(347) 552-2258 [email protected]

820-3476 - Not powering on. R7105 sizzling.

gcain

gcain

New member
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

gcain

New member
S5_PWRGD is solid at 3.3v

Replace U7501?


Replaced U7501 without change.
 
Last edited:
D

dukefawks

Administrator
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

gcain

New member
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.
 
D

dukefawks

Administrator
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

gcain

New member
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.
 
D

dukefawks

Administrator
PPBus @ R7005 is 16.48v what is that about then? As I said check stuff around the ISL6259, resistance between pins 17/18, 27/28, DCIN pin voltage.
 
gcain

gcain

New member
dukefawks said:
PPBus @ R7005 is 16.48v what is that about then?
Click to expand...


As I said check stuff around the ISL6259, resistance between pins 17/18, 27/28, DCIN pin voltage.
Click to expand...

Pin 17/18 = 3.4Ohms
Ping 27/28 = 153Ohms.... Should be around 20Ohms right?

R7105 was out of spec (35Ohms). Replaced it, no change to behaviour.
 
J

JohnB8812

New member
R7105 was likely fine. Resistance between 27 and 28 is way too high. Check R7121 and R7122 both should be 10 ohms. If either or both are blown, replace them. There is a chance that fixes the problem. If both are ok, then you likely have a broken path in that area.
 
J

JohnB8812

New member
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

gcain

New member
R7185 was blown, replaced.

Can't find anything else in that vicinity that's blown.
 
Last edited:
D

dukefawks

Administrator
and what does R7185 have to do with the resistance between pin 27/28? It must be 20 Ohm.

R7102 can never have 16V on it either, it is the pull up resistor to 3V42 for SMC_reset line.
 
gcain

gcain

New member
dukefawks said:
and what does R7185 have to do with the resistance between pin 27/28? It must be 20 Ohm.
Click to expand...

Absolutely nothing. But you did tell me to measure around U7100.

R7102 can never have 16V on it either, it is the pull up resistor to 3V42 for SMC_reset line.
Click to expand...

I'm more concerned about the missing PPBus. That would be the first thing to restore before anything else right?
 
J

JohnB8812

New member
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

gcain

New member
OK.

Resoldered U7100 and both current sense resistors and now the resistance between 27/28 is 20.1Ohms.

PPBus @ R7005 is still 4.8volts.
 
gcain

gcain

New member
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.
 
You must log in or register to reply here.
Top