Lenovo Thinkpad W540 no power

[cyngo]

please help where the problem is or if anyone has experienced please share. On the thinkpad W540, the voltage on the VINT20 drops gradually & slowly. If R380 is removed, at point DOCK_PWR20 appears voltage 20V. inject voltage on VINT20, nothing short. has been replaced mosfet Q9 and Q36, replace the processor, flash bios. but no change.

[cyngo]

any suggestion?

[mon2]

Hi.

1) Remove all power -> meter in resistance mode (lowest scale) -> check the resistance to ground of VINT20. What is the reading ? Also post the meter scale.

If the meter reports '1' or 'OL' (over limit) -> switch to a higher meter scale.

2) Check the first 2 mosfets for defects using the usual mosfet resistance checks.

With NO power. Meter in resistance mode.

check the resistance of each mosfet:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

post the readings of Q9, Q36 mosfets along with the meter scale.

3) With the power on -> meter in 20v scale -> check the voltage reading of the following pins:

ACDC_IN_CONN
ACDC_IN
F2, Pin # 1
F2, Pin # 2

U7, ACDET pin # 4
U7, pin # 36 (AVCC)
U7, pin #15 (REGN)


4) Are you using a docking station ?

5) Are you using the official and original power adapter ? The ID pin on the adapter is being used to identify the presence of the original adapter so it must be used.

[cyngo]

now the 20V voltage can enter across R340 by removing Q79 and adding R504. on the power button there is also a voltage of 3.3V. But still can't be switched on. after analysis, the -PWRSHUTDOWN signal only appears shortly after the PSU is connected, after that it disappears. does that indicate if the ThinkEngine chip is faulty? Has anyone experienced it?