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Project Specific Discussions => Filters/Equalizers => Topic started by: jsteiger on November 04, 2013, 09:44:48 AM

Title: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on November 04, 2013, 09:44:48 AM
Since the kits have started shipping, it's time for the support thread!  :)

**This is a somewhat complicated build. A touch harder than a VP28 but easier than a Love Child. I recommend reading 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.

**Resident build/pic/blogging expert 'Chunger will be working his magic on a build sometime soon. His wonderful photo pics will be in the posts immediately following this one. In the meantime, please use my pdf Assembly Aid for your builds.

--------------------------------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------------------------------


Some details can be found here http://capi-gear.com/catalog/product_info.php?cPath=22_117_120&products_id=222

(http://www.capi-gear.com/catalog/images/gallery/capi_temp/temp-ML2.jpg)

Cheers, Jeff
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: chunger on November 04, 2013, 09:45:36 AM
OK. . . a bit late to the party, but here is a walk-through of the ML2 build top to bottom.  First, let's have a look at the kit components as they come out of the box.  This revision really simplifies the assembly of the Missing Link units and moves this kit from one of the more difficult and involved CAPI builds to an exponentially easier project.

(http://studio939.zenfolio.com/img/s7/v163/p638770515-4.jpg)

(http://studio939.zenfolio.com/img/s5/v129/p753984720-4.jpg)

First, assemble the 2 discrete follower boards.  The parts are contained in this bag.

(http://studio939.zenfolio.com/img/s12/v173/p583922540-4.jpg)

(http://studio939.zenfolio.com/img/s7/v158/p959539848-4.jpg)

It is helpful to organize and sort the parts before assembly.

(http://studio939.zenfolio.com/img/s5/v128/p753871626-6.jpg)

Once all of the components are identified, begin by installing the header.  I clamp the header tight to the PCB and leave 2 pins exposed on one side and solder those first.

(http://studio939.zenfolio.com/img/s12/v181/p1006343920-4.jpg)

Then, re-position the clamp to expose 2 pins on the opposite side and solder.

(http://studio939.zenfolio.com/img/s12/v186/p820266412-4.jpg)

And solder the pins  in the middle with the clamp removed after the outer 4 pins are secured.

(http://studio939.zenfolio.com/img/s7/v169/p1011262126-4.jpg)

A convenient way to bend the resistors for vertical mounting is to use a small screwdriver .

(http://studio939.zenfolio.com/img/s7/v157/p700033559-4.jpg)

And, we populate the discrete follower PCB's according to the BOM and silk screen markings.

(http://studio939.zenfolio.com/img/s6/v134/p791309424-4.jpg)

(http://studio939.zenfolio.com/img/s5/v121/p285757606-4.jpg)

(http://studio939.zenfolio.com/img/s6/v145/p119452973-4.jpg)

(http://studio939.zenfolio.com/img/s7/v168/p203464503-4.jpg)

It is probably optional in this particular build, but I use some 90% isopropyl alcohol and a toothbrush to dunk and scrub the PCB's to remove all of the solder flux.  None of the components on the discrete follower PCB are susceptible to damage from the IPA solution.  If you do decide to clean the board, do not go half way and just dab a few drops of alcohol on the board.  It will just smudge the flux everywhere and make a sticky mess.  Commit and scrub the back side down thoroughly with a toothbrush until all of the flux is dissolved and removed.

(http://studio939.zenfolio.com/img/s7/v157/p44160965-6.jpg)

(http://studio939.zenfolio.com/img/s5/v126/p405191274-4.jpg)

Discrete follower boards assembled and all cleaned up.

(http://studio939.zenfolio.com/img/s12/v171/p147662668-4.jpg)

Next, we procede to the main PCB.

(http://studio939.zenfolio.com/img/s12/v186/p271683667-4.jpg)

The first step in assembling the main PCB is to attache a small sub-PCB for switches.  So, start by cutting apart the sub-PCB's and cleaning up the edges with a file.

(http://studio939.zenfolio.com/img/s12/v179/p411900231-4.jpg)

(http://studio939.zenfolio.com/img/s2/v73/p173112781-4.jpg)

This is the board we are after.

(http://studio939.zenfolio.com/img/s7/v154/p19107180-4.jpg)

And it fits onto the main PCB like this:

(http://studio939.zenfolio.com/img/s12/v179/p442032326-4.jpg)

The board is mounted via plated through holes with component cut-off leads.

(http://studio939.zenfolio.com/img/s5/v123/p222297025-4.jpg)

Once the leads are set in place, the board can be clamped and soldered.

