More info on my Amplifier that blew a diode ..................
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| Posted on October 10, 2023 at 14:27:39 | ||
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Posts: 18449
Location: Minneapolis - St.Paul Area Joined: September 2, 2000 Contributor Since: May 16, 2021 |
So, yesterday I tested my 4 KT88 tubes that were in the amplifier when the diode blew. I had marked the tube that had the blown diode in it so I double tested that one. They all tested Strong, No shorts, No leakage... .. So, I had a free day today, I put the Original KT88s back into the amplifier. This time, I put the Tube that was in the Bad Diode circuit on the opposite side of the Amplifier from where it was when the Diode Blew. After about 2 hours, my wife's sensitive nose, smelled the Ozone like smell. I took the Temp of the Power Transformer where the 'Bad' Tube was and sure enough it was about 60 degrees hotter than the other transformer. So, I took the amp apart and sure enough the diode was shorted where the 'Bad' Tube was. This time it was the opposite side of the amp. No burned wire this time, so it was probably the overheating transformer that caused the smell. So, I had a bad KT88 tube that I disposed of.... Obviously the Tube Characteristics changed after a couple hours of heat. I have read that a Power tube can develop a Short after being operated for a few hours and is exposed to a lot of heat. Amp is back playing fine and will stay that way with new KT88 Tubes.
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