloo on May 22, 2015, 11:28:40 AM
BTW, by changing R41 to 750R, I have verified on multiple units here that the -10V rail stays rock solid from a supply voltage ranging from -14.5V to -20V. That is a supply voltage at the gold fingers coming to the card. The 2.5V rail is rock solid as well from the same voltage range.

Jeff, will I need to re calibrate if I make this change to mine?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: orenradio on May 22, 2015, 12:33:27 PM
I imagine this resistor is the recommended replacement for R41?  I haven't had the chance to start my pair of compressors just yet, might as well get the right resistor in there before I start.  Jeff I know you are out of town, so no rush... just want to be sure

http://www.mouser.com/ProductDetail/Xicon/271-750-RC/?qs=sGAEpiMZZMu61qfTUdNhG6G26YXWwWp0cxSUK4uuyRQ%3d
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 22, 2015, 04:07:09 PM
TP9 is giving me -8.56.
OK that is your issue for TP10. I am changing the kits and including a 750R for R41 on the main PCB. Right now its a 1k2. Swap that out if you have something close and then make sure you have -10V at TP9. That is a crucial measurement to take. If its not -10V, the Q-Bias and meter cal will never happen correctly.
Did the swap on R41 to a 750r TP9 is now 10.02v but I can only get TP10 to 2.06v. Only the bottom led on the meter will "trim off" at that voltage.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 22, 2015, 11:32:08 PM
Dan, you should not have to recal after making that change. Just verify that your -10V rail does not change. This just means that the -10V rail will be stable no matter what rack or power supply voltage you use.

Yes orenradio that is the right part. I can mail them to you when I get home on the 31st.

radrobgray, I would start by adjusting the front panel trimmer and the 100K trimmer to their mid position at 50% rotation. Just turn them until you hear them clicking when they reach the end, and then turn the opposite way approximately 12 rotations. That should be near the center. If the 100K trimmer gets turned to far it will seem like you cannot adjust the front panel trimmer to bring the voltage up properly. Hope that makes sense.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: bacbacou on May 26, 2015, 11:05:35 AM
hello Jeff,

I have +/-15V power supply, so I am going to put R41 750r,
but do I have to change another resistor to stabilize the 2,5V rail ?

regards,

Richard

Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on May 26, 2015, 01:00:48 PM
radrobgray, I would start by adjusting the front panel trimmer and the 100K trimmer to their mid position at 50% rotation. Just turn them until you hear them clicking when they reach the end, and then turn the opposite way approximately 12 rotations. That should be near the center. If the 100K trimmer gets turned to far it will seem like you cannot adjust the front panel trimmer to bring the voltage up properly. Hope that makes sense.
Tried that to no avail. Any other things I should check. Still only trims to 2.07v.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 26, 2015, 01:13:58 PM
hello Jeff,

I have +/-15V power supply, so I am going to put R41 750r,
but do I have to change another resistor to stabilize the 2,5V rail ?

regards,

Richard
Nope just R41
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 26, 2015, 01:15:36 PM
radrobgray, I would start by adjusting the front panel trimmer and the 100K trimmer to their mid position at 50% rotation. Just turn them until you hear them clicking when they reach the end, and then turn the opposite way approximately 12 rotations. That should be near the center. If the 100K trimmer gets turned to far it will seem like you cannot adjust the front panel trimmer to bring the voltage up properly. Hope that makes sense.
Tried that to no avail. Any other things I should check. Still only trims to 2.07v.
I'm out of town at the moment so can't help much until I return.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 30, 2015, 04:56:56 PM
strapped R41 (1K2) with 2161R (771R resulting).
checked R14 is 5K1, both look correct, without outright pulling them.  Color code right, read reasonably right in circuit.
checked CR1/Q1 placement, both units correct.
PSU back to +/-16.04V, +/-16.01 at connector.

#1
TP9 -9.98V
2.595V at CR1: F#CKED
tried meter cal, still 3 yellow lit with +2.487 at TP10

#2
TP9 -9.98V
2.573V at CR1: F#CKED
tried meter cal, still 2 yellow lit with +2.487 at TP10

Now officially more time in troubleshooting than building.....

bad CR1's?  What else? 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 30, 2015, 06:01:13 PM
What are you using for the ground reference Doug? The green zero LED is suppose to trip just below the ref voltage at CR1 or at point #1 in my above pic of the meter PCB.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 30, 2015, 06:03:15 PM
GND at top of board as specified.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 30, 2015, 06:17:44 PM
Ok. Does the ref voltage (high as it is) fluctuate if you raise or lower the positive supply voltage? I am still not back to the lab but in my previous tests, mine was solid. I tried to make it go above 2.5 but could not duplicate your situation. I would not go less than 14 V or higher than 20 V when checking it.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 30, 2015, 06:40:05 PM
I'd assume that's a test done with op amps out?   

I did note one was easy to trim to +2.487, the other jumps around quite a bit during adjustment and is lucky to land at +2.486 or +2.488.

I'm wondering if this is a rack problem, grasping at straws.  The test bed is an OSA rack, 8 other types of modules work fine in it.  I have the 10R at the connector for front/back ground.  I should try it in a different rack, which is a bit of a PITA to arrange. 
http://groupdiy.com/index.php?topic=48324.0
This may be it.
--EDIT: IT IS!---
As well, my extension jig has no pin 1 connection, so that's a 'double no pin 1'.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 30, 2015, 07:00:19 PM
I did it with opamps in. I would adjust the negative rail by a volt or 1.5 and then the pos by a volt or 1.5, stepping my way up to 20 and down to 14. I have so far had my hands on nearly 30 of these completed modules and never had one with the meter reference voltage higher than 2.5. Once calibrated on my bench supply, they have ended up in various different API racks as well as BAE and the green zero LED illuminates right away with no trimming required.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 30, 2015, 07:16:01 PM
Doug, can you check the attachment I posted on page 4 of this thread. Post #79. I know your reference voltage will start out a bit high, but see if the rest of yours follows a similar pattern to mine. This is the reference voltage down the resistor string that the comparators look at.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 31, 2015, 08:12:50 PM
I never mention the green LED, but it does light, along with the specified # of yellow.

Spoiler:
Both units, moved to 51X rack, only green LED lit.  F!  OSA rack!!!!

backtracking:

Is this a (lack of) pin 1 problem with OSA rack?
FC526 top and bottom ground planes link through 10R between pin5 and pin13.
FC526 pin1 - 10R - pin13 - 10R - pin5
FC526 GND lug is pin13, shorted.

Connecting OSA pin1 to PSU chassis changes nothing.
If I short pin5/13 while in OSA rack, yellow LED’s go out leaving only green on both units, and green turns off in ABI on both.


Pin5/13 not shorted in these measurements, 2.486V TP10.
      is:      should be:      
IC2-5      2.362      eight) 2.276   (Eight does this 8) dangit stupid sh#t 8))
IC2-7      2.339      9) 2.253   
IC2-9      2.264      10) 2.178   
IC2-11      1.771      11) 1.685
   
IC3-5      2.466      4) 2.38   
IC3-7      2.437      5) 2.351   
IC3-9      2.412      6) 2.326   
IC3-11      2.386      7) 2.3
   
IC4-7      2.584      1) 2.498   
IC4-9      2.536      2) 2.45   
IC4-11      2.504      3) 2.417

Other w/2.487V TP10:
      is:      should be:      
IC2-5      2.359      8) 2.276   
IC2-7      2.336      9) 2.253   
IC2-9      2.262      10) 2.178   
IC2-11   1.773      11) 1.685
   
IC3-5      2.462      4) 2.38   
IC3-7      2.434      5) 2.351   
IC3-9      2.408      6) 2.326   
IC3-11   2.383      7) 2.3
   
IC4-7      2.597      1) 2.498   
IC4-9      2.55      2) 2.45   
IC4-11   2.518      3) 2.417

ready to align in 51X rack!!  Rewire damn OSA rack!!

Note the 51X rack and the OSA rack are on the same power supply. A module on the extension jig in the 51X rack  shows only the green LED with that extension jig lacking pin1 chassis connection .

No chance yet to check CR1 or LM339 voltages again in 51X rack.   Since the lack of pin1 on the test jig makes no difference here, I'm not sure yet what's actually different.  Pin5/13 shorted in the 51X rack?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 31, 2015, 10:29:41 PM
.....and green turns off in ABI on both.
This is totally normal and to be expected. Switching to All Buttons In takes the FET fully out of the conductive range so the green LED will turn off. The same thing happens with a real 1176. If the meter is in GR mode, when pushing ABI (or just 4 and 20), the meter will increase (positive voltage) by the amount of the FET cal which will typically be 1dB in a later model real one, providing that the meter and FET are all cal'ed in correctly!

As for the rest, it is now making sense that the 10R between the ground planes is offsetting the 2.5V reference since the OSA rack must not have a link between pins 5 and 13 internally.

I was curious before about how consistent your reference voltage was at the top of the string (IC-4 pin 7) when running your PSU voltage up and down. Even though it is offset above 2.5V, it should stay consistent and never change. Would be swell if you could verify this  ;)

Option #1, I would cal the units in the 51x rack so the voltages you are looking for are easy to hit and already known. Once you move them to the OSA rack, just simply re-zero the green LED. Do this thru the front panel while racked up. I would not measure the voltage. Just make sure the green LED just barley comes full on. The meter cal should stay set from before as everything will shift together.

Option #2, remove the 10R that links the top and bottom ground planes and replace with a jumper wire or zero ohm R.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: djroshi on May 31, 2015, 10:47:57 PM
Checking in.

R41 is now a 750R and I have a solid -10 at TP9.

Still unable to calibrate the meter.

1. With GR off and +2.487V at TP10 green led is lit.
2. Engage GR and green led is now OFF. I have 7db GR verified and TP10 is greater than +2.245V so I turn RV8 CCW till I reach the desired voltage - green led is still OFF.
3. I disengage GR and TP10 is now less than +2.487V so I turn RV1 CW to get the desired voltage.
4. Repeat 2 and 3. The voltages seem to get further and further apart needing greater adjustments.

I have gone thru and compared the voltages at the comparator ICs and they seem to align closely to the measurements you posted Jeff (thanks for that BTW).
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on May 31, 2015, 10:50:59 PM
Yup on the ABI action, just confirming it's acting right which also shows that alignment step 1 is correct, if I'm not mistaken. 

It is not simple to change the PSU voltage here.   I'll try to wind it down a bit and see.  It goes up no further than +/-16.37V.

I haven't taken the time to dig further into proper VPR wiring standard, so 5 and 13 are typically shorted in the racks?  I'm sure you have a chart somewhere....

Good to know the details of option 1. 

I think I will try option 3: rewire the damn OSA rack properly.  I mean really; XLR output shells as only thing wired to chassis?  How often is that likely to work (sarcasm intended)?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 31, 2015, 11:28:33 PM

2. Engage GR and green led is now OFF. I have 7db GR verified and TP10 is greater than +2.245V so I turn RV8 CCW till I reach the desired voltage - green led is still OFF.
Take a look at the directions again. It is a little weird to do because when the 2.245V is off a bit, you must turn the trimmer in the OPPOSITE direction farther away from the target then turn GR off and reset the 2.487V.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 31, 2015, 11:31:26 PM
It is not simple to change the PSU voltage here.   I'll try to wind it down a bit and see.  It goes up no further than +/-16.37V.
Don't worry about it Doug. Now that we know what the dealio is, I should be able to replicate and try it here. I am 99% sure it will be no issue. The low voltage was the original issue anyhoo not higher but I still think we are good.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: djroshi on June 01, 2015, 12:31:54 AM
Yeah that works, sorry I misunderstood... I now have 2.245 with 7dbu GR and 2.487 with no GR. Again, green LED is lit with GR off and no LEDs lit with GR on.

Is there anything else I can check?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 01, 2015, 12:37:31 AM
Are you sure you are at 20:1? Check the voltages at the comparators pins that I attached in post #79 of this thread.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: djroshi on June 01, 2015, 01:22:55 AM
20:1 absolutely sure.

As I said, my measurements at the comparators are comparable to yours:

1 = 2.503
2 = 2.456
3 = 2.423
4 = 2.385
5 = 2.356
6 = 2.331
7 = 2.305
8 = 2.281
9 = 2.258
10 = 2.183
11 = 1.687
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 01, 2015, 09:48:15 AM
I would check the orientation of the top yellow LED, the one adjacent to the green one. It sounds like that one is in backwards and blocking the voltage flow below the green one.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: djroshi on June 01, 2015, 10:56:02 PM
Would that cause the green LED to not light up though? Because with GR engaged nothing is lit.

Measuring the voltage between GND on the main board and the leads of the LEDs gives some confusing results.

With GR OFF I get -14.76V on all leads except for D11-G anode which is at -12.69V and accordingly the green LED is lit.

D-11GA = -12.69V
D-11GC = -14.76V
D-10YA = -14.76V
Everything else = -14.76V

With GR ON I start getting positive voltages, whereas with GR OFF the voltages are negative.

D-11GA = +14.51V
D-11GC = +12.89V
D-10YA = +12.89V
Everything else = ~10mV

The LEDs definitely appear to be installed correctly? Pretty difficult to get a photo in which the knicks on the anode were clearly visible, but the length of the internal lead is pretty clear and the longer ones definitely have knicks in them.

Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 02, 2015, 12:22:43 AM
With GR engaged, turn the input pot down all the way. I assume the green LED will illuminate. The GR on/off switch does nothing more than  turn the audio going to the sidechain amp off. It does nothing directly with the LED's.

When the voltage at TP10 goes just below the voltage that is at the comparator pin, the respective LED will illuminate.

So, using the data that you posted, when the voltage at TP10 drops just below 2.503, the 0dB green LED will light.

When the voltage at TP10 drops just below 2.456, the -.5dB yellow LED will light.

When the voltage at TP10 drops just below 2.423, the -1dB yellow LED will light.

And so on.

Your voltages at the comparator pins look good so the only other thing left in the circuit is the LED's.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: daveriot on June 03, 2015, 04:11:57 PM
here is a fun one. my leds dont do anything. when i first put the kits together it seemed to work but they werent doing what they were supposed to.
now when i turn them on one of the unit blinks all of the leds and the other does not
otherwise the units seem to be working
any ideas where i should start looking?

i have verified that the polarity is correct on the leds
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on June 03, 2015, 04:24:49 PM
radrobgray, I would start by adjusting the front panel trimmer and the 100K trimmer to their mid position at 50% rotation. Just turn them until you hear them clicking when they reach the end, and then turn the opposite way approximately 12 rotations. That should be near the center. If the 100K trimmer gets turned to far it will seem like you cannot adjust the front panel trimmer to bring the voltage up properly. Hope that makes sense.
Tried that to no avail. Any other things I should check. Still only trims to 2.07v.
I'm out of town at the moment so can't help much until I return.
Any further assistance? I really have no idea where to go from here. Thanks.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 03, 2015, 04:51:25 PM
my leds dont do anything. when i first put the kits together it seemed to work but they werent doing what they were supposed to.
now when i turn them on one of the unit blinks all of the leds and the other does not
otherwise the units seem to be working

Blinks momentarily when powered on, and then back off for good, or ?  Not clear to me. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 03, 2015, 10:24:34 PM
radrobgray, I would start by adjusting the front panel trimmer and the 100K trimmer to their mid position at 50% rotation. Just turn them until you hear them clicking when they reach the end, and then turn the opposite way approximately 12 rotations. That should be near the center. If the 100K trimmer gets turned to far it will seem like you cannot adjust the front panel trimmer to bring the voltage up properly. Hope that makes sense.
Tried that to no avail. Any other things I should check. Still only trims to 2.07v.
I'm out of town at the moment so can't help much until I return.
Any further assistance? I really have no idea where to go from here. Thanks.
With no GR taking place, can you measure the DCV at TP7 (top left corner of the PCB)? Also what make and model of DMM are you using?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 03, 2015, 10:28:33 PM
here is a fun one. my leds dont do anything. when i first put the kits together it seemed to work but they werent doing what they were supposed to.
now when i turn them on one of the unit blinks all of the leds and the other does not
otherwise the units seem to be working
any ideas where i should start looking?

i have verified that the polarity is correct on the leds
Sounds like you have different issues with both units? I think this should be handled one by one. It would be best to get one unit functioning correctly and then use that as a benchmark for the other. I have had guys install one or more of the LM339's backwards. That can be easily overlooked at first.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 03, 2015, 11:04:41 PM
The first Rev of the Test Points Guide has been added to the first post of this thread. This is just a start for now. I will be adding more info to this doc soon.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 03, 2015, 11:20:42 PM
I see 1_Classic-FC526-Rev-A.2-PCB-BOM has been changed, but the Rev version didn't move forward.

Thanks for the test point guide, very handy.



Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 03, 2015, 11:38:12 PM
I see 1_Classic-FC526-Rev-A.2-PCB-BOM has been changed, but the Rev version didn't move forward.
I made part # and tolerance corrections for the 300k and 1M R's. I also changed R41 from 1k2 to 750R. I like to keep the Rev of the doc the same as the Rev of the PCB so things don't get too confusing.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: radrobgray on June 05, 2015, 12:40:03 PM
radrobgray, I would start by adjusting the front panel trimmer and the 100K trimmer to their mid position at 50% rotation. Just turn them until you hear them clicking when they reach the end, and then turn the opposite way approximately 12 rotations. That should be near the center. If the 100K trimmer gets turned to far it will seem like you cannot adjust the front panel trimmer to bring the voltage up properly. Hope that makes sense.
Tried that to no avail. Any other things I should check. Still only trims to 2.07v.
I'm out of town at the moment so can't help much until I return.
Any further assistance? I really have no idea where to go from here. Thanks.
With no GR taking place, can you measure the DCV at TP7 (top left corner of the PCB)? Also what make and model of DMM are you using?
I got -.302vdc at TP7 w/ GR off. I'm using a Victor VC9805A DMM.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 05, 2015, 01:38:12 PM
I got -.302vdc at TP7 w/ GR off. I'm using a Victor VC9805A DMM.
OK this is super high, or too close to 0V. When the VVR FET is properly biased for 0.5dB of loss, this reading should match (or be close to) the bias voltage I have written on the bag with the SN that the FET came in. My pinch-off range is typically from -1.4V to -1.7V for the VVR FET.

I can think of 4 possibilities why this would not match or be pretty close.

1. I use a Fluke 177 to sort and record all FET data. If the input Z of your meter is not close to mine, it will drastically skew the measurement since that part of the circuit is so high impedance. From the looks of your meter's spec sheet, the results should be similar. FYI, the Fluke has an input Z of >10M. My B&K 889B bench meter has an input Z of 1M. I cannot use it to sort FET's or confirm my Fluke readings. So, probably not that.

2. The MTR FET and VVR FET somehow got swapped during assembly. They are not at all interchangeable like with other 1176 style kits. I chart, measure and make sure that the transfer characteristics of all FET's fall into a certain range at multiple predetermined amounts of gain reduction. This means that the MTR FET will accurately reflect what the VVR FET is doing. These 2 FET's do not need to have the same pinch-off voltage. This only means that the MTR FET pinch-off must be equal to or closer to 0V than the VVR FET. If these got swapped, once the MTR FET gets biased in the incorrect VVR position, the VVR FET that ended up in the MTR spot will essentially do nothing. Now, the FET's that have a too high pinch-off voltage for VVR purposes, get sorted into the MTR position. So far, they have all been in the -1.1V to -1.399V range. This does not exactly explain your situation either but will for sure save somebody some time in the future.

3. Your VVR FET is not biased correctly for the 0.5dB loss. The more your turn the Q_Bias trimmer CCW, the lower the output will get and the lower the bias voltage reading at TP7 will be. I would recheck this adjustment and I would actually look here first.

4. There is something else messed up in the -10V part of your build that we have not uncovered yet.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 07, 2015, 04:58:36 PM
Happy Sunday folks!

I have finally had some spare time to expand and elaborate on the support docs for the FC526 project. I have just posted new docs and links that can be found in the first post of this thread.

Here's a recap of what is new:

I have added a Meter Zero Adjust doc. This will mostly help folks who are buying assembled modules but I suggest that anyone who has a FC526 take a quick peek.

I have updated the Test Points Guide. It now includes some specific info on testing the audio path and the sidechain elements of the build. Also included are some things to look out for as well as meter voltage specifics.

