1966 Fender Princeton Reverb

[xtian]

On the bench is a near-mint '66 PR. It plays and sounds OK, but anemic (only 2w output, with a little assymetric ringing). Voltages are all close to spec. Tubes are all original, so may be weak, or original filter caps are weak (however, no hum, very low 2v AC ripple at B+1, no ripple on bias voltage).

Weird behavior: Tremolo is full strength, even with Intensity control at zero. Intensity pot reads 35 ohms at minimum, so maybe it just need to be replaced. Tremolo stops when foot switch is shorted, so that's OK.

Weird behavor: Amp whistles loudly when Reverb pot is turned up above 1 or 2, whether tank is connected or not. No change when replacing 12AT7 driver. At 1 on the dial, some faint reverb is heard.

Ordered cap can.

IMG_2059.jpg

[didit]

Hello Aaron --

Cap can replacement in process, good. Was -34V power bias part of "voltages are all close to spec" tests? Can you scope the output of reverb recovery when in "whistle" mode?

..

[martin manning]

Wow, that's a clean piece! What's the plan? Is it going to be a player? Likely needs a full set of electrolytics, maybe replacement of drifted CC resistors.

[xtian]

Yes, bias voltage was -34 or very close. I'll remember to scope the output if I still have oscillation after replacing the filter caps.

Owner decided it's to be a player. Needs new power cord, lift death cap, check resistor drift, etc. Next week. Thanks, peeps.