Black Hole sound issue

[playpin35]

OK, I noticed that the cap for the -12V (C41) is supposed to be installed opposite of the other three (negative lead away from the edge connector). No offense intended, just pointing it out as it is different from the others and an easy mistake to make.

Regarding your volume pot getting warm... one possible explanation I can think of is that there's DC flowing there. There shouldn't be any; the output coupling cap, C36, is supposed to keep DC out of the signal while passing the AC thru. You might consider replacing C36 (470µF 35V), or at least measuring to see if there's a DC voltage drop across your 100ohm volume pot (between the two outer lugs).

C41 is installed correctly(opposite of the other 3). C36 was also replaced and still no change.
As far as warm components go, the U15 6532 riot does get hot. Not burning hot, but more than just warm to the touch.

 

[DarrenF]

OK. I can't think of anything else...

So far as I can tell, the DACs are the only other thing that uses the -12V.
I know of nothing else to suggest except replacing them to see if that keeps the -12V from being pulled down.

 

[playpin35]

It's definately a problem on the sound board pulling down the -12 v. I put my haunted house sound board in there and had no issues with the sound and the -12 was reading
-12.02 v. I also noticed that when the hum would fade in and out, the - voltage would increase from -3.75 to -5.85

 

[ixtlann]

It's definately a problem on the sound board pulling down the -12 v. I put my haunted house sound board in there and had no issues with the sound and the -12 was reading
-12.02 v. I also noticed that when the hum would fade in and out, the - voltage would increase from -3.75 to -5.85

your hh doesnt have a sc01a sound synth chip does it? at first I wasnt sure you has another system 80 to swap stuff with. i was about to say I would send you a sys 80 sounds board to component swap till u got r done, cept i have 4 system 80s and 1 good sound board, and it hums anyways lol!

 

[playpin35]

So far as I can tell, the DACs are the only other thing that uses the -12V.
I know of nothing else to suggest except replacing them to see if that keeps the -12V from being pulled down.

Finally got around to changing the DACs and it made no change all. Guess I'm gonna have to hunt down another board?

 

[playpin35]

Changed the ceramic disc capacitor at C19. The voltage only came up to -7.78v, but it seems to have taken care of the hum issue for now.

 

[DarrenF]

Changed the ceramic disc capacitor at C19. The voltage only came up to -7.78v, but it seems to have taken care of the hum issue for now.

Interesting. I never suspect those little suckers.
There's another ceramic disk cap on the -12V line: C26. Replace that guy and see if the -12 goes back to normal.