Lastly, I have updated and improved the Calibration Guide. This includes some important pitfalls to look out for as well as a much easier and versatile way to bias the VVR FET. Not only does it make the bias adjustment easier, it also double checks your audio path at the same time.

That's it for now so please visit the first thread and update your support docs folder for this build.  ;)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: kosi on June 10, 2015, 12:11:36 PM
Here a little pic for motivation !
They are all not properly calibrated, but as there is no stereo option, I don't care too much, they sound superb the way they are.
I updated the color scheme on the knobs with orange, which I like a lot more then yellow.
The 2 orange ones use 1731, the yellow one uses red dots. All relatively transparent.
I ordered 2 Raindog OP Amps from Hairball. let's see, wether they give a bit more color.

In which position will they have the most coloration ? Any tips ?

at last, I'm always a bit confused with the direction of the GR switch, it's the only one which goes up to work.

fantastic workhorses,
yeehaa
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: kante1603 on June 10, 2015, 02:36:13 PM


In which position will they have the most coloration ? Any tips ?


ABI?


 8)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: kosi on June 10, 2015, 02:48:01 PM

I meant the OP Amps , in which position do they give the most color,
Signal Input ?
Receiver ?
or Output ?

Didn't have so much time to play around, cause I use them always...
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 10, 2015, 02:55:52 PM
I think Dan Deurloo has messed around a lot with opamp placement. Maybe he will chime in. I have really only used then with all reds or all gar1731's. Most of my Nashville pals like both for different uses.

Another thing to do is intentionally increased the THD with the null trimmer. I would find the low spot and then turn the trimmer CW up to maybe 0.5% or 0.75%. Typically, the highest THD during normal use will be when the unit is knocking back 6-7dB of gain reduction.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: steveau on June 12, 2015, 08:56:01 PM
Jeff,
 I'm about ready to start calibration, but I notice my DCV's are slightly off,
 at -10.03 at TP9 and 2.53 at TP11,
my voltage at the CAPI  PSU is 16.6 V,
my voltages at the DOA are  +15.84/-15.88,
Is that close enough to start biasing the VVR?
(I did use the 750ohm for R41),
Thanks,
-Steven G
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 12, 2015, 09:03:26 PM
Yeah, you look good to go Steven  :)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 13, 2015, 09:57:39 PM
The rack is now right, the voltages look right everywhere, and I'm still a fail.   I can get to the proper green LED starting point now with 2.487V. 

At 20:1, once I trim RV8 to 2.245V it always lands at -5dB GR.   I eventually maxed out RV8 doing the RV1/RV8 trimmer dance, never seeing any difference in GR reading.  Maybe I'm totally misreading the directions somehow, the voltage difference at each comparison just got wider and wider apart with no significant change in meter result.   After each retweak of RV1 the GR meter always read high.  On the last go at RV8 it dropped to -6 somewhat later than previous attempts. 

If I switch to 4/8/12:1, it reads -7dB.  2:1 reads something like -1dB.  Maybe this indicates a problem in the ratio switch?

No time to try unit 2 tonight....
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 10:42:37 AM
At 20:1, once I trim RV8 to 2.245V it always lands at -5dB GR.
Doug, I'm not sure I follow you here. Do you mean that with 2.245V at TP10, the LED's are only lit up to the -5 yellow one, the -7 doesn't come on?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 10:50:29 AM
At 20:1, once I trim RV8 to 2.245V it always lands at -5dB GR.
Do you mean that with 2.245V at TP10, the LED's are only lit up to the -5 yellow one, the -7 doesn't come on?

Correct for 20:1.  When finished with the RV1 set, it's up at -10, then trimming RV8 to the correct voltage it drops to -5.  If I switch to the other ratios from 4 to 12, it reads -7 as it should, with 2:1 reading -1 or so. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 10:59:03 AM
Well, what its interesting here is that the comparator string doesn't know or care what the ratio is. Its just looking at the incoming DCV from the meter circuit. The meter will show something different if the only control changed is the ratio BUT, that is only because the amount of GR will be different. If you set the ratio to say 4:1, and then adjust input and output for exactly 7dB of gain reduction, the meter will work exactly as before. 2.245V will trip the -7 LED.

So the ratio switch will change the amount of gain reduction but it does not alter how the meter works. The meter will show the proper amount of gain reduction regardless of the ratio switch position.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 11:05:49 AM
Meter readings for actual -7GR at 20:1, consistent at each attempt to align, up until RV8 hit an end stop. 

2:1 -1
4:1 -7
8:1 -7
12:1 -7
20:1 -5
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 11:33:02 AM
Meter readings for actual -7GR at 20:1, consistent at each attempt to align, up until RV8 hit an end stop. 

2:1 -1
4:1 -7
8:1 -7
12:1 -7
20:1 -5
What is the DCV at TP10 for each one of those?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 11:38:21 AM
BTW Doug, have you seen the "Classic-FC526-Test-Points-Guide-Rev_2.pdf" that I posted last week at the beginning of this thread? The last part of it gives a little insight into the meter.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 11:46:25 AM
+2.245V at TP10 at 20:1, I didn't make note of it at other ratios. 

I did note that once RV1 is set for +2.487 (1 green LED lit) that it stays the same for the lower ratios as well, though it does jump and has a resettling time when the ratio switch is changed. 

I have to find time to go through the next unit, see if there's any comparison.    I do have the new docs.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 12:09:17 PM
.... I do have the new docs.
OK. All of the ratio switch and other things aside, the meter is just a simple set of comparators much like any other LM339 style meter. The only difference is that I am using them "backwards". So, once the incoming test voltage drops below the respective comparators reference voltage, that LED will light. If the meter reference string is correct (see the meter test points), no setting on the comp will alter this.

For example, if you run bipolar 16V to the meter PCB along with a 0V ground reference, you can use the FC526 meter to indicate any incoming DCV from 0 to 2.5V. This can be easily tested without being connected to the comp's main PCB.

The fact that 2.245V does not trip the -7 LED tells me that your reference string as shown in the test points doc is not right. Meter point #3 cannot be 2.253V.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 01:07:13 PM
The fact that 2.245V does not trip the -7 LED tells me that your reference string as shown in the test points doc is not right. Meter point #3 cannot be 2.253V.

Ah, but we tested the reference string a few weeks back, and it was all dead on once the rack offset was discovered.   I posted measurements previously.   This weeks results are with the basic +2.5V and -10V confirmed again before starting. 

What would make the 20:1 setting read LESS GR than the lower ratios, with -7 dB actual measured at 20:1? 

I'm gonna run RV1 and RV8 back mid position and start the whole thing over again with Q bias, although this has not appeared to shift once I've run it once.   I might tackle unit 2 before doing this, I might not. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 01:15:49 PM
What would make the 20:1 setting read LESS GR than the lower ratios, with -7 dB actual measured at 20:1? 
Only something funky with the meter board. What's important to note is what the DCV is at TP10 when this unexpected result happens. Just remember, all each individual comparator channel is doing is looking at the reference voltage and the incoming test voltage. Once the test voltage drops just below the reference, that LED will light. That part is pretty straight forward and will never change.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 01:19:47 PM
I should phrase it another way.

Regardless of meter alignment, if you change ratios and have less actual GR, why would a higher ratio show less (correct or incorrect) GR than the lower ratios? 

I have to wonder if that points to a problem external to the meter circuit. 
Other thought is around the previous attempts to align while the rack offset voltage existed, can you get RV1/8 to points which are too far off base to use as starting points, but which still look like they are working?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 01:31:46 PM
Regardless of meter alignment, if you change ratios and have less actual GR, why would a higher ratio show less (correct or incorrect) GR than the lower ratios?
Well, setting the unit up  20:1, attack/release both full CW/fast, input/output to a resulting 7dB of actual gain reduction, then only changing the ratio switch will alter the amount of GR. This is simply a matter of how the 1176 circuit works. This will not at all change the meter but will change the voltage at TP10, which will change what the meter shows.

Meter LED's aside, with the above typical 7dB of GR setup, when monitoring the output level so that 0dB is showing (+7dB at the input).....

switching to:
12:1 will yield -1.45dB
8:1 will yield -1.94dB
4:1 -1.74dB
2:1 +1.92
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 01:43:26 PM
It feels like we are talking at cross-purposes, maybe not. 

Yes, change to a lower ratio will alter the amount of GR to a lesser amount than found at a higher ratio. 

I'm wondering if there's something about this particular 20:1 not being right, which would feed the meter incorrect information, or if it's an idiosyncrasy of the 1176 circuit that looks more obviously strange with peak metering versus VU metering. 

Meter LED's aside, with the above typical 7dB of GR setup, when monitoring the output level so that 0dB is showing (+7dB at the input).....

switching to:
12:1 will yield -1.45dB
8:1 will yield -1.94dB
4:1 -1.74dB
2:1 +1.92

Those ratio change dB numbers are relative output change or metered GR?   I think I'm reading it as relative output change. 

More measurements to do, theorizing isn't revealing anything. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 02:01:42 PM
Yes, change to a lower ratio will alter the amount of GR to a lesser amount than found at a higher ratio.
No, not necessarily. There are many other things at play like onset of compression and knee. This will change depending on how much GR is taking place. Depending on how much GR is taking place, the opposite will happen.

Quote
I'm wondering if there's something about this particular 20:1 not being right, which would feed the meter incorrect information...
This is possible but the if the test voltage going to the meter is 2.245V, then the -7 LED will fire. If not, its a problem on the meter board. No matter what the ratio setting is, if the comp is producing 7dB of gain reduction, TP10 will be 2.245V if all is cal'ed correctly. I have verified this with every ratio setting.

Quote
Meter LED's aside, with the above typical 7dB of GR setup, when monitoring the output level so that 0dB is showing (+7dB at the input).....

switching to:
12:1 will yield -1.45dB (resulting in 8.45dB of GR)
8:1 will yield -1.94dB (resulting in 8.94dB of GR)
4:1 -1.74dB (resulting in 8.74dB of GR)
2:1 +1.92 (resulting in 5.08dB of GR)

Those ratio change dB numbers are relative output change or metered GR?   I think I'm reading it as relative output change. 

More measurements to do, theorizing isn't revealing anything.
Yes, relative output change. I have added some info to them to clarify.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on June 14, 2015, 03:35:27 PM
Ok, sounds like there's non-linear stuff happening with the ratio/threshold, maybe even one of those funky 'S' curve knees that a few comps produce. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 14, 2015, 04:04:28 PM
Slightly off topic but related. Dorks like me will find this fascinating! SSLTech explains ABI things nicely. http://prorecordingworkshop.lefora.com/topic/3841871/All-Buttons-In-1176#.VX3dvWAVqFJ
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: steveau on June 15, 2015, 12:28:45 PM
Jeff,
 I'm having problems with the calibration section.
My signal generator only goes down to 0.1 volt, so I don't think it can generate anything less than -26dBu,
I tried to use a computer generated signal, but my fluke DMM readings are jumping around and I don't know if I can trust it.
 Sorry to be so technically challenged, is there a louder level that could be used to calibrate?
Thanks,
-Steven
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 15, 2015, 12:59:34 PM
Jeff,
 I'm having problems with the calibration section.
My signal generator only goes down to 0.1 volt, so I don't think it can generate anything less than -26dBu,
I tried to use a computer generated signal, but my fluke DMM readings are jumping around and I don't know if I can trust it.
 Sorry to be so technically challenged, is there a louder level that could be used to calibrate?
Thanks,
-Steven
You should be fine at -26dBu. Just keep in mind that all levels stated will be 4dB hotter. This is only during the first few steps (VVR adjustment & audio path dbl check). I chose -30 because one can safely run both pots wide open and not worry about anything clipping.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: tctonn on June 16, 2015, 04:12:23 PM
Jeff, et al

Howdy. I am having some issues with calibration on both of my units. When I feed aprox -30dB (-.024v) in to test the audio path I am getting the same voltage reading at TP1. At TP3 I have 2.898v.

I have a 1731 in the receiver slot and red dots in the other two opamp slots. All three opamps work well in my VP28.

Seems obvious that something is wrong with my audio path but I am no expert on these and am not sure where to start trouble shooting. Any suggestions would be greatly appreciated.

Thanks!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 16, 2015, 05:58:42 PM
Jeff, et al

Howdy. I am having some issues with calibration on both of my units. When I feed aprox -30dB (-.024v) in to test the audio path I am getting the same voltage reading at TP1. At TP3 I have 2.898v.

I have a 1731 in the receiver slot and red dots in the other two opamp slots. All three opamps work well in my VP28.
So you get appx 24mV AC at TP1 with 24mV AC signal at the input? Try different opamps in the receiver spot. If it persists, post a pic of the group of R's between the receiver amp and the output transformer.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: tctonn on June 17, 2015, 08:30:46 PM
Jeff, et al

Howdy. I am having some issues with calibration on both of my units. When I feed aprox -30dB (-.024v) in to test the audio path I am getting the same voltage reading at TP1. At TP3 I have 2.898v.

I have a 1731 in the receiver slot and red dots in the other two opamp slots. All three opamps work well in my VP28.
So you get appx 24mV AC at TP1 with 24mV AC signal at the input? Try different opamps in the receiver spot. If it persists, post a pic of the group of R's between the receiver amp and the output transformer.

BINGO! Thanks for the quick reply Jeff. I swapped out a couple opamps and touched up a couple dodgy solders and everything works perfectly. I don't know exactly what was wrong but I don't care now because this thing is great. Thanks again!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 02, 2015, 08:07:09 PM
'Chung has been making some progress on the build! He has 2 sets of pics up in the 2nd and 3rd post of this thread.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 04, 2015, 03:59:31 AM
I'm setting up the build for my pair and I'm doing sorting sheets. Just noticed a possible minor error on Chung's beautiful pics. I believe the white metallized polyester C6 & C7 caps are labeled '•22J63' and not 'n22J100' (which is the C5 cap). I'll PM Chung in case he doesn't see this.
Edit: Chung's inbox is full, and I wasn't able to reach him thru his homepage, so perhaps Jeff could alert him?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: tonycamp on July 04, 2015, 11:25:44 AM
to clarify, on C6 and C7, just ignore the "22n j100" to the right of chungs sort sheet, his marking of ".0 22uf 63v" on the left is correct.
Jeffs build guide and the PCB Bom are great. I just grab the bag he suggests in the BG, then grab whatever resistor hits my fingers? put it on my MM, look at his PCB Bom that lists values( in low to high order), read the position of the value in hand, and stick em in till their gone.
It seems the step of organizing with sheets is a waste for me because my obsessive nature will not allow me to NOT put the part on my MM just before I install it haha

that said, Chung's build threads are legendary!

btw, i also suggest building in pairs, it's like double checking yourself as you go  :)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 06, 2015, 07:55:26 PM
Jeff, I remember reading somewhere that when soldering a couple of transistors you switch between them to not overheat. This is the first time I'll  solder ICs directly to the PCB. Are those sensitive to heat too? Make sense using the same method?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 06, 2015, 08:22:07 PM
Jeff, I remember reading somewhere that when soldering a couple of transistors you switch between them to not overheat. This is the first time I'll  solder ICs directly to the PCB. Are those sensitive to heat too? Make sense using the same method?
Yes they are and I use the same alternating method for them.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 08, 2015, 03:54:53 PM
Jeez Jeff, this kit, build wise, is my fav so far. Everything fits perfectly and it looks super neat. Kudos.

I have a problem w calibration. Everything measured and seemed perfectly by the book until the final stage at step 8 of the GR meter calibration. I noticed that the action of RV8 isn't 'backwards' as described, resulting in (I believe) that when toggling GR on/off and trimming RV1 and RV8 accordingly, the measurements gets more and more off. Anything obvious comes to mind?

BTW, I have the Litz version (triple checked the wiring..)

Cheers
Paul
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 08, 2015, 04:10:17 PM
I noticed that the action of RV8 isn't 'backwards' as described, resulting in (I believe) that when toggling GR on/off and trimming RV1 and RV8 accordingly, the measurements gets more and more off. Anything obvious comes to mind?
This part of the build is a little odd and hard to describe. RV8 does not work backwards but the entire procedure is conceptually "backwards". If you are getting farther away, then turn RB8 in the opposite direction.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on July 08, 2015, 05:07:56 PM
when toggling GR on/off and trimming RV1 and RV8 accordingly, the measurements gets more and more off.

I have not been able to return to mine, but this part seems to match my last attempt.  Regardless of rotational direction, the instructions specify an order in which you set each voltage, and doing exactly that, one after another, made the opposite measurement get further away when returned to, until the trimmers maxed out.   Maybe the directions need a rewrite.  I'll be re-trimming to the mid points and trying again whenever I can get to it. 
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 08, 2015, 05:37:10 PM
I noticed that the action of RV8 isn't 'backwards' as described, resulting in (I believe) that when toggling GR on/off and trimming RV1 and RV8 accordingly, the measurements gets more and more off. Anything obvious comes to mind?
This part of the build is a little odd and hard to describe. RV8 does not work backwards but the entire procedure is conceptually "backwards". If you are getting farther away, then turn RB8 in the opposite direction.

Ahh I get it! The manual says:
"This can be a little tricky since it works opposite of how you might think", which I thought referred to how the RV8 trimmer behaves, because that trimmer is mentioned in the previous sentence. But it's just a description of a little backwards procedure overall.

So Doug, if you read it the same way I did: If (when) you get an off value with GR on, just blindly turn the RV8 a couple of turns in the 'wrong' direction, making the measurement even further away from the target 2.245V. Then switch GR off and adjust RV1 to 2.487V. Keep doing that and you'll get closer and closer.

I did that and was able to get one unit perfect and the other almost, because the RV8 hit the bottom and I settled for 2.489V with GR off and 2.235V with GR on. The meter behaves, but Jeff would you say that is close enough, or is there something funky about the RV8 hitting the bottom?

Going to play with these now!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 08, 2015, 06:05:02 PM
the turning was specific to the correct direction to hit the voltage listed for the step at hand.
Exactly what I did at first. But you shall not aim for the listed voltage when trimming the RV8 (GR on), instead trim further away. Then, because of the interaction trimming the RV1, with every step you'll get closer instead of the opposite.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 08, 2015, 06:06:58 PM
I did that and was able to get one unit perfect and the other almost, because the RV8 hit the bottom and I settled for 2.489V with GR off and 2.235V with GR on. The meter behaves, but Jeff would you say that is close enough, or is there something funky about the RV8 hitting the bottom?
I think that is a little funky. There should be plenty of room on both trimmers to cal the meter in perfectly.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 08, 2015, 06:30:52 PM
I did that and was able to get one unit perfect and the other almost, because the RV8 hit the bottom and I settled for 2.489V with GR off and 2.235V with GR on. The meter behaves, but Jeff would you say that is close enough, or is there something funky about the RV8 hitting the bottom?
I think that is a little funky. There should be plenty of room on both trimmers to cal the meter in perfectly.
Thanks Jeff! Played with them for a while (GOOD SH*T MAN!!!) and they seem to sound/behave very similarly, so I'll probably have to get back to this more later. But now, while at it, any suggestion on where to start looking except go over all solder points?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 08, 2015, 06:47:48 PM
Yes that and R's behind the Grayhill switch and around the IC opamps.
Title: SORTING SHEETS
Post by: Unit7 on July 08, 2015, 07:14:18 PM
Unlike Tony I feel lost without sorting sheets  :)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on July 13, 2015, 08:33:06 PM
I did that and was able to get one unit perfect and the other almost, because the RV8 hit the bottom and I settled for 2.489V with GR off and 2.235V with GR on. The meter behaves, but Jeff would you say that is close enough, or is there something funky about the RV8 hitting the bottom?
I think that is a little funky. There should be plenty of room on both trimmers to cal the meter in perfectly.
The issue with one of my units was probably because my old solder station was ready for retirement. Got a new really nice Weller today and reflowed most of the joints on the main board and both units are now operational! Thanks Jeff!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 13, 2015, 08:40:20 PM
I did that and was able to get one unit perfect and the other almost, because the RV8 hit the bottom and I settled for 2.489V with GR off and 2.235V with GR on. The meter behaves, but Jeff would you say that is close enough, or is there something funky about the RV8 hitting the bottom?
I think that is a little funky. There should be plenty of room on both trimmers to cal the meter in perfectly.
The issue with one of my units was probably because my old solder station was ready for retirement. Got a new really nice Weller today and reflowed most of the joints on the main board and both units are now operational! Thanks Jeff!
Great news Paul! Thanks for the update  ;)
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Kevinkmny on July 15, 2015, 01:42:58 PM
Hi guys....

