Pitch Antenna / Heterdoyne not working

Posted: 5/5/2011 5:53:13 PM

Joined: 5/5/2011

I recently finished building my Theremax and have had endless trouble with the pitch antenna. I initially fixed it by resoldering the shield cable and it worked flawlessly. However, yesterday, i switched out the pitch antenna for a coat hanger so I could try to bend it and attach different sized plates (school project). This failed horribly and i was unable to get a pitch heterodyne, so I switched it back for the original antenna. However, I am now unable to tune the darned thing! I can tune the volume oscillator easily enough, however the pitch oscillator is not producing the pitch heterodyne. I hear an increase and decrease in pitch multiple times as i turn the pitch slug and none seem to stand out, nor are any very loud. Whenever I tune to one of the heterodynes (There should only be one right?) i am unable to control the pitch with the pitch antenna, and instead the volume antenna controls volume AND pitch. Any help will be greatly appreciated!
Posted: 5/5/2011 5:59:40 PM

Joined: 5/5/2011

Also, the volume heterodyne is MUCH louder than any pitch "heterodyne" I can hear
Posted: 5/11/2011 1:42:27 AM

From: Colmar, France

Joined: 12/31/2007

That means that most probably one of both pitch oscillators is not working. You may check that at PIN4 of L1 and L2 and at the emitters of Q1 and Q2 with an oscilloscope.

If you got them working, take a frequency counter in order to pre-adjust L1 and L2 for about the same frequency. This brings you already close to the correct heterodyning point and will allow you to fine-tune it by a fraction of a turn on L2 after (re-)assembling all.

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