• Dell Precision 7720 - Shorted main power rail

It is currently 2 February 2026, 17:51

Dell Precision 7720 - Shorted main power rail

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#1 Dell Precision 7720 - Shorted main power rail

by MendUsThis • 2 February 2026, 15:23
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)

Image

Re: Dell Precision 7720 - Shorted main power rail

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#2 Re: Dell Precision 7720 - Shorted main power rail

by matic • 2 February 2026, 16:07
MendUsThis wrote: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 wrote:Injecting voltage does not help, as only the grounds are heating up
At what electrical current did you perform the short circuit test?

#3 Re: Dell Precision 7720 - Shorted main power rail

by MendUsThis • 2 February 2026, 16:25
matic wrote:Did you measure this resistance when the CPU is cooled to the room temperature?

Yes.

matic wrote: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.

Re: Dell Precision 7720 - Shorted main power rail

by Google Adsense [BOT] • 2 February 2026, 16:25
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