I was doing so great...made it all the way thru the build until the LEDs...

Soldered one side then removed the meter pcb to solder the other side...now I can't get the face plate back on to the front with the LEDs aligned properly and have snapped one of the LEDs in the process...

Any helpful tips?

Thanks in advance!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 15, 2015, 02:01:59 PM
Hi guys....

I was doing so great...made it all the way thru the build until the LEDs...

Soldered one side then removed the meter pcb to solder the other side...now I can't get the face plate back on to the front with the LEDs aligned properly and have snapped one of the LEDs in the process...

Any helpful tips?

Thanks in advance!
The faceplate should be in place before inserting the meter PCB.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Kevinkmny on July 15, 2015, 05:15:48 PM
Seems so obvious now that you mention it :)

Thanks Jeff!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 15, 2015, 05:30:09 PM
What LED's do you need to replace? Send me an email and I'll hook you up jsteiger1965 at yahoo
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Kevinkmny on July 15, 2015, 07:35:54 PM
Thanks Jeff, I'll e-mail you...

I may have met my match with this meter pcb...I just can't get it seated..

I wonder if the best solution isn't to remove the existing LEDs and try again...

Not sure how to prevent the certain movement of the LEDs when you remove the PCM to solder the other side....
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 15, 2015, 08:02:17 PM
I wonder if the best solution isn't to remove the existing LEDs and try again...
Yes either that or look for the one or two that are holding things up and straighten them.

Quote
Not sure how to prevent the certain movement of the LEDs when you remove the PCM to solder the other side....
I have never had trouble with this. The LED leads are very stiff so I have never had them move. I am always pretty careful with them too.
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Kevinkmny on July 15, 2015, 08:05:06 PM
Success! Now to move on to calibration and testing!
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Kevinkmny on July 15, 2015, 09:14:42 PM
Well this isn't starting off well...

257 ohms at all 3 op amp V+
179 ohms at all 3 op amp V-

Any ideas?
Title: Re: [BUILD] FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 15, 2015, 09:38:37 PM
What are the other opamp V DCR measurements? Basically we are looking for a direct short. I have never had one this low myself but it could be possible. I would try and make sure none of the 33µF caps have their pads shorted. If this all looks clear, I would power it up with no DOA's installed and make sure the PSU is stable and that you have expected +/- voltages at all of the opamp sockets.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: furn1979 on October 14, 2015, 10:03:09 PM
Hi Jeff...

Just finishing my first of two 526's. Things went pretty smooth!

I believe 4 x 22p capacitors are missing from the 4 Opamp Adapter Kits. Can I swap them with caps of other value?

Thanks!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 14, 2015, 10:15:25 PM
I believe 4 x 22p capacitors are missing from the 4 Opamp Adapter Kits. Can I swap them with caps of other value?
No they are not required for the LME49710's. I only added the spot on the PCB in case someone uses a 5534.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 16, 2015, 09:07:39 AM
Hi everybody,

I build to kit of FC526, one is ok, and calibrate; and the other has a problem.

my problem :

for TP1 I find 0.02volts with the Bypass toggle up to BYP and 0.002volts with the Bypass toggle down to ACT ....  :'(

I change the opamp and retake some solder between the receiver and the output transfo...

I need some help!!!
thanks for yours!!!

Jérôme

(http://)

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 16, 2015, 09:27:43 AM
(http://)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 16, 2015, 09:28:55 AM
(http://)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 16, 2015, 09:29:46 AM
(http://)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 16, 2015, 09:30:06 AM
Sounds to me like the relays are not activating. Check the components around them especially the location of the zener diodes as well as the 3904 transistor.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 16, 2015, 09:33:25 AM
I also see many questionable looking solder joints. It could be one or more colder solder joints. What temp is your iron set at? I run just below 800˚F. Maybe a good cleanup and reflow would help.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 18, 2015, 09:50:53 AM
Hi jeff,

My iron is set at 752°F (400°C), I put it at 800°F(426°C) and reflow all the solder joints; no changes come...

I look at the zener diodes and the 3904 transistor, they are in place and the soldiers arround the corner are clean for me.... can I tchek or do something else?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 18, 2015, 10:24:58 AM
Check these points for ACV with the unit in ACTive mode and some signal applied to the input. This is essentially immediately after the input relay.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 18, 2015, 11:34:04 AM
I find 0.042V

(thanks for not let me alone :-) )
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 18, 2015, 11:47:23 AM
You should have the same AC voltage when measuring between those 2 points as you do measuring the source signal you are injecting into the card.

Are your opamps fully seated? http://capi-gear.com/catalog/DOA_Install.php
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 18, 2015, 01:46:21 PM
???

I inject 1kHz sine wave at -30dbU, about 0.02Volts

so I must find between the 2 points you show me the same voltage, 0.02Volts, but I was founding 0.042, and now that I have done again this 2 solders you show me, I find 0.003Volts or 0.004????

Yes my opamps are fully seated!

but what's happening? I'm a litle lost....

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 18, 2015, 01:48:15 PM
It sounds to me like the relays are not working. Can you hear them "click" when you flip the bypass/active switch back and forth?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 18, 2015, 02:06:22 PM
yes I can hear them, back and forth
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 18, 2015, 02:15:45 PM
OK well its hard to tell if both are flipping or not. At least you know something is happening. You will have to check the relay pins for continuity.

The pic attached shows what should have continuity in ACT mode. It will be the other contacts when in BYP. Make sure both poles of the relay are functioning correctly. K1 is the input relay and K2 is for the output.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 19, 2015, 12:59:00 PM
Hi again :-)

I make the continuity check between all the poles you show me and the continuity between them are fine in the  picture attached it mean's there is a continuity between B and C ; and between B' and C' in "BYP" mode ; and there is continuity between C and D ; and between C' and D' in "ACT" mode
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 19, 2015, 01:01:34 PM
I make the test continuity on K2 to, and it's ok on K2 to...
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 19, 2015, 01:16:49 PM
Hi again :-)

I make the continuity check between all the poles you show me and the continuity between them are fine in the  picture attached it mean's there is a continuity between B and C ; and between B' and C' in "BYP" mode ; and there is continuity between C and D ; and between C' and D' in "ACT" mode
OK good. Well, there is nothing between the ends of R78 & R82 but PCB traces and C36 & C38. Maybe the solder job on those caps is the problem?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 19, 2015, 02:13:04 PM
I just clean the solders of C36&38, and do them again, and redo the mesure..... they aren't stable... when I touch C36&38 I can ear some "mouse scream" like a charge and discharge of condensator....
I have a second pair of FC526 not build yet, so I think I can change C36&38 are you agree?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 19, 2015, 02:21:51 PM
I just clean the solders of C36&38, and do them again, and redo the mesure..... they aren't stable... when I touch C36&38 I can ear some "mouse scream" like a charge and discharge of condensator....
I have a second pair of FC526 not build yet, so I think I can change C36&38 are you agree?
The chance of both of those caps being bad would be incredibly high. If they are making noise when touching them, its solder joints somewhere.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 19, 2015, 02:29:43 PM
You mean solders only before this caps, or every where?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 19, 2015, 03:14:15 PM
You mean solders only before this caps, or every where?
Its hard to say. I would start with the caps. I run my iron just under 800˚F.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 27, 2015, 12:22:55 PM
Ok Jeff!

Sorry for not answering you before! But you are the Boss!!!! for sure!!!!

I decide to reflow some solders which could look better and now I have the good value everywhere :-)

But I want to calibrate RV7 and doesn't understand which punkt I must put my oscilloscope?

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 27, 2015, 12:53:35 PM
You can monitor the final output or TP3 for the RV7 THD trimmer.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 27, 2015, 02:20:20 PM
Yes Ok Jeff!
but now I see any changes in the monitor, and doesn't understand why...  :'(
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 27, 2015, 02:37:46 PM
Yes Ok Jeff!
but now I see any changes in the monitor, and doesn't understand why...  :'(
Maybe you are not zoomed in enough with your scope? The trimmer will go from about 1% down to around 0.3 something % back up to 1%. You should see it if you zoom into the top of your waveform close enough.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on October 27, 2015, 07:37:36 PM
First sorry for my english  ...

but if I understand, the "movement" of the sinusoid is very very little?

my scope is tektronix 2465, an old one.... can I see that little movement with it?

because I zoom a lot, almost the max I can.... and I just see a sort of vibration but is it what I must observe? 
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 27, 2015, 07:55:41 PM
Yes. Sorry but I cheat and use an Audio Precision so its easy for me.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: the new frenchy on November 04, 2015, 06:15:02 AM
yes I understand... no pb... I try to find this kind of oscillo!

But for now, I test the FC526, Great great great!!!!! about the sound! I like a lot, for sure!!!

But another question:

I have build 2 compressor, The LED Gain Reduction Meter doesn't react exactly the same, on the same sound... What can I have done wrong? because I would like to use this 2 compressor on a stereo signal?

is it possible, a sort of link?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on November 06, 2015, 11:03:28 AM
There is no link function. Dual mono is the only solution.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: furn1979 on November 09, 2015, 03:03:00 PM
Hi guys!

Finished my first of two builds.

Having some calibration issues. Pre calibration and Bypass signals are normal.

When circuit is activated:

TP 1-2-3 are fine but I can't get past 11dBu at the output (should be around +14).

Where should I look?

TP9 is -9.98 VDC. That cool?

Thanks!


Nevermind! Had metering issues... ALL (BUTTONS IN) IS GOOD!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Lud on November 18, 2015, 06:19:40 AM
Hi Jeff, i'm on the end with the making and my transfo has no blue green and brown wires. Instead it has a grey a pink and a purple. Could you enlighten me?
Cheers.
Lud.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Unit7 on November 18, 2015, 06:47:53 AM
Hi Jeff, i'm on the end with the making and my transfo has no blue green and brown wires. Instead it has a grey a pink and a purple. Could you enlighten me?
Cheers.
Lud.
I'm not Jeff, but it seems you've ordered the kit with the Litz wire transformer (instead of the standard EA2623). Check your order to confirm, then follow the table on the datasheet found via a link on the product page for, or here: http://www.capi-gear.com/catalog/images/gallery/2623/2623-1-L-specs.pdf
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Lud on November 18, 2015, 07:19:44 AM

I'm not Jeff, but it seems you've ordered the kit with the Litz wire transformer (instead of the standard EA2623). Check your order to confirm, then follow the table on the datasheet found via a link on the product page for, or here: http://www.capi-gear.com/catalog/images/gallery/2623/2623-1-L-specs.pdf
[/quote]

Thanks for your help!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Lud on November 18, 2015, 10:21:22 AM
 I've tested the opamps, one does not work, one woks but makes lots of noises/cracks  and one works.

I' tested the 526 with the 2520 in receiver and my two red dot as preamp and output.
when the Lb is switch on all lights are illuminated exept the red and the 20orange. The 20orange, when once i pushed a little bit the modul in its fram, get iluminated for a second.
Nothing works exepted when i turn the ratio (which is really really hard to turn) on ABI and everythink turns off. When i turn again the ration on what seems to be 20 the leds turn on from the green to the 10orange and stay iluminated what ever i do.

Any help and suggestions will be awesome.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on November 18, 2015, 10:34:24 AM
Have you tested the audio path and other test points per the docs? I would not worry about trying it with a bad opamp installed.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Lud on November 18, 2015, 12:30:29 PM
Have you tested the audio path and other test points per the docs? I would not worry about trying it with a bad opamp installed.

No i did not... Sorry for that.

The 2520 kit that seems to work well when tried in a vp25 placed at the output gives me around 3mv when the reddot gives me around 1.7/1.8mv.
tp1 and tp3 give me nothing.
On my sound analyser the input & output knobs react well as the BYP switch.
Actually only the tp3 gives a value.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on November 18, 2015, 01:02:10 PM
TP1 is right after the receiver stage. The rest of the audio path does not matter if signal is not getting past the receiver amp. The most likely cause will be the receiver opamp or something wrong with the relay circuit and signal is not even coming into the receiver opamp.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Lud on November 18, 2015, 03:56:14 PM
Ok, so i've made other tests and here is what i have noticed :

tp1 : is still at zero.
tp2 : still at zero
tp3 : 2.3mV DC
tp4 : 0.012V AC
tp5 : 2.08V DC
tp6 : 2.08V DC
tp7 : ?
tp8 : 1.84V DC
tp9 : 10.01V DC
tp10 : ?
tp11 : ?
All the points on the meter board are right.

I run some OH in it and things seemed right exept for the ratio that i don't noticed the changes and so the HPF switch.
The differents attack times seem pretty discreet while the release time is obvious.

Have you got ideas of what to check?

Thanks
Lud.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on November 18, 2015, 05:32:38 PM
Lud, maybe you are misunderstanding the tests. TP1 is just after the balanced receiver stage. If you have signal applied to the input and this TP has no reading, the input stage is not passing audio. If the input stage is not passing audio, there will not be any audio getting to the rest of the circuit. Maybe you are measuring here for DC? If you are using a DMM, you can only measure audio in ACV mode.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Lud on November 20, 2015, 11:01:17 AM
Lud, maybe you are misunderstanding the tests. TP1 is just after the balanced receiver stage. If you have signal applied to the input and this TP has no reading, the input stage is not passing audio. If the input stage is not passing audio, there will not be any audio getting to the rest of the circuit. Maybe you are measuring here for DC? If you are using a DMM, you can only measure audio in ACV mode.

Hi Jeff, yes i do understand.
Just to be clear about the opamps : I have bought three gar2520 kits and i already had 2 red dot perfectly working in my couple of VP25. One kit is working, one makes noises, and one is not working. I have tested the 526 with the opamps working.
Today i've mixed some drums like i would do with any of my comps and everything was working (i did not noticed yet the impact of the HPF though). I'm not used with the input/threshold pot but i'm pretty pleased with the results so far! Thats my first FET gear.
So obviously i should have something at TP1. I must do something wrong. I do the measures with my poor DMM so that could be the issue. I'll ask some help with people who knows about electronics and who could give me access to an oscilloscope and could help me for all the tests and calibration. Those guys could also help me with fixing the opamps.

I'll keep you informed.
Cheers.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Golgoth on January 05, 2016, 04:18:44 AM
I am about to order a LC53A and a FC526 to complete an amazing channel strip along my VP28 in a custom enclosure. What is the difference between All Discrete, +1 and +2 for the FC526?

Thanks,
G
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on January 05, 2016, 08:43:34 PM
What is the difference between All Discrete, +1 and +2 for the FC526?
The all discrete will need 3 discrete opamp kits with it.

The "+1" comes with one IC adapter opamp kit so two discrete amps will be needed.

The "+2" comes with two IC opamp kits so only one discrete amp is needed.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Golgoth on January 06, 2016, 04:00:23 AM
Oh okay! Tough choice...
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on February 27, 2016, 10:20:40 AM
I thought I would share some info I recently discovered. It relates to folks having calibration trouble and the symptom of "running out of room on the RV8 trimmer" when trying to calibrate the meter.

I shipped a pair of kits to a TapeOp magazine reviewer. He said one kit cal'ed up just fine but was having trouble with the other. He described the above symptom and that the RV8 trimmer would "bottom out" before he could achieve the proper meter voltage at TP10. I would normally not do this but under the circumstance (magazine review) I thought it would be a good chance to see what the deal was since a handful of people have experienced a similar phenomenon so I asked him to ship it to me.

I wanted to start at the beginning so when I got the unit in, the first thing I did was bottom out both RV1 and RV8. I did this by turning in one direction unit I could hear them acoustically "click". I then count 12 turns back in the opposite direction. Since they are 25 turn trimmers, this puts them very near their factory set mid position.

Next I wanted to adjust the VVR FET safely out of conductive range so I could dbl check the audio path. I set the unit the 20:1 and followed the steps in the guide. That is when I discovered that the VVR FET was NOT set properly and actually not conducting at all.

The audio path was perfectly fine so I adjusted the VVR FET for the stated 0.5dB of loss.

It took me 3-4 turns of the RV1 and RV8 trimmers to get the meter voltage set just right. Absolutely no trouble at all.

In conclusion, if you are having trouble cal'ing the meter, make sure the VVR FET is properly biased. If not, you will never get the meter set right. Also you must be set to 20:1 (not ABI). You should also check the bias voltage of the FET at TP7. If this reading matches what was marked on the pink FET baggie, (and there are no build blunders), you should be able to cal in the meter spot on with no trouble.

Hope this helps!
Best, Jeff
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: New Soul Rebel on February 28, 2016, 11:51:40 AM
 :(

i am trying to calibrate my FC526. Made a bit of mistake. I somehow 'touched' something on the meter PCB. I smelled a little bit of a burning but it was like, really temporary. And the unit still seemed to be working. Anyway, went ahead with testing/calibration.

Three known good opamps on board
When I try and calibrate, my meter JUMPS from 2.24v straight up to 2.5v (not able to 'tune' the voltage to 2.487 on the front panel RV1 without it shooting straight up).

When I try and use the compressor, it compresses but I can't really tell if the attack/release are working correctly because the Led literally 'switches on' (up to 7) and off. In fact it seems like the compressor is only working in an On/Off fashion, if I increase the input level up to a certain level. Its like the compressor 'kicks in' rather than smoothly comes in

I've calibrated one FC526 successfully already. Anyone got any ideas what might have got f**ked during this final stage, that might be causing this?

Matt

Jeff, can you advise if there are any voltages I should be reading to tell me where the problem may lie?

Matt
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on February 28, 2016, 02:28:45 PM
Matt

I would check all of the TP voltages in the doc's as well as the meter PCB voltages that are published. There are many. You can also verify how much compression you are getting by noting the level with and without the GR switch engaged. It should be easy to verify smaller amounts.

You can also pull the meter PCB from your good working unit and try it on the unit in question. That may tell you if the issue in fact resides on the meter PCB. There will be no adjustments needed to swap the boards. Do not change anything except  unplug one meter PCB and plug in the other.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mr. Steve on February 29, 2016, 09:02:41 AM
hey guys,

this thread also needs a picture of the new design! ;)

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 30, 2016, 06:54:18 PM
'Chung has recently posted the last of the build pics. They can be found on the first page of this thread. He goes thru everything including initial startup tests.....but no calibration as of yet. Thanks 'Chung!!  ;)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: NinjaFighter on May 01, 2016, 05:18:21 PM
hey jeff,

I seem to have a short somewhere in the meter pcb, I'm getting about 2.5 k on the +V and only 42 ohms on the -V. When i disconnected the meter ribbon cable from the main pcb i get around 2.5 k on the -V but the n the +V fluctuates like crazy from 100k and up.

Here are the pictures of the meter pcb. I've never put up pictures before so i hope they show up.
(https://farm2.staticflickr.com/1470/26733154906_b05bb93397_k.jpg) (https://flic.kr/p/GJjpzU)DSC06293 (https://flic.kr/p/GJjpzU) by Jose Jimenez (https://www.flickr.com/photos/[email protected]/), on Flickr

(https://farm2.staticflickr.com/1655/26664958002_13050dcd39_k.jpg) (https://flic.kr/p/GChT2d)DSC06290 (https://flic.kr/p/GChT2d) by Jose Jimenez (https://www.flickr.com/photos/[email protected]/), on Flickr
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 04, 2016, 10:59:44 PM
Jose, I am not really seeing anything jumping out at me.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 777artin on June 02, 2016, 03:43:08 PM
Hello,

i just built my first FC526. I already built 2x VP312 et 2x VP28 (including both DOAs in each) and did not get too much in trouble.

Now testing my FC526 i'm getting 14.24V at TP10 so 14.24V goes up to the MTR's ICs.

- Why is this happening?
- Have i burnt the LEDs?

I'm getting -10.02 at TP9 and +16.35 / -16.17 at the edge connector.

Thanks for your help.

Martin
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on June 02, 2016, 08:28:09 PM
I fixed a friend's build(s) here in town a few weeks ago. His main problem was that he intermixed 470R, 4k7, 47k and the 470k R's. They were randomly swapped around and it caused many different issues. I would recommend checking all of these as well as the other like R's. They will have to be verified with the color codes at this point since you can't accurately measure a resistor unless you desolder one lead.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 777artin on June 02, 2016, 08:46:02 PM
Well you are right.  Yellow / purple / black / Red  or Yellow / purple / black / orange.

