vibro champ tone controls problem

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I'm looking at a SF vibro champ today with something strange going on with the treble and bass controls. The amp is loudest with both controls on 1. If I turn either the treble or bass control to 10 there is no volume. The wiring looks original except the 6V6 cathode resistor and bypass cap have been replaced. There is also a small cap across pins 5 and 8 of the 6V6 socket that I don't see on the schematic. I've checked it against a schematic and layout, looking for shorts or mods, and have reflowed the solder joints on the tonestack and pots with no sucess. Has anyone run into this before?

[booj]

My scat shows a 330pf cap from cathode (8) to grid (5). Probably to minimize parasitic oscillation problems.
Good luck on the tone control issues! Sounds like someone did an expert job of wiring them backwards.

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Booj, thanks for the info on the cap. I looked at a different schematic and found it. As for the tone controls, I wish it was that simple. They look to be wired right... I guess it's going to take some digging.

[MWJB]

Broken 250pf treble cap? Take the guesswork out, replace tone caps & 100K slope resistor.

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MWJB, thanks for the reply. I went ahead and replaced the tone caps and slope resistor. Also replaced the pots for treble and bass. It's running well now; very sweet little amp! Thanks again,

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