Quote:
Originally Posted by Bobby Dip
Has anyone seen a detector like this?
Bob D.
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At first glance I thought this resembled a (push-pull) voltage doubler more than any FM detector that I'd ever worked with.
I thought I'd compare it with a known pre-WWII TV AM sound detector and looked at the RCA TRK-5 and got a surprise:
http://www.earlytelevision.org/pdf/r...-rider-tv1.pdf
In that set, V-10 the
6B8 pentode, is the 2nd sound IF and its two plates on pins 4 & 5 are the AM detector.
You will notice a circuit similarity (although the TRK-5 detector cathodes are common, and yours are not), and it is drawn quite differently.
It is a known fact that some of these 1939-1940 sets detector transformers were intentionally mis-tuned (for AM) to keep them running in the early days of FM sound when replacement parts were not available.
I'd say that this circuit could probably work as either an AM detector or an FM detector depending on the tuning.
Notice the other components inside the transformer in the TRK-5 circuit.
Also, notice that one of the diodes has both sides connected to ground, therefore it is not used.
In your circuit, I think they were trying to increase gain by capturing both polarities of the slope to increase level.
Jas.