Need help with this HP laptop please - no power

[survivalbloke]

Model - ENVY 15m-eu0023dx
Serial - 8CG1161RLX
Board# 448.0ML05.0021
HP Board part# M45488-601

I really wanted to figure this one out on my own, but after some time, I'm stumped. It is in for no power and have confirmed that.

With battery disconnected, plugging in the power supply, it is drawing .165a and the EC chip is warming, then the draw drops to .005.

With battery connected, it is doing the same, but the lower left-most mosfet is getting very hot, and the machine is drawing 3.5a.

This picture is with measurements while battery disconnected.

[mon2]

Who is getting hot? PU4403?

[survivalbloke]

Who is getting hot? PU4403?

Yes, correct. When the battery and charger are both connected.

[mon2]

Remove all power. Meter in resistance mode.

1) Test the resistance to ground on the source (1-2-3) pins.
2) Test the resistance to ground on the drain (5-6-7-8) pins. For each, testing if there is a short on the load. What is the resistance in ohms?

3) Next, measure the resistance across the mosfet pins:

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

Post each measurement. No power to the board during these tests. Remove the battery as well before testing.

[survivalbloke]

Remove all power. Meter in resistance mode.

1) Test the resistance to ground on the source (1-2-3) pins.
2) Test the resistance to ground on the drain (5-6-7-8) pins. For each, testing if there is a short on the load. What is the resistance in ohms?

3) Next, measure the resistance across the mosfet pins:

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

Post each measurement. No power to the board during these tests. Remove the battery as well before testing.

Thank you so much for all the help! I've got a question. I've taken most of these measurements now, and I just realized that on some of these mosfets, I get different readings(very different) depending on which pins I have red and black on. For example, measuring gate to source on one of them, red on source gets me 100k, where as if I switch the leads, I get 3M. Why is that? And which way is correct?

[mon2]

I can only assume there is a slight charge on the mosfet that leads to these variances. Suggest to unplug from the AC socket and then press the on/off button to force the power supply to drain out the charge in the capacitors. Then try again. If there is a fault in the mosfet, the low resistance values will show during your measurements. If the resistance keeps climbing that likely no issue here. We are testing for low resistance values.