Wow, I am a posting fool today! The Quad Reverb involved in the "Four Terminal Pot" thread is having (possibly) another problem. After being fixed for about two days, the owner (my roommate) informed me that it had failed again. He says a loud pop and a bright flash occurred, after which he shut it off. After trying to energize it again, he says it made a loud buzzing noise. Taking a look today, I could see no burnt components, but a stupid wiring mistake I had made (in regards to the "Four Terminal Pot" thread
). Fixing the wiring mistake, I replaced the tubes, and plugged the amp in. Energize. I saw nothing happen in the interior of the amp, but there was certainly a loud, ugly buzz. My roommate, who was looking at the tubes yelled "Whoa!" and jumped back. After calming down, he informed me that one of the tubes was arcing within the envelope! I simply replaced that tube with another good tube, and the amp seems to be running fine (I observed it in the energized state for about 10 minutes before shutting it back off). It seems to me that this seems a bit more than "coincidental" that this amp's power tubes keep catastrophically failing! Does anyone have any suggestions as to what the cause could be? I have checked plate and screen voltages, and they are a bit high, but only by about 20v or so.
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