Vermona Synthesizer: Keyboard maintenance and calibration

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Synthfluencer
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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.
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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?
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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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