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Post subject: Twin trouble ?
Posted: Mon Mar 17, 2008 8:00 pm
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Has anybody ever had this problem ? I have a 1972 twin, the other nite I was playing it at a normal "inside the house" level and all of the sudden it let out an extremely loud high pitch squeal, I had to shut it off to make it stop.The reverb and vibrato were both on. The amp normally works real well. It hasn't had any mods or anything done to it and is all factory.I've had it for 20 years and have never changed the tubes, could this be it ? Any advise?


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Post subject:
Posted: Thu Mar 20, 2008 7:05 am
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Yeah you probably have a bad preamp tube for sure. If you just want to find the bad one turn the amp on and tap all the preamp tubes with a pencil until you find the bad one. I would go ahead and do a full retube if I was your though. 20 years is a LONG LONG time without tube change.


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Posted: Thu Mar 20, 2008 7:41 am
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Yea, I'm going to put new pre amp tubes in but the tube diagram shows three different tubes and everybody says to replace them all with 12ax7, whats up with that? Also pulled my reverb tank and found one of the springs busted, got a replacement on the way.


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Posted: Fri Mar 21, 2008 3:20 pm
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They don't make the 7025 tubes anymore. They haven't for a very long time and if you can find them they'll cost you an arm and a leg. The 7025 tube was manufactured to military specification for use in military equipment. The 12AX7A is a direct replacement for the 7025


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Posted: Mon Mar 24, 2008 2:13 pm
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