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Old 03-13-2018, 01:44 AM   #2
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Join Date: Jan 2016
City & State: Valbonne, 06
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Default Re: ASRock B75M-GL dead /water damage/

If this is a high-side MOSFET it can kill the CPU. But it may be fine too, the only way to find out is to test it on another board (or try to fix this one).
The easiest way to find out if this is a high-side MOSFET is to measure resistance between yellow and black wire on the P4 power connector. With CPU connected you will measure a few ohms, without CPU you will measure a few kiloohms. If you get more than a few kiloomhs with the CPU connected, no high-side MOSFET is shorted.

It can be a low-side MOSFET. In this case you will usually measure a full short between either the output inductors (black gray cube next to the MOSFET) and ground, or across the output capacitors (the blue/gray capacitors inbetween the inductors and the CPU). A full short is lower than 1 ohm. CPU resistance is usually at least a few ohms.

The board should turn on when you disconnect the P4 power connector but obviously the CPU will not be powered on.
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