(http://studio939.zenfolio.com/img/s12/v177/p31915777-4.jpg)

And the excess trimmed off.

(http://studio939.zenfolio.com/img/s10/v102/p460157396-4.jpg)

If you have decided to clean off the solder flux from the boards, now is as good a time as any to scrub off the flux with 90% IPA solution.

(http://studio939.zenfolio.com/img/s7/v166/p521915478-4.jpg)

Next, locate the small bag containing the hardware.

(http://studio939.zenfolio.com/img/s5/v120/p269433378-4.jpg)

And locate the discrete op-amp sockets.

(http://studio939.zenfolio.com/img/s7/v155/p50916462-4.jpg)

Insert into the main PCB from the back side and solder in place.  Note: significant heat may be needed to get these pins started.  Aim to flow enough solder into the sockets to bleed onto the back side, but not so much that it goes all the way down and intrudes into the actual pin interface area.

(http://studio939.zenfolio.com/img/s6/v151/p332249735-4.jpg)

(http://studio939.zenfolio.com/img/s7/v169/p209863080-4.jpg)

(http://studio939.zenfolio.com/img/s5/v129/p331048704-4.jpg)

And, while there are few components on the main PCB, it is easy to scrub flux off of the board at this stage.

(http://studio939.zenfolio.com/img/s5/v124/p459808413-4.jpg)

I also noticed that I missed one junction point for the sub-PCB that mounts the push switches, so I insert that now.

(http://studio939.zenfolio.com/img/s10/v108/p336444005-4.jpg)

Next, locate the bag with the electronic components to populate the main PCB.

(http://studio939.zenfolio.com/img/s6/v138/p323532555-4.jpg)

And, we identify the components and organize them for easy access to avoid mistakes.

(http://studio939.zenfolio.com/img/s7/v169/p1035137463-6.jpg)

Pay particular attention to the small diodes because the markings are very hard to read.  CR9 looks like this:

(http://studio939.zenfolio.com/img/s7/v161/p958837975-4.jpg)

And CR10 looks like this:

(http://studio939.zenfolio.com/img/s7/v161/p852784507-4.jpg)

CR1-CR5, CR8, CR11, and CR12 look like this:

(http://studio939.zenfolio.com/img/s10/v114/p971362080-4.jpg)

Next, populate the diodes making sure to set the side with the perpendicular line on the component facing towards the silk screened triangle on the PCB.

(http://studio939.zenfolio.com/img/s5/v119/p586778555-4.jpg)

Take the time to confirm proper orientation of all the diodes.

(http://studio939.zenfolio.com/img/s7/v168/p604969520-4.jpg)

Bend the leads sharply near the PCB to hold the diodes in place and then solder each connection.  The aim is to keep the iron on the piece as short as possible while flowing a nice bead of solder that transfers a to the opposite side of the board, so both sides have a smooth fillet.

(http://studio939.zenfolio.com/img/s10/v102/p628689862-4.jpg)

After soldering, trim the excess leads close to the PCB.

(http://studio939.zenfolio.com/img/s6/v150/p773065756-4.jpg)

(http://studio939.zenfolio.com/img/s5/v118/p866616271-4.jpg)

And, it never hurts to clean the board a bit while we have full access.

(http://studio939.zenfolio.com/img/s12/v172/p862185019-4.jpg)

Next, populate the resistors in similar fashion.  It does not hurt to verify resistor values with a multimeter before bending and inserting them into the board.

Next, locate and identify the capacitors and relays for the main PCB.

(http://studio939.zenfolio.com/img/s6/v144/p788830977-5.jpg)

Pay attention to the polarity of the electrolytic capacitors.  The side with the line corresponds to the "-" marking on the PCB.  The end with the longer lead should go into the side marked "+".

(http://studio939.zenfolio.com/img/s12/v171/p933458142-4.jpg)

Some of the axial capacitors also have polarity so watch for the perpendicular line indicating "-" side.  We want to avoid smoke and excitement when we power up!

(http://studio939.zenfolio.com/img/s5/v118/p777479226-4.jpg)

Here, the capacitors are populated.

(http://studio939.zenfolio.com/img/s10/v109/p667508151-4.jpg)

Next, install the previously built discrete follower boards onto the main PCB.

