A1398 - 820-00138 - No display and Fan on high speed.

[ronaldopdias]

Hi everyone.
I need help with this Mac, please.

No signs of liquid, no short on the board.
It turns on, but will not display. The fan goes to high speed.

L3095 - 0V
L7520 PP5V_S4 - 5.05
L7130 PPVBAT_G3H_CHGR_REG - 12.59V
L7560 P3V3S5_LL - 3.32V
L7630 PP1V05_S0_REG_R - 1.05V
L7430 vPP1V35_S3RS0_CPUDDR - 1.36V
L7870 P1V5S0_SW - 1.51V

L7310 PPVCC_S0_CPU_PH1 - 0V
L7320 PPVCC_S0_CPU_PH2 - 0V
L7330 PPVCC_S0_CPU_PH3 - 0V

I assumed CPU MOSFETs were faulty and replaced all of them, but I still had the same issue.

Please can someone help me?
Thanks

[mon2]

Re: A1398 - 820-00138 - No display and Fan on high speed.

About a month ago we had this model in the building (A1398) - not sure of the exact logic board number. Client wanted the rivetted keyboard replaced for cheap. Not possible to do.

We thought we killed the logic board but @mferna14 chimed in to state that this model requires a known good battery.

After applying a fresh charged battery, the laptop worked fine (as it always did before). We returned the unit back to the client as a no fix.

Confirm that you are doing the same.

BTW: While we were wasting time, we found that the CPU Vcore resistance to ground was 1 ohms yet the laptop was working fine. So do not panic, just test with a good battery first.