MSI GF65 Thin doesn't turn on, shorted on dc-in, how to find the culprit?

[im_trying]

Hi, thanks for helping.

The motherboard is from a gaming laptop, msi gf65 thin 10ue, 16W21/11S.

For starters, it doesn't power on. I measured a "short" on the second DC-IN mosfet, right around the charging port but I don't know how to find the component that's shorting it.

I already tried checking the mosfet for internal shortage (by desoldering and measuring) but no short. The drain on the motherboard is the one that's shorted, next to the gate (that's not shorted).
The photo below shows this better than words.

Thanks for anyone that helps!

[mon2]

Is your meter a manual scale type or automatic for selecting the resistance? The ‘1’ may indicate that the meter scale is too low so switch to a higher resistance scale till you have a proper measurement.

[im_trying]

Automatic scale, but it measures in ohms. I wrote the ohm in the picture, it's around 6 to 3 Ohms. Which seems pretty low to me for a DC-IN. Right?

[mon2]

Yes, very low. Flux and carefully remove the brown ceramic capacitor showing in your pic as shorted. Then measure the resistance again without power to the board.

[im_trying]

Done. Capacitor is good, no short on him. The short is still present, 0 ohm on the south pad and 4 ohms on the north one.

[mon2]

Which charger IC is onboard? Share the topside smd markings. We may be able to learn about your board through reference datasheets on the internet. Any other silk screen markings on this logic board? Perhaps a schematic is available.

There is a concern about the 2nd DCin mosfet which is often leading to the main power rail. That is, the main power rail may be shorted due to CPU / PCH damage.

The highlighted pins on the left mosfet are the source pins (1-2-3). You are measuring this cluster to ground and are with ~6 ohms?

Remove all power. Meter in resistance mode.

Measure the resistance across these mosfets:

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

Each measurement should be hundreds of k ohms or higher else is a suspect. Post each measurement. If you have a low resistance to ground of the source / drain pins, then the load side of the mosfet is shunted.

[im_trying]

So, I just found a schematic for the board. It's here on badcaps so I'll just link the post: https://www.badcaps.net/filedata/fetch?id=3486425

Just to be sure that it wasn't the BQ chip, I desoldered and measured, no luck. The short is still there. BQ chip has been resoldered on.

Measurements:
Source to drain: 450kOhms
Source to gate: 240kOhms
Drain to gate: 700kOhms

[mon2]

Locate the VCORE caps as attached. Yellow tips of the parts are the VCORE rail.

Measure the resistance from the source (1-2-3) mosfet pins you are referencing to these caps. What is the resistance? We are checking if there is a high side mosfet leak of the vcore power rail.

[im_trying]

Done. From the source of the second dc-in mosfet to the highlighted caps in yellow it's the same 6 Ohms. The same caps relative to ground are 2.5 Ohms.

[mcplslg123]

PR344 should be desoldered and then you need to inject 1V/5A on the shorted side from dc supply and wait for 10 mins to see if anything getting warm.

Put black probe on the shorted side of PR344 and touch red probe on every coil on the board(meter in diode mode).The one which shows same value as the shorted side on PR344, is likely the culprit.