On the back panel just under the power cable is a rocker switch(seen pictures with toggle switches) I just bought this amp from a pawnshop on ebay. When I powered it up it sounded great, punched the channel switching footswitch and no problem, worked fine. I was under the impression the toggle switch was just a manual switch for the lead to clean but not here. This rocker switch is in the "B" position and when switched it totally loses power. When I contacted the seller, he also thought the switch was just a manual lead/clean switch and didn't bother with it since it had a foot switch. Does anyone know anything about this function, I've looked everywhere and nothing is explained about this switch, I'd appreciate if anybody knows, and yes I'm gonna buy new matching tubes next.