This was for producer Gino Wong of ReRed Recording, but I was excited to get it working for my own reasons, so that I could sample the drum sounds into my Electribe. Once I did get it working, I discovered that the SCI Drumtraks is super easy and fun to make beats on! I didn’t know this before, but the sounds on here are not synthesized, but rather are low-fi samples each on their own EPROM.
When the Drumtraks arrived, the display and the digital control side of things seemed to be working normally, but it made no sound. When I checked out the PSU, the +15V and -15V rails were showing 0V. Only the 5V rail was working, and that was enough to run the entire upper (digital) board. The power supply for this is surprisingly simple, even simplistic. So it was easy to identify that the tantalum capacitors between each voltage rail and ground were the culprit, shorting to ground. Once I replaced them (and the big electrolytics) everything sprang to life and I was jamming on those charming 80’s drum sounds. Just a little bit more mostly-preventative work was required.
I found out that there are alternate sound chips you can buy (from Wine Country Sequential, for example) and that with an EPROM programmer, it’s possible to burn an EPROM with the appropriately-formatted sample of whatever sound you want.
Of course then I was thinking about how it would be funny to return a client’s Drumtraks with just one of the samples replaced by a fart sound or something. I would never do that though because it’s obnoxious and unprofessional. And I don’t have an EPROM programmer.
Service Tips: the conformal coatings on the PCBs melt a lot as you desolder, leaving behind brown burnt-flux residue as usual, but also leaving behind a colorless residue that when it is on the solder pads is not visible but will give you a bad connection when you solder there again. It’s important to clean the pads really thoroughly with isopropyl alcohol after desoldering, even if it doesn’t look like there’s anything on them.
Work done: recapped PSU to troubleshoot failure, then tested all functions, recapped other boards, replaced memory battery and deconstructed and cleaned tactile switches/buttons as needed.