Missile Command - puzzling fault

Solder

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I have a problem with a Missile Command board - it works fine on my test bench, but when put into a cab there are problems with the audio - the sounds are mostly working OK, the main problem is the sound that plays at the start of each wave - it's distorted. Other problem is that game sounds intermittently cut out in one of the speakers. This has happened before, and in the end took out the -5V on one of my AR2s.

It must be a problem with the MC PCB rather than anything else as I have no audio problems using my spare MC PCB. It's almost as though the MC PCB is putting too much strain on the AR2.

The Pokey is fine, the LM324 has been replaced. Not much else left really, or am I missing something obvious?

Thanks.
 
Check the -5V and +12V on the card. I bet there's something other than the LM324 that's draggging one or both of those down.
 
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