Asus P8P67 EVO EATX 12v shorted fix
Someone called yesterday about this board. Told me he made the big mistake of letting the board auto set its voltages when overclocking, and it worked for 2 hours then died. Would shut down the power supply when the EATX 8-pin connector was plugged in.
I asked him to repeat the test without the CPU. He reported that it did the same thing, so i said the CPU has likely survived, and the board is at fault. Told him to bring it in.
When the CPU was installed, the 12v EATX connector read about 5 ohms to ground. Not a dead short, but pretty close. Seemed fine with the CPU out, but i was sure it wasn't, so i started probing the MOSFETs. All FETs in plain sight checked out okay, so i decided to remove the VRM heatsink and take a look. Sure enough, a group of 5 MOSFETs on the high side read shorted drain to source.
Murphy's law applies, the shorted FET was the last one i pulled. They were FPH7030L btw, i soldered the good ones back on. I happened to have an Infineon part on hand, which was close enough to the original. Thought it would work for a test.
Dropped the CPU back in, and sure enough, the 12v EATX connector didn't read shorted anymore. Put the video card in and it fired right up.
I told him to keep it at stock for now, the original MOSFETs are no longer manufactured, so i will be ordering a bunch of PSMN4R4 which are superior in all aspects, and they're 75 cents each. I'll be swapping the entire high-side of the VRM.
I asked him to repeat the test without the CPU. He reported that it did the same thing, so i said the CPU has likely survived, and the board is at fault. Told him to bring it in.
When the CPU was installed, the 12v EATX connector read about 5 ohms to ground. Not a dead short, but pretty close. Seemed fine with the CPU out, but i was sure it wasn't, so i started probing the MOSFETs. All FETs in plain sight checked out okay, so i decided to remove the VRM heatsink and take a look. Sure enough, a group of 5 MOSFETs on the high side read shorted drain to source.
Murphy's law applies, the shorted FET was the last one i pulled. They were FPH7030L btw, i soldered the good ones back on. I happened to have an Infineon part on hand, which was close enough to the original. Thought it would work for a test.
Dropped the CPU back in, and sure enough, the 12v EATX connector didn't read shorted anymore. Put the video card in and it fired right up.
I told him to keep it at stock for now, the original MOSFETs are no longer manufactured, so i will be ordering a bunch of PSMN4R4 which are superior in all aspects, and they're 75 cents each. I'll be swapping the entire high-side of the VRM.