Princeton Reverb tremolo squeal

[jazrok]

Hi,

I stripped and rebuilt a Fender '68 Custom Princeton Reverb with a Deluxe Reverb Output Transformer and a 150mA Upgrade Power Transformer (APD-2000H) made by Heyboer. I love it! Sounds fantastic BUT there is a really high-pitched squeal when I turn up the Tremolo Intensity knob. So high-pitched that as a 50 year old, I can't even hear it... but some young folks told me about it and I verifed it on my Frequency Analyser. It does it even with the amp volume off.

The only thing I've done so far is replace V4 (phase inverter/trem oscillator) and it made no difference.

Any thoughts?

Thanks in advance.

J

[sluckey]

Disconnect the NFB wire from the speaker jack. Any better?

[jazrok]

Hi Sluckey

Yes, that seems to have stopped it. I can't see that high frequency on the frequency analyser anymore. So what does that mean is wrong? Can you suggest a fix?

J

[jazrok]

I tried reversing the OT secondary leads and got a hugely loud low oscillation so it's not that...

[Stevem]

Is the wire that feeds that pot running anywhere near either of the PI output coupling caps?

[R.G.]

Any substantial rebuild would profit from a (re)reading of The Remaking of a Champ from Glass Audio.