Good job on the repair. FYI, your method of testing the capacitor didn't actually tell you the capacitor was OK. It measured capacitance, but not leakage current, which is the critical property of the cap in this application. Film caps, including the polystyrene are more likely to fail by developing...

The slide switches, octave transpose switch, or a power switch? If the slide switches, I have a couple original ones left:

https://synthchaser.com/product/origina ... de-switch/

Besides the reset line going high the CPU also needs a working clock signal to execute instructions.

Ditto to inspecting the board for damage (battery leakage) first, particularly on this machine. If it looks OK, I have a few videos on my youtube channel showing how I go about troubleshooting dead drum machines (all lights on and nobody home is typical of a non-running microprocessor)

Yeah, Im really not keen on the idea of parting it out. As a matter of fact, I'm sorely tempted to press on and get the divider board back into working order. But in the end I know I won't be able to give this instrument the home it deserves, so it will have to be moved on sooner or later. And how ...

Sounds like calibration differences between or mismatched voice chips.

I wish I had buddies that gave me broken gear. Mine always ask me to fix their broken gear.

Perhaps a bad 4051 pot multiplexer on the KLM-369 board?

Sounds like a stuck data bit or bits going to the DAC (which in this case is just fixed resistors). I'd check the buffers (inverters) on the data bus ahead of it with a logic probe or scope. IC18 & IC21.

Google "how does a voltage divider work" and you'll see why it doesn't matter if the pots aren't exactly the same values, or if they are replaced with different ones.

Yeah, you'll need a 2732 EPROM. Each manufacturer had their own prefixes and most of the time, the only differences were the programming voltages. So you just need to find a chip that your EPROM programmer is compatible with... Then maybe download the datasheet for it and compare the pinout to the O...

Sounds like you just need to burn an EPROM and you're good to go!

It's been a while since I worked on one with JL Cooper MIDI, but to revert to stock most likely all you need to do is: 1. Unplug the daughterboard from the main board (I think 2 ribbon cables? 1 into processor socket as pictured and probably another into a DIP-14 socket which was for a CD4011) 2. Tr...

There are a bunch of chips (the ones you listed included) that were on earlier revisions of the main board, but were removed by your revision.

I think I may have showed this in one of my Prophet 5 repair videos, but a good reason is if the oscillator isn't stable, and it comes in and out of tune. Find the oscillator in question and attach a scope to the CEM3340 chip and you'll get to the bottom of it very quickly.