Archive of the former Yahoo!Groups mailing list: Vintage Simmons Drums (UK) Users Group

First off, I'd like to thank those that have helped me along with repairing this, but I'm currently at a standstill.

What's been replaced so far: all the caps and IC's in the input mux and mux/demux circuits. This hlped the issue with the low tom circuit with the constant triggering.

The unit also had a random triggering issue with all but the bass channels, almost like the autorun function was stuck, but instead of sequentially triggering, it would randomly trigger channels until all were triggered at the same time constantly, causing basically a constsant buzz noise. Someone mentioned that it may have been an issue with the logic circuit. So, I decided to replace the IC's in the logic/computer circuit as they were pretty reasonably priced. Only the main processor chip: P8031AH, and the PPI chip P8255, were not available as new. I did find New Old Stock chips though, that did appear to be new and unused.

Now the issue: when I turn the unit on, the 4 led's for the kit bank (A,B,C,D) BREIFLY come on and go out, but the "mode" led and the 7 segment led never come on. The unit does generate an amplified hiss through the headphone output jack, like normal amp noise waiting for something to happen is the best way I can describe it. When I try to trigger the unit with the pads, I get nothing. Also, the select buttons do not seem to do anything either. I've checked and rechecked the board to make sure no circuits were damaged from the IC replacements and have found no damage. The unit seems to act like it's waiting for data, but not seeing it. I have tried a few different OS EPROMs, including the original one which did work before and there is no change. I also tried the original processor chip (it is in a socket, s no big deal to change) and it does the same thing with either processor chip. I'd like to note that I did NOT replace the 6116 RAM chip for fear of data loss, so that is original.

What am I missing here? Is there an initialization sequence I need to do that I am unaware of? Is it possible that the PPI chip (P8255A) that I got is defective? The best way I can describe what the unit is doing is like this: it is like an old DOS based PC, whereas you have the blinking cursor on the screen waiting for you to tell the computer what to do. Does this make sense to anyone?