Electric organ repair.

[BPJ]

[crochambeau]

Unsure how this one works, but it appears each key is wired, indicating the need of a common reference being fed to the keybed. Make sure that's intact, electrically, and generally poke around some more.

The screwdriver assisted trim pot is probably going to dial over all tuning that the top octave generator is running at.

Confirming there is a pulse being fed out of the top octave would be another step on my short list.

[BPJ]

There's definitely a common reference, you're right. My laptop is busted so I'm having to operate off a telephone, slowing things down because my eyesight is getting worse every day.

This is going to be a very long project. At least it cost me nothing. I'll keep posting here as I go along for the fun.

[crochambeau]

Radical. Thanks for sharing your organ with us BPJ!

The culprit is usually a bit of dirt, oxidization, or failed caps pulling power rails down. Lots of switches and contacts in the works with these. Happy hunting!

[BPJ]

For any body interested, here is a PDF of my organ. I had to email Hohner because there's no reference at all to this model I could find.

https://ufile.io/tetbzkwi

[BPJ]

Very late second part.

[BPJ]

I think I realised what those definitely not capacitors are for, I think they stop the different notes adding to each other, like you would do on a mixer if that makes sense.

[crochambeau]

Yeah, those resistors look to be providing a load for each always running oscillator note. My guess (and PLEASE bear in mind I have not devoured the schematic, nor do I have the bandwidth to do so) is that the "live" side of the resistor is switched at the keyboard.

Key switching comes from the per note spring (in orange) connecting to the input bus (one big solid wire, in blue). Those parts look pretty tarnished and could use a cleaning. That might be the entire fix right there.

When probing around crusty old shit I like a sharp point like on a multimeter lead - because sometimes you need to break through a layer of oxidization or other ancient funk in order to get a solid measurement.