16-04-2017, 03:41 PM
I suspect TX7 is the FM oscillator. It looks like the oscillator is coupled via C40 into the emitter of mixer TX5. If I'm right, TX6 is the first FM IF. TX4 is the RF input amp.
The connection via R38 is interesting. It looks like it might be AFC, given that it's fed from the output of the discriminator. Varying the bias on TX8 changes the capacitance of its collector-base junction (a bit like a varicap diode).
If I'm right about this, then yes, it should have worked from new, but with no or poor AFC. Whether this would have been noticed is obviously up for debate.
Interesting circuit - quite different to the norm. Thanks for posting
The connection via R38 is interesting. It looks like it might be AFC, given that it's fed from the output of the discriminator. Varying the bias on TX8 changes the capacitance of its collector-base junction (a bit like a varicap diode).
If I'm right about this, then yes, it should have worked from new, but with no or poor AFC. Whether this would have been noticed is obviously up for debate.
Interesting circuit - quite different to the norm. Thanks for posting