I'll correct and test it tomorrow.

Thanks man.



Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: drummingninja on June 06, 2016, 10:09:47 PM
Hey there, on mtr point 11 I'm getting 2.505v and 2.509v on two different builds. I see this is outside of the 2.498-2.502 range specified, is this problematic?

Also one of the two I'm building gives a fairly large volume boost on switching to ABI, but the other does not. Which is the normal behavior? Do you have any suggestions for what this may be?

Thanks so much for your time
 
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: drummingninja on June 10, 2016, 10:28:49 PM
Dove deeper, got measurements from the audio path test that definitely deviate from numbers given:

with -30dbu (.024v) 1k test tone and fully CW RV2:

TP1 .012v
TP2 .212v
TP3 1.694v
Output 3.38v

Second unit has very similar readings. Litz transformer on these builds.   One is 1731s, another is 2520s that are confirmed to work from a pair of LC53s. I do have -10v at TP9. The unit passes audio, sounds awesome and is functional other than issues with calibration.  Using a true RMS meter. Thanks for the help
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: drummingninja on June 14, 2016, 06:35:01 AM
Just wrapped up two VP28s that turned out great! Still not sure what to do with the FC526, thanks to anyone with some insight.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 777artin on June 27, 2016, 09:00:15 AM
Hello there,

I'm also having a different voltage at mtr point 11. I'm getting 2.506v.

What could cause this to happen?

I'm testing my FC526 from my 6 spaces API lunchbox.

Thanks.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: noneother on July 20, 2016, 12:31:33 PM
Hey Jeff, I've recently completed my build of this compressor and had a few questions.  I was getting voltages that were just barely out of the acceptable levels, so I bought a good quality multi meter (Fluke 87V) to replace the cheaper one I was using and got better/closer results, but I just wanted to run them past you to make sure everything is ok.  I'm attaching your directions along with my actions/measurements for continuity.

**Pre-Flight Measurements**
1. With your DMM set to read resistance, clip your black probe to the GND lug. Now touch your red
probe to the “+V” DOA socket for each of the three discrete opamps. The resistance should be not
less than 500 Ω. Repeat for the “-V” sockets. Again, the resistance should be not less than 500 Ω.
Basically we are looking for direct shorts. Those are no good.

V+ at all three sockets were 2.592 K Ohms
V- at all three sockets were 641.8 R Ohms
Is it ok that the V- is that much lower than the V+


**Initial Power Up**
1. 1. The module needs to be flat in front of you on a bench or table and under power. A 500/51x
Extension Jig will be the easiest solution.
If you don’t have an Extension Jig already, here is a link to the subcategory at the store.
http://capi-gear.com/catalog/index.php?cPath=22_117_185

I'm using the Sound Skulptor Extension Jig for my tests.  Verified to work correctly.

2. Apply power to the FC526 module. No opamps should be installed at this time.

Check

3. Set your DMM to DCV, clip your black probe to the GND lug. For each of the three discrete
opamps, check both the “+V” and “–V” socket with your red probe to verify approximately 16
volts.

V+ for all sockets was 15.33 V
V- for all sockets was -15.21 V


Is this too low?  The rack I'm using is a fairly new Heritage Audio OST-4.  On a previous build (Sound Skulptor Compressor) using the same rack in the same slot, I've seen V+ voltages be at 16.06 and V- voltages be at -15.96 so I'm fairly certain its not the power supply.

4. Measure DCV at TP9 to confirm between -9.98V and -10.02V. This is a critical measurement!

I get -10.02 but it will quickly jump back and forth to -10.03.  Is this enough to throw everything off?   I'm still new enough to DIY kits that I'm not sure.

5. Disconnect the module from the Extension Jig.

**Pre Calibration Information**
1. Before proceeding forward with any of the calibration steps below, make sure you have
between -9.98V DC and -10.02V DC at TP9. See the Test Points Guide for more info.

Done.

2. Before proceeding forward with the meter calibration steps below, make sure you have
between +2.498V DC and +2.502V DC at the “top” of the the meter resistor string for the
LM339 comparators, which is MTR point #11 in the pic. See the Test Points Guide for
more info.

Here I get 2.502 V, right at the edge of the tolerances.

My question is am I good to proceed with the calibration or is this indicative of a possible problem with the assembly?

Thank you!

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: drummingninja on September 03, 2016, 02:10:27 AM
Still haven't cracked the issues I was having above if anyone has any insight. Thanks!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: IndietownRecording on October 20, 2016, 09:49:19 AM
Has anyone calibrated these with their DAW? (PT11, Mac OSX) Or do I have to go buy a scope? Can someone recommend a plug to monitor the THD component of the output (Mac OSX)?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Blackdawg on December 09, 2016, 03:18:07 AM
Hey Jeff!

I am eyeing your 526 compressor kit.

Im curious about the Opamps. I definitely am going all discrete but am curious if mix and matching is recommended? Do certain ones sound better on the input vs the gain reduction stage and output? Or is it better to match all three?

I have heard the SLReddots and the gar2520s. To me the Gars are smoother and SLs are punchier. Haven't experienced the 1731s but have read they are more Neve sounding? How about the VF600s or 918s?

Any advice?

Thanks for all the work you do! Love your kits.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on December 21, 2016, 11:58:52 PM
Was measuring some other stuff and realized I never measured these.  I find the pair I have are fairly tightly matched for response, and unlike many comps, there are no response changes for any GR setting or SC filter setting, only level reduction measured.  Those measurements were made with unity gain throughput knob positions close to the meter alignment setting positions, GR off, then checked with GR on. 

bandwidth:
-0.5dB average of the two is 9Hz and 22kHz
-1dB average of the two is 6Hz and 32kHz
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: orenradio on February 22, 2017, 10:58:49 PM
anyone use the JE990 opamp in these comps?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: New Soul Rebel on June 22, 2017, 12:38:30 PM
Guys

Does anyone here have any experience calibrating an FC526 using a standard digital multimeter and Logic X ?

Its a pain in the ass trying to calibrate - logic meters are dBFS not dBU.

I know its possible as i've watched Hairball's vid. So looking to hear from anyone who has calibrated theirs this way.

Cheers Matt
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: New Soul Rebel on June 22, 2017, 01:11:41 PM
Also - is it absolutely necessary to have a multimeter that measures AC at 1 khz.

It seems to me that a normal one is not accurate enough.

What's the best gear to do this job. Can you guys give me the lowdown. Cheers

Matt

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: New Soul Rebel on June 22, 2017, 01:45:12 PM
Do I need a true RMS multimeter?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 02, 2017, 12:38:42 PM
BUMP :o :o :o :o

Lot's of folks here trying to find a way to calibrate ITB, myself included! Want to order the new version as there's no THD calibration, but I don't want to bite off more than I can chew. Having watched the hairball compressor calibration video's and understanding the the basic principles behind analog  dbu &  digital dbfs and it's relativity to you're interface/AD daw  etc... it's all a bit much. Care to chime in DIY Gods?
Its just some simple math and depends on your DAW reference level. For example, if your system is -18dBFS = 0dB, then just offset my -30dBu numbers by -18 so you would use -48dBFS. For the +7dBu level you would use -11dBFS and of course for 0dBu it would be...you guessed it -18dBFS.  ;)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 14, 2017, 03:48:19 PM
EDIT I SWITCHED UP the 470 RESISTORS: PROBLEM SOLVED!

Thanks Jeff, got all the numbers sorted out and written down now thanks! Just built a pair and testing with Rogue 5 op amps and I'm getting the same results on both.... Preflight I get -9.96v DC at TP9 & +2.49DC @ MTR point 11 so looking good there.

 
however upon  flipping to active after turning all the knobs to their respective positions I noticed no led's light up, and  I get a signal drop not an increase to +7.75

STEPS

So is it possible I've flubbed both builds audio path, and need to go on to the testing points now?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 14, 2017, 06:22:11 PM
You will have to use the test points guide and trace thru the audio path. Maybe something went sideways on the DTO5 amps...
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 19, 2017, 04:23:30 PM
Please post a pic of the top of the PCB for one of these.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 19, 2017, 04:49:25 PM
Please post a pic of the top of the PCB for one of these.

Sure thing here's a link including Test Tone settings + Dt05
https://www.dropbox.com/sh/kdhtmnl9ekghx9t/AADTpgihw2YvpSdha_xjQlSZa?dl=0
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 19, 2017, 09:23:27 PM
You can (and should) confirm that what you think is 0dBu from your signal generator actually measures 0.775mV AC with probes between XLR pins 2 and 3 of the output of your convertors or what you are using for a signal generator.

Your TP1 results look close but things go south at TP2. That tells me its something with the DTO5 or surrounding circuity.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 19, 2017, 09:24:21 PM
Are you 100% sure the FET is not conducting?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 19, 2017, 10:10:31 PM
Are you 100% sure the FET is not conducting?

I believe so turned rv2 fully CW till it clicks. I'll confirm the output with the Dmm here shortly.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2017, 12:21:09 PM
Is your DMM set to AC volts?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2017, 12:46:37 PM
I believe so, In auto range mode and switching to manual for me I'm getting the same readings
Attach a pic of the DMM as you are using it.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 20, 2017, 01:51:07 PM
Ok so after much finagling and clearing everything in totalmix fx( a nightmare btw) I'm finally getting the proper signals out of both generators.

Changed cubase signal settings to -9 as that's my +4dbu


Attached pics with settings. Going to go ahead and continue with trace point measurements. More posts to follow
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 20, 2017, 04:23:08 PM
Alright so finally working out all the kinks at confirming that I'm getting 1.219v whilst sending a 0db signal out at -9dbfs. not .775mv


Sending the 1kz out at -39dbfs and flipping to active:

TP 1: 9.5mv
Tp 2: 1mv
Tp 3: 6.9mv
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2017, 04:30:05 PM
Alright so finally working out all the kinks at confirming that I'm getting 1.219v whilst sending a 0db signal out at -9dbfs. not .775mv


Sending the 1kz out at -39dbfs and flipping to active:

TP 1: 9.5mv
Tp 2: 1mv
Tp 3: 6.9mv
OK so change your output lower by 4dB so you get 0.775mV. That would be -13dBfs. Your offset will be 13dB below my specific -30dBu.

For this test, do you have a known good 2520 amp installed and is the module under power? Connected to a rack or extension jig?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 20, 2017, 04:36:16 PM
Alright will do thanks jeff! And yes with a rogue 5 I have other known working gars around too. And yes under power through the extension jig
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 20, 2017, 04:47:03 PM
Ok at -34

Tp1   6 mV
Tp2  .7mV
Tp3  4.2mV

Are all signs pointing to the dto5? I can also try another op amp though brad's rogue 5 is brand new.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2017, 06:38:53 PM
Ok at -34

Tp1   6 mV
Tp2  .7mV
Tp3  4.2mV

Are all signs pointing to the dto5? I can also try another op amp though brad's rogue 5 is brand new.
Yes its the DTO5 area.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2017, 06:42:31 PM
Ok at -34

Tp1   6 mV
Tp2  .7mV
Tp3  4.2mV

Are all signs pointing to the dto5? I can also try another op amp though brad's rogue 5 is brand new.
I just zoomed in on your pics and I can see that you have mixed up some R's. Not sure of the extent but I for sure see that R28 should be a 470k and you have a 470R in that position.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 20, 2017, 06:52:04 PM
Oh wow well that's what I get for using my old dmm- was going to go over all the resistors here after dinner! Nice catch!!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2017, 07:21:33 PM
Oh wow well that's what I get for using my old dmm- was going to go over all the resistors here after dinner! Nice catch!!
There are also 47k's on the build so you gotta be careful.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 21, 2017, 12:58:10 PM
So as previously mentioned,  I flubbed  and swapped those on BOTH modules...having accidentally switched 470R and 470K resistors.  Double checked the other close looking resistors (47k & 470R) to confirm they are correct as well.  Firing them up and now I'm finally getting proper readings at the trace points.

They are as follows

Tp1:    6 mV AC
Tp2:    119mV AC
Tp3     958mV AC

Alright so looks like I'm good to go ahead with calibration!

Thanks Jeff, when I'm in nashville a Beer is on me!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 26, 2017, 02:55:47 PM
.....Sending out a 0db signal with 0db=-13dbfs gives me the .775 reading, that's what I want right? So I want -30dbu below that being -43dbfs correct? I can do the rest of the math myself just wanted to make sure thats good!
Yes this sounds correct.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 28, 2017, 03:05:00 PM
Just checking in, little confused and wanna get these babies all ready for a session tomorrow 8)
I am swamped packing orders today.

I read your post twice and I'm not sure I follow what you are saying. You need to have 7dB of gain reduction and if you are not close with the pot settings I have specified...then something else is messed up. I just use "+7dBu to 0dBu" because its easy. Make sure you have the FET biased properly for the 1dB of loss.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 28, 2017, 07:26:13 PM
Sorry jeff, pack away get to me when you can no problem I completely understand you're one busy man!

I guess I'm just confused as to what is 7db of gain reduction for step 9 of the Meter calibration:

With the input at 10ish and output at 1ish I get  the signal to exactly  +7dbu  but  when I flip the GR toggle in step 6 of the gain reduction meter calibration , I get no difference of output level. Is this correct or should there be a difference?
You've gotten dyslexic with the controls. If you look again at step #4 and then #11 under the **Gain Reduction Meter Calibration** section, you'll see that the input should be around 1:00 and the output around 10:00. If you are at these positions and truly have a +7dBu signal at the input and don't have close to 7dB of gain reduction, then something else on your build is jacked up.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on August 29, 2017, 02:28:42 PM
You've gotten dyslexic with the controls. If you look again at step #4 and then #11 under the **Gain Reduction Meter Calibration** section, you'll see that the input should be around 1:00 and the output around 10:00. If you are at these positions and truly have a +7dBu signal at the input and don't have close to 7dB of gain reduction, then something else on your build is jacked up.

Jeff,what a wizard you are! I did switch that input output...ugh this is what happens when I'm walking the plank with math and reread everything a million times  ;D ;D :)...GOT THAT DIALED in and the rest of the calibration was a breeze. THANKS for popping my calibration cherry and helping me out. TREMENDOUS!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 29, 2017, 02:44:20 PM
Jeff,what a wizard you are! I did switch that input output...ugh this is what happens when I'm walking the plank with math and reread everything a million times  ;D ;D :)...GOT THAT DIALED in and the rest of the calibration was a breeze. THANKS for popping my calibration cherry and helping me out. TREMENDOUS!
Yeah glad you got there. It is really super easy but folks hear the word "calibration" and get all freaked out!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on September 06, 2017, 02:47:15 PM
After building nearly a dozen CAPI kits for myself and others, I find my self stumped for the first time.    My FC 526 build looks good to me.  Clean.  No solder bridges.   It passes audio just fine in bypass mode, but when I engage the compressor, everything sounds like its passing through a high pass filter.  The bottom end just drops out, and the overall level drops, regardless of whether GR is on or off.   The sound is not distorted, just lacking in bottom end and gain.  I've gone over the PC board very methodically with the BOM and check all the resistors.  They appear to be in all the right places.   All the diodes are correctly oriented.  It's not the opamp, as the same thing happens with my pre-built Red Dots (I'm using the gar 2520s that I built from a kit.)   Jeff suggested that I post on this forum instead of messaging him privately, so here I am.  Could I have a faulty FET?   I had that happen in a Hairball Lola kit I built, and replacing the FET totally fixed the low gain/distortion issue.   Faulty relay?  If anyone has any ideas, that would be most helpful.    Many thanks in advance.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on September 06, 2017, 02:58:11 PM
After building nearly a dozen CAPI kits for myself and others, I find my self stumped for the first time.    My FC 526 build looks good to me.  Clean.  No solder bridges.   It passes audio just fine in bypass mode, but when I engage the compressor, everything sounds like its passing through a high pass filter.  The bottom end just drops out, and the overall level drops, regardless of whether GR is on or off.   The sound is not distorted, just lacking in bottom end and gain.  I've gone over the PC board very methodically with the BOM and check all the resistors.  They appear to be in all the right places.   All the diodes are correctly oriented.  It's not the opamp, as the same thing happens with my pre-built Red Dots (I'm using the gar 2520s that I built from a kit.)   Jeff suggested that I post on this forum instead of messaging him privately, so here I am.  Could I have a faulty FET?   I had that happen in a Hairball Lola kit I built, and replacing the FET totally fixed the low gain/distortion issue.   Faulty relay?  If anyone has any ideas, that would be most helpful.    Many thanks in advance.
My first guess would be something is wrong in the audio path. I suggest injecting signal and following it thru the circuit via the Test Points doc. We need to narrow down where things go south or we're simply shooting in the dark.

It most likely won't be the FET. Each and every VVR or MTR FET is tested/graded in an actual FC526 circuit. We monitor freq response and THD to make sure there are no weird issues.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on September 06, 2017, 11:21:45 PM
So here's my measurements of the audio path:

with .0258 VAC appearing at the input:

TP1 - 5.7  mVAC
TP2 - 110.3 mVAC
TP3 - 882.3 mVAC

The first tow seem in the zone, but the last measurement seems low to me.

All measurements take  with
input - full CW
output - full CW
attack - full CW
release - full CW
switched to Active
GR on
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on September 07, 2017, 01:06:47 AM
I would dbl check the output transformer wiring especially if you are using the Litz version.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on September 07, 2017, 10:51:09 AM
I would dbl check the output transformer wiring especially if you are using the Litz version.

Thanks Jeff.  I'm pretty sure I ordered the EA version.  My invoice says "2 x   FC526-XFMR Entire Bundle".  The transformer says "2623-1      605-1634" on it.  Is that the Ed Anderson, or Litz?  From the first set of numbers, it looks like an EA transformer.   If that number is an EA version, then I can confirm that the colour codes of the wiring are correct, and that the solder joints look good.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on September 07, 2017, 10:59:49 AM
OK, to quickly rule out the output transformer, desolder the Red lead from the PCB and see if your TP3 value changes, following the same procedures as you did in your previous audio path test.

I forgot to ask, have you turned the Q_BIAS trimmer CW so no level changes are seen? Take it out of its conductive range.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on September 07, 2017, 12:28:00 PM
OK, to quickly rule out the output transformer, desolder the Red lead from the PCB and see if your TP3 value changes, following the same procedures as you did in your previous audio path test.

I forgot to ask, have you turned the Q_BIAS trimmer CW so no level changes are seen? Take it out of its conductive range.
   I did forget to readjust the QBIAS full CW.

Bit of a face palm moment I'm afraid.  I've spent a few days agonizing over this, and it turns out that the issue was a faulty slot in my patchbay!  I moved the test jug over one slot to the right, and all was well!   It's now calibrated and sounding glorious with all the bottom end and gain a fellow could ask for!  On the one hand, I'm glad that my assembly skills were up to the task, but on the other hand, I must genuinely apologize for taking up your precious time.   These things are slamming!  Awesome sound, and well worth the effort!    Now to dive into that patchbay...
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on September 07, 2017, 12:57:11 PM
   I did forget to readjust the QBIAS full CW.

Here are the revised readings.  De-soldering the red wire does not change TP 3

TP 1 - 5.7mVAC
TP2 - 126.1 mVAC
TP3 - 1.0089 VAC
OK those readings look more on target. You can monitor the signal unbalanced by leaving the Red output transformer lead desoldered and taking the signal from the Red solder pad. See if that is full range.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on September 07, 2017, 01:58:58 PM
OK those readings look more on target. You can monitor the signal unbalanced by leaving the Red output transformer lead desoldered and taking the signal from the Red solder pad. See if that is full range.
  As I mentioned in my modified post above, it turns out that the Comp is fine.  It was a faulty patchbay slot!   I changed slots on a hunch and was rewarded with tones of bottom end and gain.   It's all calibrated and groovy now.   See my profuse apology for taking up your time above!   Thanks again, Jeff.   Your modules are awesome and your support has been fantastic!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on September 07, 2017, 02:08:28 PM
  As I mentioned in my modified post above, it turns out that the Comp is fine.  It was a faulty patchbay slot!   I changed slots on a hunch and was rewarded with tones of bottom end and gain.   It's all calibrated and groovy now.   See my profuse apology for taking up your time above!   Thanks again, Jeff.   Your modules are awesome and your support has been fantastic!
Ah, good news. I typically don't read modified posts only new ones when I get the email notification.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: alocaster on October 20, 2017, 11:13:28 PM
Jeff, I have a recent build that appears correct in components and solder. Alas I have some audio problem giving me 2.5mv at tp 1. On an O-scope it looks more like noise than signal.

thanks
rob
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 21, 2017, 12:47:16 PM
Jeff, I have a recent build that appears correct in components and solder. Alas I have some audio problem giving me 2.5mv at tp 1. On an O-scope it looks more like noise than signal.
Rob, TP1 is directly after the discrete follower which follows the input transformer. The only thing before that are the bypass relays.