(http://studio939.zenfolio.com/img/s5/v133/p641021523-4.jpg)

(http://studio939.zenfolio.com/img/s7/v158/p655901077-4.jpg)

Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: chunger on November 04, 2013, 09:45:53 AM
and hold for more pics
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on November 07, 2013, 10:41:29 PM
The first post has been updated with all current build documentation.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: dandeurloo on November 07, 2013, 11:55:00 PM
Finally!  I can't wait to start on a few.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on December 27, 2013, 09:16:17 PM
I have made a few slight alterations to the final steps of the ML2 Assembly Aid. The latest version has been uploaded for your viewing pleasure.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on January 27, 2014, 07:14:27 PM
Is there a CMRR adjustment guide for the VC528 ML?  I've been reading over the CMRR guide for the VC528 ST2 but there seem to be difference.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on January 27, 2014, 07:28:48 PM
The overall concept is identical to the first version. Most people have been buying my Extension Jig which has the proper R's fitted to it as well as instructions. There is a pic in the ML2 Assembly Guide that shows where to measure the signal.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 01:04:38 AM
Well, I had a good time building the gar2520 DOAs and the VC528 ML2 but now I'm stumped.

After finishing the build I ran the CMRR calibration with the CAPI extension jig.  Everything seemed to go fine but now that I'm running audio through it I find there to be a serious lack of low frequencies.  The frequency response starts to roll off around 4K and at 100Hz the unit shows -13db from flat.  There is also a less pronounced high frequency roll off.  I swapped A3 with A4 (DOAs) and while this had just the tiniest affect on the frequency response of the unit it did create a 3.7db drop in the output.  You can view a frequency response chart below. I generated this by sending a 20Hz to 20K sine wave sweep through the unit both before and after swapping A3 with A4.

I built the DOAs from the kit available from classicapi.com.  I'm hoping someone here can help me out. Does the information above give any hints that my problems might be with the DOAs?  Does the -3.7db output drop give an indication of which DOA might be the problem?  I don't have any other units to swap these into for testing so I'm wondering if I should buy another DOA kit or spring for one of the fully built & tested 2520's.

Any suggestions would be greatly appreciated.

Thanks.

p.s. One other detail about the testing of my VC528: The wacky frequency response curve is unaffected by the bypass switch. If I toggle it into bypass the lows freqs still roll off but the overall output of the unit jumps up by 8db.

(http://vid.firepixie.com/skitch/VC528_freq_response-20140202-134847.png)
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 03, 2014, 09:46:36 AM
Well it seems like there may be a few issues coming into play. The bypass switch is a hard bypass so the relays directly connect the input pins to the output pins. So if that part of the circuit is working properly, the odd freq response is not module related but coming from the rack, cable, interface etc. You can check continuity while using the extender card. When bypassed, card edge pin 2 should connect to pin 10 and pin 4 should connect to pin 8. You should also be able to hear both relays clicking when flipping the bypass/active toggle.

The fact that there is a level change when swapping opamps, definitely suggests one or possibly both of the opamps have issues.

It is very hard, typically impossible to troubleshoot a fresh module build with 2 fresh opamp builds. You need something known and good to test the opamps in or known to be working opamps to test in the ML2. I would suggest a couple of prebuilt opamps of some sort like maybe a pair of red dots from Scott.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 10:48:31 AM
Yeah.... too many variables.  I get it.  I just emailed Scott Liebers about purchasing a couple of his opamps.  Thanks for the tip on checking the bypass switch.  I'll poke at that and report back when I get the red dots. 

Thanks again.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 04:00:35 PM
Well it seems like there may be a few issues coming into play. The bypass switch is a hard bypass so the relays directly connect the input pins to the output pins. So if that part of the circuit is working properly, the odd freq response is not module related but coming from the rack, cable, interface etc.

I ran a sweep through my converter, through the rack with a different module (bypassed) and back and I got a very flat response.  There was a bit of a roll off in the very low freqs but nothing like what I get with the VC528.




You can check continuity while using the extender card. When bypassed, card edge pin 2 should connect to pin 10 and pin 4 should connect to pin 8. You should also be able to hear both relays clicking when flipping the bypass/active toggle.


Well... I seem to have a problem with my bypass circuit.  I get continuity between 2&10 as well as 4&8 all the time.  Regardless of the switch position.  When I flip the switch to ACT I can hear at least one of the relays click but when when I flip the switch up into the BYPASS position all I hear is the switch, I hear no relay clicking.

