Inside the Lell PSR Drum Synthesizer, Part 1

A returning customer of mine found a vintage Soviet drum machine and asked me if I was willing to recombobulate it. I took the challenge... and this is the first part of a little series of insights on this interesting device. It's a microprocessor system with RAM, ROM, VFD, keyboard, DACs, whatnot... Given the political & economic situation, it's interesting to go through it. It's pretty typical Soviet electronic engineering with all the ICs using Soviet rather than Western markings, so I had to do some research to find the equivalents and determine their purpose. A lot of work has been done off the camera, and it was a great learning opportunity too. Who would have expected that I'd not only have to program EEPROMs, but also deal with programming voltage level mismatch and make a level shifter to get it to program at all? That's engineering, that's what I do for a living... Sorta. 0:00 Intro 2:44 RTFM! 4:50 Overview 9:25 Discombobulation 15:12 Bottom Board Top View 18:15 Getting To