fender amp vibrato plate voltage

[musicman3858]

Hello again, I am stumped on a problem for a 73 bandmaster that I am refurbing into blackface mod. (subtle) I am getting a high voltage on the plates of the vibrato tube. I measure the voltage before the plate resistor and after and there is no drop of more than 10 vdc. I've replaced the resistor and no diff. Could it be a short? I have replaced the cap also thanks

[soundguruman]

There won't be a drop, unless the tube is amplifying signal.
The more amplification, the more voltage will drop.

[pdf64]

Assume it's not oscillating, in which case both triodes should be in cut off, therefore your observation is to be expected.
Or is the fault that it isn't oscillating?
Pete

[musicman3858]

yes it is not oscillating. I don't have a pedal plugged in. I thought I heard that you need a pedal in to finish the circuit. Would that be the case? Thank you for the information. That makes sense. I was also getting some highter than normal readings other places too but I think it's due to the change in ac voltage since 73...just wanted to check.

[52 Bill]

yes it is not oscillating. I don't have a pedal plugged in. I thought I heard that you need a pedal in to finish the circuit. Would that be the case?

The pedal connection has to be grounded for the oscillator to run. Either use the pedal or short the connection at the RCA jack with a temporary jumper wire.