John,
Off hand, I would not guess the filter caps. Why? If there were an open or a short with one or more caps, it would not be all of them at once that would be needed for leading to the no high voltage situation. If there were a short in the RF deck, the 0.82 ohm resistor in the supply would be blown; a visual inspection from outside the cabinet would show that. Generally if there is a HV short in the RF deck there is usually a sound associated with it, like a bang if there is a plate to grid short taking out one of the grounding RF chokes. My guess would be a diode problem or something with the high voltage transformer, 50 K 50 watt bleeders arcing to ground, or HV wiring. An open diode or two in the voltage doubler circuit might result in a loss of HV DC. However, the fact that the breaker(s) did not trip suggests that there was not a hard short in the supply unless you turned it off just as things were "starting to happen". Take it slow, and safe. Wait until you've healed completely. High voltage does not give second chances. Visual inspection of the components inside the power supply might be a good place to start. Please keep us informed of your progress so we can all learn from you. 73, Evan, K9SQG -----Original Message----- From: John King <k5...@yahoo.com> To: Drakelist <Drakelist@zerobeat.net> Sent: Thu, Jan 16, 2014 10:12 pm Subject: [Drakelist] "grunting L4B" Yesterday, I turned my L4B on and the tubes lit up and the blower ran and the plate voltage was up to par. Today, I turned the L4B on and I heard a loud buzz/grunt. The breakers did not trip in the power supply. I turned the AMP off and scratched my head. I suspect the filter caps in the HV power supply. There was no HV showing on the meter . I left the power supply on for only 2 or 3 seconds. I have 8 new caps to replace the old ones with, but I just had surgery yesterday and can't get up enough steam to check it out. I am wondering if any of you have witnessed the way your power supply acted when the capacitors shorted? Your experience? Thanks and 73, John, K5PGW _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
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