No. When the vibrato is engaged I only get a flashing display on my DMM and no reading.Don't assume the 79 schem is "right", balance it against the voltages that you actually have.
Was the vibrato footswitch RCA shorted (on) when you took the readings at V5?
Shouldn't I care about the 0V on the cathodes of V5?
Current draw test:Trace the problem methodically, power down & remove ALL tubes (except rectifier). Now reinstall the power tubes, do the ammmeter accross the standby trick again, you should only have plate & screen current showing (90mA-ish?). If so, carry on & install the PI tube...by how much does the current rise? If all is good, fit the vibrato tube, keep going until you see what upsets the applecart. Use known good (new) tubes, unplug from the wall between installing new tubes, as the standby is shorted and you'll have full dc on the tubes from the moment the power switch is thrown.
- only rectifier and OLD power tubes: 130mA (plate current: 80mA)
- like above with NEW tubes: 144mA (plate current: 90mA).
I stopped putting the other tubes because it is clear that the problem is not related to preamp or PI tubes, right?
So where's the problem?
I have kept the amp on for about two hours (no guitar plugged in) and the PT got very hot...153mA is probably around the max current that the PT was designed for.