I was sent a Roland CSQ-100 Sequencer that was dead. It took a bit to follow the architecture of this unit, and it made a lot of sense as I was designing microprocessor systems at this same time, including my own home DIY computer. The repair turned out to be an IC failure that required some recalibration. I also made new control dust covers out of black felt as these had hardened and disintegrated on touch. Once repairs were complete, the owner wanted me to do the non-volatile memory upgrade which is described on the AMS Synth site.
Although they sell the completed upgrade daughter board, I chose to buy a part from Newark and the board from Oshpark. I didn't understand that Oshpark aggregates orders to fill a panel and then processes the entire panel. That's a pretty neat process for these types of PCBs.
This is the daughter card installed on the CSQ-100 PCB.
Here's a quick video showing power-on and playback of a stored short sequence (Jimi Hendrix Machine Gun). There is a brief sound as the sequencer powers up and the outputs stabilize.