Hello, I have an ASUS ROG GL551JM laptop that recently died.
I took the motherboard out for a quick inspection and probed around to check power rails. On first checking I noticed the 19V main power rail was missing after the first MOSFET. The gate voltage was very low causing high resistance in the MOSFET and only allowing ~0.8V through the MOSFET source. I checked for possible shorts on this power rail but did not find anything suspicious. As a test I removed the MOSFET and shorted the source to the drain and the laptop appeared to power up fine. (I assume this is probably not recommended) However, now the battery would no longer charge. The battery itself is good and is detected with the percentage in Windows, but does not charge. The computer will also run off of the battery without AC adapter.
Looking at the boardview I am trying to piece together why this behavior is occurring and whether this is maybe due to missing voltage at the gate of the first MOSFET? (Since it's only source->drain short). Or perhaps a bad battery killed the charge IC which caused a problem in the first place.
I can take more measurements if needed.
The battery itself is outputting 10.5V and the laptop does power on with the required power rails 19V, 5V, 3.3V, etc.
I have attached the BoardView file (cannot be opened in OpenBoardView due to format but can be opened in BoardViewer).
I was unable to find any complete schematics online, but I did come across a diagram detailing the "power flow" and power-on sequence which I have also attached.
I would like to hear your thoughts.
Thank you very much!
I took the motherboard out for a quick inspection and probed around to check power rails. On first checking I noticed the 19V main power rail was missing after the first MOSFET. The gate voltage was very low causing high resistance in the MOSFET and only allowing ~0.8V through the MOSFET source. I checked for possible shorts on this power rail but did not find anything suspicious. As a test I removed the MOSFET and shorted the source to the drain and the laptop appeared to power up fine. (I assume this is probably not recommended) However, now the battery would no longer charge. The battery itself is good and is detected with the percentage in Windows, but does not charge. The computer will also run off of the battery without AC adapter.
Looking at the boardview I am trying to piece together why this behavior is occurring and whether this is maybe due to missing voltage at the gate of the first MOSFET? (Since it's only source->drain short). Or perhaps a bad battery killed the charge IC which caused a problem in the first place.
I can take more measurements if needed.
The battery itself is outputting 10.5V and the laptop does power on with the required power rails 19V, 5V, 3.3V, etc.
I have attached the BoardView file (cannot be opened in OpenBoardView due to format but can be opened in BoardViewer).
I was unable to find any complete schematics online, but I did come across a diagram detailing the "power flow" and power-on sequence which I have also attached.
I would like to hear your thoughts.
Thank you very much!
Attached Files
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