820-3476 - Not powering on. R7105 sizzling.

[gcain]

Cup of black coffee went straight through the laptop.


So originally I noticed that R7020 was incredibly hot.
Beauty, short.

C7102::1 had 0v to ground in diode mode, so I figured shorted U7100. Had a ton of these.

Issue ended up being C5002 dead shorted to ground. I also had to replace Q1840, Q1842 and Q3088 because the looked like ass.

Got fan spin. Yay! Then it stopped. /groan

Now PP3v3_S5 is cycling; looking further SMC_PM_G2_EN is cycling too.

 

[gcain]

S5_PWRGD is solid at 3.3v

Replace U7501?


Replaced U7501 without change.

 

[dukefawks]

S5_PWRGD should not be high if G2_EN is cycling of course. Any shorts around U7501? VREF2, VREG3, VREG5 and the outputs? PPBUS stable?

 

[gcain]

I'm not sure where I got the S5_PWRGD from, must have measured the wrong component.

R8141::1 is a solid.3.3v but R8141:2 is cycling down to 0.3v and back again.


C7500::2 measures 0.102 in diode mode which I think is low.

PPBus @ R7005 is 16.48v and at F7140 is 4.8v I just noticed.

F7014 in diode mode gives me .120v to ground. :/


VREF2 is unstable. VREG3 is 3.3 and I can't find VREG5.

 

[dukefawks]

Uhm F7140 and R7005 are tied together, there should be no voltage differential and PPBUS should certainly not be 16.5V! ISL6259 issue/Q7130 and sense resistors need checked.

 

[gcain]

I know F7140 and R7005 are on the same wire, that's why I mentioned it.
Thought I was going crazy for a moment but I can now think the measurements are fluctuating.

PPBus is sitting at around 5v.

 

[JohnB8812]

Do they both measure 10 ohms now? 98 ohms is for sure too high. Sounds like you have issues with the traces. Also check R7120 it should be 0.02 ohms it is much less likely to blow, but you never know.

 

[gcain]

R7185 was blown, replaced.

Can't find anything else in that vicinity that's blown.

 

[gcain]

R7102::1 = 16.6v
R7102::2 = 6.7v

Could this be a faulty U7100?

 

[JohnB8812]

U7100 is NOT your problem with 27/28 unless the pins are bridged/corroded. Either the two current sense resistors are blown (or one), the shunt resistor is blown (unlikely), or the traces are corroded/broken.

 

[gcain]

Laptop fires up with a charged battery. Shows power connected and disconnected but not sure if it's actually charging yet.

Maybe the battery is dead. Won't fire up so I can't tell what the original battery is doing.