Etherwave Plus pitch field growing...

Hello all,
I just bought my first Etherwave Plus, used, but looking/sounding good...except that: The pitch field is constantly growing after some time, as the instrument heats up. When I first turn it on (after, say, a day being off) I can tune it, find the zero beat etc...But as time passes, the zero beat moves behind me and keeps moving maybe forever. So the theremin gets higher in pitch and I have fewer octaves available to play (around 2.5). Also, I can not tune it anymore with the pitch knob, as this is already all the way up, at 5 o clock....Turning the pitch anti-clockwise, would raise the pitch even higher! Note: When I first turn it cold on, I find the ideal zero beat/lowest note with the pitch knob at 4.30-5.00 o clock. 

I would appreciate any help!
Thank you in advance,
M.

Not good, get your money back from the seller.

My first "guess..." this is a damaged variable oscillator transistor, most likely from static discharge when touching the pitch antenna and why the Seller got rid of it. Most likely he was aware of it.

Christopher

Hmm it's bought from a local listing 2 months ago, I am now finding the time to play with it and to get to know how a theremin works...so a bit difficult to prove it's been faulty from the beginning and not because of my (zero) use. :-(

So, in the case I want to service it, would it be possible? 

Let's see what other(s) have to say...

Wild guess: I've never seen one drift like that, but perhaps it is mistuned.  Mistuning can allegedly hurt / destroy the oscillator transistors.  ESD can hurt / destroy all kinds of stuff, and those antennas are just bare metal.

Where do you live?

I live in Greece. Should I contact a local synth repair centre and, if yes, what do I have to tell them to investigate for? or there's anything i could try on my own? Thank you!

My first guess is that the EW might need tuning: if the zero beat on cold start up is already at the 4:30 to 5 o'clock position, then warming up will only have the zero beat slide further round beyond the tuning capacity of the pitch knob.

See Thierry's reply 3rd post.
http://www.thereminworld.com/forums/T/27695?post=186752#186752

Yes, exactly! I cannot turn the pitch knob any further...If I could, I have the sense that I could tune it...

So, do I need to adjust this L6 by 1/12 of a full circle? And how do I get to find that?

Unfortunately, I also suspect there are no expert theremin tuners around my area...

Hello escape,

The  TW forum needs some entertainment so let me say more and hope the ladydog does not get offended.

I live near Los Angeles California and in my twenty years of theremin experience have never met a thereminist much less someone who could repair them. I might be that person here ... but the EtherWave circuit board copper traces are like tissue paper so whenever removing a part this must be kept in mind. Also the Theremin works with a series of interconnected events, you throw one off the rest crumbles.

The odds of making your theremin better are 50/50. Maybe sell it to the next guy. Theremin's are so strange maybe the new buyer will not notice.

If you destroy your theremin, not all is lost, it could be a blessing. I have an interesting idea if you can solder properly. If you are near Athens I have a brilliant theremin build student who will read this post and may contact you.  John is in his finals at the Universities there so his time will be limited right now. I am jealous of such young talent as my time runs out.

Edit: My own work has no thermal drift, wake up in the morning and it is still on the same musical note, barely. Drift comes from an imbalance in the circuit design or a defective component. I also have a perfectly linear pitch field. A few people know about this and John will validate it. This makes the instrument much easier to play. While bragging my work has the original classic sound to die for, not a muffled whistle buried in reverb.

Christopher

escapedpuma, the Etherwave is a difficult thing to own if you aren't up to tinkering a bit now and then.  The variable inductors are fairly clearly marked on the printed circuit board, and there are instructions here and people here (Thierry mostly) who can help you if you feel up to it.

Do you have the plastic hex tuning tool that normally accompanies Etherwaves?  If not, you need to get your hands on one.

Hey, thanks all for your responses. 
- Oldtemecula, I don't live in Athens, but I go there quite often. If you speak to John you could maybe bring us in contact? Or what's his username here, so I can DM him?
- Dewster, in general, I'm definately up to tinekering, I had tried to build an open theremin (arduino theremin) once...Just hoped that soldering and messing with electronics stuff I don't know would end when buying a moog...Seems I just got completely unlucky, not to say tricked. No, I don't have a plastic hex tool, but found this at another TW post here. Is this the one? http://www.landmelectronics.com/product.cfm/28643/

Also I found this video about L5 and L6 tuning process..is it trustworthy? : https://www.youtube.com/watch?v=AllJZSuB-uc