help with Theremax

Posted: 12/15/2005 11:25:17 PM
Travis

From: Ma

Joined: 10/4/2005

my theremax is not functioning properly, the volume antena seems to be controling just the pitch, and the pitch antena is not doing anything.
but for some reason the volume trim is also controling pitch and the pitch trim is not. i think it may be the tuning, i will retune it. if it works then i will repost.
does anyone know how to help?
Posted: 12/16/2005 12:27:32 AM
kkissinger

From: Kansas City, Mo.

Joined: 8/23/2005

(This answer copied from another Theremax thread)

The volume antenna affected the pitch depending on the setting on coil L4.

This procedure worked for me:

After tuning the pitch oscillators, before you remove the VCA jumper, go ahead and turn the adjustment on L4 and you may find a place where L4 interacts with the pitch oscillator. Adjust L4 to a position where the pitch is stable as you move your hand to and from the volume antenna. Then, remove the jumper and tune L3 to achieve your desired volume response.

============================================

Also, might be worth your while to go to Forums/Theremin Construction/Theremax ... The problem you are describing has happenned to others and I have been able to reproduce the problem on mine. Also, PAIA's website has some troubleshooting info (written by Scott) that discusses this issue. Hang in there -- the Theremax is not the easiest kit to build however most problems are due to the tuning of the coils, damage to the coils from overheating during soldering, cold/weak solder joints, and improperly polarized components.

So get out your schematic, your magnifying glass, and hang in there. The Theremax has a clear tone and you will enjoy it once you get it working.
Posted: 12/17/2005 10:03:14 AM
Travis

From: Ma

Joined: 10/4/2005

Thank ou very much!
i apreciate the help.
Posted: 12/17/2005 1:12:14 PM
Travis

From: Ma

Joined: 10/4/2005

it started working, and then i moved it. once i turned it back on it was way out of tune and not working correctly. every time i bump it it goes further out of tune.
whats wrong with it? might it be the oscilator coils? can i fix this problem easily?

-Travis
Posted: 12/17/2005 1:22:22 PM
kkissinger

From: Kansas City, Mo.

Joined: 8/23/2005

You might want to double check your antenna connections... make sure they are tight. Also, be sure that the shield is not making contact with the antenna lead -- when that happens, you will get no pitch signal.

Also, the tuning will change depending on what is in the vicinity of the antennae. You will likely have to tweak coil L2 for the first couple of weeks of use to find the best setting for it. And yes, the coils on the Tmax are known to be very sensitive.

Sounds like you are making progress.
Posted: 12/17/2005 10:45:03 PM
Travis

From: Ma

Joined: 10/4/2005

thank you for your help, i finaly got it working.
it will just take a few more tweaks and it will be off to band practice with me tomorrow!

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