Check the bottom of R71 for input + signal and bottom of R73 for input -. If you don't have audio there, your relays are not switching over properly.

If that is good, check the top of R42 which is immediately following the 2622's secondary.

If that is good then I would look at swapped transistors or something for Q1 and Q2.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: alocaster on October 24, 2017, 03:11:26 AM
Jeff following your guidance i traced the signal to q1 and q2. This is where it dies. The orientation of the transistors appears correct. I have made it no further yet. Do you have q1 and q2 voltages. Thank you.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on November 02, 2017, 07:07:18 PM
Jeff following your guidance i traced the signal to q1 and q2. This is where it dies. The orientation of the transistors appears correct. I have made it no further yet. Do you have q1 and q2 voltages. Thank you.
Sorry I missed this.

Q1, BC560C:
C -15.43
B  -.588
E .046

Q2, BC550C:
C 15.14
B 0
E -.589
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: alocaster on November 16, 2017, 12:31:34 AM
After installing the new pots post drop test. I re checked the audio path beginning with the transistors. The values you provided were close to my build. I then went back to the primary side of the transformer and found the signal not what it should be it appeared as if the transformer was loading the ckt. I reflowed the secondary side where there was almost no signal. No improvement. I then removed the transformer after which pin one had the correct amplitude. I hoped to check the transformer statically from the CA2622 schematic. I found 68 and 70 ohms on each of the primaries and 1.59K on the secondary. Should these values be representative of the listed 150/600 and 10Kohm printed. Thanks for the help.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on November 16, 2017, 12:55:26 AM
After installing the new pots post drop test. I re checked the audio path beginning with the transistors. The values you provided were close to my build. I then went back to the primary side of the transformer and found the signal not what it should be it appeared as if the transformer was loading the ckt. I reflowed the secondary side where there was almost no signal. No improvement. I then removed the transformer after which pin one had the correct amplitude. I hoped to check the transformer statically from the CA2622 schematic. I found 68 and 70 ohms on each of the primaries and 1.59K on the secondary. Should these values be representative of the listed 150/600 and 10Kohm printed. Thanks for the help.
No, the datasheet specs are AC impedance values not DCR measurements. Your DCR numbers are right in the ballpark for a normal transformer.
Title: FC526 XFMR
Post by: toga on December 13, 2017, 01:27:23 PM
Hi all,

intending to commence a build of the FC526 XFMR tomorrow. In the absence of a build guide for the updated XFMR model am I right in thinking I can still use Chunger's guide as a general aid? Anything to look out for in terms of particular difficulties associated with the build of the XFMR model?

All the best.
Title: Re: FC526 XFMR
Post by: jsteiger on December 13, 2017, 01:36:52 PM
Hi all,

intending to commence a build of the FC526 XFMR tomorrow. In the absence of a build guide for the updated XFMR model am I right in thinking I can still use Chunger's guide as a general aid? Anything to look out for in terms of particular difficulties associated with the build of the XFMR model?

All the best.
Yes you can use it as a general guide. It is similar and easy overall in comparison.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: toga on December 13, 2017, 03:29:15 PM
Yes you can use it as a general guide. It is similar and easy overall in comparison.

Many thanks.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: toga on December 19, 2017, 05:24:45 PM
So my GND to opamps (-V and +V)  resistance readings checked out as did the 15V test when plugged in. The TP9 DC rail reading is at 10V. Audio passes and the meter functions (uncalibrated) but the audio is very distorted when unit is switched to the active position. I touched up the solder joints but resistors PR3 and PR4 burned out on powering up . Any thoughts? Does it sound like a problem with the DTO5?  The soldering of Transistor at Q5 was very poor and I was unable to remove it and replace.

All the best.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on December 19, 2017, 06:42:57 PM
So my GND to opamps (-V and +V)  resistance readings checked out as did the 15V test when plugged in. The TP9 DC rail reading is at 10V. Audio passes and the meter functions (uncalibrated) but the audio is very distorted when unit is switched to the active position. I touched up the solder joints but resistors PR3 and PR4 burned out on powering up . Any thoughts? Does it sound like a problem with the DTO5?  The soldering of Transistor at Q5 was very poor and I was unable to remove it and replace.

All the best.
PR3 and PR4 are specially for the DTO5 so if they burned you have something wrong on that board. I would check for wrong facing diodes or misplaced transistors.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: toga on December 19, 2017, 07:30:40 PM
To which board do you refer, DT05 or main? Many thanks.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: toga on December 19, 2017, 08:46:35 PM
Diodes and transistors on DT05 all correctly positioned and aligned though Q4 is bodged. Being that initial test readings were good without opamps and unit appears to work correctly only with distorted audio, points to issue lying with the DT05? Happy to order a new DTO5 in the New Year.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on December 20, 2017, 12:22:15 AM
PR3 and PR4 are specially for the DTO5 so if they burned you have something wrong on that board.
The DTO5 board.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: toga on January 09, 2018, 07:54:03 PM
I'm replacing one of the Fairchild 2N5088 transistors on the DT05. Which to choose from? 

https://www.mouser.dk/Search/Refine.aspx?Keyword=2n5088

Thanks in advance.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on January 09, 2018, 08:44:06 PM
I'm replacing one of the Fairchild 2N5088 transistors on the DT05. Which to choose from? 

https://www.mouser.dk/Search/Refine.aspx?Keyword=2n5088

Thanks in advance.
I ship Fairchild with the kits. I think ON SEMI bought them a while back. Most of the suffixes are different packing. Bulk, reel, etc.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: AndyKolp on January 14, 2018, 11:41:13 AM
Hello all,

I'm having some issues straight away when trying to calibrating my FC256 XFMR with Litz compressor.

I'm supposed to have between +2.498V DC and +2.502V DC at the “top” of the the meter resistor string for the
LM339 comparators.

I measured 2.506VDC at this test point. Is this too far outside the range given? Will this effect accuracy of the meter? How do I bring this value to the proper level? Different resistor value somewhere else?

Thanks for any advice.

Andy
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on January 14, 2018, 12:05:08 PM
I'm supposed to have between +2.498V DC and +2.502V DC at the “top” of the the meter resistor string for the
LM339 comparators.

I measured 2.506VDC at this test point. Is this too far outside the range given? Will this effect accuracy of the meter? How do I bring this value to the proper level? Different resistor value somewhere else?
That should be fine Andy. I wouldn't call it a problem exactly.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: AndyKolp on January 14, 2018, 04:13:56 PM
That should be fine Andy. I wouldn't call it a problem exactly.

Thanks, Jeff.

Calibration is complete as far as I'm able. Followed the guide several times until I believe I caught all of the steps that I missed in previous attempts. I will say that while the compressor sounds really good, the metering is SUPER sensitive. I'm running a simple drum loop for testing. Meter goes from no gain reduction to slamming 20dB reduction with very little action in between. I'm assuming I may have made a mistake as far as signal generator levels during calibration.

**Gain Reduction Meter Calibration**

3. Apply a 1kHz sine wave @ +7dBu to the input.

I assume that any dBu level mentioned as far as input singal in the cal guide needs to have the dBFS relationship of the interface deducted from your values?

So, a sine wave @ +7dBu from my signal generator in my DAW to theinput would really be -11dBu?
I believe I read elsewhere that this is also RMS level and NOT peak?

Is it also correct that monitoring the output level as mentioned in step 5  (adjusting the compressor output pot when looking for +7dBu output signal) does NOT have dBFS subtracted? Rather, I'd use the VAC of the signal when monitoring any output? In this case, +7dBu = 1.73VAC

I will say, I've learned a ton by working on this unit, which is always a good thing.

Thanks,

Andy
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Tschem on January 20, 2018, 11:51:45 AM
Hello Jeff!
i have the same issues on both of my fc526-xfmr: in audio path i do not get the expected value on the test point T1:
input: 0,025V (-30dBu)
TP1: 0,01V instead of 0,0058V

Comp1: Seems like i'm "off" by the factor of 2
TP1: 0,01V
TP2: 0,254
TP3: 2,055V
Output: 1,014 V

Comp2: Same on the input but there some deviation between DTo5 output and TP2:
DTO5 input: 0,01V
DTO5 out: 0,250V
TP2 & TP3: ~0V
output: 0,009V

every pot full CW, RV2 full CW, DOA works, Litz wire xfmr connections exactly like here: http://www.capi-gear.com/catalog/images/gallery/2623/2623-1-L-specs.pdf

What could be the reason for getting 0,01V at TP1 on both units?
What could be the reason for the deviation on DTO5 output and DOA input?

thx a lot in advance
br, T
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on January 20, 2018, 01:50:07 PM
Could possibly be a DMM rounding thing? .0058 would round to .01. Not sure what meter you are using but if the rest of the circuit is correct on the first one I would say its your DMM.

On the 2nd one I'd say you have something wrong on the DTO5.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Tschem on January 20, 2018, 02:08:09 PM
comp1: at first i also thought about some kind of rounding, but that doesn't explain the other values.
input: 0,025V
TP1: 0,01V
TP2: 0,254
TP3: 2,055V
Output: 1,014 V

this deviates much from the values in the test point guide... 7.75dBu on the output means about 1,9V.
are these values still acceptable?

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 07, 2018, 11:46:25 PM
Hi I have just started calibration and Houston  we have a problem :o 

Test point data received..............

Sine wave at 1k @  0.024vAC into balanced input


Main pcb

TP 1 .      @ .     0v
TP 2 .      @ .     0v
TP 9 .      @ .     -10.01vDC

Meter pcb

TP 11 .   @ .      2.771
TP 5 .      @ .      2.572
TP 1 .      @ .      1.955




Maybe hi res pictures of a finished boards for reference?  Also schematics would be super helpful for me to be able to troubleshoot.
Thank you  for you time and what a fun and beautiful build design, with all parts accounted for. It means a lot to me
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 08, 2018, 10:22:28 AM
Scroll back to Reply #276 of this thread for TP1 problems.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 08, 2018, 08:50:39 PM
Rob, TP1 is directly after the discrete follower which follows the input transformer. The only thing before that are the bypass relays.

Check the bottom of R71 for input + signal and bottom of R73 for input -. If you don't have audio there, your relays are not switching over properly.

If that is good, check the top of R42 which is immediately following the 2622's secondary.

If that is good then I would look at swapped transistors or something for Q1 and Q2.

R71 and R73 are good
R42 Not sure where to ground the O scope so using the ground point and no signal at R42
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 08, 2018, 08:54:32 PM
R71 and R73 are good
R42 Not sure where to ground the O scope so using the ground point and no signal at R42
Post a quick pic of that part of the build.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 08, 2018, 10:09:08 PM
Post a quick pic of that part of the build.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 08, 2018, 10:28:30 PM
Did you check R42 closest to C17 or the other end?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 08, 2018, 11:06:39 PM
Did you check R42 closest to C17 or the other end?

Yes I did use the top of R42 closest to C17.

Using ground point for ground.
 
 
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 09, 2018, 07:53:09 PM
Waiting for a reply. Should i pull the transformer out and test?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 10, 2018, 10:32:51 AM
Waiting for a reply. Should i pull the transformer out and test?
Yes. You should measure the windings for DCR. That would be from pin-5 to 8, pin-1 to 3 and pin-2 to 4.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 10, 2018, 02:33:19 PM
Yes. You should measure the windings for DCR. That would be from pin-5 to 8, pin-1 to 3 and pin-2 to 4.

pin 5-8 = 1.698k
pin 1-3 =  64ohm . when testing here the meter jumps around at first for about 1 second then settles down. and measuring a few min later its 62.8ohms
pin 2-4 = 71 ohm

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 10, 2018, 06:16:03 PM
I put the transformer back in and tested everything again.
The signal good at R71 & R73.
No signal at R42 and ground.
 :P
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 10, 2018, 07:55:08 PM
I put the transformer back in and tested everything again.
The signal good at R71 & R73.
No signal at R42 and ground.
 :P

With the transformer out I get 165.4ohms across pins 1 & 3 of the CA2622 location on the main PCB.

Transformer back in.

If I turn my O scope I can see this @ R42(yellow)
My noisy  sine on the  balanced input in blue @ 0.024vAC
This scope is not very accurate as far as voltages and frequencies.
Frequency & voltage  were measured with a true rms DMM
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 10, 2018, 08:58:50 PM
The 2622 DCR looks correct.

Maybe you have the 2 transistors swapped immediately after the 2622?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 10, 2018, 10:20:45 PM
The 2622 DCR looks correct.

Maybe you have the 2 transistors swapped immediately after the 2622?

Q1 is a BC560
Q2 is a BC550
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 10, 2018, 10:24:51 PM
Check DCV at the top of R36 and then R37. Check on the ends closest to R40.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 11, 2018, 12:18:29 AM
Check DCV at the top of R36 and then R37. Check on the ends closest to R40.

R37= -15.15vdc
R36= +15.13vdc
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 11, 2018, 01:35:10 AM
Sorry I missed this.

Q1, BC560C:
C -15.43
B  -.588
E .046

Q2, BC550C:
C 15.14
B 0
E -.589


My values are very close

Q1, BC560C:
C -15.13
B  -.564
E .053

Q2, BC550C:
C 15.11
B 0
E -.564
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 11, 2018, 04:04:00 AM
If I put in an AC sine1kHZ and  -6.1dbu or 0.380v than TP1 = -42.4dBu or appx 5.8mV AC
TP2 @ 0.161vAC
TP3 @  1.286vAC
output 2.57vAC  appx 10.4dbu
funny thing is in my DAW its -27db on its meter now
 :o
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 12, 2018, 07:53:00 PM
Whats the word O keeper of the schematics?  I have been waiting a couple of days to hear back what to do next.
 
Out of about  60 DIY kits from effects to synths including the ARP 2600 clone, samplers, drum machines this is the most painful support, at this rate I guess i will have a 500$(Canadian dollars the cost for me )distortion unit. I have never had a project I could not get going even faulty circuit designs i have help provide insight into what could be going wrong why do you make this so hard for me? Some hi res pictures and a schematic I am guessing I could tell you where the problem is.

 :-\
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 12, 2018, 08:16:58 PM
Whats the word O keeper of the schematics?  I have been waiting a couple of days to hear back what to do next.
 
Out of about  60 DIY kits from effects to synths including the ARP 2600 clone, samplers, drum machines this is the most painful support, at this rate I guess i will have a 500$(Canadian dollars the cost for me )distortion unit. I have never had a project I could not get going even faulty circuit designs i have help provide insight into what could be going wrong why do you make this so hard for me? Some hi res pictures and a schematic I am guessing I could tell you where the problem is.

 :-\
I do not publish the schematic for this project. I never have. I am honestly lost as to where you are and what your problems are. I got the impression from your last post that something dramatically changed when you put it all back together. I do not have all of the test point data memorized so it would be helpful if you could post what you have vs what it should be.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 12, 2018, 10:52:26 PM
What test points would you like? all of them? I am stuck at TP.1= 0volts AC


BUT


If I put in an AC sine1kHZ and  -6.1dbu or 0.380v

My test TP1 = -42.4dBu or appx 5.8mV AC
MY TP2 @ 0.161vAC
MY TP3 @  1.286vAC
MY Output 2.57vAC  appx 10.4dbu

Your notes that tell me to "Apply a 1kHz sine wave @ -30dBu to the input."

So instead of  -30dbu i am putting  -6.1dbu thru to get the signal to TP.1




Your calibration notes
**Audio Path**
TP1 Immediately follows the balanced receiver opamp, just before the RV6 input pot. Signal
here should be 12.4dB lower than the balanced signal level at the input of the module.
TP2 Immediately follows the signal preamp opamp, just before the RV5 output pot.
TP3 Immediately follows the output opamp, just before the T1 output transformer. Signal level
here will be approximately 6dB lower than the module’s balanced output.
Audio Path Test: With the VVR FET fully out of conductive range (RV2 fully CW), turn both
input and output pots wide open or fully CW.

Apply a 1kHz sine wave @ -30dBu to the input. 

Why not include the volts AC above??

You should have the following:
TP1 = -42.4dBu or appx 5.8mV AC
TP2 = -16.3dBu or appx 117.7mV AC
TP3 = +1.73dBu or appx 939mV AC
Module’s Output = +7.75dBu

Basically it seems as all switches and knobs work meter responds but the sound is very thin unit seems to boost to the high frequencies and cut to the low frequencies on spectrum analyzer with white noise, triangle waves come out as squares on O scope
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 13, 2018, 10:49:27 AM
You can monitor any of the 3 audio Test Points by listening or scope or whatever. If you have issues at TP1, the following audio TP's do not matter as it won't magically come back. I thought you said something changed but it seems that is when you put a higher level signal to the input which is not suggested anywhere. If your levels look fine at the input of the 2622 (R71, R732) and nothing at R42, then it still points to the 2622, which is odd. I have not had a bad one yet from this winder. Are you sure its orientated right? The outside mu-can ground wire should be facing the opamps.

You will have to pull it again and see if there is any shorting between windings. Also check from the signal pins to the outside mu-metal can. So make sure pin-1 only has DCR to 3 and not to 2, 4, 5 or 8 and also not to the outside of the can, rinse and repeat for all signal pins.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 13, 2018, 08:41:47 PM
Everything checks out with the 2622. After your tests  I also put a sine wave thru pins 1&2 together as + and  3&4 as - and it amplified and put the signal out on pins 5&8 fine

What about a picture of a working unit? Or I can send you more of mine besides the one in Reply #301
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 14, 2018, 10:45:28 AM
Everything checks out with the 2622. After your tests  I also put a sine wave thru pins 1&2 together as + and  3&4 as - and it amplified and put the signal out on pins 5&8 fine

What about a picture of a working unit? Or I can send you more of mine besides the one in Reply #301
Not to name drop but I dropped my last 2 built units off to Ryan Hewitt yesterday so I don't have any here currently to take more pics of.

There is not much at all between the 2622 and TP1. Just the BC550/560 transistors, their R's (R36, R37, R41, R42) and C15. Maybe you should try replacing the transistors? If so I would do it one at a time, although the voltages looked normal.
Title: transistors
Post by: toga on March 14, 2018, 05:10:36 PM
Hi,

just getting back to this build. Finding it difficult to get hold of the 2n5087 and 2n5088 transistors without paying the mouser postage premium. Any suitable transistor alternatives? Thanks.
Title: Re: transistors
Post by: jsteiger on March 14, 2018, 07:30:25 PM
Hi,

just getting back to this build. Finding it difficult to get hold of the 2n5087 and 2n5088 transistors without paying the mouser postage premium. Any suitable transistor alternatives? Thanks.
BC550C and BC560C will work fine but the pinouts are turned 180˚.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 14, 2018, 11:36:03 PM
Not to name drop but I dropped my last 2 built units off to Ryan Hewitt yesterday so I don't have any here currently to take more pics of.

There is not much at all between the 2622 and TP1. Just the BC550/560 transistors, their R's (R36, R37, R41, R42) and C15. Maybe you should try replacing the transistors? If so I would do it one at a time, although the voltages looked normal.


Pulled and replaced transistors they were fine in parts tester, but put new ones in anyway.  Looked at all the R's you mentioned they all look right then pulled and tested C15 its fine and still nothing at TP1 at the calibration level.
 :'(

-30 dBu is 0.024volts ac right?
 
