Hi guys
I have a Gigabyte GA-EP45C with a VRM problem
When attaching an ATX power supply the motherboard trips out the PSU
If I disconnect the 8 pin 12V connector it will power up
I was seeing about 36 ohms from 12V 8 pin connector to ground, and 0 ohm across the high side MOSFETs drain/source
There are 6 supply phases. I removed the High side MOSFETs one at a time.
Logic said to start with the three at the side of the PCB as they were easiest to desolder as there were less surrounding components
Sods law said that the short circuit MOSFET was the last one I unsoldered near the back panel connectors
The other five all test OK on my multimeter diode mode. I can turn the FETs on and off by touching +ve or -'ve to the gate, so they look just fine.
Having removed all the high side MOSFETs, I now have about 1Mohm from 12V 8 pin connector to ground, but I have about 48 ohm from the drain of the low side MOSFETs to ground. It starts a few ohms lower and increases like a capacitor charging. This is with no CPU fitted. So it's not a short just a bit of a low resistance.
I thought it was a good guess to unsolder the two low side MOSFETS on the phase that had a short circuit high side MOSFET.
However once i did that those also test OK on my multimeter, I now have 52.6ohms from Drain of low side MOSFETs to ground, again starting lower like a capacitor is charging up.
I could proceed to unsolder all the low side MOSFETs but I'm not sure if this really is a fault and don't want to be wasting my time unnecessarily (and I'm feeling lazy lol).
Maybe Vcore supplies something else like North Bridge and that is what I am reading?
I'm also thinking maybe to refit the five good high side MOSFETs are power the board up with 5 phases running just to see what happens?
High side MOSFETs A2726 and low side are A2724. They are not expensive.
Rich.
I have a Gigabyte GA-EP45C with a VRM problem
When attaching an ATX power supply the motherboard trips out the PSU
If I disconnect the 8 pin 12V connector it will power up
I was seeing about 36 ohms from 12V 8 pin connector to ground, and 0 ohm across the high side MOSFETs drain/source
There are 6 supply phases. I removed the High side MOSFETs one at a time.
Logic said to start with the three at the side of the PCB as they were easiest to desolder as there were less surrounding components
Sods law said that the short circuit MOSFET was the last one I unsoldered near the back panel connectors
The other five all test OK on my multimeter diode mode. I can turn the FETs on and off by touching +ve or -'ve to the gate, so they look just fine.
Having removed all the high side MOSFETs, I now have about 1Mohm from 12V 8 pin connector to ground, but I have about 48 ohm from the drain of the low side MOSFETs to ground. It starts a few ohms lower and increases like a capacitor charging. This is with no CPU fitted. So it's not a short just a bit of a low resistance.
I thought it was a good guess to unsolder the two low side MOSFETS on the phase that had a short circuit high side MOSFET.
However once i did that those also test OK on my multimeter, I now have 52.6ohms from Drain of low side MOSFETs to ground, again starting lower like a capacitor is charging up.
I could proceed to unsolder all the low side MOSFETs but I'm not sure if this really is a fault and don't want to be wasting my time unnecessarily (and I'm feeling lazy lol).
Maybe Vcore supplies something else like North Bridge and that is what I am reading?
I'm also thinking maybe to refit the five good high side MOSFETs are power the board up with 5 phases running just to see what happens?
High side MOSFETs A2726 and low side are A2724. They are not expensive.
Rich.
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