[jsteiger]

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.

--------------------------------------------------------------------------------------------------------
September 21st, 2015 Update:
All support docs for this project can be found on the recently added Support Docs page at www.capi-gear.com
--------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------
March 5th, 2016 Update:
Rev B boards are now shipping for the LC53A. To easily identify, the Rev B boards are green and they have the CAPI® label affixed. The receiver circuit has been changed so that a CMRR adjustment is no longer needed. Besides that, most of the circuit is the same. To find out what else has been changed, please read the Rev B Addendum. Like with all projects, it is crucially imperative that you follow the BOM that matches the revision of the PCB that you are building.
--------------------------------------------------------------------------------------------------------

Some details can be found here http://capi-gear.com/catalog/product_info.php?cPath=22_117_119_171&products_id=327



Cheers, Jeff

[jsteiger]

Here are a few pics to help point out some important things. They are not the best quality but will hopefully make their point until 'Chung can work his magic.

Click them to enlarge!!

This is the recommended LED bending.


This shows the standoffs and how the 2 boards fit together.


This shows the proper orientation of the Main-PCB to the steel bracket tabs.


In this pic you can see that none of the leads or solder joints protrude above the steel bracket.

[chunger]

Don't mind me.  I'm just getting situated here.

What's in the box?



A little inventory to get the lay of the land.



I think Jeff has really raised the bar a few more notches on this kit.



OK. . . from the top.  Jeff suggests building the Main PCB first.  The parts needed are pictured below:



Referencing the BOM, I identify and sort all of the electronic components.



Make sure you are able to read the small markings on the ceramic capacitors.



First, I place my resistors.



Then, bend the leads and solder from the back side.



And, we're populating. . . CR1 and CR2 were next.  Generally, I just place the components in order of shortest to tallest.





Polarity matters on the Electrolytic capacitors.  Make sure you align the stripe side with the "-" marked holes.  Also, the longer of the legs on the radial caps are "+".  It does not hurt to triple check these before soldering.





Next, locate the opamp sockets for A1 and A2.



Insert these from the back side of the PCB.



I had to set my soldering temp up significantly to get these to flow in smoothly.  I solder from the back side and attempt to just flow the solder down into the front side of the PCB securing the sockets. 



When new, the sockets are REALLY stiff. . . so, if you are building your own opamps, now is a good time to run one of the loose pins into and out of each socket a couple of times.  This will make initial insertion of opamps much easier and you run a smaller risk of bending pins.



This PCB is now ready for CMRR calibration. . . but, I happen not to have op-amps on hand for the build.  According to Gary's post in this thread, it seems the GAR1731 is a VERY tasty choice for this build and it makes a lot of logical sense in an EQ especially when cranking on those frequencies to have the smooth 1731 in line.  So, for me. . . for this build, I'll start out with some GAR1731's.  NOTE: Please test opamps thoroughly prior to using them in a fresh build.

Since I'm actually building a pair, I will need 4 GAR1731's.  Each EQ requires 2 opamps.  There are a lot of flavors and excellent options available from Classic Audio Products.  I usually default to the GAR2520 complete kits because they have performed really well for me as a nice baseline that is true to the vintage API sound. . . and I'm cheap, but Jeff also carries Scott Leiber's nice red dot and blue dot assembled op amps and for that matter assembled and tested GAR2520 and GAR1731 op amps as options on these LC53A kits.

It's slow but therapeutic to build op-amps, so I decided to build a few up myself.



and, we're populating.

















And there we are. . . 4 freshly hatched GAR1731 op-amps.



With opamps built, I set up for CMR calibration per the VC528 instructions and jeff's assembly aid document posted above.  This is the way I have configured my JLM powerstation for 51X use, and it is handy for testing and calibration on the bench.



In this thread, a very slick calibration adapter is pictured that I think is absolute genius.  Not so much genius but equally functional is my calibration cable that I made per the VC528 CMR calibration instructions with 2 closely matched resistors.  These were the photos taken when I made my cable re-posted here as they are pertinent to this build.





Here I mark the cable so I know it's a calibration cable.





Setting aside the "-" cable on one end to feed identical signal to pins 2 and 3.





and the other end of the cable wired as normal



My test cable complete.



Here, I set up my 400Hz signal on a function generator and send through my special test cable into the main board.  I also connect my scope to the negative side of C2. 





notice, per the instructions, I am using a tested/proven GAR2520 instead of my freshly hatched 1731 for this calibration.  I did confirm on my new opamp though to verify that the setting was the same on the opamp designated for this build.

