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Old 12-04-2021, 11:09 AM   #1
grimacelord
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Default 820-4924 - No Power - Gets Green Then Orange Light

Board had previous liquid damage. It was initially ultrasonic cleaned. Keyboard, battery, and trackpad flex cable were all replaced and it worked fine. Board is back for no power. Hoping someone can help me out here. Voltages taken with board, DCIN board, and original 85W charger only, no battery.

PPPBUS_G3H - 12.54V
PP3V42_G3H - 3.42V
ALL_SYS_PWRGD - 0V (No pulse when triggering SMC_ONOFF_L )
PM_SLP_Sx_L - Pulses when triggering SMC_ONOFF_L
PM_RSMRST_L - 3.28V
PM_PWRBTN_L - 3.42V
PCH_DSWVRMEN - 3.18V
PM_DSW_PWRGD - 3.43V
PPVCC_S0_CPU - 0V, No pulse
PLT_RESET_L - 0V, No Pulse
PP3V3_S0 - 1.69 - 1.75V fluctuating.
PP3V3_SUS - 3.33V


L7520 0v
L7430 0V
L7560 3.33V
L7710 0v
L3095 11.6v
L7130 12.54
L7320 0V
L7310 0V
L7630 26mV

U1950 PIN 5 - 0.8mV - 0.9mV seems to change (pulse?) between these two measurements.
U1950 PIN 6- 0V, no pulse

Board DOES start in SMC Bypass Mode with high fan spin.

I'm really not sure what to do here. I'm still new to board level repair so I was hoping someone can look at this and help me figure out what is wrong. Thank you.
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Old 12-07-2021, 07:30 AM   #2
reformatt
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Default Re: 820-4924 - No Power - Gets Green Then Orange Light

With liquid damage, corrosion is often an ongoing process, especially if it's gotten under a BGA or two. Don't rush to ultrasonic clean a board; the original corrosion spots are your biggest clues in fixing the fault(s). Once you clean the board, all those pointers are washed away. If you have an iffy track/pad/via, they can be very difficult to find without those hints.

Take photos of the affected areas before rework so you know where to check if the job bounces. A good eye is very important when dealing with corrosion. Sometimes you can get crap under a BGA (like SMC etc) so this can cause all manner of issues.

Having said that, PP3V3_S0 being low is where I'd start.
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Old 12-07-2021, 12:08 PM   #3
grimacelord
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Default Re: 820-4924 - No Power - Gets Green Then Orange Light

Quote:
Originally Posted by reformatt View Post
With liquid damage, corrosion is often an ongoing process, especially if it's gotten under a BGA or two. Don't rush to ultrasonic clean a board; the original corrosion spots are your biggest clues in fixing the fault(s). Once you clean the board, all those pointers are washed away. If you have an iffy track/pad/via, they can be very difficult to find without those hints.

Take photos of the affected areas before rework so you know where to check if the job bounces. A good eye is very important when dealing with corrosion. Sometimes you can get crap under a BGA (like SMC etc) so this can cause all manner of issues.

Having said that, PP3V3_S0 being low is where I'd start.
Thanks for the tips.

I went back and sort of studied the schematic. That lead me to U8030. I pulled it and a couple of it's pads looked kinda crappy, so I cleaned them and reballed U8030. Not only did it restore PP3V3_S0, but the computer boots now.

Thanks again.
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