I checked the solder points on the switch and the relays.  I double checked the polarity of the relays as well as the diodes around the general area. I looked up the datasheet on the switch and checked it's terminals in both positions and it's functioning correctly.  There's something obvious that I'm missing.
 :-\
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 03, 2014, 04:37:54 PM
Can you post a pic of that section of the board? The most common error is not identifying the 4V3 zener diode. The bypass switch is either connecting ground to the relay control circuit or leaving it open.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 05:31:57 PM
Here you go:

Pic 1
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 05:32:33 PM
Pic 2
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 05:32:59 PM
Pic 3
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 05:35:24 PM
Pic 4
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 05:36:26 PM
Pic 5 (the back)
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 03, 2014, 07:00:01 PM
Well, nothing is jumping out at me but I also cannot tell the parts numbers on CR9 and CR10.

Do the Bypass status LED's work as expected?
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 03, 2014, 07:38:53 PM
Yes, the bypass LEDs work correctly.  With a magnifying glass I can make out "4v3" on CR10 and I think "24" on CR9.

Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 03, 2014, 08:24:35 PM
OK, I would like you to check continuity at the pins of each relay. You will have to do this from the bottom of the PCB. The attached screenshot is a view from the top side of the PCB so keep that in mind when looking at the bottom of the board.

In BYP, pin 3 should connect to pin 2 and pin 8 to pin 9.

In ACT, pin 3 should connect to 4 and pin 8 to pin 7.

Check both relays.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Sparqee on February 04, 2014, 06:36:00 PM
First of all let me say thank you for all your help Jeff.  You kept me from feeling adrift on a sea of ignorance.  Your troubleshooting process was specific and easy to follow.  However.... it seems that my final solution was..... magic.  :/   I'm not sure I believe in elves that come to my workbench late at night and fix my broken projects but.... <shrug>

Let me back up.  Yesterday I took the PCB out of the metal L bracket to inspect the solder points.  Today I hooked the PCB up to the test jig and got correct results from testing the relay pins.  I didn't expect that so I ran my sine wave sweep though the module and lo and behold I got an excellent frequency response through my analyzer plugin.  I ran more tests: bypass in and out, filters in and out with varying slopes and cutoff points.  All of it looked excellent on the scope.  I ran some music through the module and it sounds fantastic.

I'm not one to look a gift horse in the mouth but.... WTF!?  I seriously pondered over whether my testing had been flawed but from the beginning I could hear the extreme low frequency roll off.  I tested the module in two different 500 racks and I checked the freq response of my converter, patchbay, rack and other 500 modules.  I tested the VC528 after swapping the DOAs and got different but equally messed up results.  Yesterday the bypass switch did not affect continuity between edge pins 2&10 or 4&8 yet today bypass is working correctly.

Yesterday I did touch my soldering iron to the solder points on the bypass switch and the relays.  Perhaps my memory fails me and I didn't retest after that?  I thought I was being pretty thorough as I went through step by step. Testing after each change.  I also hot touched the legs on one of the DOAs but again I could swear I tested after that and got no improvement.

Well, the most important thing is that I now have my VC528 working beautifully.  Yesterday I went ahead and ordered a couple of prebuilt 2520's from Scott Liebers but that's ok.  I'll use them when I build my second VC528.  ;)  I suppose I'll put one of his and one of mine in each module for balance and hopefully I won't have so many problems with the second build, or if I do perhaps my late night elves will sneak in and fix that one as well.  <shake head>  Really.... it's enough to make me question my sanity.

Thanks again.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: OOstudio on April 06, 2014, 05:16:59 PM
Hello all,

