81 Fender Princeton rev tremolo not working
Posted: Thu Feb 14, 2019 2:30 pm
I'm working on a 1981 PR w/boost pedal (not a PR II) and the tremolo doesn't work when the amp is warmed up and on. I can hear the tremolo when a chord is strummed and the amp turned off and the power is decaying. It comes through strong at that time. I've pulled every component in the circuit and they all check within tolerances. Checked continuity of all the connecting wires. Replaced V4 several times. Here's a table of voltages I've measured (Fluke 112) with the trem at 0 and 10.
Tr=0 Tr=10
BIAS -32.5v -31.5v
Plate 200-280(unstable) 240v
Cathode 1.25v 1.8v
The plate voltage varies greatly except on the other side of the 220k resistor where it's stable at 392v. The schematic calls for 250v on the plate and 2v on the cathode.
Is there anyone out there that can point me in the right direction?
Tr=0 Tr=10
BIAS -32.5v -31.5v
Plate 200-280(unstable) 240v
Cathode 1.25v 1.8v
The plate voltage varies greatly except on the other side of the 220k resistor where it's stable at 392v. The schematic calls for 250v on the plate and 2v on the cathode.
Is there anyone out there that can point me in the right direction?