I also connected the ground of my scope to the common terminal on the other opamp.  It's here that I accidentally shorted the common to the -16V rail and created black smoke on my power supply which required a full stop and a trip to the electronics store



Please use caution if you decide to use this terminal in your testing.  I used it because it gave me a slightly cleaner visual from my scope to observe because I was at the limit of my instrument's ability to read with such a small signal.

With a few twists on the trim pot, I was able to reduce the signal to the lowest measurable level on my scope.



I increased the output of my signal generator a bit so I could see a slight sine wave change continuously all the way through the lowest point of adjustment and set my trim pot there.  Hopefully this methodology is sound.



Previously, I used the DAW method in studio to calibrate my VC528's, but I do not have a functioning DAW currently at my house, so I decided to try the scope this time around.  If I recall correctly, the DAW method was just as accurate if not a bit easier.  Certainly it did not involve frying my test power supply.

[chunger]

OK. . . next we start in on the cut/boost PCB.



First step is to locate and install the sockets for the CT05 and DF.2 opamps and discrete voltage followers.





These are installed and soldered from the TOP SIDE of the PCB.



It cannot be emphasized enough on this step.  Use sufficient heat to smoothly solder these sockets and most importantly. . . USE ONLY THE ABSOLUTE MINIMUM AMOUNT OF SOLDER TO SET THE PART!!! Remove heat and solder IMMEDIATELY when when the solder liquifies and the socket settles into the PCB.



After soldering in these sockets, insert one of the cut-off leads from a large capacitor to break it in as it can be quite difficult the first time a pin is inserted into the socket. 



You may discover as I did on this step that solder can migrate very quickly under this socket and seize up the contact fingers making it impossible to seat a pin.  I fancy myself a rather smooth soldering iron pilot and seldom muck things up, but I managed to mangle 3 of these sockets (3 extras are luckily provided in the kit) by keeping heat on the joint too long and/or using too much solder.  The "C" or common terminals that are connected to the ground plane can be EXTREMELY difficult to remove if they are mucked up.  I found the only way I could remove them was to go from the back side of the PCB and fill the socket with hot solder and push it out the front side w/ the soldering iron.  I almost destroyed one of the pads, but eventually cleared the solder from the pad by using Hakko 808 de-soldering tool on the front side while simultaneously sticking my soldering iron into the pad from the back side.



Rather exciting. . . the 2nd LC53A kit went together without any issues because I remembered to use the absolute minimum necessary amount of solder and keep the heat on only long enough to set the part.



Next, I sort the resistors for the CB board.  There are a few



And, place them on the PCB.



Bend leads to hold the components in place, and solder from the back side.



As recommended by jsteiger in the build manual, I purchased a CHP-170 cutter on Ebay for ~$6.00  It really does allow you to cut close to the PCB as required on this board to provide clearance for the metal frame.





resistors are populated.





One more view of closely-cut leads on the back side of the PCB using the CHP-170 cutters.



Ok . . . resistors are done.  Now for capacitors.



Note the marking conventions on the yellow polyester film caps.



and, we're populating.  Ceramic caps first.



Mind the polarity on the electrolytic caps.  Solid line indicates negative side.







Next, locate the baggie with headers.



And locate these parts.



And install J3 and J4





Use the 3M jumpers to set output load to "HiZ"



Next, locate the baggie with switches.



And pull out SW1 which looks like this.



and install. . .



and trim leads tight to the PCB.



Next, pull out 2 of the grayhill switches.  Make sure to pull the ones with single front pin (some have 2).



And install SW4 and SW6



I solder 1 pin only on each.





and verify that the grayhill is sitting flush to the PCB and the front face is perpendicular.





Once everything is lined up, solder the remaining leads in and trim the leads tight to the PCB.

[chunger]

Next, locate the baggie with stand-offs and mounting hardware.



and pull  3/8" screws and 1/8" standoffs.



Intall screws on the back side of the CB PCB.



And standoffs on the front side.



Center these screws to the best of your ability in the solder pad on the PCB and tighten fully.



Next, dig out the 7 pin header.



And place on the CB PCB.  important: DO NOT SOLDER THIS HEADER AT THIS TIME.



Locate these bits:



And assemble the main PCB to the CB PCB.



Loosely install the long standoffs on the outside locations.





