Unstable Pitch?

hey everyone,

i've owned and played my moog etherwave standard for about a year now with no problems until a few days ago. i was practicing with my quartet when, about half an hour in, my instrument's pitch started jumping everywhere. i replaced an adjustable inductor i thought i may have cracked when i built it a year ago, but the problem came back the next day.

sample (http://www.mediafire.com/?b4byg9lj4mclj78)

my wall adapter seems to be putting out a steady 14.8vac with no load. i should also mention that when this problem is evident(intermittently), adjusting the brightness knob also changes the pitch. weird, right?

any help is greatly appreciated. my theremin ensemble's next gig is in 6 days!

My first guess is a loose connection around the GROUND power plug. Check for board and solder cracks at the circuit board.

Next but less likely is a loose antenna fitting or solder joint.

You might add this natural effect into your music, sounds sort of like a hurricane blowing past a cracked window.

I'd sign my name but what if I am wrong?

the problem may have been affected by moving the plug around, but i can't be sure. there are no board or solder cracks, but the plug is loose. i'll try gluing it in place.

no good. the jack isn't going anywhere, but after 5 minutes of testing, the problem is back.

That sounds as good a most of my own music!

Did you try a different power outlet, a loose ground is still my first call. Then a wobbly antenna fitting. It is most likely a physical intermittent contact issue somewhere...but where?

Does your EW use a three prong power plug? Seems like some of the originals did not, I don't know.

it is a three prong adapter. i tested it with a multimeter and the ground is fine, even when i kick the cord around a little. where else would i test?

keep in mind that this problem happens not just when i'm playing the instrument. i've turned it on staring at the pcb and antennae until it started to warble again. nothing visibly moved.

i also seem to get a few good minutes after turning it on of stable pitch before it starts to jump around. i just get the impression that the problem isn't a physical contact...

Ethan said:

[i]i also seem to get a few good minutes after turning it on of stable pitch before it starts to jump around.[/i]

Now that is a good clue pointing to the issue (thermal) but you need more than me, maybe a gifted remote viewer.

Thierry should be waking up soon, I wish you the best.

thanks for your help. i don't know about thermal, since it's such a low voltage/low current system. i was thinking something electronic, like a stray static voltage or something... anyway, i await another expert's opinion.

Ethan said:

[i]"adjusting the brightness knob also changes the pitch. weird, right?[/i]

I missed you mentioned this clue, being retired I was sitting in the living room watching the Jerry Springer Show and it's female physical contact sport wondering how us passive hippies inspired some of today's generation to have such flaring tempers, anyway that stirred a thought...

There is physical contact in all your Pots, that brightness Pot is telling us something!

Read this eHow Article (http://www.ehow.com/way_5756516_diy-guitar-potentiometer-cleaner.html).

[b]Don't use WD-40![/b]

Edit: This is when an oscilloscope comes in handy to peek at the power supply and individual pitch oscillators.

Hi there,
I'm experiencing this same problem (my Etherwave is sounding identical to Ethan's sample). It started happening after a fuse blew in the apartment I just moved into. The electrician who came to fix it said some of the wiring in this place is pre-1930s.. cloth insulated crap.

I know nothing of electronics; I just play the thing. Do I have to open it up and do something, replace the power adapter, or something more difficult? Can I use it in this old house?

Ethan, did you get yours working yet?

Thanks in advance, everyone.