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]

Re: Lenovo Thinkpad W540 no power

any suggestion?

[mon2]

Re: Lenovo Thinkpad W540 no power

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]

Re: Lenovo Thinkpad W540 no power

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?

[aletec]

Re: Lenovo Thinkpad W540 no power

I have the same laptop, with the same problem. I discovered that with the battery it turns on and stays on. The issue is that when the source is connected, it does not charge the battery. This does not turn on with the source either and the voltage drops.
https://www.youtube.com/watch?v=b6XN7BhChA8

[mon2]

Re: Lenovo Thinkpad W540 no power

Carefully measure the voltage to ground of the following pins, with the power adapter connected. Remove the battery before testing.

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

Post the measurements.