Centipede Speaker Hum

Well I've also deduced that my problem is on the pcb as well. I hooked up an audio cable to the AR2 and was able to hear music through the speaker just fine. I'm afraid I may have screwed up my PCB however. When I hooked it back up I got a mess of sprites over a yellow background. I had replaced the op amp on the PCB without messing anything up but also without fixing the problem. But I assume I must have done something wrong now that the game is screwed up.
 
If HUM related to the logic board, more than likely it the LM324 OPAMP at K10, as andrewb has already remarked.
 
I'm afraid I may have screwed up my PCB however. When I hooked it back up I got a mess of sprites over a yellow background.

I'll retract my prior comment, thankfully this new issue was just a dirty connector. cleaned with deoxit and the game came back up... so did the buzz/hum of course

If HUM related to the logic board, more than likely it the LM324 OPAMP at K10, as andrewb has already remarked.

I replaced that part on mine last night... unfortunately no change.
 
I replaced that part on mine last night... unfortunately no change.

Humm ... next I would check for excessive AC ripple on +12V and -5V at the LM324. Also visually check all components around the Opamp.

Might also swap the POKEY for a known good one and see if there is any change in the audio.

(With the assumption that the grounding in the cabinet and at the edge connector is all good)
 
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