No sound from Etherwave Standard Theremin

I recently purchased an Etherwave Standard from eBay, and don’t get any sound when plugging it into an amplifier. The power supply isn’t buzzing, so it’s not a power-cable issue, and when I plug headphones into the 1/4-inch jack, I get a small chirp when turning the unit on, but if I turn it off and on again, the chirp disappears. The chirp is only heard if you unplug the Etherwave from a wall outlet and plug it back in, and only appears the first time you turn it on.  I’ve tried turning all the knobs/adjusting the pitch field to no avail.  I assume the unit got damaged in shipping, (the listing said it was fully working,), but the fact that the seller’s not accepting returns seems sketchy to me.   I’ve read Hot-roding your Etherwave, and assume my next step would be to try and tune the induction coils with a non-conductive tuning tool,  but  I’m blind, and don’t feel comfortable opening up the unit and  poking around in the circuitry.
Could I not be getting sound because there’s a tiny bit of space between the volume loop’s back nut when it’s tight, while the front nut is flush with the case when screwed on?
Or maybe it’s  an outlet-grounding issue? I’ve tried both a power strip with surge-protection, and a three-pronged wall outlet, but with the same results.
Does anyone know what might be wrong, or know of any Theremin repairers in Boston, MA?
Thanks so much to anyone for any help.

Hi Motya105,

The chirp at power-on is encouraging, but beyond that it probably needs someone with an oscilloscope to take a look at things.  I don't know of any Theremin repair persons up there in MA.

Thanks so much—I’ll take it to a local Electronic repair shop who’ve repaired an Etherwave before. 

Motya105 I'd volunteer to take a look at it (I live in NJ) but I don't have replacement parts should something like an IF transformer or RF choke be the issue.  The magnetics in the Etherwave are disappearing with the advent of SDR (software defined radio).

Thank you so much! I’ll try my local repair place first—if they can’t fix it, I’d send it to you. Thanks for making the time to help me out!