[sdiy] Vox Continental key noise

Nathan Trites nathan at idmclassics.net
Fri Apr 30 21:56:47 CEST 2021

Hi all,

I've got a continental v301e here where I'm getting a nasty contact noise
on all keys, which varies in level (seemingly due to where the waveform
falls). It's definitely not just dirty bus bars & j wires, which have been
cleaned pretty aggressively. Most of the finger connections seem good, all
electrolytics replaced, and a few of the (film?) caps replaced for being

With all tone boards in, each bus has an offset of low double digit
millivolts. With a single tone board in it still occurs with an offset in
the single digit mV and it still happens. I've replaced coupling caps in a
few and they still have noise.  I can see the spikes on the scope even
without the preamp board installed. Would such a small offset cause popping
like that on the switches?

The continental is a fair bit older than gear I'm used to working on so I'm
still getting my bearings on the construction and haven't checked this yet,
but I suspect the ground from the draw bars or going to the tone boards
needs to be looked at closer.  I do get some very low noise on the power
supply (even with nothing installed) again in the 10s of mV range p-p.

Schematics can be found here:

Any guidance or advice would be appreciated! If anyone knows of a good
transistor organ repair forum or list that would be very helpful too.


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