Only when this happens when the power supply failed when it's tested without the motherboard.
You could do this test also by disable the pin 3 wire between the psu and the motherboard.
When it's still failed as you have measured, then I would replace the ic, but check at least the diode if it's leaking before you do the other things.
Useless to say that you need to remove the diode, or at least one side from the pcb to test it with a multimeter on diode settings.
Or else, just replace the diode to see if it solves the issue.
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Johnny B.

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