Lenovo laptop
Pcb model : A14HV0X rev 4.0
Problem Reported :- No Power On,
Observation :- Power on process is little bit different to others models, as we have seen most of the laptop motherboard wake on 3v, 5v pwm supply after full fill basic requirements of io controller , but that case is little bit different , one of the comman IO requirement not fulfilled WRST# / LRST1# that is EC reset must be pulled up with 3v alw , was missing,
Solution :-
Start checking power on requirement step by step ,
VIN ,3.3/5V ,PwrBtn voltage ,RTC_VCC, 32.768khz Frequncy
Everything was available but PwrBtn_out not present,
Someone already made an attempt to reprogram bios
So firstly checked with bios but no luck ,
Now Big suspect to any one of io controller requirement is missing,
Then started searching for IO requirements
Found WRST#/ LRST#( EC_Reset) missing
Further tracing for problem found 3.3V on pull up resistor R451 but not on PIN 14 of IO controller
So biggest and only suspect as seen in schematic is C661
Removed and Bingo
The board turned on and
Job done
