[BUILD] CAPI LC53A~500 Series~Love Child EQ Kit~Official Support Thread

[fancytimestudio]

And the top.

 

[jsteiger]

I would reflow the points on the bottom while heating and adding a touch more solder. Its hard to tell in the pic but a few of them look like they could use it.

On the top, I should have been more clear but I wanted to try and verify all of the components and their placement.

 

[fancytimestudio]

My apologies. Were the quality of photo good enough? They look a little blurry on here... I'll do the soldering and if that doesn't fix the problem post some more helpful photos. Thanks again Jeff!

 

[fancytimestudio]

Here is pic 1

 

[fancytimestudio]

Pic 2

 

[fancytimestudio]

pic 3

 

[fancytimestudio]

Pic 4

 

[jsteiger]

OK, is it possible that two of transistors got mixed up? You would have to gently pry the adjacent ones apart so you can read the part #'s on them. Besides a cold solder joint, there is not much left on the board. The R's and diodes look placed correctly.

 

[fancytimestudio]

I checked the transistors and they are all in the correct places. I'm going to try one more time to dump a bunch of solder on this puppy and if that doesn't work I might just hit you up to get another one. I really appreciate you taking the time to help me solve this. Thanks a bunch Jeff!

 

[fancytimestudio]

Hey y'all, after ordering a new DTO5 from Jeff I’m still having issues with this. The new DTO5 worked for about 10 seconds, then distortion. I pulled the transistors and found a bunch of the 2N5088 and 2N5087 transistors from both the old opamp and the new one were open or shorted. I ordered a bunch more from a parts distributor and replaced them today.  After replacing Q3, Q4 ad Q5 I plugged it back in and it sounded clean for about 10 seconds and then smoke and distortion from the opamp that’s been giving me trouble. I'm thinking that there is something surrounding the opamp it that isn't working properly. Do you have an indication of voltages from different test points on the module? This thing is starting to drive me nuts! Any help is much appreciated!

 

[jsteiger]

I would start by measuring the +/- voltages at the opamp sockets.

 

[fancytimestudio]

They all look the same at around 15v dc at all 4 points.

 

[fancytimestudio]

Could be closer to 16v but I'm on an analog meter.

 

[fancytimestudio]

Ok, depopulated the transistors. Q3 tested good but Q4 and Q5 are no good.  The smoke came from R5 and R6 which are totally fried now. Not sure if this helps.

 

[fancytimestudio]

seeing some variation in the diodes... I'm going to suss this out and post my findings.

 

[fancytimestudio]

So one of the diodes in the new (D1) DTO5 wasn't working properly (chicken and egg scenario, not sure which issue caused what, perhaps I was a little too beast-like when I bent the leads???). I replaced it with one I got from Mammoth Electronics, replaced the burned out resistors with the ones from the old DTO5 and the burned out transistors with some I got from Mammoth and now IT IS WORKING!!!!!!!!!!!! (knock on wood) The little pc board looks a little post-apocolyptic now from all of the parts getting swapped out  but oh man, I'm so excited! Going to try out some different opamps in it soon but I honestly don't want to look at the inside of that thing for at least a week. Thanks Jeff for all of your help. I learned a lot in this process and I can't wait to have a heap more questions for  you when I decide to build 9 more of these things! 

 

[PeteJE]

Looking for suggestion - This would be my first capi project (I do have diy audio experience) and my first product with gar op amps.  I ordered one each of the 2520 and 1731 to build first.  I understand the admonitions to use a known working op amp in the LC53A, but I will only have my built ones and nothing to test them in.  How would you proceed?  Do I have to buy a built up op amp, or could I test the gars I make thoroughly enough with qc'ing the boards closely and a dmm? 

 

[Chryst]

Dear people,

I'm building a couple of LC53A's right now. I have a question: with calibrating the units, is it important to keep the main PCB separated? Or can I also do the calibration after the units are finished? I have the main PCB's connected to the CB PCB's, should I separate them again to calibrate properly? The reading should be in the tenths of microvolts AC right (0.1, 0.2, etc.)?

Thanks a lot for your help!!

 

[jsteiger]

It doesn't matter if the PCB's are all assembled or not. The CMRR adjustment is only dealing with the first stage receiver amp.

 

[Chryst]

Thanks for the quick reply. One more question though and I hope I'm not overlooking something really obvious here.
The problem is that the trimmer does not seem to influence the measurement of either my DAW or a good DMM.

I have made and tested the cable with the resistors. I've tried both a signal from my DAW as well as a signal from a signal generator. Both come through and give a reading of -35 dBu to -45 dBu, but the trimmer doesn't seem to have any influence. I've also tried swapping out the opamps (red dots). I'm building three units and all the trimmers have the same problem.

As said I've connected the PCB's already, but this shouldn't have any influence according to the last post. Am I overlooking something?


Thanks for your help.
It's very much appreciated!!