[sdiy] Oberheim DMX wackiness

[Eric Frampton]

Hey y'all -

So I've just acquired a DMX that I'm bringing back from the dead. I've got it making the proper noises, and the computer seems to be working, battery is swapped out, corroded sockets, etc. But it's got two weird problems that I'm hoping you guys can help me with.

1. the first few characters of the display are prone to show incorrect - but not random - characters. It looks like the display is hanging off the same data bus as everybody else, and since the rest of the machine seems to be OK, I'm not sure where the trouble is. I've tried swapping out the 74LS42 driving it to no avail.

2. The hi-hat card is working, and the Tom 1 card is working, but only in any slot except the one they're supposed to go it. As in, the hi-hat doesn't work in hi-hat but does work in tom/snare/bass/etc, and the same for the Tom 1 card. Ideas?

Also, the battery in this thing leaked. It didn't actually spill its guts on to the motherboard, but the gasses corroded a bunch of things in the surrounding area - luckily all the traces are intact. It seems like whatever those gasses are really do the whammy to any solder, such that it makes it really difficult to melt. Is there some chemical I should try, or a trick that any of you can recommend, for making the corroded bits easier to remove? I've been very fortunate to not have had to deal with this problem (to this degree, at least) before.

Thanks a bunch,
Eric