Prophet 08 PE edition desktop - cannot use any knob or change parameters

[cwhiley]

I have a p08 PE that I put away for about 2 years without using. I just pulled it out of storage and it’s malfunctioning.

If I move ANY of the controls, it goes haywire and multiple parameters begin jumping around randomly. It doesn’t matter if it’s one of the potentiometers (metal shafts) or any of the endless encoders (plastic shafts with detents)…the synth works and plays but the moment I move any control it malfunctions.

I’ve opened it up, disassembled it, cleaned all the grimey shafts, used a little deoxit, but it made no difference whatsoever.

It must be something other than the controls themselves because it’s all of them.

I did notice 5 HCT4051 8-channel analog multiplexer/demultiplexer chips that must be the IC’s that handle the inputs from all the controls. I tried to trace it back and found they eventually go into the ribbon cable that goes to the cpu board but haven’t figured out where it goes from there.

I’m a fairly competent tech but there are no schematics available and I’m flying blind.

I reached out to support but I don’t think they’re going through be able to help much as I think this is a pretty big problem.

Would appreciate any guidance.

[cwhiley]

Apparently I overthought the heck out of it.

Reached out to sequential support and he suggested I make a video of the behavior and send it to him. He instructed me to disconnect the midi I/O first. 🤦‍♂️ The problem went away immediately. Apparently I had a device in my studio (MFB Tanzbar lite drum machine) that has been sending errant random midi cc messages that my prophet was picking up! I didn’t know until I looked further and found the problem.

Anyhow it’s working great now!