?Hallo F5RCT
I dont really undestand the constant courrent circuit Q01, even if I have known it since FP-707. I know what it does, but I dont know how it does it. BTW Yaesu has always used too much filtering capacity, FP-707 uses 0.1mF, what means litle angle of conduction and high peak intensity. Trafo suffering. So it is a good solution to reduce capacity as long as PS works. In the FT-980 I found best solution was to wire it for 234VAC and feed it with 200VAC, heath reduced a lot. I used a VariAC but if I used the radio as TX I would place an autotrafo 230/200VAC,? this PS maybe is not best Yaesu design.
I think the first capacitor in 13.5V PS Q01 must be an schematic error, of course it must be placed before the FET.
But all these Yaesu PS's? have one capacitor after the FET, and as I said, I dont know how it works, but it worked very well in the FT-980 TX13.5V short circuit failure (PA tantalun capacitors). Voltage went down to 3V and no damage in RF unit placed between PS and PA.
I mentioned the crowbar, because I have seen it in LA of over 1kW, with transistors at 50V that die easily by overvoltage. I had this problem in one LA (4 transistors blown by 69V) and the LA is in the way to be changed linear PS for a 48V switched PS, it has a design fault and I dont trust it anymore.
73 EA1FC
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