Building a Art Harrison 145 (help)

Posted: 10/30/2006 3:32:52 AM

From: MN

Joined: 10/30/2006

I've been working on a 145 for the last few weeks. I've had the pleasure to hear it working 4 times, and the agony of losing my oscillations each time. Until now I have always been able to find a broken connection or burnt transistor. Now I am utterly stuck. If anyone can help you will be a hero, not only to me but to a entire class at the U of Minnesota who are looking over my shoulder.

Here's what I have so far:

I have narrowed the problem down considerabley. Right now I have 1 oscillator working. The oscillator hooked to the atenna is doing fine. The one with the variable capsitor is giving me nothing. I thought the problem was someplace with the two 2n3906 transistors (Q1 and Q2), but I have replaced both and recently took off Q1, Q2, R2, C4, and R4 and redid that whole section. Still nothing. There is a current of 6.379 volts where I should see a sine wave. There is the 7.5 volts coming into R2 as it should be, but even at the bottom of R2 I get no wave form at all, just a straight 6.4 volts. The 6.4v goes into the Q1 transistor and the same comes out the conductor. The base is showing 5.7v. The 6.4v showes up at the top of the coils, C3, and C6 and the left side of C7. I've disconnected C3, C5 and R10 to try to isolate the problem. I've checked my wiring a hundred times, and the fact that it has worked leads me to believe that I have the wires and components in the correct places. If you have any hints or resourses to send me to, I would be very appriciative.

Posted: 10/30/2006 1:40:44 PM

From: MN

Joined: 10/30/2006

link (
Posted: 10/31/2006 10:44:21 AM

From: washingtondc metro area

Joined: 2/8/2006

e-mail art.
Posted: 7/31/2016 1:00:51 AM
Art Harrison

Joined: 3/17/2010

Yes, please feel free to e-mail me, if you still have this theremin and can't make it work. My pages moved a while back to


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