And the crush washer and nut in the middle location.



Place the assembly on a flat, straight surface and set the length from the front of the PCB to the end of the connector pins at 5.87 inches.  I use my trusty dial calipers to make the measurement.



 It may take a few tries to get everything square and correct on the length, but when you have everything lined up, tighten down all of the nuts and standoffs to final torque which is as tight as you can go without breaking anything.



Flip the assembly over, press the 7 pin header towards the main PCB and solder.  Pushing the header this direction makes it so you do not have to cut the pins after soldering as they will sit low enough to clear the metal chassis.



And solder the 7 pin header on the main PCB side as well.



Next find the baggie with pushbuttons and stickers.



and pull the cap for SW1





Next we insert our assembled unit into the metal chassis.



locate these 2 1/4" screws.



and fasten the back side of the main PCB to the chassis after aligning and possibly tweaking the chassis to fit.



temporarily place the faceplate.



Align the faceplate with SW1



and loosely secure the grayhill switches to the faceplate.  Here I am using some console tape over my socket to protect the faceplate from scratches.



Align the faceplate center and dead parallel to the metal chassis so the gaps are even on both sides.





and tighten down the grayhill switches just firmly enough to temporarily hold.

Next, install the LED.  Note:  The short lead on the LED goes into the PCB hole that the arrow is pointing towards.



The leads must be bent to align with the holes.  I also had to sand the ends of the LED with some 220 grit sandpaper because they were slightly too wide to fit into the PCB's holes.



The LED will look something like this with a few 45 degree bends.



Position the 1/2" clear pieces of shrink tubing on the LED's leads.




And position the LED.



Before soldering, grab an available Grayhill switch and insert.



check to make sure the LED leads clear the grayhill switch and will not short to the switch's chassis.



Once confirmed, solder the LED and cut the leads tight to the PCB.



Next, I install the 2 toggle switches.  build manual says to solder only 1 leg of the switch at this time, but since the switch remains in position quite well from friction, I decided not to solder and wait until everything is installed in the chassis.





Next up is SW3 (grayhill switch).  Now that the LED has been installed and positioned, we can place this switch.



Solder 1 pin to hold in place but still allow room for re-positioning.



and make sure everything is tight to the PCB and straight.



Solder the remaining pins and trim tight to the PCB.



Next, locate these header sockets.   It's important to install these on the CB PCB and not the other way around.  If installed on the wrong PCB, they will not fit into the chassis.







Make sure these sockets are vertical and tight to the PCB.

[chunger]

Next, install the output transformer.  Locate the baggie with the transformer mounting hardware.



and locate these parts.





Install flat washers to the 2 long screws.



And insert into the transformer from the top side.



While holding the 2 screws in place with your fingers, install 2 additional flat washers on the bottom side of the transformer.



And place the assembly onto the PCB maintaining the flat washer between the transformer and the PCB.



Add lock washers on the bottom of the PCB.



Install nuts.



Tighten with a screwdriver on the front side after verifying the transformer is aligned with the marked box on the PCB.



Cut, strip and tin the leads 1 or two at a time making sure not to cut too short.



I use small pieces of head shrink tubing to organize the wires as I install them into the PCB according to the marked colors.





And, transformer is installed.



Next, refer to the provided document for CB PCB Grayhill switch stop pin positions and insert the appropriate pins into the 3 grayhill switches.



They should look something like this.  Careful with these.  Drop one on the floor and it may just dissipate into the ether and never be found again.



And install the silver stickers to retain the pins.



Next, I move to the DF.2 discrete follower boards.





Sort the electronic components.



This is my chosen method for installing the pins into the PCB.  (NOTE: This procedure deviates from the recommended build order in the assembly manual)  This is just he way I've grown accustomed to installing opamp pins and I did not feel comfortable risking a solder leak onto the side of the pin that would contact the socket on the PCB for fear of sticking everything together inadvertently.  Jsteiger may very well have much steadier hands and perhaps a finer soldering tip than I am using.

At any rate, I insert pins into the PCB first.



Then, place the discrete follower PCB onto the pins and solder.







I am using the recommended component bending method in the build manual using my smallest screwdriver as a bending tool.