So stumped after about 30 hours of troubleshooting this, Pissing me right off! >:( Having  finished two other projects in the meantime with no problem at all.  JLM opto  comp kit is next, I wonder if it will be working before this? Or what will become of this CAPI kit? I wish it would just work. I love the sound of good compressor and have no doubt  this one sounds amazing when its working properly.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 15, 2018, 10:18:35 AM
Did you check DCR from the outside of the 2622 mu-can to the winding leads when you had it out last time?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 15, 2018, 07:53:42 PM
Did you check DCR from the outside of the 2622 mu-can to the winding leads when you had it out last time?


Yes. Checked that like you asked three days ago.

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 16, 2018, 07:12:44 PM
So I pulled up R42 and and the signal does not get to that spot, when I take it out of bypass then it kills my sign-wave going into the unit and turns it in to noise at the balanced input jack. The two dials control the level of the noise at the top of R42,  I find that strange maybe c17? anyhow thats what i got today
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 16, 2018, 08:02:29 PM
So I pulled up R42 and and the signal does not get to that spot, when I take it out of bypass then it kills my sign-wave going into the unit and turns it in to noise at the balanced input jack. The two dials control the level of the noise at the top of R42,  I find that strange maybe c17? anyhow thats what i got today
C17 and R40 form the Zobel network for the 2622 so its likely not that. Pulling one end of R40 will effectively remove the Zobel from the circuit so taking it out of play if you care to check.

Were you able to look up the spec of your DMM? Most importantly the input Z? If the Z is high like I mentioned in the email, I would be convinced its the 2622. Oddly enough, this will be the first bad 2622 from the new winder and we are well over 2k units shipped but sh*t happens. In fact, at this point I'm happy to send you one just so we know 100%.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 17, 2018, 07:51:59 PM
OK well its hard to tell if both are flipping or not. At least you know something is happening. You will have to check the relay pins for continuity.

The pic attached shows what should have continuity in ACT mode. It will be the other contacts when in BYP. Make sure both poles of the relay are functioning correctly. K1 is the input relay and K2 is for the output.


So i have been going back in to the circuit surprised by what was happening with  the test signal at the input and decided to pull K2 out to see if I could hear K1 switching since it was not passing the continuity tests, and I can hear only silence so i will try the BYP switch, but hear it click on power up.  I must have been getting bad readings at R71 and R73?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 17, 2018, 09:07:38 PM

So i have been going back in to the circuit surprised by what was happening with  the test signal at the input and decided to pull K2 out to see if I could hear K1 switching since it was not passing the continuity tests, and I can hear only silence so i will try the BYP switch, but hear it click on power up.  I must have been getting bad readings at R71 and R73?
So the relays are not changing over when flipping the BYP switch? If that's the case then maybe the 4V3 zener is not in its right place? Could have been switched with a 914?

You should be able to test both relays for continuity in both states from the back of the PCB.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on March 17, 2018, 11:34:48 PM
So the relays are not changing over when flipping the BYP switch? If that's the case then maybe the 4V3 zener is not in its right place? Could have been switched with a 914?

You should be able to test both relays for continuity in both states from the back of the PCB.

I tested both relays for continuity in both states from the back of the PCB and K1 failed thats what was trying to say in the previous  post


K1 was bad  when I put K2 in its spot i can hear it switching with the BYP switch

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 18, 2018, 01:14:31 AM
I tested both relays for continuity in both states from the back of the PCB and K1 failed thats what was trying to say in the previous  post


K1 was bad  when I put K2 in its spot i can hear it switching with the BYP switch
Wow very odd. I can send you a replacement.

In the meantime, I would jumper over the pads on the missing relay just for testing the audio path etc. The thick green lines in the attached screenshot would be for the module to be in ACT mode. Jumpers are shown for both  relays.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Thekahn on March 22, 2018, 09:49:41 PM
Hi guys, new to the forum. I've built one successful VP28, but I am hitting a pretty big hiccup when i'm testing my newly built 526-Litz.

I am reading 10.02 V DC at TP 9. I am reading 2.503 V DC at MTR point #11.
I've sent a 1k test tone thru my DAW and i'm getting  243.3 mV AC into the unit, as well as  243.3 mV AC on the output of the unit while bypassed.
I have turned RV2 clockwise probably 20-30 turns clockwise.
input gain, output gain, attack, and release are all fully CW, and 20:1 Ratio is confirmed selected.


Once I turn it to active, GR OFF, and SC HPF disengaged, I am getting the following readings, with my DMM set to AC voltage, one lead on the ground lug, and the other lead to the following:

TP 1: 56.6 mV AC
TP 2: 1.14 V AC
TP 3: 9.17 V AC
At the output, i'm reading 18.29 V AC


With the unit active, and GR on, i'm getting the following readings:
TP 1: 56.6 mV AC
TP 2: 0.951 V AC
TP 3: 7.0 V AC
At the output, i'm reading  15.25 V AC

With the unit active, GR on, and SC HPF In, i'm getting the following readings:
TP 1: 56.6 mV AC
TP 2: 0.928 V AC
TP 3: 7.46 V AC
At the output, i'm reading  14.87V AC

I have confirmed that none of my capacitors , diodes, or transistors are in backwards (I triple checked but who knows).  And I did as Chunger suggested,  I put all the resistors in before soldering anything that way everything is copasetic.  I also spent about 4 hours yesterday double checking every single resistor with color code method, I checked every single capacitor, transistor, switch, IC.. I literally went through the build with a fine tooth comb.  I cannot see where this went wrong.
I’ve also used 3 OP amps and get the same test values +/- a couple of mV.  I’ve also tried a couple of different slots in my Lindell 506 power supply with very similar results too.  At this point the only thing I can think of is maybe a bad solder joint. I have confirmed there are no solder bridges as far as I can tell (and I’ve stared at the thing at least 4 hours lol).  Any help would be awesome, thanks in advance.

Kahn


Oh and by the way this is an awesome community that I'm proud to be a part of, and Jeff has been extremely helpful thus far.
:)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 22, 2018, 09:59:58 PM
-30dBu is 24.3mV AC not 243mV. Not sure what is up with the measurement system but something is not right in that regard.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Thekahn on March 22, 2018, 10:39:43 PM
Man I'm such a noob!  :o :-[
Thanks Jeff.

When I input a 24.4 mV  (as close as I could get to 24.3 mV) signal i'm getting:
TP 1: 5.7 mV AC
Tp 2: 108.4 mV AC
TP 3: .906 V AC
Output: 1.808 V AC

It does look a tiny bit lower than the numbers in your test guide, but do you think it's close enough?


You should have the following:
TP1 = -42.4dBu or appx 5.8mV AC
TP2 = -16.3dBu or appx 117.7mV AC
TP3 = +1.73dBu or appx 939mV AC
Module’s Output = +7.75dBu
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Tschem on March 23, 2018, 07:03:51 AM
Hi Jeff, sorry to bother you again.
Same old problem, also after installing a fresh DTO5:
@0.025V Input:
 0.006V @ TP1
0V @ TP2

Input of DTO5 == 0.006V
Output of DTO5 == anode of D4 == ~0.140V
cathode of D4 == 0V

Do you think it might be D4? any suggestions how to go on from here?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 24, 2018, 12:22:41 PM
Hi Jeff, sorry to bother you again.
Same old problem, also after installing a fresh DTO5:
@0.025V Input:
 0.006V @ TP1
0V @ TP2

Input of DTO5 == 0.006V
Output of DTO5 == anode of D4 == ~0.140V
cathode of D4 == 0V

Do you think it might be D4? any suggestions how to go on from here?
D4 is part of the peak circuit. The anode of D4 should equal the output of the DTO5 since there is a PCB trace directly between them. The ONLY thing between the output of the DTO5 and TP2 is C8. If you have signal at the output of the DTO5 then you will have signal at the negative end of C8. You should also have the same signal at the positive end of C8. C8 and TP2 are directly connected by PCB tracks.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Tschem on March 25, 2018, 03:57:23 AM
It's definitively C8. 0.140V on cathode, 0 on anode. direction is correct, i also re-soldered the solder joints without any effect.
guess i have to find a replacment.
thx a lot for support!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: 420troll on April 03, 2018, 09:45:44 PM
All the new parts have been put in relays, transistors, but in the audio path still have the same problems and test point problems. Audio sounds thin and the test points all fail. I am getting 1.48vAC at output with all knobs CW with 0.024vAC going in.
Guessing this week is going to be be going over the test points and calibration procedures a few more times.
I notice that when monitoring the input at the edge connector when active mode is engaged the input voltage of 0.024vAC changes and drops to 0 volts and when in bypass it is normal 0.024vAC same thing happens at the relay on the side that heads to the input transformer, it drops to zero.
I was really hoping you would have sent a new transformer like you said you would to be safe.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 04, 2018, 10:48:30 AM
All the new parts have been put in relays, transistors, but in the audio path still have the same problems and test point problems. Audio sounds thin and the test points all fail. I am getting 1.48vAC at output with all knobs CW with 0.024vAC going in.
Guessing this week is going to be be going over the test points and calibration procedures a few more times.
I notice that when monitoring the input at the edge connector when active mode is engaged the input voltage of 0.024vAC changes and drops to 0 volts and when in bypass it is normal 0.024vAC same thing happens at the relay on the side that heads to the input transformer, it drops to zero.
I was really hoping you would have sent a new transformer like you said you would to be safe.
Last I remember hearing you found a problem with a relay. After that, sending the 2622 didn't cross my mind when I sent you the pot. I will make a note to send one now.

Are you 100% sure both of your relays are switching over completely?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Thekahn on April 14, 2018, 03:10:44 PM
Man I'm such a noob!  :o :-[
Thanks Jeff.

When I input a 24.4 mV  (as close as I could get to 24.3 mV) signal i'm getting:
TP 1: 5.7 mV AC
Tp 2: 108.4 mV AC
TP 3: .906 V AC
Output: 1.808 V AC

It does look a tiny bit lower than the numbers in your test guide, but do you think it's close enough?


You should have the following:
TP1 = -42.4dBu or appx 5.8mV AC
TP2 = -16.3dBu or appx 117.7mV AC
TP3 = +1.73dBu or appx 939mV AC
Module’s Output = +7.75dBu


Hi Jeff, not sure if you saw my post (quoted above), but could you please respond when you have a chance?
Much appreciated,
Chris
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 14, 2018, 03:40:05 PM
Hi Jeff, not sure if you saw my post (quoted above), but could you please respond when you have a chance?
Much appreciated,
Chris
These look pretty OK to me. Might just be a DMM accuracy thing.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: fnhscar17s on April 17, 2018, 11:40:21 AM
Hello all,

I have completed a 526 build. I am using the collective cases psu.

Everything looks decent measurement wise I was just wondering about my output level.

Tp1 12.6mv rms
Tp2 246 mv rms
Tp2 1.97 v rms

All measurements taken with a rigol oscilloscope with a 50 ohm feed through termination Bnc (my signal generator is 50 ohm output).

Output 10dbu at 2.44 v rms

I feel like the output is not quite as high as it should be as stated in the test points document. Do you guys have any ideas or is this suitable to move forward?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: fnhscar17s on April 18, 2018, 10:57:13 AM
Any insights?

Am I good to go level wise. Output is basically about 4dbu short
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 18, 2018, 12:10:35 PM
Any insights?

Am I good to go level wise. Output is basically about 4dbu short
Sorry I have been crazy busy. I assume the 2nd TP2 in your post is actually TP3? If so, that is just before the transformer. If that is what it should be and the output is truly low, I would dbl check the transformer wiring. Also, not sure how you are measuring the output but at that point remember the balanced lines are floating with no reference to ground. If using a meter, do not check each phase to ground. Only measure between the +/-.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: fnhscar17s on April 18, 2018, 12:18:10 PM
Thanks for the response. I am measuring across the positive and negative leads on the output via a feed thru terminated oscilloscope. My signal generator is 50 ohm outputting to the positive and negative leads for the input. Yes my 2nd tp2 is tp3 my bad that was a typo.

I am using a litz transformer and it was wired according to your pinout specified on your site I figured it could be the tx which I double checked it I'll make sure again to be sure. I also reflowed all of my solder joints on the board and no change.

Thanks Jeff you are always very helpful
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Thekahn on April 18, 2018, 09:36:29 PM
Hi Jeff,
I was checking the DC voltage at point 11, and it was reading around 2.5V, but then I accidentally bridged a connection or two by accident with my DMM probe and now my voltage is down to 0.136volts DC,
any idea how I can pinpoint what happened?

here is how it's reading:

11=0.136V
10=0.134V                                                                   
9=0.132V
8= 0.130V
7=0.129V
6=0.127V
5=0.126V
4=0.125V
3=0.124V
2=0.120V
1=0.094V
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: fnhscar17s on April 18, 2018, 09:43:48 PM
So checked the 2623 output tx. I am using the litz version tx

Wired as follows:
Red on board wired to black on tx
Orange on board wired to red on tx
Blue on board wired to gray on the tx
Green on board wired to pink on tx
Brown on board wired to violet on tx
Black on board wired to orange on tx


Pulled the tx out to measure resistance:
Tx primary measures 16 ohms between red and black on two dmm including a third I threw in the mix.

The secondaries:
Violet and orange- 352 ohms on one multimeter and 305 on another
Pink and gray- 300 on one dmm 348 on another

Note the primary at 16 ohms was across the board on 3 different dmm

All dmm have 1meg input impedance I am pretty sure. Two fluke 8060a and one sperry dm6400

A had a hunch about the tx since all my other levels are good. But not too sure what to make of the readings here. I guess that would mess with the ratio of the winding I imagine? Or am I completely off here?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 21, 2018, 02:01:44 PM
Hi Jeff,
I was checking the DC voltage at point 11, and it was reading around 2.5V, but then I accidentally bridged a connection or two by accident with my DMM probe and now my voltage is down to 0.136volts DC,
any idea how I can pinpoint what happened?

here is how it's reading:

11=0.136V
10=0.134V                                                                   
9=0.132V
8= 0.130V
7=0.129V
6=0.127V
5=0.126V
4=0.125V
3=0.124V
2=0.120V
1=0.094V
Maybe you fried the 2.5V shunt reference? You should have around 15.5V at the top of R12 (closest to the meter board edge) and 2.5V at the other end of it. If you have the 15.5V and NOT the 2.5V, I would bet you smoked the 2.5V shunt reference.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 21, 2018, 02:05:31 PM
So checked the 2623 output tx. I am using the litz version tx

Wired as follows:
Red on board wired to black on tx
Orange on board wired to red on tx
Blue on board wired to gray on the tx
Green on board wired to pink on tx
Brown on board wired to violet on tx
Black on board wired to orange on tx


Pulled the tx out to measure resistance:
Tx primary measures 16 ohms between red and black on two dmm including a third I threw in the mix.

The secondaries:
Violet and orange- 352 ohms on one multimeter and 305 on another
Pink and gray- 300 on one dmm 348 on another

Note the primary at 16 ohms was across the board on 3 different dmm

All dmm have 1meg input impedance I am pretty sure. Two fluke 8060a and one sperry dm6400

A had a hunch about the tx since all my other levels are good. But not too sure what to make of the readings here. I guess that would mess with the ratio of the winding I imagine? Or am I completely off here?
For the Litz 2623-1 you should have the following:
Black to Red, 15.7Ω
Pink to Gray, 31.5Ω
Violet to Orange 31.5Ω

Make sure your DMM range is set to below 200Ω. Make sure all leads are floating and not touching anything including each other.

There should be no measurable resistance between leads except for the ones shown above.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Thekahn on April 21, 2018, 07:18:20 PM
Maybe you fried the 2.5V shunt reference? You should have around 15.5V at the top of R12 (closest to the meter board edge) and 2.5V at the other end of it. If you have the 15.5V and NOT the 2.5V, I would bet you smoked the 2.5V shunt reference.
Hi Jeff
So I have 14.98V on the top side of R12, and 0.140V on the other side of R12,. Does this mean R12 is blown and I need to replace it?
Thanks,
Chris
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 21, 2018, 10:34:50 PM
Hi Jeff
So I have 14.98V on the top side of R12, and 0.140V on the other side of R12,. Does this mean R12 is blown and I need to replace it?
Thanks,
Chris
No it won't be R12 it will be the 2.5V precision shunt CR1.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: nanuflas on April 28, 2018, 12:43:25 AM
Hello Everyone. I'm having some trouble with my build. Everything works perfect and it sound great except that I get a pop when I hit the bypass switch and even louder pops when I switch between ratios. When I switch ratios, in addition to the pop, I get a huge spike on the meter. Any idea of what could be wrong?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 28, 2018, 05:47:10 PM
Hello Everyone. I'm having some trouble with my build. Everything works perfect and it sound great except that I get a pop when I hit the bypass switch and even louder pops when I switch between ratios. When I switch ratios, in addition to the pop, I get a huge spike on the meter. Any idea of what could be wrong?
The meter jumping when changing ratios is not unexpected.

A pop when bypassing would likely mean there is DC present on the relay contacts which means there is DC present on either the output of the device going into the comp or the input of the device the comp is going into. The FC526 is transformer isolated at the input and output so there should be no DC from the comp itself.

I'm not sure about the audible pop when switching ratios. This should not happen though as far as I recall.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jroq82 on May 18, 2018, 02:47:31 AM
Good day everyone,
 
I’m having trouble with the 526 xfmr build. Once I plugged it in to the 511 rack I built with XLR I get no response from the comp.  I can hear a click once the rack is powered on. But I don’t see any LED’s light up, and turning the dial doesn’t do anything either for the LED’s.  No sound will pass through it either.  Does anyone here have any suggestions? Or ideas of something. Thank you in advance.

James
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on May 18, 2018, 10:16:37 AM
Good day everyone,
 
I’m having trouble with the 526 xfmr build. Once I plugged it in to the 511 rack I built with XLR I get no response from the comp.  I can hear a click once the rack is powered on. But I don’t see any LED’s light up, and turning the dial doesn’t do anything either for the LED’s.  No sound will pass through it either.  Does anyone here have any suggestions? Or ideas of something. Thank you in advance.

James
James, you will likely need the extension test jig so you can work on the module flat on a bench in front of you. You will need to test the audio path. I highly suggest reading back thru this thread as it will give you helpful clues on what to do.
Title: PR3 Burning - XFMR model
Post by: toga on July 05, 2018, 12:48:16 AM
Hi,

PR3 burning was attributed earlier in this thread to an error on the DTO5 board. However, PR3 is now burning up on power-up with opamps removed.

Any thoughts? All components' placement/orientation checked.

NB. DTO5 (I-)  terminal is jumped to R27 replacing destroyed tracking. Just noting this, though the PR3 issue existed prior to broken tracking.
Title: Re: PR3 Burning - XFMR model
Post by: jsteiger on July 05, 2018, 12:54:35 AM
Hi,

PR3 burning was attributed earlier in this thread to an error on the DTO5 board. However, PR3 is now burning up on power-up with opamps removed.

Any thoughts? All components' placement/orientation checked.

NB. DTO5 (I-)  terminal is jumped to R27 replacing destroyed tracking. Just noting this, though the PR3 issue existed prior to broken tracking.
Sorry, I am away until mid next week.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 08, 2018, 01:45:50 AM
Finishing my build of the fc526 kit and I can't find info as to the rv7 jump. Is that a fisical jump I need to do? Thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 08, 2018, 11:57:38 AM
Finishing my build of the fc526 kit and I can't find info as to the rv7 jump. Is that a fisical jump I need to do? Thanks
Yes it is required. It says JUMP on the PCB and it says jump on the BOM for RV7, IIRC.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 08, 2018, 05:14:45 PM
Thanks Jeff
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 09, 2018, 12:31:35 AM
Well Jeff, I feel like a noob. Well I guess I am, this is my 4th build.I tested the fc526 without the jumper last night before your reply. Tested  -10.02V DC at TP9; +2.502V DC at MTR point 11. Applied 1kHz sine wave @ -30dBu. Read .024 at input & output. All good readings. Started the Q bias calibration and read deferent than specs, so tested tp1 and read 0's. Figured it was the jumper so installed the jumper... fired back up and I'm reading 0's at tp9; at meter Point 11 zeros at TP1 zeros. The DT05 over heats. I must have fried something. Any advise on where to start looking? I know your on vacation so take your time getting back and enjoy.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: glazer56 on July 09, 2018, 04:57:18 PM
Hi Jeff,
I'm having a hell of a time with this build... Got everything built, Voltages checked out good, and passed audio fine. But could not get the unit calibrated for the life of me. TP1 was low, the output with input and rel CW was a bit low. I checked every component a few times and all looks ok. TP9 is fine. Pulled the DO5 opamp to check values and replaced it. Still passing signal, but now voltage at TP1 is 0. But its passing audio OK.

