820-4924 Charger LED green then orange, no battery connected, no power on

[PDXlaptopRepair]

This board is new to me and I'm not really sure where to start troubleshooting. As a side note for background, the laptop was dropped what was described as less than 6 inches causing this issue. This board is mine now, I prefer not to learn on customer boards.

It might be obvious but I will state it anyway:
g3 hot: present
PP3V42: reads 3.38v (slightly varies depending on where I measure but no more than .02v - .03v)
PPDCIN: reads 16.5v ish

 

[larossmann]

A drop typically points to a damaged BGA or a crack inside the board internally which you will not be able to see which makes it a bad candidate for learning. Even for more experienced people like Duke & I these usually wind up in the trash heap.

That being said, troubleshooting should begin by checking all the rails and seeing what is missing. See if any of them have short circuits on them, come back with what is missing. Does PM_SLP_S4_L pulse when you plug the charger in? It will be very quick so you'll want to have someone else plug it in while you have your hands on the meter probes to catch it.

 

[PDXlaptopRepair]

PM_SLP_S4_L briefly jumps .3mv then .7mv then sits at .1mv. If this is the pulse you refer to then yes.

additional testing:

Q7180 Pin3 (CHGR_AGATE_DIV) 6.93v
Pin6 (CHGR_SGATE_DIV) 16.29v

Is this normal?

CHGR_AGATE goes through R7186 then drops to 3.8mV for connection to pin 1 on U7100 (That doesn't seem right to me, not sure)

a new wrinkle.....I was probing different points around the SMC investigating SMC_DCIN_VSENSE, I had to walk away for a minute and when I came back the fan was spinning and the CPU was definitely getting warm.

Since the system powered on once now I only get charger LED for about 30 seconds then it goes off. (Edit: this was a problem with the magsafe charger I was using)

I'm going to troubleshoot ONEWIRE circuit now and see if anything come to light. (Edit: all seems correct)

 

[PDXlaptopRepair]

Now I think I'm getting somewhere.

no voltage present on Q5480 Pin 2 (PBUSVSENSE_EN)
I do have voltage on Q5490 Pin 2 (DCINVSENSE_EN)

from what I'm able to figure out, it seems that PBUSVSENSE_EN is generated by the SMC.

If that is correct then my root cause must lie with the SMC itself, please confirm.

 

[larossmann]

All of those sensors have nothing to do with the problem. PBUSVSENSE_EN says "Enables PBUS Vsense divider when in S0." S0 means on. PBUSVSENSE_EN not being present means it is not on.

It's like not having your sense of smell while in a coma. You fix the coma first, not the sense of smell.

1) what does pin 8 of U1950 look like under a microscope?

2) Is PPVRTC_G3H present when it is unable to turn on?

3) Is PPBUS_G3H present when it is unable to turn on? If it is, is it 12.56v or 12.23v?

 

[PDXlaptopRepair]

No Title

1) what does pin 8 of U1950 look like under a microscope? Not bad as far as I can tell, getting 3.39v. I added a pic. (my microscope is crap)

2) Is PPVRTC_G3H present when it is unable to turn on? Yes

3) Is PPBUS_G3H present when it is unable to turn on? If it is, is it 12.56v or 12.23v? Yes and it reads 12.58v