Hi. I built a theremin around '66 from a magazine (Pop Electronics?) article, don't have the magazine anymore, and can't find any reference to the design online. Details: 2 6BE6's, a 6X6, a 12AU7, and a 6AN8A. Also, (uniquely?), a 500kHz radio crystal, which I couldn't find, so I substituted a 27.6 mHz one, as the article said the harmonics of higher frequency crystals made them work OK. Anyway, I want to revive the beast, and would appreciate it if someone could tell me when and where the design was published? Also, the tone oscillator wasn't stable -- each time you tuned it down to the lowest bass, it would creep up to beyond audible in about a minute. Any suggestions as to how to fix this?
Thanks.
Thanks.