oldman55
Well-Known Member
Finished recapping a HK a500. Left the B+ wire off of the new diodes (trans still connected). Fired it up, power tubes arced and red plated and bias cap blew.
Found the loose wire and replaced cap but I must have damaged something else as B+ voltages are all 10-20% down. Bias supply is high at 75v (vs 30v spec). The 330 ohm resistor at the bias balance pot started smoking (6.5 watt resistor replacement for a 3 watt) and scratching my head. I didnt have B+ so I dont know how I could have damaged anything on the power supply line. Since this is kind of cathode bias, that should isolate the problem I would guess but have no clue where else to look. Tubes were all replaced with a working set after the red plate. Any suggestions?
Thanks
oldman who blew it again
Found the loose wire and replaced cap but I must have damaged something else as B+ voltages are all 10-20% down. Bias supply is high at 75v (vs 30v spec). The 330 ohm resistor at the bias balance pot started smoking (6.5 watt resistor replacement for a 3 watt) and scratching my head. I didnt have B+ so I dont know how I could have damaged anything on the power supply line. Since this is kind of cathode bias, that should isolate the problem I would guess but have no clue where else to look. Tubes were all replaced with a working set after the red plate. Any suggestions?
Thanks
oldman who blew it again
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