While checking voltages on Q1 and Q2 I shorted something and smoked PR7 and PR8. - Replaced both resistors and Q1&2.  Double checked resistance of V+ and V- to ground, and while V- looks gook at around 3K, V+ is all over the place. Ohms range from 1K-1M, the meter is literally cycling up and own within that range as I test it. Nothing else seems to be blown visually, I checked the Diodes with the meter too. Where else should I look for something that may be blown?
(NOTE: Like a dumba$$ I forgot to plug the meter card back in before I tested the ohms. Problem solved)

I'm using an old signal generator  and a Fluke 117 for calibration (Pins 2&3), Is the DMM accurate enough for this purpose? trying to set 24mv was tough as the readings fluctuated a bit on the DMM.  Also, I'm using a Vintage King 6sp rack for testing, I was about to try alignment in the CAPI rack when things went south. Emailed 420troll to see if he got his up and running as we had similar problems, and he said that his rack had some grounding issues with pin 1, which was causing calibration issues. So i'm thinking now that my unit may have been fine all along, and that I just needed to calibrate it in the capi rack?

So to make a long story short, need a little guidance  to get the ohms thing fixed with V+, and if my meter setup is sufficient for calibration? Many, many thanks! All your stuff is awesome, and am looking forward to getting this up and running. Hope you had a good vacation!

SG

(UPDATE: Got the comp aligned and it works great, trickiest part was to get the gain reduction set right, but once that was done it was simple. turns out i was unable to calibrate in the VINTAGE KING 6sp rack, once i moved operations to the CAPI rack I had no problems. The mv drift on the meters i encountered was negated. I checked pin 1 to chassis on the VK rack, and it is indeed grounded, not sure what may be different about this rack, but for others that may have one you'll need to calibrate on a different rack. As a suggestion, it may be a good idea to mention this issue with certain racks in the build guide. And if it's a grounding issue that can be fixed on the PCB, maybe include a jumper that can solve the issue for calibration? Either way, the unit sounds great, thanks to EmRR and 420Troll for the help!)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: EmRR on July 09, 2018, 05:20:35 PM
find my odyssey about grounding in an OSA rack in this thread.....
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: glazer56 on July 09, 2018, 08:18:13 PM
Thanks,
It looks like Pin 1 does connect to chassis ground in my rack though. Will have to look elsewhere. I still would like to try this in the CAPI rack once i get it operational again.
Thanks
Title: To Build or Not to Build ? CAPI FC526
Post by: jasonashworth on July 12, 2018, 03:25:15 PM
Hello— I'm not sure if this is the right place for this question.  If not, I'd appreciate anybody directing me to the right place.

Essentially I am hoping to build the CAPI FC526 compressor.  I have seen the red text warnings mentioning the difficulty, and wanted to inquire a bit about this.

I have never built a DIY audio electronics kit.  I have, however, built some simple synthesizer circuits on proto-PCB from schematics I've found online, and have CNC milled some circuit boards of my own.  I would say I have a decent understanding of basic electronics/circuits for somebody who didn't study this in school, along with pretty good soldering skills.  I'm also able to follow instructions carefully.

Knowing this, is there anything that might prevent me from being successful on this build?  Other than crowded components and a careful calibration process, what makes this a difficult build?  I've seen people describing issues here and there on this thread, but each seems to be unique to the person and eventually conquered.

Any thoughts or input is greatly appreciated. 

Thanks,
Jason
Title: Re: To Build or Not to Build ? CAPI FC526
Post by: jsteiger on July 12, 2018, 07:25:48 PM
Hello— I'm not sure if this is the right place for this question.  If not, I'd appreciate anybody directing me to the right place.

Essentially I am hoping to build the CAPI FC526 compressor.  I have seen the red text warnings mentioning the difficulty, and wanted to inquire a bit about this.

I have never built a DIY audio electronics kit.  I have, however, built some simple synthesizer circuits on proto-PCB from schematics I've found online, and have CNC milled some circuit boards of my own.  I would say I have a decent understanding of basic electronics/circuits for somebody who didn't study this in school, along with pretty good soldering skills.  I'm also able to follow instructions carefully.

Knowing this, is there anything that might prevent me from being successful on this build?  Other than crowded components and a careful calibration process, what makes this a difficult build?  I've seen people describing issues here and there on this thread, but each seems to be unique to the person and eventually conquered.

Any thoughts or input is greatly appreciated. 

Thanks,
Jason
Hey Jason

I myself don't think its a hard build at all. We have built a ton of them and never had a single issue at the shop. I just think people should be aware that this is not a great first out of the gate project although it sounds like you have some experience. The calibration is probably what scares most people. It is fairly simple once you grasp what is going on. There are a lot of parts and proper identification is the main key.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jasonashworth on July 13, 2018, 01:33:52 PM
Hi Jeff-

Thanks for the quick response.  That's all the reassurance I needed— placing an order this evening.

-Jason
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 15, 2018, 03:33:16 PM
Hi Jeff, hope you had a great vacation. Any thoughts on post #631. Thanks, Patrick
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 15, 2018, 11:08:52 PM
Well Jeff, I feel like a noob. Well I guess I am, this is my 4th build.I tested the fc526 without the jumper last night before your reply. Tested  -10.02V DC at TP9; +2.502V DC at MTR point 11. Applied 1kHz sine wave @ -30dBu. Read .024 at input & output. All good readings. Started the Q bias calibration and read deferent than specs, so tested tp1 and read 0's. Figured it was the jumper so installed the jumper... fired back up and I'm reading 0's at tp9; at meter Point 11 zeros at TP1 zeros. The DT05 over heats. I must have fried something. Any advise on where to start looking? I know your on vacation so take your time getting back and enjoy.
Maybe its a meter resolution thing? Try using a 400Hz tone instead of 1kHz. If the DTO5 is getting hot I would look at that PCB. Something must be wrong there. It honestly seems like there are maybe multiple things going on which makes it very hard from this end.
Title: Re: PR3 Burning - XFMR model
Post by: jsteiger on July 15, 2018, 11:16:09 PM
Hi,

PR3 burning was attributed earlier in this thread to an error on the DTO5 board. However, PR3 is now burning up on power-up with opamps removed.

Any thoughts? All components' placement/orientation checked.

NB. DTO5 (I-)  terminal is jumped to R27 replacing destroyed tracking. Just noting this, though the PR3 issue existed prior to broken tracking.
PR3 goes to the +V pin of the DTO5 and nothing else. Maybe you have a small solder bridge to the ground plane or something? If to wasn't there before and is now it is indeed a solder type issue.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 17, 2018, 03:19:21 AM
Jeff, do you think that when I did the tests, then installed the gar2520 and continue testing without the jumper installed, screwed something up?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 17, 2018, 10:16:36 AM
Jeff, do you think that when I did the tests, then installed the gar2520 and continue testing without the jumper installed, screwed something up?
I don't see how that could but I have never done that myself. The jumper is really only related to the DTO5 amp so should not have taken out the other DC rails.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 23, 2018, 03:35:54 PM
Hi Jeff, I just got back from vacation. I'll start checking all the components on the board. I've already looked for the obvious soldered bridges, diode & capacitor polarity, etc. So far nothing stands out.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Cheadle96 on July 27, 2018, 12:47:48 PM
Can some one explain what RV8 trimmer is doing?   Maybe give a technical reply and a laymen reply for us noobs!  Thanks. 
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 28, 2018, 08:12:53 PM
Hey Jeff, I can't find anything obviously wrong with the build. I'd like to replace the DT05 since all was good until I installed the jumper. How would I purchase one? I can't find it in your store. Thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on July 30, 2018, 10:43:15 AM
Hey Jeff, I can't find anything obviously wrong with the build. I'd like to replace the DT05 since all was good until I installed the jumper. How would I purchase one? I can't find it in your store. Thanks
They are listed here. Just make sure you tell me you need the vertical version for the XFMR comp build.
http://capi-gear.com/catalog/product_info.php?cPath=71_210&products_id=328
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on July 31, 2018, 07:04:14 PM
Thanks Jeff, ordered one last night.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 18, 2018, 02:59:06 AM
Hey Jeff, I just got back to working on the unit so far the pre calibration numbers are fine.

T9 = -10.02 V dc
MTR piont 11 = +2.502 V dc

Insert a good gar 2520 and power up.

Send 1000Hz sine wave @ -30 dBu = .024 volts in and out. All good.

I flip the bypass to act and get 17.20 volts with slight fluctuations. Now if the convertion program I'm using is correct that's about +26.92 dBu.
The needed +7.75 dBu = 1.89 volts. Is this correct?

What are your thoughts. Thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 18, 2018, 10:38:35 AM
Hey Jeff, I just got back to working on the unit so far the pre calibration numbers are fine.

T9 = -10.02 V dc
MTR piont 11 = +2.502 V dc

Insert a good gar 2520 and power up.

Send 1000Hz sine wave @ -30 dBu = .024 volts in and out. All good.

I flip the bypass to act and get 17.20 volts with slight fluctuations. Now if the convertion program I'm using is correct that's about +26.92 dBu.
The needed +7.75 dBu = 1.89 volts. Is this correct?

What are your thoughts. Thanks
Not all DMM's can accurately measure a 1k sine wave. Maybe try using 200Hz or 400Hz. You could also check the specs on your DMM to see what its capable of.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 19, 2018, 03:12:35 AM
I'm using a Fluke 77 iv. Frequency is specifiedfrom 2Hz to 99.99 kHz. The sine wave is being generated from REW EQ Wizard program.
400Hz starting at .025vac in bypass
jumps between 16.80 to 17.10vac. The same results at 200Hz. No lights lit up at start of tests. Clip light is lit  in all tests when switched to act.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 19, 2018, 10:25:25 AM
I'm using a Fluke 77 iv. Frequency is specifiedfrom 2Hz to 99.99 kHz. The sine wave is being generated from REW EQ Wizard program.
400Hz starting at .025vac in bypass
jumps between 16.80 to 17.10vac. The same results at 200Hz. No lights lit up at start of tests. Clip light is lit  in all tests when switched to act.
OK, in that situation, I would "guess" you have some resistors misplaced or problems with an opamp.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 19, 2018, 02:26:35 PM
Okay, I've checked every resistor's color code and they look ok. I haven't replaced the DT05 yet. The gar 2520 came out of a working BT50. My thinking is that something burned on the DT05 when it got hot. Does this sound logical? BTW the diodes on the DT05. The leads from the black band go to the hole with the arrow correct? Thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 19, 2018, 09:08:16 PM
Okay, I've checked every resistor's color code and they look ok. I haven't replaced the DT05 yet. The gar 2520 came out of a working BT50. My thinking is that something burned on the DT05 when it got hot. Does this sound logical? BTW the diodes on the DT05. The leads from the black band go to the hole with the arrow correct? Thanks
Yes the arrow points to the end with the black band.

I think you need to check the audio path test points and find out where this crazy gain is coming from. Just checking the output is not enough.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 20, 2018, 12:56:11 AM
Wow, things didn't go well :-\

With 1000Hz sine @.024v and RV2 fully cw with input and output wide open.

Test points
1 = 0.0
2 = 0.0 to 0.1
3 = - 4.0
4 =  0.?
Smoked PR 2 on main pcb and PR 1 on the meter board. I'm guessing I souldn't have tested T4 at that point?

So I'll need to replace both.
I noticed the gar 2520 got warm before all went south.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2018, 10:17:40 AM
If the PR resistors smoke, you have some build issues related to the opamps and or follower. I believe I have posted what all PR's service above so you can narrow down your mistake. Smoking one on the meter board would tell me an IC is in wrong or you have a direct short on it somewhere.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 20, 2018, 12:14:11 PM
I went through the whole build replies and found.

PR3 goes to the +V pin of the DTO5 and nothing else

PR3 and PR4 are specially for the DTO5 so if they burned you have something wrong on that board

Couldn't  find any reference to PR2.  Also, I don't know what a follower is. Could you explain to a noob. Thanks

And BTW thanks for all the quick repies they're greatly appreciated.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 20, 2018, 09:24:11 PM
Wow, things didn't go well :-\

With 1000Hz sine @.024v and RV2 fully cw with input and output wide open.

Test points
1 = 0.0
2 = 0.0 to 0.1
3 = - 4.0
4 =  0.?
Smoked PR 2 on main pcb and PR 1 on the meter board. I'm guessing I souldn't have tested T4 at that point?

So I'll need to replace both.
I noticed the gar 2520 got warm before all went south.
If you follow my test points guide, TP1-TP3 are for audio so ACV. TP4 is the audio feeding the sidechain rectifier so measuring ACV here should not have blown anything. Possibly a coincidental timing thing with the PR's smoking.

Here are all of the PR uses:
PR1=A1 +V and feed to meter board
PR2=A1 -V and feed to meter board
PR3=DTO5 +V
PR4=DTO5 -V
PR5=2520 -V
PR6=2520 +V
PR7= Discrete follower (Q1 &Q2) +V
PR8= Discrete follower (Q1 &Q2) -V
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 22, 2018, 02:07:55 AM
Well, I screwed the pooch on this. I replaced the smoked PRs and touched up the A1 solder.  But in attempting to remove the DT05 I missed up one of the wholes and its trace on the pcb. So I'm pretty sure it's toast. Would I be able to buy a  partial kit? It's now become a personal challenge to finish this build.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: labomatic on August 22, 2018, 11:25:37 AM
Hi Jeff
Just finished the FC526, sound is perfect, but I have a problem with the metering.
all signal diodes lit.
TP9: -10,01
all values good on metering board.
but TP10 is -1,3v and RV1 & RV8 works, but always around - 1,2/-1,3v
Any clues???
Thanks
Dominique
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 22, 2018, 07:40:12 PM
Hi Jeff
Just finished the FC526, sound is perfect, but I have a problem with the metering.
all signal diodes lit.
TP9: -10,01
all values good on metering board.
but TP10 is -1,3v and RV1 & RV8 works, but always around - 1,2/-1,3v
Any clues???
Thanks
Dominique
Solder bridge or wrong placed resistors?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 22, 2018, 07:41:16 PM
Well, I screwed the pooch on this. I replaced the smoked PRs and touched up the A1 solder.  But in attempting to remove the DT05 I missed up one of the wholes and its trace on the pcb. So I'm pretty sure it's toast. Would I be able to buy a  partial kit? It's now become a personal challenge to finish this build.
It depends on what you need. We aren't equipped to do "partial kits". Maybe send me an email and we'll see what can be done.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: labomatic on August 24, 2018, 02:39:01 AM
Solder bridge or wrong placed resistors?
Everything is ok now. it was a problem in the motherboard ribbon cable connector. I had to remove it and solder a new ribbon directly on the board. When I will do my next order I will ask you 2 new connectors and a ribbon cable... Meter setup was really fast after. Sound of this little thing is just fantastic! Thanks Jeff
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 24, 2018, 08:08:53 PM
Email sent via contact us on your website. Thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 30, 2018, 02:23:53 PM
Sent a follow up email via contact us on the website.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 30, 2018, 09:55:16 PM
Sent a follow up email via contact us on the website.
Sorry I am not getting them. I am receiving others though. Please send to sales at capi-gear dot com.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 31, 2018, 12:44:05 PM
Will do.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on August 31, 2018, 08:35:55 PM
Jeff, I was wondering if the pcb is a multilayered design or is it one set of traces. I have conductivity from all pads to the next point in their trace. Maybe it's not toast after all?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on August 31, 2018, 09:51:24 PM
Jeff, I was wondering if the pcb is a multilayered design or is it one set of traces. I have conductivity from all pads to the next point in their trace. Maybe it's not toast after all?
Its 2 layer only. Top and bottom copper. All pads are plated thru holes.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on September 11, 2018, 05:34:57 PM
Hey Jeff, did you see the email I sent?
Thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on September 12, 2018, 09:44:13 AM
Hey Jeff, did you see the email I sent?
Thanks
Yes. I have been crazy slammed here.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on September 30, 2018, 08:48:13 AM
First time posting.  I built a VP26 and a BT50 - both of which sound great.  After two successful builds I expected my FC526 XFMR to work perfectly too, but my test point data is off, so I'm looking for some help...please. 
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on September 30, 2018, 08:57:32 AM
The voltage at Op Amp +V and -V look okay, not perfect, but I believe they're close enough. 

Voltage at TP 9 and MTR Board #11 are spot on.  Data at TP1, TP2 and TP3 are significantly off target.  What may be wrong or what do I need to investigate? 

Note I'm using my DAW to send 24.5mV AC to the unit at 1,000 Hz and using my Extech EX350 DMM for measurements.  Using SL-Red Dot Op Amp.

Resistance to -V on DOA socket 3.32 kΩ
Voltage at +V on DOA socket:  +15.02 DCV
Voltage at -V on DOA socket:  -14.83 DCV   

TP9 is -10.01V DC
Meter pt. #11   is 2.501V DC      
      
TP1 is 14.79mV AC  (target value = 5.8mV AC)
TP2 is 789mV AC     (target value = 117.7mV AC)
TP3 is 4.66V AC  (target value = 939mV AC)
Module's Output   is 2.511V AC as measured at card edge terminal 4:  "Output - "  (target value = 1.89V AC)
Module's Output is 2.537V AC measured at pins 1 and 3 of male end of output cable  (target value = 1.89V AC)

Thanks,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on October 03, 2018, 09:20:24 PM
The voltage at Op Amp +V and -V look okay, not perfect, but I believe they're close enough. 

Voltage at TP 9 and MTR Board #11 are spot on.  Data at TP1, TP2 and TP3 are significantly off target.  What may be wrong or what do I need to investigate? 

Note I'm using my DAW to send 24.5mV AC to the unit at 1,000 Hz and using my Extech EX350 DMM for measurements.  Using SL-Red Dot Op Amp.

Resistance to -V on DOA socket 3.32 kΩ
Voltage at +V on DOA socket:  +15.02 DCV
Voltage at -V on DOA socket:  -14.83 DCV   

TP9 is -10.01V DC
Meter pt. #11   is 2.501V DC      
      
TP1 is 14.79mV AC  (target value = 5.8mV AC)
TP2 is 789mV AC     (target value = 117.7mV AC)
TP3 is 4.66V AC  (target value = 939mV AC)
Module's Output   is 2.511V AC as measured at card edge terminal 4:  "Output - "  (target value = 1.89V AC)
Module's Output is 2.537V AC measured at pins 1 and 3 of male end of output cable  (target value = 1.89V AC)

Thanks,
Jeremiah
From the manual of your DMM:
(ACV frequency response is 45~400Hz)

That said I would use 100Hz or 200Hz or something as the test tone and not 1kHz.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on October 05, 2018, 10:01:15 AM
From the manual of your DMM:
(ACV frequency response is 45~400Hz)

That said I would use 100Hz or 200Hz or something as the test tone and not 1kHz.

Thanks Jeff.  This also explains the note on your test jig (which I clearly didn't heed) about using 400Hz signal if using a DMM. 

I've run the tests again using your recommended 200Hz, but my test results continue to be similar - well above target levels:

TP1 = 14.6.mV AC
TP2 = 735mV AC
TP3 = 4.32V AC
Output = 2.31V AC

What areas do you recommend I check?  Thanks for your help.

Best,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on October 06, 2018, 01:28:35 AM
I decided to look for bad solder joints, and ultimately decided simply to re-flow all of them, but no significant change: 

TP1 = 14.1mV AC
TP2 = 710mV AC
TP3 = 4.12V AC
Output = 2.21V AC

  :-[
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Homestudio on October 06, 2018, 07:07:51 PM
Hey Jeff, I'd still like to complete this build. Will I need to buy a new kit?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on October 19, 2018, 10:54:51 AM
I decided to look for bad solder joints, and ultimately decided simply to re-flow all of them, but no significant change: 

TP1 = 14.1mV AC
TP2 = 710mV AC
TP3 = 4.12V AC
Output = 2.21V AC

  :-[

I realize Jeff is slammed. Does anyone else have knowledge of this unit and can recommend a place to start investigating? 
Best,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on October 27, 2018, 11:11:58 PM
Jeff, thanks for your help via email:  "TP1 is right after the input stage so check the values of the R's to the right of the 2622. "

I tested all the resistors around the 2622 because I wasn't sure which direction was "right" - depending on the orientation of the board.  Also, I ended up testing a lot more resistors since I had some time. 