I just built a module. I ran the calibration, and everything is fine. I didn t have the time to test the ML2 in a session, but I think that it will be a great tool in my studio.
I just have a question. I have a doubt on the booster amp. Unity gain is ok. And when I turn the knob, the sound decrease. I understood that it's 3 db more, but i m not sûre. Somebody can confirm ? It seems logic with the sens of rotation of the knob.
Thanks a lot.
Luc
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on April 06, 2014, 05:48:18 PM
Luc, I am not exactly sure of your question?
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: OOstudio on April 06, 2014, 05:51:49 PM
Excuse my french  :). I ask if it s normal that the output signal decreases when I turn the trim knob from 0 to 3.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on April 06, 2014, 06:51:54 PM
Oh yes, this is as designed. The trim switch is configured so each step from 0 is another -.5dB.  :)
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: OOstudio on April 07, 2014, 02:44:43 AM
Great. Thanks à lot Jeff. I don t know why I had this doubt. Maybe because of the name "booster amp".
So, Everything is fine. As usual, very good kit, easy to assemble, and super quality!
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: OOstudio on April 16, 2014, 04:54:26 PM
Hi all.
I just finished my second ml2. I will calibrage this second unit tomorrow.
I d like to be sure that i understood the use of the j2.1 jumper regarding the link for bypassing 2 units.
My rack is a 51x rack from Volker.
2 questions:
-Must I use the link jumper on the rack backplane ?
-Must I use the link jumper on the both units, or only on one of them (to create a master / slave fonction).
Thank you in advance.
Best.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on April 16, 2014, 06:46:44 PM
Hi all.
I just finished my second ml2. I will calibrage this second unit tomorrow.
I d like to be sure that i understood the use of the j2.1 jumper regarding the link for bypassing 2 units.
My rack is a 51x rack from Volker.
2 questions:
-Must I use the link jumper on the rack backplane ?
-Must I use the link jumper on the both units, or only on one of them (to create a master / slave fonction).
Thank you in advance.
Best.
To link the bypass function between 2 ML2 modules, flip the backplane switch (or shunt jumper) between the 2 slots. Then move both of the DC link jumpers on both ML2 modules to Y for yes. This way, one bypass switch will indeed activate both modules into bypass (or not).
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: fragletrollet on February 17, 2015, 10:19:50 AM
Whatever happened to the rest of Chunger`s log?
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 17, 2015, 10:24:37 AM
Whatever happened to the rest of Chunger`s log?
I know he became very busy with his mic's. I will ask him. Last I heard he was pretty much done with this build/pics.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: kvothe on February 24, 2015, 08:03:19 AM
Hello everyone!
I went ahead and build 2 ml2 last week, now I am doing the pre-power measurements for the o to c sockets of the doas.
On A3: c-o 520kohm
On A4: c-o 1.5mohm
In the PDFs it is said to be the same reading for both, or doesn't it matter as long as it is over 100kohm?
All c-v measurements are ~250kohm

Have a great day everyone!


Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 24, 2015, 09:33:44 AM
Those will be fine.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: kvothe on February 24, 2015, 11:19:54 AM
Thank you Mr Steiger,

I went ahead and calibrated rv1, but with rv2 I am can only get to about 1.3dB over 0. The pot clicked and I need another 5 turns i would guess. (Anticlockwise)

Anybody had a problem like that? Otherwise everything is working correctly and I will put the next one on the table to check.

Kind regards, Kvothe
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on February 24, 2015, 11:32:43 AM
.....but with rv2 I am can only get to about 1.3dB over 0. The pot clicked and I need another 5 turns i would guess. (Anticlockwise)
This is not right. Something is wrong somewhere. There should be plenty of adjustment available. Are the opamps kits or pre-built?
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: kvothe on February 24, 2015, 05:46:06 PM
Thank you for trying to help.

They were kits, gar2520  already in use with my vp28, I also checked with 3 different pairs of red dots, still the same readings.

The other unit has the opposite problem, very little level when active, rv2 does not change anything and the fader only works until ~-34, then no gain changes until 0. From 0 to 12 again, more level, but not enough. It looks like trim is working. Filters do work, but every change clicks or pops.

Again your help and the help of those who already build a kit is very much appreciated.

I will chek my soldering and could post pictures of the areas where the problems are most likely.

Thank you!

Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: kvothe on March 01, 2015, 10:28:56 AM
I touched up every solder joint on the second unit, but no changes in behavior. When the unit is in bypass, it passes audio normally. When active the fader has no real use except for the very first click and the clicks after 0.
Could the fader be damaged, or maybe the relays?

Could someone help me out?
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on March 01, 2015, 10:55:05 AM
It is extremely unlikely that there's a problem with the fader switch. The bypass is a hard relay bypass which directly couples the input to the output so no signal runs thru the module. I suppose pulling the opamps and toggling between bypass and active would tell you if the relays are working properly. With no opamps installed, no signal should pass when in active.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: mxz174 on August 02, 2016, 06:56:33 PM
I've already sent an e-mail to Jeff, but then I came across this support thread and figured I'm post it here as well.  Just in case Jeff would rather respond here, or when we figure out the fix I can let everyone on this thread know so they have more information to go on.

I built a pair of VC528 ML2s.  One checks out perfectly.  All knobs, filters, the fader, switches all work great.  CMM worked and done and unity gain adjustment completed.  The module sounds great!

Now the other one is almost perfect as well.  Same deal that all features work just fine, and the module itself even sounds very good when music is put through it.  The only problem is the unity gain adjustment.  I'm in the right range but can't quite get to unity gain.

