Asus GA401Q only working from battery

[dr.thodt]

Hi,
I have an Asus GA401Q which only works from battery power. That suggests the board is mainly fine.
The battery status is 255%, also with a brand new battery.
The BQ24800 was replaced since it showed signs that it was part of the problem, but possibly the battery was flat at that moment.

If I insert the 19V adapter in the DC jack and measure the current sense resistor's voltage it fluctuates between 0V and 19.5V and the keyboard backlight flashes (probably because the battery is almost flat. It does the same when I run the laptop from battery).
There's a light bulb in series with the mains lead which flashes when the 19.5V fals back to 0V.

I tried to skip both mosfets at the DC jack to see what that did: nothing.
I injected 19V from a bench power supply which put a solid 19.5V on the mainrail, but no 5VDC or 3.3VDC was found. Data out and Data in on the bios chip generated one spike on the scope when I pressed the power button.

I'm ran out of options. Hopefully somebody can give me a tip.

Regards.

[mon2]

Test the voltage to ground on the smbus scl and sda pins on the charger ic. Sometimes the battery area has an esd protection device that dies from an esd transient. This causes issues.