I tested the resistors in place on the board with my DMM.  I understand tested values of a resistor in circuit may be affected by other components in parallel so I decided the following:
(1)  If the DMM results equaled the theoretical value, then I considered them okay. 
(2)  If the DMM results did not match the theoretical value, then I checked the color scheme to validate whether the resistor is correct.  I had difficulty determining colors on some of the resistors, so I also measured resistors of the same value in other positions as another means of determining whether the resistor is correct. 

With all of that said, I've attached my data for the resistors that had different measured values compared to the theoretical values and my observations/comments.  Do these data make sense to you or what may be wrong? 

Thanks for your help.

Best regards,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on October 27, 2018, 11:16:01 PM
I've also attached a photo of my board in case you're able to see something that is wrong.
Thanks,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on October 28, 2018, 02:51:07 AM
Final post for today.

After going back through much of this thread again to see if others have had similar issues I did a couple more things:
(3)  I ensured the two 470K and two 470R resistors were not mixed up -- all were correct.  I don't think these are anywhere near my issue, but can't hurt to check.

(4)  I injected the 200Hz signal at 24.5mV AC again to get voltages at R72, R73 and R42 based on previous advise, (though the issue was different in that case -- low voltage readings at TP1).  See attachment. 

I tested these because I don't know how to troubleshoot so I'm doing anything I can to get some data that may help.

Thanks,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on November 07, 2018, 12:08:23 AM
Hi Jeff,
I’m  hoping you can help soon. I’d like to place another order for a second channel strip (VP26, BT50, and FC526), but want to finalize this one first. 
Thanks,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Jeremiah Blair on November 25, 2018, 07:22:32 PM
Hi Jeff,
Per your email regarding some misplaced resistors causing the extra gain issue at TP1, I went through and checked every resistor on the main PCB based on the color bands.  I did not find any mistakes. 

Please review the attached file, which shows the color bands and my reading of the values -- all check out vs. the parts list.  I highlighted the resistors nearest the 2622 in purple (for my own benefit) but don't find any errors. 

I posted a photo of my main PCB above (Reply #409 on: October 27, 2018, 11:16:01 PM) in case  you can spot an issue.

I am hoping you can help. 

Best,
Jeremiah
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jchudyk on December 23, 2018, 08:32:47 PM
Does anyone have any idea what components control the release pot? I have 2 that were workin great, now all of a sudden, on one of them, the release pot doesn’t change the release. It seems to be set to fast all the time. The other works great. Both have been in the same api 6b rack and both have been working fine until recently.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: PerspectiveSound on January 06, 2019, 01:35:48 PM
Hi everyone, I built a new fc526 xfmr, just got the test jig built, powered up, checked opamp connectors and tp9, all good, loaded red dot opamp and began calibration process. In CAPI 511vpr rack with extension jig, test signal from DAW and monitoring signal with Southwire 10040N DMM I ran 200hz sine wave out at 24.5 mV, reading the same in bypass but significantly higher than expected in active with both gain pots all the way up. It was :
output= 2.349 V AC.

Reading the first three test points gave:
TP1= 12.1 mv, TP2= 199.2 mV, TP3= 1.587 V.

I looked through the support thread and did the first step of checking solder points, retouching anything that might be bad but no change. It seemed other people had a similar issue and it seemed possible that resistors near the input could be misplaced but I'm not sure how to test them on the board other than by colored bands. Comparing my board to pictures online of working units I can't see any differences. I'm still a beginner as far as electronics but I have also built 4 vp28s and a bt50 and they all came out well so I'd love to figure out what's wrong. I wondered if the user Jeremiah Blair had any luck tracking down his issue since it seemed similar although with different specific values. Also of course I am limited by my equipment, it is possible that the build is fine and my DMM is not accurately reading the voltage or some other outside issue I'm not thinking of. Any ideas anyone here could give me would be very appreciated, thank you!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on January 08, 2019, 09:17:51 PM
I am wondering if there is a measurement error reoccurring here.

The -30dB test signal should be verified with a DMM set to ACV. Before even looking at the comp or running signal to it...make sure you truly have the proper sine wave level from your generator of choice. With your DMM's black probe to XLR pin 3 and red probe to XLR pin 2, your DMM should show 24.5mV. That is .0245V AC. If the frequency response of your DMM will not read 1kHz then use 200Hz or 400Hz.

When checking the audio path of the FC526 XFMR, the above 24.5mV AC signal will be present at the bottom of R73 (black probe) and R71 (red probe) when the unit is in active mode. This is right after the relay circuit and essentially a "hard wire" to the input XLR of the rack. If your signal here does not match your signal generator then there is a relay bypass circuit problem. No need to go any further with audio path readings.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: PerspectiveSound on January 08, 2019, 11:38:19 PM
Yep, that's exactly what it was, I have a TRS patchbay and I think I was measuring tip to sleeve instead of ring, I checked the pinout and noticed the test signal level was lower than I had been using, from there everything was perfect, just finished calibration. Can't thank you enough, Jeff!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: dansvillalba on January 09, 2019, 07:16:04 PM
Hi! Jeff
A Few days ago I finished to build and calibrated my two FC526 compressors.
Making frequency response test in both compressors , I noticed that one of them had a roll of in  high frequencies.
Why is this happening? Did I make anything wrong?  :-\
Attached pictures with frecuency response of two compressors
(https://rapbwg.bn.files.1drv.com/y4mBFPHLp8yKApdqrNJZYHUpnPl68ifNIS4_qolVUC7laBwvQ1KIDFy-j6H3N_QGR8sMjfCkPupXKezlRx3mLm7uv7yezyZUPG-1GqcG0PdB7PHQIVCNxCmF7RpjetXQdTgnocxBLbM8sS5Jpgisc4iOo5XstsCbQ9O4gT7W2fzSaZTdYORQ7mWsEYkRLT8AEuKscnjV9faEkk9Z8nABf313g?width=885&height=740&cropmode=none)
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on January 09, 2019, 07:32:24 PM
Hi! Jeff
A Few days ago I finished to build and calibrated my two FC526 compressors.
Making frequency response test in both compressors , I noticed that one of them had a roll of in  high frequencies.
Why is this happening? Did I make anything wrong?  :-\
Yeah, looks like something is not right with one of them. You will have to visually compare the 2 units and see where you made the error.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: geardude on January 25, 2019, 08:35:26 PM
EDIT-Confirmed every piece was correct 3 times, touched up any suspect looking joints on the board, and the Dt05 op amp, and now we're golden. So no help needed here, just wanted to update so others who have a similar problem can read my solution.


Hey Jeff so having a little grief here with only one of the 4 comp's I've built... all the other 3 are great, but here's the problem with the one.


Pre-calibration figures are great and all check out. When I get to the q bias and flip the bypass to act I don't get the usual -5ish dbfs instead I get something way lower.

So something's up with the audio path....

Following the steps of the  audio path test these are the figures I'm getting

Tp1- 6 mV AC
Tp2- 3.2mV AC
Tp3-24.8 mV AC

So something apparently is up with TP 2 which if I'm not mistaken points to the DT05.

Now I thoroughly have checked every component on the Dt05 and everything is exactly as it should be.( twice to be sure) One a direct comparison with the other DT05 op amps in the other working modules as well as direct against the BOM.

Now Yesterday I checked every resistor on the meter's ( even though they came out fine in pre calibration) and the main pcb. Everything appears to be as it should so it's really got me scratching my head here.

I'm going to go through and check again to make sure every resistor is correct, I've made the mistake and had a similar result in the past when the 470R And 470K resistors were switched, but that doesn't appear to be the case this time. Any particular place I should look jeff?

Perhaps there's a weak joint somewhere?  The gar2520 is tested and fully functional as well.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: murphster_matt on February 10, 2019, 03:34:30 PM
Too All Guys having problems with TP2 during the first part of the calibration (Q-Bias) on a XFMR model and before you start scrutinizing your DT05 and resistors.....

DOUBLE CHECK YOU HAVE BRIDGED THE JUMPER ON RV7! (that little nugget costed me 4 hours)

I used logic pro x and the built in Test Oscillator plugin, output pointed towards the FC526.

0.0245 V = approx. -30dbu, measure with RMS voltmeter across Pin 2 & Pin 3 XLR out, adjust DAW out to get 0.0245 V and bypass all the patch bays and other crud

Good Luck, Mines Awesome :) Thanks Jeff!!

Matt

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: daveriot on February 23, 2019, 03:31:01 PM
i have two of the rev1 comps. one is working perfectly. the second unit tests spot on with all of the test points except in meter cal tp10 with 7dbu of GR in im getting -0.826 vdc and vr8 does not change this. meter is pegged . Ive gone through the cal several times to determine if i missed something and reread this thread.

any input would be appreciated!
thanks
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 07, 2019, 06:28:06 PM
Has anyone experienced having the Peak LED illuminating as soon as the module is plugged in?

And any issues with getting the MTR TP 11 to read the proper voltage?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 07, 2019, 06:45:10 PM
Too All Guys having problems with TP2 during the first part of the calibration (Q-Bias) on a XFMR model and before you start scrutinizing your DT05 and resistors.....

DOUBLE CHECK YOU HAVE BRIDGED THE JUMPER ON RV7! (that little nugget costed me 4 hours)

I used logic pro x and the built in Test Oscillator plugin, output pointed towards the FC526.

0.0245 V = approx. -30dbu, measure with RMS voltmeter across Pin 2 & Pin 3 XLR out, adjust DAW out to get 0.0245 V and bypass all the patch bays and other crud

Good Luck, Mines Awesome :) Thanks Jeff!!

Matt


What do you mean by "Bridged" RV7 Jumper? I was told to leave that portion blank.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 08, 2019, 10:00:16 AM

What do you mean by "Bridged" RV7 Jumper? I was told to leave that portion blank.
In the BOM it says RV7 is not used and to "Jumper it". On the PCB silkscreen for RV7 it says JUMP and theres a silkscreen line connecting the 2 pads to jump.

IF THIS IS NOT DONE FOLKS YOUR COMP WILL NEVER WORK.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 11, 2019, 01:45:46 PM
So I am encountering an issue where as soon as I plug my module into my rack, the Red Peak LED illuminates, plugging in the module also causes the preamp next to it to peak even though there is no signal going into either module. Please give me any suggestions or ideas on how to fix this issue.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 11, 2019, 09:48:19 PM
So I am encountering an issue where as soon as I plug my module into my rack, the Red Peak LED illuminates, plugging in the module also causes the preamp next to it to peak even though there is no signal going into either module. Please give me any suggestions or ideas on how to fix this issue.
Does the unit pass signal properly according to all of the Test Points?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 13, 2019, 12:00:48 PM
So I am encountering an issue where as soon as I plug my module into my rack, the Red Peak LED illuminates, plugging in the module also causes the preamp next to it to peak even though there is no signal going into either module. Please give me any suggestions or ideas on how to fix this issue.

Someone please get back to me on this. I can't seem to get this issue to stop I've tried everything I can think of!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 13, 2019, 12:32:47 PM
Someone please get back to me on this. I can't seem to get this issue to stop I've tried everything I can think of!
You never answered my question. Have you passed all audio Test Points? Is the unit properly calibrated? What 2520 style opamp is in it and who built it?

It is possible that the peak LED is illuminated and doing its job because you are clipping the unit but you have not given us any other info to go on.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 13, 2019, 01:03:48 PM
You never answered my question. Have you passed all audio Test Points? Is the unit properly calibrated? What 2520 style opamp is in it and who built it?

It is possible that the peak LED is illuminated and doing its job because you are clipping the unit but you have not given us any other info to go on.

Sorry I didn't see your original response. I will do all the tests and calibration etc that I can later today and let you know.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 13, 2019, 01:23:25 PM
Sorry I didn't see your original response. I will do all the tests and calibration etc that I can later today and let you know.
The peak LED is the last thing I would worry about. If your unit is not passing audio or is all jacked up, that could explain the peak LED. BUT one thing at a time.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 16, 2019, 11:35:04 PM
Joe the only thing that's really throwing me off, is why would plugging in the FC526, cause the pre amp in my rack to also peak,  and have the vu meter and peak led indicate that the preamp is clipping???
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 17, 2019, 01:14:30 AM
Joe the only thing that's really throwing me off, is why would plugging in the FC526, cause the pre amp in my rack to also peak,  and have the vu meter and peak led indicate that the preamp is clipping???
Who's Joe?

I have no idea but once you verify that the FC526's audio path is OK or not, we'll get to that.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Mkinsella3 on March 23, 2019, 03:26:19 PM
I didn't realize I needed to keep the VVR FET baggie so I no longer have it. Is there an average bias voltage range that should be seen at TP7?

Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 23, 2019, 04:01:15 PM
I didn't realize I needed to keep the VVR FET baggie so I no longer have it. Is there an average bias voltage range that should be seen at TP7?
I keep records of them all so I can look that up BUT that is not how you bias the VVR FET. Its done by running audio signal and looking for the mentioned amount of dB loss. Have you followed the proper calibration instructions? No where in there do I say to bias that FEY by measuring the DC voltage.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on March 31, 2019, 05:55:40 PM
HI Jeff.

I have an interesting situation that a couple of posts have touched on here, but I don't seem the get resolution from the posts.   I've built several CAPI kits (love em all!), including  a couple of FC526 units.  Both the ones I built work perfectly.   This week, an online acquaintance sent me two FC526 units to calibrate for him.  First unit fired up great, and calibrated with no issues.   7db of gain reduction show 7 on the LED stack.  The second unit passes audio just fine, and I'm able to get 7 db of gain reduction after biasing the FET, but no matter what, the LED ladder is full on all the time.  With gain reduction off, I can get the first LED to come on as it should, but checking test point 9, I can never get the voltage positive, even after sweeping the entire range of the trimmer beside TP 9.  What could this be?   I'd love to fix this for this poor unfortunate fellow, as he's already spent a fortune on shipping, and sending him back one unit with non-functioning meters is not the outcome he expected.      Thanks, and keep up the fine work!
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on March 31, 2019, 06:59:02 PM
HI Jeff.

I have an interesting situation that a couple of posts have touched on here, but I don't seem the get resolution from the posts.   I've built several CAPI kits (love em all!), including  a couple of FC526 units.  Both the ones I built work perfectly.   This week, an online acquaintance sent me two FC526 units to calibrate for him.  First unit fired up great, and calibrated with no issues.   7db of gain reduction show 7 on the LED stack.  The second unit passes audio just fine, and I'm able to get 7 db of gain reduction after biasing the FET, but no matter what, the LED ladder is full on all the time.  With gain reduction off, I can get the first LED to come on as it should, but checking test point 9, I can never get the voltage positive, even after sweeping the entire range of the trimmer beside TP 9.  What could this be?   I'd love to fix this for this poor unfortunate fellow, as he's already spent a fortune on shipping, and sending him back one unit with non-functioning meters is not the outcome he expected.      Thanks, and keep up the fine work!
Highly possible he got the VVR and MTR FET's mixed up. If the pinch off voltage of the MTR FET is not more positive (closer to zero) than the VVR FET, it will never track.

FYI...MTR FET's are usually in the -1.1 to -1.4 range. VVR FET's are in the -1.4 to -1.7 range (when properly biased).
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on April 02, 2019, 12:42:17 AM
Highly possible he got the VVR and MTR FET's mixed up. If the pinch off voltage of the MTR FET is not more positive (closer to zero) than the VVR FET, it will never track.

FYI...MTR FET's are usually in the -1.1 to -1.4 range. VVR FET's are in the -1.4 to -1.7 range (when properly biased).

Thanks for that tip Jeff.   I appreciate that you want to steer this kind of info to the support page so that other may benefit!     I'll quote your email response here for context:

"I would first verify that's what his problem is. One of the TP's is the VVR FET's gate. Depending on your DMM it can skew the reading but I would almost guess that you could check the good one and then check the bad one to see if they are close. I ship matched VVR FET's when someone orders a pair so they should only be off by no more than .005 volts."

So according to the docs:
"TP11 Gate lead of F4 the VVRFET"

So those readings are a good place to start...  I'll check back in when I'm back on the bench.  Thanks for the great service!


Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: santiagoclement on April 08, 2019, 05:40:09 AM
Hi,

I am new building preamps and comp. I´ve just build an FC526 and I would like to know for the bias, how do I monitor the output level with my DMM,? I am using a Daw and a plugin for the sine wave at 1khz.

Thanks in advance.

Regards,

Santiago
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: jsteiger on April 08, 2019, 09:58:23 AM
I am new building preamps and comp. I´ve just build an FC526 and I would like to know for the bias, how do I monitor the output level with my DMM,? I am using a Daw and a plugin for the sine wave at 1khz.
I think it would be much easier and more accurate if you would monitor the output of the FC526 by going back into your DAW.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: santiagoclement on April 08, 2019, 03:55:19 PM
Hi Jeff,

I did apply 1kHz sine wave -30dBu with the fc526 bypass, but i received -60dBu on the output level.  (It seems there is something wrong with the bypass), as it does not let out what goes in) When I flip the Bypass toggle to ACT, I have on the output monitor -22.6dBu, what it is only +8.6dBu. (I did as you said, I monitor the output of the fc526 going back into the DAW)
There is something else. Before I jumped RV7 (I forgot to do it so),  I had 2.498V DC on point #11, but after ding the jumping in RV7, and power in up the module, I find to have 2.616 V on point #11.
Do you know what could be the issue? I also have since the first time I powered it up, all the LED illuminated except the last "20" red LED.
Thabk you.

Regards,

Santiago
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: santiagoclement on April 08, 2019, 04:33:22 PM
This is another picture from the meter PCB
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: santiagoclement on April 10, 2019, 01:58:39 AM
Hi,

Testing the audio path, with 1 kHz sine wave -30dBu, I have:
-TP1=6.8mV
-TP2=118.9mV
-TP3=OL
What could be the issue not to have signal in TP3?

With the FC526 in hard bypass I get very very little signal, nothing to do with what goes in.

I have not seen any issue in the bypass relay. How could I check it out?

Thank you.

Regards,

Santiago
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: Bowener on April 10, 2019, 10:02:33 PM
Thanks for that tip Jeff.   I appreciate that you want to steer this kind of info to the support page so that other may benefit!     I'll quote your email response here for context:

"I would first verify that's what his problem is. One of the TP's is the VVR FET's gate. Depending on your DMM it can skew the reading but I would almost guess that you could check the good one and then check the bad one to see if they are close. I ship matched VVR FET's when someone orders a pair so they should only be off by no more than .005 volts."

So according to the docs:
"TP11 Gate lead of F4 the VVRFET"

So those readings are a good place to start...  I'll check back in when I'm back on the bench.  Thanks for the great service!

Well, I managed to swap the FETs, and the result is still pretty much the same.   After biasing and establishing 7db of gain reduction,  when GR is engaged, I can never get a positive voltage at TP 10, and ALL the LEDs are on.  Aside from that, it sounds great!   When I disassembled it,  I noticed that it wasn't trimmed and cleaned quite as well as I would have liked, but the build is otherwise decent.   What to check next, Obi Wan?
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: santiagoclement on April 11, 2019, 03:51:13 AM
Hi,

Finally I have got TP3. I´ve made a mistake reading it with my DMM.
So testing the audio path, with 1 kHz sine wave -30dBu, the results I have are:
-TP1=6.8mV
-TP2=118.9mV
-TP3=964mV
And output is aprox +7.75dBu

I then continued with the calibration guide, but when I got to "Gain Reduction Meter Calibration", I found that the output pot in Step #11 is in 1:00 instead of 10:00 to get +7dBu. And on TP10 I have DMM DCV = 1.416V. Far away form the +2.487V I should reading.
At the same time, GR switch does not seem to be working.

I then returned to test points guide to test "Sidechain Audio path", I am not able to even start it, as I not able to get the -10dBu Gain reduction. I don´t have any output difference while I engage GR switch. Doesn´t seem to be working or responding at all. So I am not able to measure TP4 TP5 and TP6.

Any tip????

Thank you.
Title: Re: [BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread
Post by: santiagoclement on April 11, 2019, 03:56:34 AM
Forgot to say in my last post that
TP9: -9.96V
Point #11=2.566V