How To Fix La-6753p Lenovo G470 Laptop Motherboard No Power.

 Laptop Motherboard No Power Trick, logic and solution.

 

Solution- La-6753p Lenovo G470 Laptop Motherboard No Power.

 

CASE STUDY BY 
Laptex Family Member
Asfaque
From Ankaleshwar Gujarat

 

 Steps to troubleshoot :- 

1st Step - First Checked charging light glowing but motherboard not turning on. On DC Power Supply reading showing 0.024 amps but board not triggering. 

2nd Step  - 19V shorting checked by visual inspection for any abnormality and found one capacitor in RAM section was burnt from side, same replaced with new cap then system got power on system but amp 0.413 on DC Power Supply still no display problem.

3rd Step - Then checked RAM section again for any abnormality but no any abnormality observed. 

4th Step - When checked 3v,5v S0 or RUN section or DC-DC voltage and found 3v_S0 ok but 5V_S0 only 2.1V. Then checked Q110 MOSFET drain (as showing in the schematic diagram below) having 3V only instead of 19V. Also Checked resistor value of R646 and R649 and found ok, on precautionary basis replaced these resistors with new one but problem not solved.

 
 
5th Step  - Triggering of 3 pin Q110 MOSFET getting signal SUSP at its GATE, but still on drain 19V reduce to 2.1V. So, MOSFET Q110 removed and then checked and found 19V getting transferred as it is on U38 MOSFET GATE and +5VALW getting transferred out as +5VS. 

6th Step - As per N-Channel MOSFET switching logic. There was leakage in Q110 so it was removed from the location and system turning on and display coming OK. All voltages also ok.

 

 

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