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FDP Forum / Amp Mods, Repairs, and Projects / PR Tremolo help


United States

Dale Beeks
Jan 9th, 2019 12:09 PM   Edit   Profile  

My 1965 PR is all original. The trem only works at a speed of 3 or greater and then it's intermittent. I cleaned the tube sockets and contacts and pots. What's the next step to diagnose?
Thank you in advance for any assistance

Contributing Member

Just beyond Mars

there's a world of fools
Jan 9th, 2019 12:56 PM   Edit   Profile  

Does the problem exist with the pedal plugged in and not plugged in? If it's not the pedal causing the problem...

V4B (the 2nd half of V4's dual triode) is the vibrato driver; swap in a different 12AX7 and see if the problem persists. If it does, it's not the tube itself causing the issue.

Loosen both the speed and intensity pots a little, and rotate the pot bodies back and forth a little bit, and re-snug them. This re-establishes a good ground if a poor ground existed.

If that doesn't fix the problem, you'll need to crack it open, test for proper voltages per the schematic for the vibrato section and check spec on all components there.

There are lethal voltages present in tube amps, even when unplugged. If you're unfamiliar with this stuff, it's not worth the risk to your safety or possibly frying something in the chassis. Take it to an amp tech.

(This message was last edited by Peegoo at 02:58 PM, Jan 9th, 2019)


United States

Dale Beeks
Jan 9th, 2019 08:01 PM   Edit   Profile  

Thank you!

FDP Forum / Amp Mods, Repairs, and Projects / PR Tremolo help

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