820-3332: ALL_SYS_PWRGD low, unsure what to look for.

[down1nit]

No obvious damage, good magsafe. Gets orange light, but ALL_SYS_PWRGD is stuck low and I don't quite understand how to follow back to see why.

Power rails:
PPDCIN_G3H: 20.85
PPBUS_G3H: 12.59
PP3V3_S5: 3.35
PP3V3_S4: 3.35
PP3V3_S3: 3.35
PP3V3_S0: 3.34
PP3V3_SUS: 3.35
PP5V_S5: 5.0
PP5V_S4: 5.0
PP5V_S3: 5.0
PP5V_S0: 5.0
PP1V8_S0: 1.8
PP1V2_S5_SMC_VDDC: 1.2
ISNS_PP1V5_S0_GPU_R_P: 0
PP1V5_S0: 1.5
========

Other Enables:
SMC_BC_AC_OK: 3.3
SMC_PM_G2_EN: 3.4
PM_SLP_SUS_L: 3.3
PM_SLP_S5_L: 3.3
PLT_RESET_L: 0 (no pulse)
ALL_SYS_PWRGD: 0.055 (to 0.00 when unplugged magsafe)
CPUIMVP_PGOOD: 0.055
SYS_PWROK_R: 0
PM_S0_PGOOD: 0
SMC_DELAYED_PWRGD: 0
S5_PWRGD: 3.3
SMC_MANUAL_RST_L: 2.79
PM_SYSRST_L: 3.3
PM_RSMRST_L: 3.3
PM_PWRBTN_L: 3.4
PM_BATLOW_L: 3.3
SYSCLK_CLK32K: Present at 32.7/.9K
PCH_INTRUDER_L: 3.05
PCH_SRTCRST_L: 3.3
RTC_RESET_L: 3.3
CPUVCCIOS0_EN: 0

 

[2informaticos]

Test removing Q7950; you can throw it away, is just a redundant protection.

If still low, remove power good resistors (R7963-69), one by one; keep in place R7967.
Check when ALL_SYS_PWRGD goes high.

 

[down1nit]

Q7950 removed, no change.

R7963 removed, now ALL_SYS is high and fans spin.

 

[down1nit]

Voltages around U7100 WITH R7963 removed:

PGOOD for sanity: 0.000
VCC/PVCC: 5.0
EN: 3.25
SREF: 0.536
VO: 0.032
OCSET: 0.029
RTN: 0.000
FSEL: 0.488
SET0: 0.488
SET1: 0.462
VID0: 1.05
VID1: 0.0000
BOOT: 4.708
UGATE: 0.032
PHASE: 0.032
LGATE: 0.0000

 

[2informaticos]

Change U7100, it fails a lot...

 

[down1nit]

And yep, replaced U7100 put back 100 ohm. Powers on but there's GPU / VRAM lines on the screen.

 

[2informaticos]

Disable GPU, as cheaper option repair...

 

[down1nit]

Do these respond OK to modifying nvram and then depowering the mux vcc?

Or is this a thing I need a demux setup for?

 

[2informaticos]

Hardware mod is already posted on the forum.
Please do a search...