RonaldRayGun did u manage to solve this? I'm having a very similar issue.
Thanks!

U sure that these are on the DCS board, not the pre-DCS? Still, i suppose the message is the same: change all the caps.. hmmm
Well I am still testing continueties etc, but I have soon checked pretty much every trace and all seems fine.
Next step would be to change the caps I suppose..

Please tell me more on how to test J6 (Aux out)? Is it simply a matter of tapping in speaker cables and connecting a speaker on the other end? Should something go between, like a capacitor or resistor?

So an update: i checked ALL caps with an ESR meter and compared to a working board. I replaced some suspected ones, in total I have replaced:
C32, C41, C50, C52, C15, C22.
And I cut C37, C45 without replacing these, because pinwiki says so.

I also checked continuty on most places, all resistors, all diodes, and diode tested the roms - didnt find anything.

So I plugged it in - still same problem!

Removed audio board again and resoldered some joints that visually looked like cold solder joints, but they where measuring fine.
Also noticed that one leg on C52 (that was replaced) was a little loose (but continuty was tested fine anyway), resoldered that as well.

Now, sound is still disorted but only at the first 2-3 minutes when firing up machine from cold state, after that the sound becomes perfect!!!!

If powering off and then on, sound will still be working fine.

Actually, that is how the problem was noticed from the beginning, it was showing the same symptoms as now (sound disorted when board is cold), then it went to always be disorted, regardless if warmed up.

Now I am left with the following options:
- live with it
- change C20/C21 (the 2 big caps), eventhough they are measuring fine with the ESR meter
- troubleshoot further by measuring voltages on different places on the board and comparing to the working board. I would need some hints on what to measure.

I am thinking of mesuring voltage direct after the c20/c21 big caps, and see if the voltage is increasing by time. That would indicate bad caps (c20/c21) and also explain what I am experiencing that the sound gets better after a while.

Am I thinking correct in my troubleshooting? Is it AC voltage I should be measuring after the caps?

I did not check aux out since it seems too complicated/time consuming to me, but will do it when I have no ideas left

Today I measured some voltages and noticed that the +5v line that comes from J3 seems to be where I should dig into. I measured it at C79.
It measures 4.84 VDC when started from cold state, and slowy increase until it reaches 4.91 VDC within a minute or two, and 4.93 VDC if waiting longer.

Compared with another working machine, I got 4.91 VDC at C79 right away!

This must mean that a cap is making this? C50-C79 are the ones involved according to schematics, i think.

Another increasing voltage is at C11, there I got 4.88 VDC at cold start, but it increases to 5.0VDC within 30 seconds, which makes me beleive that my issue isn't there (since it takes more than 30 seconds for the audio to become good).

I measured DC on C79. That should be correct, right?
Just tried to measure AC, with one lead at each end of C79, but showed 0. I am pretty sure it should be DC.

Actually, here is images showing 2 things that I am measuring:
1. The +5 VDC line, as stated above (2nd image)
2. The voltage after the C20/C21 caps (1st image). Easiest to measure at C18/C19 or at C10/C11. Really I think even this is DC and not AC, because the AC signal is tranfered to DC at the rectifier diodes D1-D4 = before the caps. Am I right?

20210417_192605 (resized).jpg20210417_192644 (resized).jpg

Well thank u, I suppose u mean C18 & C19, not C29?
I also am a bit afraid to remove the big caps, to not damage traces.
Do/could C20/C21 has any effect on the voltage on C79?
If yes, then I def.wiill change them as next step. If no, I think my issue lies somewhere else?

Thanks, I'll measure that right away!
If I understand u right, I should measure AC voltage on C79 (red lead on positive, black on the other end ie ground) and that should not exceed 40-50 mv?
I did not measure that accurate before, will do it again.

U guys are great, thos forum is great!
So just a quick update on some measurements I made. Regarding the ripple voltages, these should be considered unreliable since even when the DMM probes weren´t touching anything, it showed 20-60 mVAC on the DMM.

C10: -4.92 VDC
C11: 4.99 VDC
C18: 16.15 VDC, ripple: 70 mVAC
C19: -16.30 VDC, ripple: 70 mVAC
C79: 4.83 VDC (increasing with time), ripple: 80 mVAC (how is it possible that AC is present on this line?)

Compared to a working board, ripple voltages on C18/C19 are the same. Only diffrence is that C18 is 16.30 VDC on the working board, and C79 is stable and not increasing with time. I don´t know if this made me any smarter, because the measurements seems OK?

From here I think I give up on further measurements and just go ahead and replace the remaining caps C18, C19, C20, C21.

Stay tuned

So, replaced the remaining caps (including the 2 large ones) but problem is the same.
Time to throw in the towel?