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previous: Mike T I removed the rectifier tube and re... -- 1/2/1998 5:07 PM

Re: Cathode Bias Idling Current

1/2/1998 11:05 PM
stephen	Re: Cathode Bias Idling Current 250 Ohm Rk bypassed by 25/25 cap. Vp=300, Vs=250 Tubes get very hot, but no voltage across 250 Ohm Rk..... Hmm.. Is the cap polarity correct? If it's in reversed, it could be very leaky ( and very dead) by now, but I wouldn't expect it shorted enough to produce zero volts across it. Lift one end anyway, and see what you measure across Rk then. Dead-short electro's do sometimes happen, even if not wired in backwards. Don't want to seem grinding the same old topic, but you might drop a 1-okm resistor in each the cathode lead, or use your sniffer adaptors, and check what cathode currents are actually flowing. Also lift one end of the 250 Ohm and measure it. - Stephen

1/2/1998 11:05 PM

stephen

Re: Cathode Bias Idling Current

250 Ohm Rk bypassed by 25/25 cap.
Vp=300, Vs=250 Tubes get very hot, but no voltage across 250 Ohm Rk.....

Hmm.. Is the cap polarity correct? If it's in reversed, it could be very leaky ( and very
dead) by now, but I wouldn't expect it shorted enough to produce zero volts across it. Lift one end anyway, and see what you measure across Rk then. Dead-short electro's do sometimes happen, even if not wired in backwards.

Don't want to seem grinding the same old topic, but you might drop a 1-okm resistor in each the cathode lead, or use your sniffer adaptors,
and check what cathode currents are actually flowing. Also lift one end of the 250 Ohm and measure it. - Stephen

Replies:

Mike T Very strange, Stephen. I bypassed ... -- 1/3/1998 8:07 AM