TMNT PCB

[cruzlink2]

Got this from a friend and been working at it slowly for a while. The sound starts rough with noise and eventually dies out and comes back in and out. This is what I did so far guys, changed the pot, changed the electrolytic caps, changed the tantalum 4.7ufs, changed the 640khz resonators which were in rough shape, changed the opamps and main amp. Any suggestions are appreciated. I will link a video of the issue.

View: https://www.youtube.com/watch?v=hsyrG09blz4

 

[ShootTheCore]

Definitely a strange one. Are sound effects playing at all? I didn’t hear any in your video. Do you have an audio probe so you can check the audio as it feeds into the OpAmps?

 

[cruzlink2]

I have a logic probe yea the sound effects play but like all the other audio it eventually drops off and comes back and drops off

 

[ShootTheCore]

There are schematics for the board available in the manual:
https://www.gamesdatabase.org/Media...nage_Mutant_Ninja_Turtles_-_1989_-_Konami.pdf

Page 11 - 12 shows the audio section.

Not sure if the logic probe would be as helpful as an audio probe, but I’d check the inputs on the OpAmps to see if the music is cutting off on the input side - try to narrow down if the fault is in the digital or analog section. If the audio is live coming out of the OpAmp outputs then there could be a damaged resistor or capacitor on the output side of the circuit.

Since the music isn't restarting when the music cuts back in, I don't think the issue is with the digital side - if the Sound CPU was resetting then the music would be starting over.

Perhaps there's a cold solder joint somewhere? Does flexing the board make any difference?

 

[cruzlink2]

I'll get a cheap audio probe on eBay thx.