Yamaha PortaSound PSS-480 drums mystery

[mmontag]

Hello all,

I have a PSS-480 that has a weird "intermittent percussion" problem. Triggering drums with keyboard (percussion keys) might work for a few seconds, then triggers start getting ignored. Same behavior playing built in rhythm patterns or the demo song; drums go silent for a stretch and then come back.

The PCM drum sample themselves don't get clipped off; it seems to be only the *trigger* that gets ignored sporadically.

It seems to be random, I haven't discovered a cyclic pattern or anything.

Does anyone have any clue what could possibly cause this behavior and if it's worth trying to fix? Hard to imagine old capacitors could cause it.
- I downloaded the service manual PDF, available online at many fine websites.
- This keyboard uses YM3419 (RYP7) for percussion sounds.
- When started in test mode, it passes all ROM/RAM tests. But the drop-out problem remains.

[mmontag]

For a future Google searcher:

It turns out the problem was cold solder joints on the YM3419B chip.  I was about half-way through recapping the whole thing, and that didn't make any difference.

I reflowed solder around the whole chip and that was enough to fix it for good.