820-4924 voltage drop PPBUS_G3H

[dudipupan]

Hey,

I'm working on a MBP (820-4924) with fluctuating voltage on PPBUS. When I plug it in I got 12V for a moment, slowly dropping to 0.4V.
I got a green light on the charger, PP3V42_G3H is stable.
CHGR_DCIN is okay
CHGR_RST_L is okay.
Current sening seems okay.
I already replaced U7100 and Q7130 and removed F7140 with the same result.

Thank you for your help.
Dudi

 

[2informaticos]

Any history fault?
Post U7100 voltages; pins 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.
Replace C7125, just in case.
Also check R/C network from pins 5, 7, 8.

 

[dudipupan]

Don't know much about this board - some corrosion around U3210 and U3310 - but nothing too bad.

I changed C7125.
Measurements on U7100:
Pin 1: 0.04V
Pin 2: 18.3V
Pin 3: 4.4V
Pin 9: 0.3V
Pin 12: 0V <- PP3V42 is present at other points - maybe a broken trace?
Pin 14: 3.4V
Pin 15: 0.02V
Pin 17: 0.02V
Pin 19: 5.47V
Pin 20: 5.48V
Pin 27: 18.3V

Pin 5, 7 and 8: single pulse when plugging in

 

[2informaticos]

Solve the problem with broken trace first.

 

[dudipupan]

Resorting the broken trace worked - ppbus was stable then. Had a problem with backlight data line too because of another broken trace but now everything works fine - thank you!

 

[dudipupan]

*Restoring not resorting :-D