820-4924-A Logic board Dead

[mferna14]

Hi, Working on a (Apple MacBook Pro A1502) 820-4924-A Logic board which is totally dead, no green light. The initial status was it was liquid spill & the green stuff collected on R7005 & Diode D7005. Both had corroded legs & the resistor was not even showing 10 Ohms. Replaced both of them but still no PPBUS_G3H (18.5V). First checked the DC-connector & the fuse, 18.5v present. I checked Q7010 & its fine but no output. Don't even get the PP18V5_DCIN_ISOL voltages. I checked Short to ground but none & no where liquid spill, all seems to be fine. Any help will be a great help. Thanks

[piernov]

Re: 820-4924-A Logic board Dead

Voltage on gate/drain/source of Q7010?

[mferna14]

Re: 820-4924-A Logic board Dead

Thanks, I figured out, the 6.8V Zener diode was corroded too. Now I get PPBUS_G3H (18.5V) where ever requried. The Magsafe green LED is on but no fan spin. I am missing the 5V rails. I get the 3.3v rails. Not getting P5VS3_EN signal on U7501, just getting .098V. which I think is not right. I check the resistors & all fine. Missing PP5V_S3_REG no voltage at all. If you can guide me through this too. Thanks

[mferna14]

Re: 820-4924-A Logic board Dead

& one more voltage is that PM_SLP_S4_L is .197 Volts where as this should be 3.3V

[piernov]

Re: 820-4924-A Logic board Dead

PPBUS_G3H should be 12.6V
Confirm you are using a known good genuine Apple Magsafe2 60W/85W.
Go down the list of power rails and report voltages… G3H, S5, SUS, S4… (can ignore S3 and S0 for now as we know they'll be missing if SLP_S4# is missing)
Also area hit by the liquid damage will always give hints.

[mferna14]

Re: 820-4924-A Logic board Dead

I wansn't getting ALL_SYS_PWRGD.. So checked this FET Q8150, liquid spill on the pins. Replaced it & all works fine. Thanks a lot for all the help.