I have an emu e-iii synth (keyboard) with a couple of issues - the power supply is getting wonky it looks like, on power up the keyboard won’t boot until after several cycles on/off. It will power up but get black squares in the display or other nonsense. Often when I let it warm up for 20 min or so a single power cycle will get it to boot properly. The other issue is the mono-stereo audio outputs, both appeared to not work, but after playing with it I noticed that the stereo-mono outs were working but very weak, only after cranking up all gains on keyboard and mixer. Have gotten them to work normally intermittently, and the other outs 1-16 appear to be ok, but when using a specific out it will only sound one voice after several key presses. Everything else works pretty well, but do get an occasional freeze when using the OS functions. Thanks!
You might be able to rebuild the power supply without too much trouble, and replace the electrolytic caps (and if it uses any tantalum caps, you can replace those with electrolytics).
The output issue may be a failing op amp, but it’s hard to say for sure without digging into it.
Thanks for replying - found a workaround sort of for now - ran the 16 outs to an old mixer and then into my main board, a little better but still seems to be skipping a voice or two. I’m in Ohio so maybe I can find someone local to repair.