Since the RCA Radiola 60’s chassis is so similar (probably the same stock) to the theremin’s, I figured I should keep most of it intact as possible. I thought about removing the plastic plate that holds the tubes, but six of the sockets are on one strip and it would just get messy. My best bet was to re-drill holes. The Radiola uses seven 5-pin tubes and one 4-pin tube while the theremin has four 5-pin and three 4-pin tubes. Fortunately, the 4-pin socket on the Radiola is the same for the theremin, but two tube sockets needed to be re-drilled.
I measured the holes and created a jig. I found that if I rotated the tube 45 degrees, I would get 3 of the metal catches to still touch the tube pins and would have the cleanest drilling possible.
I sanded, primed and painted the transformer. I color matched the paint at Lowes.
Before:
After:
The concentrated coil is much thinner than I thought. It was hard to judge depth looking down the small coil form. As soon as it slid out after unscrewing it, I knew it was not like the theremin’s. The dimensions are 1+1/8″ O.D., 1/2″ I.D., 1/8″ thick. The coils measure 46.8 Ω. If I measured the resistance correctly, that would be about half of the theremin’s. I wonder if putting the two in series would work.
