As President Reagan once said "There you go again" The fact is that in the land of the blind, the one-eyed man is king; this applies equally to amps and choosing a good laundary detergent. I switched out the bias resistors shown in the last pic and pretty much thought I had the amp straightened out but never got around to firing it up. When you expressed interest, I turned it on and got a puff of white smoke and the plates in the 6L6s - large vertical metal pieces in the tube - started to 'red-plate', glow red hot.
Needless to say this was a source of some stress :evil: At the time, I was so busy, I made contingent arrangements to ship it to default in Philadelphia and see if he could straighten it out. By the time I got to manning up over it, I found I'd connected the bias caps in backwards. In the image below, the green box shows the filter caps for the bias supply; the red box, some of the primary DC filter caps; notice the difference in the symbols. As a practical matter, all bias voltages are negative so the (-) end of the cap is connected to the supply and the (+) end to ground; the opposite is true for the primary DC which is always a positive voltage. Anyway, I had the bias caps in backwards thereby smoking the 1st filter cap (both bias caps and the dropping resistor have since been replaced) and letting the 6L6 run wild thus the red-plating.
Despite your complimentary remarks, capnjuan (President and Chief Engineer of Juanzamps), stumbles and falls too .... :mrgreen: CJ
Needless to say this was a source of some stress :evil: At the time, I was so busy, I made contingent arrangements to ship it to default in Philadelphia and see if he could straighten it out. By the time I got to manning up over it, I found I'd connected the bias caps in backwards. In the image below, the green box shows the filter caps for the bias supply; the red box, some of the primary DC filter caps; notice the difference in the symbols. As a practical matter, all bias voltages are negative so the (-) end of the cap is connected to the supply and the (+) end to ground; the opposite is true for the primary DC which is always a positive voltage. Anyway, I had the bias caps in backwards thereby smoking the 1st filter cap (both bias caps and the dropping resistor have since been replaced) and letting the 6L6 run wild thus the red-plating.
Despite your complimentary remarks, capnjuan (President and Chief Engineer of Juanzamps), stumbles and falls too .... :mrgreen: CJ