Vermona Synthesizer: Keyboard maintenance and calibration

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Joined: Wed May 27, 2020 3:12 pm

Vermona Synthesizer: Keyboard maintenance and calibration

Post by Synthfluencer » Wed May 27, 2020 3:53 pm

Hi there,
I am new to this forum but not new to synths & electronic music; bought my first synth (Roland D-10) in 1992; own a small home studio (wife calls it "the synth cave") and I'm as of late proud owner of a Vermona Synthesizer from 1983.

Edit: Yesterday a very kind person who - as I suppose - is a former engineer at Vermona sent me the service manual. It describes how the calibration works and from its technical description I learned that the "metal bars" simply providing the power for VCO and VCA. Thus usual rust removing techniques should be applicable.
The synth is in pretty good shape, yet it shows some age marks. I gave it a quick cleanup and brought the crackling rotary pots back to life. The keyboard works overall quite well although some keys show a slightly tune instability. I suspect the corrosion (see attachement) on the "tubes" underneath the keys. There are two rows of those tubes, divided in several sections. Since the synth has two VCOs I guess these two are responsible for the control voltage given by the keys. Does anyone have a good recommendation how to clean these "tubes" (don't know if there is a better more technical term) without destroying a potentially existing resistor layer?
Additionally; I am looking for a repair manual for this rare synth, at least some how-to showing the calibration of it. There are several calibration pots on the board inside but I don't want to play around with them not knowing the "calibration strategy" ;) Already found the owners manual and patch sheets on the manufacturers website but nothing looking deeper into the tech details.

Thanks for any hints!
Best, Synthfluencer

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