I'm using a 1kHz sine wave input.  The input level is coming out as -13.4dB.  The full range of the adjustable pot takes the output from -22.2dB to -19.4dB.  I have the trim spot clicking but can't get higher than -19.4dB. 

On the 'good' module my range of adjustment goes from -15.1dB to -12.3dB.  So the full range is right about the same for both modules, just that the one has a lower overall offset.

I've tried testing out both modules now with a handful of different op amps and get exactly the same results for both, so I know it's not the op amps.

Here's another interesting piece of the puzzle, on the resistance tests i always get ~200kOhm on each of the +V and -V to C points, as well as the O to C points EXCEPT on the one module that is 'bad'.  On that module the O to C resistance for A4 (booster op amp) is 4.5M Ohm.  Now I know that the trim pot is controlling the output level of this op amp... so this looks like it could be the key to what's going on.

If Jeff is out there listening, or anyone else for that matter that has experience here let me know if you have any ideas.  As I said both modules sound really good as is on music, if I can just get that unity gain level up a bit on the second module I'll be in business!
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: trumanaudio on January 25, 2017, 06:24:18 PM
Ok, hopefully someone out there can stear me straight!

I've got a Missing Link.

I have a 400Hz sine running into the test jig, test jig into the ML, then into another channel on my DAW

The unit is active with the fader and trim set to 0

With the CMRR switch engaged on my daw, I can use RV1 to achieve the lowest value.

When I disengage the CMRR switch and try to adjust for unity gain, using RV2, nothing changes.

What could possibly be wrong? I'm using two gar2520s and I don't know where to start to look for problems.

Thanks.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on January 26, 2017, 11:27:56 AM
@trumanaudio, are the opamps you are using tested in something else so you are 100% sure they are solid? That is always the very first thing to rule out.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: trumanaudio on January 26, 2017, 11:48:01 AM
I haven't tested them in something else. I am getting pre-built opamps tomorrow that I will try.

Just seems strange because both units Im working on are functioning in the same way, same issues, and with 4 different op-amp kits.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on January 26, 2017, 12:18:38 PM
I haven't tested them in something else. I am getting pre-built opamps tomorrow that I will try.

Just seems strange because both units Im working on are functioning in the same way, same issues, and with 4 different op-amp kits.
There is likely some other issue then. Maybe something is wrong with your testing setup. Do these modules pass audio close to unity gain? I would reset the RV2 trimmers to half way. Do this by turning them repeatedly one way until you here a slight click coming from the trimmer acoustically. Then count 12.5 revolutions back the opposite way. This should be close to mid value. IIRC throughput signal will be .5dB or so low. If yours its drastically off from that then there are bigger issues at play here.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: trumanaudio on January 26, 2017, 12:47:31 PM
Maybe I'm sending a -10dBV signal into the ML2 but monitoring the output of the ML2 at +4dBu? I dont know how I would correct this using my DAW (Logic 9)
I will be using legit testing equipment tomorrow.

they both come back in at -19dB when bypassed and -20dB when active, after I reset the trimmers. Ill do what I can to eliminate the opamps, sine wave, and monitoring setup tomorrow as possible problems.

If the monitoring is the problem, that still wouldnt account for the RV2 not adjusting the signal, correct?

The Fader works as it should and the last 2 clicks bring up the crazy harmonics that are happening. I think it is something with my monitoring setup
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on January 26, 2017, 12:55:58 PM
Or the opamps are problematic and/or maybe the DF's.

You should be send a balanced +4 signal in and expecting the same thing out.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on January 08, 2018, 04:11:36 PM
I emailed Jeff to ask this but its been a week with no reply.

Does anyone who has some of these know what the current draw is? Trying to build a mixer with TAC racks and hoping to power 3 with one PSU.

Thanks!

Monte
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on January 08, 2018, 07:20:57 PM
I emailed Jeff to ask this but its been a week with no reply.

Does anyone who has some of these know what the current draw is? Trying to build a mixer with TAC racks and hoping to power 3 with one PSU.

Thanks!

Monte
Sorry I must have missed the email. Things get hectic around here. I have not had a built unit here in ages but don't think they were much over 75mA per rail per unit.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on January 10, 2018, 09:05:21 PM
Sorry I must have missed the email. Things get hectic around here. I have not had a built unit here in ages but don't think they were much over 75mA per rail per unit.

Thanks Jeff!

No worries. I know you are super busy. So so SOOO stoked for the summing mixer. Photos on IG look amazing.

