820-00840 20v 0.09a

[nininunz]

Still learning this shit so please bear with me. PPBUS_G3H is present but PP3V3_S5 is 0v. I'm lost in the schematics lol. Where is PP3V3_S5 created and what else should I check?

 

[nininunz]

PP5V_LDO5V is present. Does that mean U7800 is bad?

 

[2informaticos]

Any history available, liquid sign?
What is exact PPBUS_G3H voltage, w/ and w/o battery connected?
SMC_RESET_L comes high?

Test the board alone on the desk.
Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L; use SW9988/89 pads, instead of power button.
Check U7800 (7 OF 10) LDOs voltage.

 

[nininunz]

PPBUS_G3H - 13.13v (w and w/out batt)
PP5V_LDO5V - 4.92v
PP3V3_S5 - 0v
PP5V_S4 - 0v
PP1V2_S3 - 0v
SMC_RESET_L - 3.42v

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L; use SW9988/89 pads, instead of power button

PM_PWRBTN_L sits at 3mv
Short SW9988 or 89 to ground? Or short SW9988 to 89?

Edit:

Any history available, liquid sign?

I believe this had liquid damage around the backlight caps on the backside of the board. I had the board labeled as backlight, no image, so I believe it may have turned on at some point. But I don't believe I had another board available to confirm if it was indeed the board or if it was a faulty screen. Q8400 looks to be missing a leg for pin 3 but I don't believe this would prevent the board from turning on so I was tackling this issue after the ladder.

 

[2informaticos]

"Short SW9988 or 89 to ground? Or short SW9988 to 89?"

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

boards.rossmanngroup.com

"Check U7800 (7 OF 10)"
PP3V3_LDO3V?
PP1V25_VREF?

Check also PP3V1_RTC.

Corrosion on the backlight area is the worst scenario.
Leakage from high voltage to data lines, can easy damage CPU.

 

[nininunz]

Ok so triggering SMC_ONOFF_L causes a spark and PM_PWRBTN_L goes to 0v then back to 3mv when open again. I didn't understand what you meant by "7 OF 10"

PP3V3_LDO3V - 3.2v
PP1V25_VREF - 1.21v
PP3V1_RTC - 0.19v

Also it's probably worth noting when I plug the board into power it draws 0.2a for a second or so then down to 30ma. I believe the90ma in the title was when it was hooked up in the top case.

 

[2informaticos]

"PP3V1_RTC - 0.19v"
PCH can't start the power on sequence then.
Check diode mode to ground there; remove power first!

 

[nininunz]

There's continuity, reads 0.025

 

[2informaticos]

You can remove the filters cap, one by one, and pray isn't U7800, or PCH problem.