Dell Precision 7720 - Shorted main power rail

Hello,

On this laptop, the first mosfet (PQ5) after the DCIN connector was burnt, so I have removed it. I then discovered an exploded capacitor near PU1201. This capacitor has been removed, but I still have a 0.0Ω short to ground after mosfet PQ701. I have also removed PU1201, but still the short remains. Injecting voltage does not help, as only the grounds are heating up, so the short must be quite large.
I have removed coils PL1200, PL1201 and PL1202 and have a resistance to ground through the CPU (Intel i7-6920HQ) of 1.1Ω. This seems very low, but maybe OK for this processor, I'm not sure. If I inject 0.8v onto the coil pad, I have a current draw of 0.9A.

Before I investigate further to try and find the short to ground, can anyone confirm if the resistance I'm seeing for this CPU is OK?

Board marking is CAP10 LA-E321P Rev 1.0 (A00)

MendUsThis писал(а):resistance to ground through the CPU (Intel i7-6920HQ) of 1.1Ω.

Hello!
In my experience the normal resistance for this generation of the CPU is around 2Ω.
Did you measure this resistance when the CPU is cooled to the room temperature?

MendUsThis писал(а):Injecting voltage does not help, as only the grounds are heating up

At what electrical current did you perform the short circuit test?

matic писал(а):Did you measure this resistance when the CPU is cooled to the room temperature?

Yes.

matic писал(а):At what electrical current did you perform the short circuit test?

I started at 0.8v and 0.5A, then gradually increased in 0.5A increments until I got to 3.5A.

MendUsThis писал(а):until I got to 3.5A.

You can go up to 5A without any problem. If the short circuit resistance is really low, sometimes it's necessary to reach up to 10A to find the shorted component.
Make sure to use thick enough test wires. If necessary, the voltage limit can be increased to 1V.