Acer Predator GH51M LA-K862P NO POWER Cant Find shurt

[isa198585]

Can someon Help me, I have a GH51M LA-K862P, and there is a short somewhere after PRB3 and PRB46. I've looked for it using a thermal camera, but I can't find it. Maybe we can find it together. It's a very interesting case.

[mon2]

Can you link or post a schematic? Only in the schematic forum to keep the website organized.

What is the resistance to ground of PRB3? PRB46? Could the fault be at the CPU that is protected by a heatsink?

[isa198585]

I am using the following boardview and schematic. I believe the boardview is not exactly for this model, but it is very similar. PRB3 pins 3 and 4 have a short to GND, as do PRB46 pins 3 and 4. I used a thermal camera to try to locate the heat source. I connected a lab power supply 3A and 1V directly to pins 3 and 4. The power supply indicates a 100% short to GND , but there is no heat anywhere."

[MOD EDIT] Link to schematic/boardview --> https://www.badcaps.net/forum/troubl...01#post1654901

[SMDFlea]

Post only links to schematics/boardviews please - https://www.badcaps.net/forum/troubl...f-this-section

[isa198585]

Does anyone have any ideas?

[mon2]

Flux and remove PRB3 and PRB46 off the board. Then measure the resistance to ground of the same rails. Post the measurements. Which side of the power rail is showing the short condition?

[Sephir0th]

Personally i have never seen a charging controller causing a shorted Main Power rail. So usually this is not necessary. But what would be helpful is to know the EXACT resistance to GND there, same as the Resistance to GND of the various inductors around the CPU and GPU.
if nothing really heats up, it is per 99% a failed high-side.

[isa198585]

I removed PRB3 and PRB46, but the short on pins 3 and 4 remains. It looks like ACN_CHGR is shorted to ground because I removed PQB1 and PQB13, but the short is still there. Then I removed PLB1, but the short didn't go away
Look Video

[mon2]

Post # 5

Then measure the resistance to ground of the same rails. Post the measurements.

[isa198585]

0,025 and 0,025

[mon2]

Post a pic of the meter face while taking this measurement.

What is the units of measure? Be sure you are not in diode mode. Must be in resistance mode of the meter. If a manual type, select the lowest resistance scale on your meter.

[isa198585]

I am sorry, I was in Diode mode. hier correct measurements 0,165 and Pic.

[mon2]

So you have 16R5 = 16.5 ohms to ground. That is of concern and as per post # 6, you most likely have a high side shorted mosfet which usually means trouble. That is, this high voltage rail has passed onto a low voltage rail (due to the leaky mosfet) and most likely killed the downstream low voltage parts.

Remain on this meter scale. With no power to the board, place one meter probe here and other meter probe onto any 2 legged inductor (usually grey in color) on the board. Checking for a low resistance path between the 2 points being tested. Each such inductor has a high side mosfet. If you see a low resistance then that high side mosfet is defective.

Start with the CPU VCORE inductors. Post all suspects.

[Sephir0th]

16 Ohms is a partial short to GND and definitely indicates a High-side short as explained earlier. Unfortunately my advise was ignored so far, since the requested measurements are still outstanding.

[isa198585]

I selected PCZ102 (+VCC_CORE) I get 18,0 ohms.

[Sephir0th]

I selected PCZ102 (+VCC_CORE) I get 18,0 ohms.

DANG!

Measure resistance between PRB3 and +VCC_CORE then

[isa198585]

resistance between PRB3 and +VCC_CORE is 18.0 ohms

[Sephir0th]

Then it is not the power rail we are looking for or the previous shared measurement of the main power rail is not exact, still.

[isa198585]

I have no idea what else I could be doing wrong

[Sephir0th]

There must be another power rail which almost reads the same resistance as the Main Power rail.

One second, are you seriously measuring on the wrong side of PRB3 ?!

Solder the current resistors back, immediately. It was nonsense to remove them anyway. And then check again.

Something is very wrong right now, and it is not the board. We need to figure out what's about your previous measurements, because 18 Ohms between VCC Core and controller side of the Main.power rail means, there is actually a issue on this side (too?).

[isa198585]

No, it is the right side. As I mentioned at the beginning, this board view is not exactly like my board. Look at the picture again, it says PRB3. 'mon2' wrote that I should remove PRB3 and PRB46, message number 5. My measurements are correct; I have checked them again. With PRB3 and PRB46 or without, it doesn't change anything.
The board looks like it has liquid Damage, but it doesn't. The traces are from "Kontakt spray 530"