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<blockquote data-quote="dB-r" data-source="post: 6167031" data-attributes="member: 574699">I would say either an output failed and shorted and for some reason the protect circuit didn&#039;t shut the amp down and the power supply, now running into a dead short (the bad output is a dead short) went Poof!That&#039;s the most likely scenario.&nbsp; This has to be an OLD IA 20.1, not the new one, the new one uses TO-220 mosfets, the one in your pics uses TO-247AC mosfets.&nbsp;&nbsp; Only other LIKELY scenario is a shorted power supply transformer.&nbsp; We deal with this stuff on a daily basis and those are pretty good guesses.&nbsp; Have rebuilt plenty of older model IA 20.1&#039;s.&nbsp; They are great amps, really, If I had one I&#039;d run it in my setup.&nbsp;&nbsp; If a power supply transformer shorted, which is pretty likely too that may have happened instead of a bad output, it would also make the power supply go poof!Check the outputs to see if any of them read as a dead short.&nbsp; Something that most people don&#039;t understand about repairing an amplifier is that you have to TEST the parts, visible damage will only occur on the parts that were still good when the other parts went bad, which likely won&#039;t have a hint of smoke or anything on them, they will look good as new until you test them.</blockquote>

[QUOTE="dB-r, post: 6167031, member: 574699"] I would say either an output failed and shorted and for some reason the protect circuit didn't shut the amp down and the power supply, now running into a dead short (the bad output is a dead short) went Poof! That's the most likely scenario. This has to be an OLD IA 20.1, not the new one, the new one uses TO-220 mosfets, the one in your pics uses TO-247AC mosfets. Only other LIKELY scenario is a shorted power supply transformer. We deal with this stuff on a daily basis and those are pretty good guesses. Have rebuilt plenty of older model IA 20.1's. They are great amps, really, If I had one I'd run it in my setup. If a power supply transformer shorted, which is pretty likely too that may have happened instead of a bad output, it would also make the power supply go poof! Check the outputs to see if any of them read as a dead short. Something that most people don't understand about repairing an amplifier is that you have to TEST the parts, visible damage will only occur on the parts that were still good when the other parts went bad, which likely won't have a hint of smoke or anything on them, they will look good as new until you test them. [/QUOTE]

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