PAiA Theremax Tuning problems (esp. volume)

I was wondering if anybody has any advice for tuning/calibrating the coils the first time on a Theremax, beyond what is stated in the instruction manual.

I had this same problem with a previous Theremax I ordered off of eBay (it came, fully assembled, in the lectern case, for $125 but... didn't do anything. I used the gator-clip jumper to bypass the volume circuit and discovered the pitch worked like a charm. But with no jumper... I could not, for the life of me, tweak the volume coils to get any sound out of it)

I figured, since I didn't assemble that one and had no idea what had been done to it or how old it was, that maybe the coils were broken or something ; since I wanted to build mine into an Atari 2600 case anyway, I sold the lectern one on eBay and ordered mine.

Well, not it is all assembled and... once again, with the jumper in place I was able to get the pitch working (although it's a bit of a pain because my case design makes tuning even more difficult than usual -- I'll post pics later)

BUT when I remove the jumper and follow the directions for turning the coils, I can't get a single peep out of it.

Any ideas??

I find it bizarre that the same thing happened with a pre-built one as with a brand-new built one that I know should be fine. I must be doing something wrong...

I see from another post at TW that you are familiar with the great customer service at PAiA.
In reference to your Theremax tuning problem, have you checked the solder joints to the volume inductors? Perhaps, you may have used a bit to much heat to solder those parts to the PC board; the inductors can be damaged by too much heating.
Also, from looking at your other post, parts on the PC board could have been damaged from the wrong power supply polarity connections described.
I think your best bet for a solution to the problems with this Theremax would be to ask Scott at PAiA.com .

Good Luck!

teslatheremin

Creepy timing on this reply.. I was JUST now making another attempt at tuning it, using a fairly expansive PDF of tips and tricks Scott emailed to me.

I have to say, you are right. Scott Lee is timely and thorough and always gracious about providing help... (plus extra parts when they're needed) he's really been a lifesaver on this project! [I've contacted him probably 8-10 times between phone and email, and he's never disappointed me in the help he's provided along the way]

Myabe if there's a place on this site to post the PDF, I could upload it... it provided a lot of good advice, including a good way to tune the Theremax WITHOUT using the clip-lead jumper gimmick (also tips like... tune it with the antenna off... then it might make it a little easier to fine-tune once the antennae are attached)

I think, using these new tips, that I'm pretty sure I've found the problem: my gate/trigger (velocity) CV doesn't flicker like it should as I pass through the volume heterodyne... but it DOES flicker on and off (with rather annoying loud pops) if I wiggle the nearby pot, the connecting jack, or the LED... so it looks like perhaps there is a bad/loose solder right there which I need to fix. (overall, I've found the biggest pain the butt to be the wiring of the pots and jacks, which do not seem to like to hold a solder joint very well, even when tinned/pre-soldered)

However, I got pretty excited to hear the pitch coming through WITHOUT the jumper attached to bypass volume... so I think I'm getting closer to my destination (well, Phase I, anyway... Phase II involves some switch-toggled tone modifications, and Phase III involves installing a MIDI-Fader board with the intent of converting CV-out to MIDI-CC out instead. But I'm going to hold off on those and just play with my new toy for a long time before I decide to mess with anything further)

Thanks to everyone for all of the advice...

'Congrats' kidelectric!
I hope you will have as much fun with your T-Max as I have had with mine.

Good Luck!

teslatheremin

Well, I installed the replacement C1, proper LED, a new switch, and reconnecting power properly this time, and after consulting the alternate tuning method in the PDF, I was able to get first sound after about 3 hours of carefull adjustment of the slugs. Only one small problem. The volume loop is behaving like a pitch only theremin. Moving the hand to, and from it changes pitch, as well as volume. The pitch antanna seems to have little, or no affect. (possibly not connected right?) Also, the L1 slug must be poorly soldered, or damaged as nothing I do to it seems to affect anything

The gate trigger LED is working as it should.

Quite frankly, I'm amazed I got any sound out of it at all. I expected not to get any sound.

Hmm... L1 slug meaning the Volume pot?

I noticed the other day (when I was close to getting it to work correctly, but the connections seemed loose) that the volume knob seemed to have little (if any) effect at all... I wasn't too concerned about it, since I can control that through my amp or audio input... but it did seem odd to me that it didn't seem to affect anything. I just wasn't going to worry about it so long as my volume antenna worked and the pitch worked as well.

Unfortunately, I solidly soldered those loose connections and now... nothing works? Now I can't get it to make a sound at all. :(

Someday I will get this thing to work. I swear it. But it was very disappointing to FEEL like I had finally solved the last problem and I expected it to truly work, and then to find that I somehow broke what was already partially working. Quite unexpected and unpleasant surprise...

kidelectric,
Have you tried to retune both the pitch and volume inductors after fixing the badly soldered connections at the volume panel control?

Good Luck!

teslatheremin

Pots are cheap and readily available from Mouser Electronics. If you can't get the ones you have to solder properly, you would be best just to replace them.

Don

Just as I was about to pack up the Tmax, I got an e-mail in from Scott, advising me to turrn L1 another half to full turn in (clockwise), and to check for sheild brade wire that might have touched the pitch antenna mount which would have stopped heterodyning on the pitch side.

Luckilly, I was good to go on the antenna cable, and after just a few more minutes of V E R Y slow adjustment of L3, I found the heterodyning for the pitch antenna.

The Tmax really has a nice soft "spookey-ooowey" tone.

I think I still have a bit of adjustment to do as the volume is a bit too low at the moment, so I may not be on the "real" heterodyne band just yet.

So-o-o-- kidelectric,
What do you think of T. Grillo's advice?
I know what I think: I think it doesn't help you. I think it is just another post for poor Thomas to be noticed on Theremin World.

kidelectric, I truely hope that you have not given up on your T-Max kit. It will work, if you continue to find the construction or part faults.

Good Luck, and don't give up!

teslatheremin