Macbook Air 820-3437-b Doesn't turn on.

[sh33pz]

Hello,

The history with the MacBook Air is, the person was using on an airplane trip and it just died in their lap as they were using it.

When I received it, it did not have a light on the MagSafe(using an apple original charger, not a knockoff).

PPBUS_G3H had 8.19v, it should have been 8.6v which means SMC not talking to the ISL and it was missing the PP5V_S5 rail @c7505 as well.

I have swapped the SMC and now have the correct PPBUS_G3H 8.56v @f7140 both sides and have my PP5V_S5 @c7505 as well now.

MagSafe light does come on, green then turns to orange.


I have all of the correct voltages on the S5 rails.


I am missing PP5V_S4RS3 rail and turns out I am missing PM_SLP_S4_L.



When checking around the U0500 (system power management) IN lines:

@r5231 PCH_SUSACK_L 40mv
@r1995 PM_SYSRST_L 57mv
@r1962 PM_PCH_SYS_PWROK 0v
@r1963 PM_PCH_PWROK 0v
@r8133 PM_RSMRST_L 0v
@r1802 PM_PWRBTN_L 3.4v
@r5185 SMC_ADAPTER_EN 3.39v
@r1410 PM_BATLOW_L 3.32v
@r1450 PCH_DSWVRMEN 3.22v
@r1451 PM_DSW_PWRGD 3.42v
@r1452 PCIE_WAKE_L 3.32v


I have PPVRTC_G3H 3.32v @r1450 so I assume the u1900 chip is working.

The board has no corrosion on it at all and no liquid damge.

SMC chip did come from a donor board, so, maybe thinking in trying another?


I feel, I am missing something dumb and my brain isn't clicking at all.

What information can I get you?

 

[2informaticos]

Check if L7520 pulses at least.
Do you get 3V at PM_SLP_SUS_L?
If not, check all PCH's RTC signals.
Aso check 32KHz output from U1900.

 

[sh33pz]

L7520 0v both sides, no pulsing with the voltmeter.

@r1464 PM_SLP_SUS_L 0v

@r1301 PCH_INTRUDER_L 3.0v
@r1302 PCH_INTVRMEN 3.2v
@r1300 PCH_SRTCRST_L 3.3v
@r1303 RTC_RESET_L 3.3v

I have no oscilloscope to check for the 32KHz u1900 but took a DC volt reading:
Pin12: 440.2mV

 

[2informaticos]

PM_SLP_SUS_L should go high with these readings.
As it didn't, PCH is the suspect here, because it gets correct signals.
Use quality flux and heat PCH/CPU to 180-200 degrees, no more; just in case some crap under...

 

[sh33pz]

I did as you instructed and MacBook is now running. My question is since I reheated the PCH/CPU I am assuming this is more than likely a short-term fix and the CPU is on its way out?

 

[2informaticos]

Cross your fingers and pray it was just crap under PCH area...

 

[sh33pz]

haha ok, thank you for your help.

cheers