Just got my amp back for the 4th time.A new standby switch, preamp converted for 12AX7s, clean, bias, & adjust. I'm goin' to beat the $#!+ out of it this Friday night. I hope this is the last bug. A new tech from Boston. I had to drive two hours each way TWICE, plus a fair amount of pesos, but if it fixes the problem, then OK. I know Vic D. will want to know, so I'll report back on Saturday.