So I've got an issue that I've never seen before, and I'm confused. On one amp, if I measure the voltage on the plate of the driver tube (6350) I get around 350v which seems to be fine, but when I measure in the same place on the other amplifier, the voltage shoots up over 500v.
Does anyone have any idea what would cause voltage to end up so high here? At the bottom is where the mains trafo goes into the diode bridge, goes through a 5k resistor, and then into a 68k resistor before it's on the plate of the 6350.
I'm starting to question my sanity with this amplifier, if it didn't weigh 80 lbs I might throw it in the street.
Does anyone have any idea what would cause voltage to end up so high here? At the bottom is where the mains trafo goes into the diode bridge, goes through a 5k resistor, and then into a 68k resistor before it's on the plate of the 6350.
I'm starting to question my sanity with this amplifier, if it didn't weigh 80 lbs I might throw it in the street.
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When the plate voltage is much higher than normal, and approaching the supply voltage level, it means the tube is not conducting for some reason. It could be the cathode circuit is open or that the tube is not getting its heater hot, or that the biasing has the tube in its cutoff mode. ... Bad solder, bad PC board, bad socket...bad something. Good luck. You may just need a magnifying glass to find it if you can't find it with a meter.
