Tubes are only expensive if they are common audio types. Design to use Soviet tubes from sellers in Ukraine etc and you find tubes for a couple of Euros 🙂
Everyone and the grandmother usually uses zeners for that clamping, but TVS diodes can handle far larger transients and cost about the same so I always suggest bidirectional TVS like the ones I mentioned...600W of surge handling in the size of a 5W zener 🙂
Everyone and the grandmother usually uses zeners for that clamping, but TVS diodes can handle far larger transients and cost about the same so I always suggest bidirectional TVS like the ones I mentioned...600W of surge handling in the size of a 5W zener 🙂
TVS diodes Noted! Im still confused about: How the heck did D10/D12 fail if the current flowed towards the feedback resistors? So J1 gate must have failed first but I simply dont see how.
Current reversal caused D12 to short R20 (almost) and then C13 discharged (almost) like a short? Which caused a surge big enough to kill then? Can C7, C8, and C11 discharge into the PSU? No idea but I'd put a diode between C12 and Q7 and see if it helps. The STR10100LSS_AY_00301 would be a good choice maybe? It's got a low Vf and doesn't need a heatsink because it's in a DO-201AD Package 🙂
https://www.panjit.com.tw/upload/datasheet/STR10100LSS.pdf
https://www.panjit.com.tw/upload/datasheet/STR10100LSS.pdf
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