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Vermona Synth Question

Posted under Musical Technology at .
Tags:hardware, instrument, Synthesizer, Vermona, KHW, synthesiser, questions & answers
This is an update to Vermona Synth Boards.

Message Received

Flavio, 2016-06-06

Hi there!

Thanks for your articles on the Vermona Synthesizer - I read entirely through the first part, went a bit too techy in the second article but still very interesting.

I got my Vermona Synthesizer a couple of days ago and I’m now facing two issue, which I hope you can help/suggest how to solve them.

First of all: for VCO 2 the register buttons don’t remain pressed (none of them). I opened up the synth and I found out that the mechanism is somehow stuck in the open position (the position in which nothing gets blocked).

It can be seen in the difference to the VCO 1 register selectors: there, the right end of this longitudinal metal plate is in its rest or inner position, whereas for VCO 2 it can be seen that it is out and didn’t get back (I don’t know how to correctly describe, maybe I can show you pictures?!).

So of course, my question is: how do I repair this mechanical issue? I know it’s only mechanical, because if I keep a register button pressed, VCO 2 is playing.

Second issue is the keyboard: as some keys were having double triggers or didn’t trigger immediately, I took an eraser and tried to clean up what was accessible without removing any keys at all. I also moved the plated bars slightly a bit more left and then back right . . . now I got the lower 4-5 keys which play the same note (???) and all the others play ok but some of them are still not clean enough. What is your suggestion for this issue?

Thanks in advance and kind regards,

Flavio.

Response

Well, sometimes I am a bit too techy. Until it’s the too techy bit you want. Ignore the rest and let the search engines read it. (happy emoticon)

(I’m writing these articles because I find it useful to record all the information I discover — less or more techy; and the interesting or entertaining thoughts that happen while looking; I’m publishing them specifically because I usually can’t find the exact techy bit I want online, or anywhere else . . . )

Anyhow, I don’t remember offhand ever having to free up radiobutton sets. Individual switches, yes; and usually cleaning with contact cleaner and then relubricating (or use of a lubricating contact cleaner) has done the job. (Contact cleaner alone is inclined to make these switches stick.) So my first thought would be, oil/clean the mechanism; but that’s not based on hard facts.

So, if lubricating fails, on to facts . . . The mechanism consists of two moving plates attached to the PCB mounting plate; one seems to slide to the right (from front of synth) and back to release and lock the buttons. This is stuck in the open position, then?

radiobutton mechanism

On my VCO2, the mounting plate was slightly bent near the bolt hole at the plate-spring (right) end of the mechanism; it looks possible that if the bend was severe enough, the moving plate could come too far out and jam on this; but I’m not going to re-bend mine to test that.

radiobutton mechanism, spring clip active
the sliding plate in action, and the spring clip

Another possibility is that the spring clip which returns this plate to the lock position may be bent, corroded or missing. If missing it may be very hard to replace like-for-like, but it may be possible to provide the same function, even using the bolt to attach something, rather than the original tiny clips. Or possibly something is stuck between the plates, perhaps in a switch, which is too big to wash out with lubricant.

radiobutton mechanism, spring clip, tiny clips
tiny clips
(the two bits of copper sticking through slots)

I suppose the first question should be — can you move the plate back into the lock position manually?

The switches themselves seem to be fixed to the mounting strip by bent metal prongs, so even if desoldered you’d need to do some unbending to get them open; this may be damaging, so the options for cleaning inside the switches are probably limited. And without removing the right-end switch I don’t see any safe way of removing, and perhaps not even replacing, the spring clip.

Keyboard contact wires can be cleaned in a variety of ways, but I’d use contact cleaner and pipe cleaners. Again, use a lubricating contact cleaner, at least to finish off — helps reduce future corrosion. If the wires do have corrosion — or greasy rather than dry dirt — I’m not sure an eraser would do the trick. Depends how greasy, what kind of eraser. Note that the busbar also needs cleaning under the wires; some people will tell you to scrape the tarnished surface with a blade, but that’s dubious even with solid busbars; with these plated bars, it’s likely to permanently damage them.

Wrong notes could result from several causes. If the five keys all play A, there could be some kind of constant contact occurring between the A♭ and A positions in the chain of pitch CV resistors; I would suspect a bent contact wire; or some other loose bit of metal. (Possibly a broken spring clip from a radiobutton set. Weirder things have happened to me, which I will write about soon.) Other possibilities are highly unlikely. If (also unlikely) they play some other note, that would probably be a component failure.

Hope that helps.


Update

A simpler possibility for the sticky switches, which I came across in reassembly, is that the switches may be too tight to the case. There doesn’t seem to be much in it. If I leave out the washers, the switches won’t always stay down once the board is tightened. So you might find that putting an extra washer in under the board will solve it. If that is the problem, the switches should start working if you unbolt the board.


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