Populating. . . (Note: I deviated from the instructions again in the following sequence because I usually don't like shoving the resistors all the way into the PCB because I like to have a little solder flow onto the top side of the PCB if possible.  Due to clearance issues, I recommend putting theses resistors as low as possible into the PCB as described in the assembly aid document.  The clearances are VERY tight and the final height of the large, yellow capacitors on the LC-EP PCB are unpredictable.  Every thousandth of an inch here helps, so please push the resistors all the way into the PCB.  The build was successful, but I believe I had contact between a capacitor and one of my opamp resistors and had to go back in and jam the capacitor in further to clear.)







Discrete followers complete.





Next, I buid the 2 DTO5 discrete opamps.



Components sorted:



I use the same method to install the opamp pins.





And populate. . .



careful with the diodes.  Make sure the end with the line corresponds to the direction of the printed arrow on the PCB.







Again, watch out for the orientation of the diodes.



And the opamp is complete.





Next, build one more DTO5 discrete opamp.  I did them one at a time because they have a pair of matched transistors that I did not want to get mixed up between the baggies.  If building together, just remember to keep these HFE matched transistors paired together.

Both DTO5's complete.



All CB PCB amps ready to install.





Main PCB and CB PCB complete. . . except for soldering a couple of switches to be complete with faceplate installed.

[chunger]

Next, we do what will hopefully be the final installation of the PCB assembly into the metal chassis.



We will use lock washers now to secure the back of the PCB.  Make sure to push the PCB assemble all the way against the front of the metal bracket.





Next, re-install the faceplate.



and install the supplied nuts.  Do not use the lock washers that came with the Grayhill switches.



This is a temporary placement, so we do not need to crank these down, but we want to align the faceplate so that the gaps on the top and bottom are dead even again.



At this point, solder in the remaining switches on the CB PCB.



And trim the leads tight to the PCB.



Voila!





At this point, we are ready to test and see if the unit passes signal.  Here's I'm setting up to input 1K sine at 4dBu.





And, the output waveform looks good and the level matches at least as far as my meter can tell, so everything appears to be working on this build!



Onward to the LC-EP PCB.



First sort resistors and transistors.



And populate the flat-lying resistors first.



Then move to the free-standing resistors around the grayhill switch.  This is how I set up to solder these in.





And resistors are populated.



Next, install the 5 transistors.



And, we're sorting capacitors.



And, populating capacitors. . .metalized polymer ones here.





Polystyrene caps go in.



And polyester film caps next.  Some of these may need to be jammed pretty hard into the PCB as here is very little clearance available in the sandwich.  Check and adjust as needed.





One lonely electrolytic cap.  Watch the polarity on this one.



Next, install the inductors.



Note the dot on the sticker as well as the diagonal corner at the base indicating the "COM" pin which is labeled and has a square-shaped pad on the PCB.





Solder in the inductors and cut the leads tight to the PCB.



Inductors populated.



Next we install grayhill switches.





Solder one pin and check alignment.







After confirming perpendicular to the PCB as well as sitting tight to the PCB, solder and trim the leads tight.



Next, install toggle switches.





Only solder the middle rear pin on these at this time.  We need a little wiggle room to place the faceplate later.



Next, locate these long jumpers and install.







I solder one pin and then adjust to get them as straight as possible.

[chunger]

Install stop pins on the Grayhill switches next (refer to the proper document and confirm 12:00 and 5:00 placement.



They should look something like this when installed.



And, apply stickers to retain the stop pins.



LC-EP PCB complete.





Next, remove the faceplate from the chassis and insert the LC-EP PCB straight down into the chassis while aligning the 2 long jumpers.  Verify proper seating from the strategically placed vent holes in the chassis.



And install the faceplate.



Carefully align the faceplate so the gaps are equal on the top and bottom sides of the chassis and parallel to the chassis.  Then,  install and tighten down the all of the grayhill switch nuts.







With the faceplate aligned, solder in the 2 remaining toggle switches.



And trim the leads tight to the PCB.



Locate these 2 flat head screws.



And secure the EP-LP PCB to the chassis.



The EQ is now electronically complete.





Verify with a straight edge that there are no component leads or solder blobs protruding above the chassis on both sides of the unit.



Locate the remaining small screws.



And install the metal covers.







using pliers, rotate all of the grayhill switches to the 3:00 position.



And locate the knobs.



frequency selection knobs should be installed first because of this clearance issue.





Install the cut/boost knobs and locate color coded stickers.



Install blue stickers on the frequency select knobs and grey stickers on the cut/boost knobs.



and the build is complete!



Humans win!

