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Theremin controls not working

PostPosted: Sat Jul 30, 2016 8:35 pm
by Spectacle
Hi gang,

Lent my etherwave plus theremin to a friend, got it back and none of the pots (pitch, brightness, vol etc) are working. Still getting sound when I switch it on but can't change any parameters.

Any suggestions that I might try at home? I have no electronics understanding but happy to give it a go before I bust it more and try and find someone in my isolated region to have a look.

Cheers

Re: Theremin controls not working

PostPosted: Thu Aug 04, 2016 1:36 pm
by d'ni
Hi Spectacle,
Murphy's Law ? What happened to your instrument?

just guesswork, but very possible is a blown out Transistor, T9. (2N3906)

If you have a Multimeter, you could check the voltages on the cables going to the front panel.
Green wire : Ground
Black wire : -11.3V
Orange wire: +12V
Brown wire: 0 - +12V depending on the Brightness setting
Red wire: 0 - -11.3V depending on the Waveform setting
Blue wire: 0 - -11.3V depending on the Pitch setting
Violet wire: 0 - -11.3V depending on the Volume setting

all the best

Re: Theremin controls not working

PostPosted: Mon Dec 04, 2017 6:16 pm
by Kollo
Hi there! This is my first post :D I have exactly the same problem on my etherwave plus. All the knobs are totally dead. Did you find the problem? Was it the T9 transistor?
Greetings from sweden!

Re: Theremin controls not working

PostPosted: Fri Dec 08, 2017 10:44 am
by d'ni
whatsup? still looking for a multimeter, checking voltages or something? or even solved the issue? just joking.
the t9 hint might be only one source of malfunction. if you can't read those voltages as mentioned above, it's t9. most probably. at least in my case some loong time ago. a oscilloscope is still a good help to check the oscillators. or (very)roughly the old radio trick (by using a simple analog radio, tuned to multiples of the theremins oscillators frequency.)works to check for basic oscillation.