• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Peavey 6505+112 Clean Tone not Working

I have a Peavey 6505+112, and the Clean Tone is not working properly. I can change between Rhythm and Lead Channel, with both the front panel and the foot switch. However, when I try to go to Clean Mode, the amplifier remain in Crunch Mode. I pressed the switch from the panel, and the foot switch led remains always off. It used to work before, so something blow off. I have the schematics but I have troubles to understand what could go wrong. Any help is appreciated.
 

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