Re: Second opinion on g750js motherboard power circuit.
The bad FET you found is part of a buck regulator for the CPU power rail.
When the high-side FET (the one connected between the positive supply and the output of the regulator) in a buck regulator is shorted, it can often take the FET driver chip with it.
Buck regulators need a PWM controller (handles the on/off timing) and a driver (handles sending voltage to the gate of the FETs). They are usually combined into one chip now. But not always.
In this case, the shorted FET belongs to one phase of a 3 phase regulator. The other 2 phases use drivers in the control chip. But the phase with the problem has a separate driver chip (PU8001).
Long story short, PU8001 may be bad. If so, it will just keep destroying the high-side FET. You have to replace both the FET and the driver chip at the same time.
The bad FET you found is part of a buck regulator for the CPU power rail.
When the high-side FET (the one connected between the positive supply and the output of the regulator) in a buck regulator is shorted, it can often take the FET driver chip with it.
Buck regulators need a PWM controller (handles the on/off timing) and a driver (handles sending voltage to the gate of the FETs). They are usually combined into one chip now. But not always.
In this case, the shorted FET belongs to one phase of a 3 phase regulator. The other 2 phases use drivers in the control chip. But the phase with the problem has a separate driver chip (PU8001).
Long story short, PU8001 may be bad. If so, it will just keep destroying the high-side FET. You have to replace both the FET and the driver chip at the same time.
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