Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ScooobyDont on December 30, 2022, 02:39:57 pm
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Hey all,
Hoping someone might be able to help me with something. I have a 1972 sf deluxe reverb with an odd issue on my vibrato channel. As I turn up the treble control I lose volume. When control is at 10 there is no volume. This only happens with the vibrato channel. Normal channel is fine. I've switched out tunes, checked voltages to preamp tube, checked the wiring of the tone circuit, checked resistance of the treble pot, checked continuity from the wires off the pot to the board. It all seems fine. Unfortunately I do not have an oscilloscope or I could do more troubleshooting. Im thinking of doing some guerilla tactics and replacing the caps in the tone stack. Any other ideas come to mind???
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Sounds like the top of the treble control has become grounded. Ohm-meter (POWER OFF!) would be a thing to check.
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There is 2 treble pot capacitors, one may be defective if you do right test on the pot.
Compare the measurements with the normal channel which works fine, you should find out where the problem comes from.