Pitch Drift Problem

Posted: 5/20/2018 12:51:16 AM

From: West End, Queensland, Australia

Joined: 5/20/2018

Hello all,

I hope you guys don't mind if I ask a noob question. Recently the pitch on my cheapie theremin (this one: http://www.soundslikeburns.com/New_Items/zep.html ) has started drifting continually upwards. It happened last night while I was busking and it's still doing it this morning.

I've re-arranged the layout of the room to check for interference, but the result is the same - I adjust the pitch knob to my liking, I turn the volume up a bit (I use a foot pedal), and I test it out with my hand perfectly still at a low note. Pretty much immediately it begins to rise, and keeps rising.

I've never had this sort of problem before in the space I practice in. Do you think this is a hardware problem, maybe some sort of damage? I read the entries in this thread: (http://www.thereminworld.com/Forums/T/27747/pitch-drifting) but none of them seem to have helped. For reference, I've had the theremin for about a year and a half, and there's a fresh battery in it.

Thanks in advance for your patience

Posted: 5/20/2018 11:06:13 PM

From: Tucson, AZ USA

Joined: 2/26/2011


Only a defect in the circuitry could cause this severity of drift to happen, maybe the issue was caused by static discharge, I do not know. In the end the simplest answer is to replace the unit. If I was to attempt to repair it I would first change the two oscillator transistors with a matching set cut from the same tape side by side whatever that means.


Posted: 5/21/2018 9:05:06 PM

From: West End, Queensland, Australia

Joined: 5/20/2018

Hey T,

Thanks for the response, I'll crack it open soon and do some research.

 - Cam

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