Msi gt70 2qd dominator dead

[andiukas223]

Hello, my friend asked me to take a look at his MSI GT70 2QD DOMINATOR
laptop which doesn't power on and no charger or other lights appear on the laptop.

I took it apart and connected to the charger to see whats up.
Motherboard code: MS-17631

I noticed that buck converter chip TPS51125 was getting hot and there was missing 5V and 3.3V lines , so i tough it had shorted somehow, i replaced it but nothing happened. So i tried to check caps and resistors around for shorts, but found nothing- i guess i suck at finding whats wrong.

I would really appreciate your help

[piernov]

Re: Msi gt70 2qd dominator dead

Still getting hot? Measure voltage and resistance to ground on pins 8 and 17.

[andiukas223]

Re: Msi gt70 2qd dominator dead

Hello Piernov, after my post i resoldered the old chip in hopes to find what could have shorted the chip in the first place. I meassured what you asked:
pin 8 is about 130 Kohm's
pin 17 is about 40 Kohm's
But pin 7 is short to ground when i meassure in diode mode.

i will check is i didn't short it out by resoldering it wrong, but after that sould i inject 1V in that power line and see whats getting hot?

I don't have lot of knowledge on short detection and especially not a lot of understanding where should i inject voltage to not damage the board further.

[piernov]

Re: Msi gt70 2qd dominator dead

Measure exact resistance to ground on pin 7.
If it is indeed shorted to ground it means the 3.3V rail is shorted to ground, you can inject 1V at the inductor for the 3.3V rail.

[andiukas223]

Re: Msi gt70 2qd dominator dead

Exact resistance at pin 7 is 1.2ohm, i will try to inject 1V and trace whats getting hot.

[KvnTM]

Re: Msi gt70 2qd dominator dead

Don't forget to limit the current to a reasonable amount to avoid blowing a trace or cause more damage due to an exploding cap if something is shorted.

[andiukas223]

Re: Msi gt70 2qd dominator dead

Okay will do, is 1V 2.5A is sufficient?

[KvnTM]

Re: Msi gt70 2qd dominator dead

Okay will do, is 1V 2.5A is sufficient?

Yes that's enough. This would generate 2.5 Watts of heat if something is dead shorted.

If the current immediately shoots to 2.5A you should reduce it to 500mA or so. 2.5 Watts can light a 0805 or smaller component on fire pretty fast.

[andiukas223]

Re: Msi gt70 2qd dominator dead

I injected 1V and the current draw was 0.17A, so i increased voltage to 2.5V so did the current draw increased to .35A, but its very hard to pinpoint whats getting hot. I will try to pour some iso-alcohol and inspect for shorts, but if i can't find nothing i will ask my friend to help my with his flir thermal camera on wednesday.

If you have some ideas i will try them, tho i already tried freeze spray.