| Re: Audio Note power transformer [message #63074 is a reply to message #63070] |
Sat, 05 June 2010 23:29   |
Thermionic
Messages: 208
Registered: May 2009
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I've used dozens of those old-model Jensen/Audio Note PIO caps, and have been fortunate that (to my knowledge) not one has ever failed in service. Of course, I observe some extra precautions when using PIO caps. I avoid using them where very high internal chassis temperatures are present. I also use carbon composition grid stopper resistors with them, as the composition media is a poor conductor of heat, and helps isolate them from heat conducted from the power tube socket.
Many PIO caps have poor thermal stability; when cold their DC resistance may be hundreds of megohms, but it plummets as they become hot. I once saw a Chinese-made PIO totally lose it just a few minutes after turning the amp on, due to heat conducted into it through its leads. You could see the results of the DC leakage as it increased; the power tube began to glow in a tiny spot or two, and then eventually hotplated all over. I replaced it with a Jensen, and about 5 years of daily use later, the amp is still doing well.
Thermionic
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