Fujitsu laptop 2.6V on charging port

[Adenitz]

Hello laptop repair experts.
My laptop H700 Celsius just suddenly turned off and it is not possible to start any more. It worked when battery was charged.

Charger is Ok and I can measure 19.5V. However, when I connect crager to the charging port, there I can mesure only 2.6V. So it means there is a short on the input charging port circuit. Since I measure 2.6V on the charging port connector, it is very possible that something is shorted before input MOSFETs. Based on your experience, where is the best place to start seaching for short? I plan to use isopropyl acohol to locate the shorted component.

Thank you!

[Adenitz]

Re: Fujitsu laptop 2.6V on charging port

Hello,

one more question. Is it normal that resistance on power rail (measured to ground) for NVIDIA Quadro FX 880M GPU on motherboard is about 2 Ohms?

I have found a burning hot component (N channel MOSFET) M8001 and removed it. After that there is no more short circuit, at least seen from charger port side. Now, on the port and on the fuse voltage is 19.5V again and not 2.6V any more.

This Mosfet is very near to GPU chip, and it is possible that it used to create voltage for GPU core. I'm not sure about this because I don't have schematics.

Before changing a MOSFET (actually I need to wait quite a bit for the delivery) is there something else I need to check? Maybe short is still present after this MOSFET?


Thank you

[mcplslg123]

Re: Fujitsu laptop 2.6V on charging port

If the shorted mosfet is part of gpu power circuit, then you should replace both the mosfets(even if it tests good) along with its PWM.

[Adenitz]

Re: Fujitsu laptop 2.6V on charging port

I have replaced both MOSFETs and the short is gone. Laptop boots, it reaches windows logon windows after few secs just turns off. It's like thermal shutdown, but nothing is getting too hot.