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

[Homestudio]

Thanks Jeff

 

[Homestudio]

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.

 

[glazer56]

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 **** 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!)

 

[emrr]

find my odyssey about grounding in an OSA rack in this thread.....

 

[glazer56]

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

 

[jasonashworth]

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

 

[jsteiger]

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.

 

[jasonashworth]

Hi Jeff-

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

-Jason

 

[Homestudio]

Hi Jeff, hope you had a great vacation. Any thoughts on post #631. Thanks, Patrick

 

[jsteiger]

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.

 

[jsteiger]

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.

 

[Homestudio]

Jeff, do you think that when I did the tests, then installed the gar2520 and continue testing without the jumper installed, screwed something up?

 

[jsteiger]

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.

 

[Homestudio]

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.

 

[Cheadle96]

Can some one explain what RV8 trimmer is doing?  Maybe give a technical reply and a laymen reply for us noobs!  Thanks. 

 

[Homestudio]

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

 

[jsteiger]

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

 

[Homestudio]

Thanks Jeff, ordered one last night.

 

[Homestudio]

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

 

[jsteiger]

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.