Hi all,
Friend asked me to look at his Lenovo laptop that is completely dead. Upon inspection , I found faulty DT7 (protection diodes off USB connector). Chip had small hole in it. Replaced, but still no power. No obvious shorts further on the board. Small resistors and SMT fuse I found all measure OK.
Measuring voltages on large caps I can see 5V and 9V present on the board.
I tried to remove all peripherals and disconnected battery -- still same. With battery in or out, charging LED is always off.
Now, for the interesting part. Dead with original charger. I tried with my Apple MacBook charger and it turned on. Put back original adaptor and unit is dead. Put back my Apple charger -- still dead, although charging LED flashed once or twice. Voltages measured above are same with original and Apple charger connected. I have a gut feel that there is a crack in PCB somewhere, but can't prove it. No amount of "bending" or moving seem to work.
Without schematics or board view, it is a bit difficult to troubleshoot further.
Does anyone know what voltages i should expect from power adaptor and what components I will be able to measure them on? Also, where is power module that generates 1.8V and 3.3V (I assume any modern electronics will need those).
Any help on this unit is greatly appreciated
Rudolf
Friend asked me to look at his Lenovo laptop that is completely dead. Upon inspection , I found faulty DT7 (protection diodes off USB connector). Chip had small hole in it. Replaced, but still no power. No obvious shorts further on the board. Small resistors and SMT fuse I found all measure OK.
Measuring voltages on large caps I can see 5V and 9V present on the board.
I tried to remove all peripherals and disconnected battery -- still same. With battery in or out, charging LED is always off.
Now, for the interesting part. Dead with original charger. I tried with my Apple MacBook charger and it turned on. Put back original adaptor and unit is dead. Put back my Apple charger -- still dead, although charging LED flashed once or twice. Voltages measured above are same with original and Apple charger connected. I have a gut feel that there is a crack in PCB somewhere, but can't prove it. No amount of "bending" or moving seem to work.
Without schematics or board view, it is a bit difficult to troubleshoot further.
Does anyone know what voltages i should expect from power adaptor and what components I will be able to measure them on? Also, where is power module that generates 1.8V and 3.3V (I assume any modern electronics will need those).
Any help on this unit is greatly appreciated
Rudolf
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