I have an interest in old, analog, drum machines, and take them in for service. Sheldon brought to of these model FR-1 units in for service; one was in pieces, the other had gummed up switches, and was generally sad. The biggest issue I has was a lack of schematic, so if anyone has one to share I would appreciate it. They also wired the boards into these units in a way that makes it extremely difficult to work on them. A full service was carried out on both, and both were fully re-cap’d as one had low volume, and the other excessive hum.
There was also a severe crackle on one unit that was traced to a noisy germanium transistor, that thankfully NTE had a replacement for (NTE103A). You had to adjust the bias afterward, but the pot fell apart on touching it, so that was replaced and all was well.