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Old 07-12-2018, 04:58 PM   #1
ATB57791
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Default Asus P8P67 LE shorted VRM

Hi all, I am trying to repair a motherboard from asus that suddenly stopped working. There was a shorted mosfet in the vrm. I connected the cpu power pins to a lab power supply and a Nikos P0903BDL mosfet (second row in the picture) got very hot. After replacing it with a P0903BDG (already replaced in the pic) the motherboard starts but does not post.

I noticed that the cpu doesn't get hot without a cooler when the motherboard is turned on. I suspect that there are other defective components in the VRM.

I have a tester that can test mosfets. Should I just remove all the mosfets from the VRM one by one to test them? Or is there something else I should check first?
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File Type: jpg mosfets.jpg (472.6 KB, 50 views)
File Type: jpg tester.jpg (134.8 KB, 40 views)

Last edited by ATB57791; 07-12-2018 at 04:59 PM..
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Old 07-13-2018, 03:23 AM   #2
piernov
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Default Re: Asus P8P67 LE shorted VRM

In the CPU VRM section you need to match the MOSFET or else they will be unbalanced and one of them will heat up and die again. Use the same model, and if possible replace both MOSFET of one phase with the same batch.
Also usually it's better to replace the driver IC and/or the buck controller as they either could have caused the MOSFET's death, or die at the same time as the MOSFET.

Boardview attached if needed.
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File Type: zip P8P67_LE.zip (251.5 KB, 27 views)
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Last edited by piernov; 07-13-2018 at 03:26 AM..
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Old 07-17-2018, 03:29 PM   #3
ATB57791
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Default Re: Asus P8P67 LE shorted VRM

There was also one P0403BDG that had gone bad in the VRM. I don't have a similar replacement for that.

Can I replace the mosfets and drivers from an Asus P8P67-M REV 3.00 motherboard? I have one that has all voltages OK, but no post. There seems to be a similar design, but the mosfets are of type A09N03 and A09N06 compared to P0903BDL and P0403BDG on the P8P67 LE.
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Old 10-23-2018, 07:06 AM   #4
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Default Re: Asus P8P67 LE shorted VRM

thanks for the boardview. Is there any schematics available for this mainboard?
I searched the net and did not find it.
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Old 10-24-2018, 12:55 AM   #5
piernov
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Default Re: Asus P8P67 LE shorted VRM

Usually no schematics for Asus, only boardviews which is already a nice thing to have.
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