Re: Asus Z87 Expert - No Power, LDO Regulator Gets Hot!

When I inject 3V to the board, it is taking 4.7 amps from power supply. And power supply voltage drops to 2.3 volt.
The multimeter currently I have cannot read fine resolution. It can read 0.1 ohm.
I’m not injecting voltage to the LDO, because LDO is not in 3VSB power rail, and there’s no ground pin on LDO. From LDO 3VSB_ATX (3VSB_ATX is not shorted to ground, only 3VSB is) goes to MOSFET (PQ301 on board view) and that MOSFET is connected to 3VSB power rail, so I’m injecting voltage to 3VSB pin...

Re: Asus Z87 Expert - No Power, LDO Regulator Gets Hot!

Voltage injection makes PCH warm. So the PCH is shorted then.

Re: Asus Z87 Expert - No Power, LDO Regulator Gets Hot!

I can see the whole 3VSB rail is short to ground. No, Ethernet was not connected when surge occurred. I checked LAN and audio chips, only 3VSB pin is short to ground. I guess the chip is ok?
How do I find which component is short? Should I use external 3V to burn the component?

Re: Asus Z87 Expert - No Power, LDO Regulator Gets Hot!

I found one resistor, one pin goes to regulator output and the other goes to +3VSB ATX.
Boardview shows it should have 1.15K OHM. But multimeter reads 1.13K OHM. Is that a problem?

Due to a power surge my Asus board does not power on, when I connect 24 pin power connector to motherboard (without turning on the board), the LDO regulator (UZ2085G / PU300) gets hot immediately. Hot I mean insanely hot! which burns my finger.
I replaced the LDO regulator, but it didn't help. Probably something is using high ampere and causing the regulator become hot.
So which components should I check? What's the best way to diagnose the issue?

Thanks

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