Thats good news for me! Cemal said as long as its around 100ma we can make it work. Thanks!
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on February 20, 2018, 06:24:14 PM
Jeff,

Do these have pin 7 and 9 active? I just figured out that to do send and returns on my new 500 chassis that it uses pin 7 and 9 for the send and return. Hoping to use these as the faders for a mini 500 series console with this chassis, but if the ML2 doesn't us pin 7 and 9 then not sure what ill do.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on February 20, 2018, 06:50:34 PM
Dang I found Chugger's full build write up and was able to count the card..no 7 or 9 on the card.


Well....crap. So much for that idea.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: ninopelo29 on December 31, 2019, 11:00:11 PM
Hello,

I own two ML2 Rev B.3 units and one of them has an issue with the LED's for Bypass and Actuate: neither will light in either position of the respective switch.

I pulled the unit and PR4 is completely burned. It still reads 9 ohms in-circuit (PR3 is reading as 10.1 ohms), but it is clearly damaged.

I can replace the resistor, but I imagine there is another issue that is causing the current to be too high through that resistor.

Would you be able to provide a bit of direction of what could be wrong? I am able to read schematics and repair the unit if you see fit to send me one.

Thanks for your help.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on January 01, 2020, 12:14:40 PM
Hello,

I own two ML2 Rev B.3 units and one of them has an issue with the LED's for Bypass and Actuate: neither will light in either position of the respective switch.

I pulled the unit and PR4 is completely burned. It still reads 9 ohms in-circuit (PR3 is reading as 10.1 ohms), but it is clearly damaged.

I can replace the resistor, but I imagine there is another issue that is causing the current to be too high through that resistor.

Would you be able to provide a bit of direction of what could be wrong? I am able to read schematics and repair the unit if you see fit to send me one.

Thanks for your help.
The LED circuit for this build is very simple. I would first think that you have them in backwards.

PR4 is the power damping R for A3, the receiver opamp. You have a build error on that opamp or it is not seated fully.
https://capi-gear.com/catalog/DOA_Install.php
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: ninopelo29 on January 02, 2020, 10:09:18 PM
Quote
The LED circuit for this build is very simple. I would first think that you have them in backwards.

PR4 is the power damping R for A3, the receiver opamp. You have a build error on that opamp or it is not seated fully.

SOLVED: The LEDs were installed correctly, but one was making contact with one of the pads from the Bypass switch, so it was shorting out. I added shrink tubing to keep things copasetic. Something to check for anyone experiencing dead Bypass LED's.

The burned resistor (PR4) is a bit more mysterious. I replaced it with a similar 10 ohm resistor and measured the current with both a known-good Receiver amp and the "bad" one and read 0.02A on both.  I let it run for about 30 minutes with no issues.

Initially I thought the shorted LED might have drawn excessive current through PR4, but after taking the whole thing apart, I discovered that the LED's are connected before the damping resistor.  Current thru PR4 is only for Receiver +V.

I've had power issues recently that have caused some power supplies to get damaged. It's since been fixed by the power company, but maybe this was another casualty. Maybe the Receiver re-seat did the trick?

Not sure, but everything is good now.  Thanks, Jeff! :)
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on May 02, 2020, 01:12:59 AM
Hell Jeff,

I have one unit calibrated, went smoothly.

2nd unit thought quite odd. The level is is almost 45dB different. It is lower, signal going out is -14.8dBFS(+10dBu) and return is -42.4dBFS.

Obviously the trimmer does not have enough in it to get it back up to where it needs to be. I've looked at all the resistors and they appear to be correct with the calibrated unit. No Caps are backwards. Is there somewhere I should look specifically?

These units are stock by the way, not modded.

Thanks!

Monte
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on May 02, 2020, 01:35:26 AM
Hi Monte

I would first rule out opamps, if they were built from kits.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on May 02, 2020, 10:32:28 PM
Hi Monte

I would first rule out opamps, if they were built from kits.

Hi Jeff,

Definitely not the op amps. I'm using two Rogue5s from LTLO. In fact to make sure I used the same two in the first unit that calibrated just fine.

Monte
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on May 02, 2020, 11:07:14 PM
Hi Jeff,

Definitely not the op amps. I'm using two Rogue5s from LTLO. In fact to make sure I used the same two in the first unit that calibrated just fine.

Monte
OK since you have a good module, inject a sine wave and measure AC voltage at the Test Points. Notate all of you readings on the good one. Then do the same on the bad one and report back where things go bad.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on May 03, 2020, 11:35:37 AM
OK since you have a good module, inject a sine wave and measure AC voltage at the Test Points. Notate all of you readings on the good one. Then do the same on the bad one and report back where things go bad.

