MSI GE62 Laptop Motherboard with Short on main power rail

[worlor]

Hello,
I am currently learning to repair laptop motherboard and I need some advice/help.
I have a MSI GE62-6PQ laptop that didn't boot. It's an old laptop that got a glass of coke :/
I have cleaned the motherboard with isopropyl alcohol and a brushteeth.
The motherboard is a MS-16J51. I put the schematics attached.
I also attach high res pictures of the board.

Symptoms :
When I connect it to the power supply, it goes into protection.

What I have done :
Checked the fuse : OK
Visual check OK : No burned components

I have measured the resistance between PWR_SRC (main rail) and GND : 0.2 Ohm
The main rail is shorted, but where

The resistance between PWR_SRC and CHOKE9 (5V rail) was very low (<1ohm), so I have measured the resistance betweend source and drain of MOSFETs PQ13 and PQ15, both shorted. So i removed them. But the short is always here
You can look at page 40 of the schematics
I have tested the MOSFETs separatly, they seems OK.

The resistance between PWR_SRC and PL4 and PL5 are very low too. I think there is also a short near the CPU power. But I want to resolve the short on the 5V rail first

The others mesurement seems OK

What can I check to find this ***** short ? Any help/advice appreciated

[mcplslg123]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

When power supply goes into protection, its your +19V rail which is shorted. Locate the CLR after 2 dc-in mosfets and remove it from the mb. Measure resistance on both pads of CLR(after removing it. One side will show short to Ground. Inject +1V/1A with dc supply and gradually increase AMP(not Voltage) upto 5Amp and find out what is getting hot. However, if you inject more then 1V/5A , then there is risk of onboard CPU/GPU getting shorted if one of the high side mosfet is leaky/shorted on cpu/gpu rail. So try the above steps and report back.

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

When power supply goes into protection, its your +19V rail which is shorted. Locate the CLR after 2 dc-in mosfets and remove it from the mb. Measure resistance on both pads of CLR(after removing it. One side will show short to Ground. Inject +1V/1A with dc supply and gradually increase AMP(not Voltage) upto 5Amp and find out what is getting hot. However, if you inject more then 1V/5A , then there is risk of onboard CPU/GPU getting shorted if one of the high side mosfet is leaky/shorted on cpu/gpu rail. So try the above steps and report back.

Hello, thanks for help

I am not sure about the CLR you talking about. Is it PR17 ? 0.005Ohm resistor
See image attached

[mon2]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

Yes, PR17.

CLR = current limiting resistor.

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

Yes, PR17.

CLR = current limiting resistor.

OK, thank you, gonna desold and try with a power supply

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

OK I have injected current on main rail. 1.1V but with 3A because supply can't do more.
I have searched for hot zone on the mainboard.
I have found one place that became very hot near +VCCSA mosfet PQ24.
The mosfets from +VCC_Core were hot too.

I think to desold choke and capacitor on these rails to see if the short gone.
Am I right ?
Any better idea ?

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

Hello
After removal of chokes, I have found the PQ20 MOSFET was shorted.
I have removed it, and I have now 3kOhms between pwr_src (19V) and gnd.
I will replace it and see what happens when I put DC IN

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

But I have measured 0.4ohm between GND and +VCC_Core. Do you think it's good ? Or CPU is shorted ?

[mcplslg123]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

0.4 Ohms is bit low and likely cpu is shorted.

[coffinsupply]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

did it fix?

[mosfetratus]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

0.4 Ohms is bit low and likely cpu is shorted.

Mosfet can cause cpu to be shorted.

[mcplslg123]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

Mosfet can cause cpu to be shorted.

Yes as long as it is high side mosfet as there is 19V on its drain and when shorted 19v will reach to cpu-damaging it.

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

did it fix?

Hello,
No I have the new mosfet but I didn't took the time to solder it :/

mcplslg123 killed my hope of saving it

[deathtob]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

did you ever end up soldering the mosfet to see if it worked?

[reformatt]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

Absolutely no point since the CPU is shorted. It's a common enough failure mechanism that I personally wouldn't even bother. High side FET goes short, allows full rail into CPU/GPU etc, killing the silicon.

[worlor]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

Hello
Just to give news :
Yes I have replaced the mosfet
Yes the CPU was shorted

I have bought a new mainboard, non-shorted CPU report 2.4 ohms on same VCC line.

[Krilan1990]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

In my laptop there was a damage to the usb2.0 socket, after initial measurements it turned out that between the mass and the date - there is 10 ohms and between the date + and the mass is about 60 kohm. there is also a high impedance between vcc (5V and ground. The laptop is msi ge62 2qd motherboard ms16j21 ver1.0. is it possible that there is some element between the bridge and usb that could be damaged and ground date-. I found a diagram on the vinafix website but it is a bit too expensive for me to download it. and the free versions of the schematics may not be complete. generally the laptop works fine, the temperatures oscillate between 40-50 degrees and the other components work. Please advise what could be done with it, how to save these usb and is it profitable and how much can it cost.Thanks in advance for all suggestions

[mon2]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

The USB port is not working ?

[Krilan1990]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

I do not recognize devices, I have the impression that one line is shorted to ground

[Krilan1990]

Re: MSI GE62 Laptop Motherboard with Short on main power rail

I do not know if the bridge or some element before the bridge is damaged, after measurements I noticed that the date pin is shorted - it is on the motherboard
maybe someone on the forum has schematics from the vinafix website and could share