A1706, Touchbar, 820-00239-A, No Chime

[rkrishnan]

Hello folks,

I recently bought a water damaged A1706 touch bar that doesn't have any chime (and obviously no display or fan). When connected to a USB-C monitor, the monitor turns on but no display (indicating its drawing some power). Here are the measurements I took - do you have suggestions on where I should check next? There was a considerable amount of water residue / corrosion near the battery area.

CPU gets luke warm (not really hot) after leaving it for 5 minutes.

820-00239-A
PPBUS_G3H - C6483 - 12.89V
PP5VS4 - L7600 - 5.06v
ALL_SYS_PWRGD - R7103 - 3.19v
CPU_VCCST_PWRGD- probe point - 0.98v
PM_PCH_SYS_PWROK - probe point - 3.29v
SMC_DELAYED_PWRGD - R5191 - 3.38v
PPBUS_HS_CPU - C7903 - 12.03v
PPVCC_S0_CPU - 0V (resistance to ground 17 ohm, which I assume is normal)
PP5V_S0_VCORE1 - Pin 3 U7210 - 5.07v

PP5V_S5 - probe point - 5.06v

I tried reading the schematic but am lost at how PPVCC_S0_CPU is produced. I guess it could be U7210, but was hoping someone has seen something like this before.

Thank you! I really hope this isn't a dead CPU, as I was hoping to resurrect this as my personal laptop.

 

[2informaticos]

Any liquid sign around U7100, or U7210/20?
Do you get voltage at L7270?

 

[rkrishnan]

Everything near U7100, U7210, and U7220 looks really clean.

CPUVR_SWSA - L7270 - 1.10v
PPVCCSA_S0_CPU - R7270 - 1.03v
CPUVR_PGOOD - 3.02v

CPUCORE_PWM1 (the PWM pin to U7210) - 2.48v (measured as DC)
CPUCORE_FCCM - 14.1mV (600k to ground) - Another clue I am guessing contributing to why I'm not getting anything out of U7210. I'll continue looking near U7100 I guess.

 

[2informaticos]

Very likely something affected by corrosion.
Disconnect anything from MLB and check if PPVCC_S0_CPU appears.