Asus X532FL 3.2V at source and gate

[Lvsitano]

I am having some trouble with troubleshooting a Asus X532FL rev 2.0 motherboard, which does not power on. So at the first MOSFET, I am getting 19V at the drain, and then 3.2V on both gate and source (compared with ground). Of course, the 2nd MOSFET's source will have 3.2v at source.

First MOSFET is a QM3056M6 and 2nd MOSFET is a QM0930M3

I already checked first MOSFET and source and gate are not shorted (drain with source not shorted either). Also I have 1.7V at the LDO rail (measured at the keyboard connector, as the power button is on the keyboard).

First question: why am I getting 3.2V at the drain, with only 3.2v at the gate?

And then, if I understand correctly the board view, the gate voltage is generated by the BQ24780S IC ? (Board shows SN2867 IC, but they used a BQ24780S)

[reformatt]

The BQ IC's have short circuit detection so will disable the first MOSFET in that event. 2nd MOSFET being shorted can cause this as well, but most common issue on Asus laptops that I see is a shorted cap on the main power rail. So check at the current sense resistor after the 2nd MOSFET for a short to ground.

[mcplslg123]

Besides @ reformatt's suggestion, do check voltage on REGN and VCC of BQ24780S

[Lvsitano]

The BQ IC's have short circuit detection so will disable the first MOSFET in that event. 2nd MOSFET being shorted can cause this as well, but most common issue on Asus laptops that I see is a shorted cap on the main power rail. So check at the current sense resistor after the 2nd MOSFET for a short to ground.

There is no short at the main power rail, I have checked that in the first place. I am going to check the 2nd MOSFET as well, did not check that one.

[Lvsitano]

The 2nd MOSFET QM0930M3 was shorted, replaced with another one. Now I am getting 19V at the 1st MOSFET's source, but the 2nd MOSFET is now fluctuating voltage at drain, between 3.2V and 4.4V