I just did up a project Guns n Roses machine for a mate. And he is having intermittent sound issues.
It happened a few (3 or 4) times to me when i was playing it (over about 70 games or so).
It seemed to happen when the machine was cold, but this might be coincidence.
It would start fine, then about 1 minute into the 1st ball, the sound would cut out - sometimes the sound effects would keep going, but no music, other times, nothing at all. Then when the ball would drain and the new one was launched, same thing again - sound OK for a bit, then cut out.
Once, when i was at the ready, i managed to measure some voltages between balls when there was no sound.
The +12 going into the sound board was fine, but the +5 was 4.76 or so (this was measured with the plug in the sound board) - now my memory is a bit hazy here, but i thought i measured 4.95V at the power supply board at the same time (is this possible?) where the plug goes out of the power supply board and into the sound board.
Then, when i started the new ball, and sound worked, back up to 4.95V at the sound board.
Then, it was fine for another 20 games. Now old mate powered it up after being off for 6 hours, sound cut out, power cycled it 3 times, same problem. Let it sit for 5 mins and all working fine!
What i did:
Replaced the 1000uf cap on the sound board
Replaced 4 caps on the power supply board - can't remember the numbers off the top of my head, but i thought they were all of them except the 4 large same sized ones.
Replaced BR1 on power supply board and triple checked there were good solder connections, and ran a couple of trace wires as well off this.
Reseated sound ROMs
My initial thoughts are that it may be an issue on the sound board (maybe other caps in the 5v line - but i'm not sure which ones?) due to the seemingly different voltages on the osund and power supply boards - but as i said, i don't 100% recall whether i measured this difference at exactly the same time or not (should have written it all down!)
Forgot to add - i put the power supply board from my Jurassic Park in, and still once had the problem (before i replaced the sound board capacitor), so i guess this points that the issue almost has to be in the connectors or sound board.....maybe??
