I had a similar faiure once (no short, just loss of power) with still tiny bit of output (approx 20db down).? ?Problm was plastic movement of SOLDER which ended up with poor connection for one of the final MOSFETs? ? Re soldered, worked fine!
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If you are in there, and can get access to Aluminum nitride insulators, I would consider replacing the mica with the alum nitride which have much better thermal conductivity.? ?Might keep the junction considerable cooler by making the heat sink considerably HOOTTER.??
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Of course, could have fried the mosfet.? ? The latter has only happened to me once and it resulted in a shorted mosfet -- comletely shorted
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Good luck!
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While in there, it is up to you whether to add back in the TVS diodes.? ?They are incredibly tiny.....? Ashhar thinks they are unnecessary with the V3 ciruitry.
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I do not think that you can put in the IRF520 beause the V3 circuitry is not designed to drive the much higher input capacitance of the IRF520
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73
Gordon KX4Z
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