[submergent]

anyone having trouble soldering the milmax recepticals into the main board? specifically the "C" one? in both DOA positions i had one hell of a time trying to get solder in there... almost like a giant heatsink on there. Tips?

-pete

(adding)...
same deal with the super little ones for the DVF and the other DTO5s .. the "c" is impossible to solder... is this because these pads are part of the ground plane which takes up a lot of metal on the pcb, sinking most of the iron's heat? should i jack up the heat for these pads? something > 600deg F?

[jsteiger]

Yes indeed that is why. A special note for these is in my nearly finished Assembly Aid document. The C is the hardest to solder and it is because they connect to the ground plane. What temp are you running? I am usually around 740F or so. I have done numerous builds and while not easy, they are always doable. Maybe try tinning the top of the pad without the socket in place. After it cools, drop the socket in and reheat while applying a little bit of solder. One thing to also watch for is the socket sticking to your iron tip when you remove the iron. I try to pull away horizontally, never vertically.

While we are on the subject, one can only solder from the top with these little sockets, never the bottom.

[submergent]

ahh... yes- i'm doing EVERYTHING at 550ish... too low? are you saying you solder everything in this build up in the 700 range? or just the "c" pads?

another question...

in my other builds (vp25s) i inserted the DOA mil max sockets on the top of the PCB and soldered them from the top (the same way you do these little sockets...) this worked fine and the units are all good (and sounding wonderful)... i did the same for the main board of the lc53a here.. and a DOA fits fine, but i'm realizing that there's a lot less room in the enclosure and these may "stand" too high off the pcb... so  jeff... do you think this will be a problem ??

thanks!!

-pete

[jsteiger]

I am always at that temp and never change it.

You should be fine with the sockets for the 2520's the way you have them. The opamps should still sit far below the 2503 right? I would guess yes so no worries.

[submergent]

quick update: bumping up to 700-ish deg. makes the ground plane related soldering much much easier. thanks jeff!

-pete

[jsteiger]

I have added the just completed LC53A Assembly Aid link to the first post of this thread. Please check it out and let me know if anyone finds any silly errors.

BOM's for the larger PCB's are coming in a few minutes.

Thanks for being patient guys! 

[jsteiger]

Links for all of the BOM's and build docs have been added to the first post of this thread. Currently, the only thing I am missing are the docs for the DF.2 and DTO5 PCB's. Will try to get those completed ASAP. I think the above will buy me 16-20 working hours though!

[a zombie]

For the Milmax DOA sockets I first use a flux pen on the pads, top and bottom.  Then I pre-cut six pieces of solder to the same length, then I solder each pin with one piece of solder each, at 750º.  Be sure to heat the pad and socket and not pull out the socket when you remove your iron.  The length of your solder pieces will vary, I use a piece long enough to give me a nice concave volcano, by using the same amount of solder on each one you get a nice consistent look from the top.

I solder the sockets first and use non-noclean solder, clean the board thoroughly, then stuff the rest.

[jsteiger]

Alrighty folks, the DF.2 and DTO5 build guides and BOM's have been added to the first post. That should cover it for build docs. Everything is now complete.

Happy soldering! 

[kante1603]

Alrighty folks, the DF.2 and DTO5 build guides and BOM's have been added to the first post. That should cover it for build docs. Everything is now complete.

Happy soldering! 

Awesome support,a great work you´re doing,I owe you one in advance.
Looking forward to receive my ordered (and paid ) pair,I´m sure I´ll love them.

Best regards from munich,germany,

Udo.

[jsteiger]

Hey guys

I added a few pics to the 2nd post of this thread. They point out a few important things.

I forgot to do the board overlays so guess I am not finished after all!

Cheers, Jeff

[rob61]

Can't find my precision resistors, so can I complete the build and then do the CMRR alignment once its all assembled?

[BUILD] CAPI VP2X~500 Series~Preamp Kit~Official Support Thread

Started by jsteiger « 1 2 ... 48 49 » Preamplifiers

[Build] CAPI VP312~500/51x Series~Preamp Kit~Official Support Thread

Started by jsteiger « 1 2 ... 7 8 » Preamplifiers

[BUILD] CAPI VP312DI~500/51x Series~Preamp + Direct Inject~Official Support Thread

Started by jsteiger « 1 2 ... 18 19 » Preamplifiers

[BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread

Started by jsteiger « 1 2 ... 23 24 » Dynamic Processors