               
Hi Jeff,

Here are my measurements.



                 Unit 1   Unit 2
TP +1   1.718   1.716
TP -1   1.728   1.729
TP 2   1.708   1.706
TP 3   3.043   3.042
TP 4   0.75   0.04
TP 5   0.748   0.04
TP 6   0.744   0.04
TP 7   0.742   0.04
TP 8   0.742   0.04
TP 9   1.775   0.078


Something g definitely off from TP4 onwards
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on May 03, 2020, 02:33:27 PM
               
Hi Jeff,

Here are my measurements.



                 Unit 1   Unit 2
TP +1   1.718   1.716
TP -1   1.728   1.729
TP 2   1.708   1.706
TP 3   3.043   3.042
TP 4   0.75   0.04
TP 5   0.748   0.04
TP 6   0.744   0.04
TP 7   0.742   0.04
TP 8   0.742   0.04
TP 9   1.775   0.078


Something g definitely off from TP4 onwards
The only things between  TP3 and TP4 are the output transformer T1, the stepped fader and the trim switch. I would make sure that the fader is set to 0 and then first probe at the T (top) of the fader connection.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: Blackdawg on May 03, 2020, 05:29:50 PM
The only things between  TP3 and TP4 are the output transformer T1, the stepped fader and the trim switch. I would make sure that the fader is set to 0 and then first probe at the T (top) of the fader connection.

Think I figured it out.

the Elma switch wafer is backwards. The cable connections on the working unit face towards the bottom of the module. On the one that doesn't the wires are on the top.

I confirmed this by twisting the knob. While running -12dBFS to the unit, where 0db is marked my output measures -38.7dB. The -12dB mark on the faceplate shows -1.7dB.

To get it where I think I could trim it with the timmer I have to go to -24dB on the Faceplate. Then its at -13.1dB.

So will take the wafer off and swap it!

The Key on the switch is facing all of the green SMDs and should be facing the Black correct?



Edit:

That fixed it. My Elma wafer was backwards. easy fix!
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: grievousangel on August 29, 2020, 11:28:28 AM
Any idea why I am seeing ~ 4VDC at the ML2 output? This seems like an usual  failure point ... has anyone seen this before?

This happens only if ML2 is active and A3 or A4 is installed.

First thought was something related to K2 (relay that by-passes A4/T2 ouput. Looking in this area now.  Appear OK so far. I checked all diodes for proper junction voltage drop, all OK.

I am also looking at the DF.1 (A1 and A2).

Not likely a bad 2520 right? I see the DC when either A3 or A4 is plugged in.

CMR adjustments would have no bearing on this correct?

Since this is  a coupling capacitor design, I would think a electro capacitor related issue, but test OK so far.

TP V+ / TPV- read as expected, ie. ~ Input voltage.

Suggestions?

Thanks.
Title: Re: [BUILD] VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: SoundStudio412 on August 29, 2020, 12:23:27 PM
The overall concept is identical to the first version. Most people have been buying my Extension Jig which has the proper R's fitted to it as well as instructions. There is a pic in the ML2 Assembly Guide that shows where to measure the signal.

Is there any more detailed information on the CMRR final adjustments? I'm really struggling to understand the directions and can't find any other resources on this.

Thanks,
-G
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: jsteiger on August 30, 2020, 02:59:20 PM
4 volts of DC at the output is not likely since the final output transformer would be blocking DC. I suspect you have a problem with the relay circuit.
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: grievousangel on August 30, 2020, 03:13:47 PM
4 volts of DC at the output is not likely since the final output transformer would be blocking DC. I suspect you have a problem with the relay circuit.

Thanks. I'm digging around in the relay circuits now.
 
Title: Re: [BUILD] CAPI VC528 ML2~500 Series~Missing Link 2~Official Support Thread
Post by: grievousangel on August 30, 2020, 03:34:15 PM
Has anyone building a ML2,  found  their Elma fader with the rear PCB wafer (SMT side)  NOT facing  the front faceplate?

It was posted a little while back that his gain structure was off a few steps due to due the SMTs on his Elma were facing the ML2 faceplate and NOT the rear. He said it corrected his problem.

My Elma's wafer PCB SMTs are facing the front which seems to agree with Elma's Web site product date sheet.

I am having  some ML2 issues and ran into his post while checking the ML2 post out.

Later.