This system has 5 RAM boards installed, for a total of 288KB. With a ZPU-B board and a 4-port HSIO board, it was probably running MP/M or the TSS Operating System.

After cleaning up the system, I removed all the boards, disconnected the power supply from the mainboard, and reformed the large electrolytic capacitors using a current limited bench supply. The DC voltages from the power supply looked good, although a bit high (normal for these old systems). The fan is not working. I reconnected the mainboard and one of the tantalums went up in smoke and flame. I replaced it, and a second one popped. I ordered a batch of tantalums (6.8uf, 2.2uf and 22uf), and replaced all of them on the mainboard and the individual cards. After that, I found a bad 7812 regulator on the mainboard and replaced that.

The system powered up with no further fireworks, but no action from the diskette drive. I installed a system monitor board and was able to verify the ZPB board and the first 64K RAM board were operating normally. There's something wrong with the MDS-AD3 FDC, which I'll have to get to later.