Watkins Scout Tremolo Circuit

[Ted]

I have a mid 60s Watkins Scout here. I just fixed the tremolo by replacing a couple of caps in the phase-shift network of the oscillator.
Couldn't find a schematic anywhere, but it seems to share the trem circuit of the Watkins Westminster(V1A and V1B)

http://www.vintagehofner.co.uk/brita...inster10w.html

It is not as other trem circuits.
So:
V1B is the oscillator and the trem works by modulating the plate voltage of V1A. But why does the footswitch go to the output of V1A? And what is that 50nF cap from the plate of V1b to ground?

[trobbins]

The 50nF is one of a few means to attenuate the trem signal harmonics (relative to the fundamental frequency).

The footswitch would typically go to ground, to allow the feedback loop to have sufficient phase shift to oscillate. Returning it to the grounded side of V1A output provides a resistive path to ground to allow the CRCRCR phase shift, and I'd guess may provide some positive feedback to enhance the oscillatory response.

Not many trem circuits go for plate voltage modulation, but I think simplicity of circuit configuration would have been seen as a benefit - common cathode bias and bypass, and not trying to inject trem signal in to the V1A cathode. Seems like a neat technique - may be well worth trying.