I got this Chieftec half-sized ATX PSU (don't know the model right now, but it is ATX sized, just shorter) that is smells and does not turn on.
It is a single transistor forward with 2 transistor stand-by. One cap bad at +5 V SB, OK replaced both. Than there was some diode burned, seemed like a -12 V eh? Replaced with more fat shottky. Wrong. It whistles and there is 16 V at +5 V SB!! It was 6.8V transil which was there to bring the voltage down. No wonder it was completelly baked and blown after those years. And it makes reason there was 16V cap after the stand-by rectifying diode and not sooner than in the end there was 10V, just next to the transil.
I will probably replace it with 6V transil but in bigger package, DO201 and for 1500W spikes. And replace the caps with 16V/1000uF KZHs. Also thinking about maybe relocating the transil a bit as it is under coil for passive PFC without much cooling possibilities.
It is a single transistor forward with 2 transistor stand-by. One cap bad at +5 V SB, OK replaced both. Than there was some diode burned, seemed like a -12 V eh? Replaced with more fat shottky. Wrong. It whistles and there is 16 V at +5 V SB!! It was 6.8V transil which was there to bring the voltage down. No wonder it was completelly baked and blown after those years. And it makes reason there was 16V cap after the stand-by rectifying diode and not sooner than in the end there was 10V, just next to the transil.
I will probably replace it with 6V transil but in bigger package, DO201 and for 1500W spikes. And replace the caps with 16V/1000uF KZHs. Also thinking about maybe relocating the transil a bit as it is under coil for passive PFC without much cooling possibilities.
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