820-3437 bad SMC or CPU?

EsteTron

New member
Currently working on a 820-3437 where power supply is pulling .02Amps. Device has no signs of liquid damage. Always present power rails are present. SMC_RESET_L is present. PM_SLP_S4_L is missing. Board does not boot in SMC Bypass. I discovered the tiniest amount of corrosion under SMC on Pad 64 which is SMC_PWRFAIL_WARN_L. Did not find corrosion anywhere else on board. I reflowed SMC to remove the corrosion and device still pulls .02Amps and does not boot in SMC Bypass. Before I spend the time pulling off SMC and Reballing, is this a sign of a dead CPU?

Sorry for the brief explanation.
 

JohnB8812

New member
Try another SMC to be safe. If no change, could literally be anything including the CPU causing no S4. Inspect as closely as possible for corrosion elsewhere.
 

2informaticos

Administrator
Staff member
What about PM_BATLOW_L?
Magsafe 2 charger for sure?

Check if PM_PWRBTN_L reacts when triggering SMC_ONOFF_L; use R5115/16 pads for this.
Be sure PM_RSMRST_L is high.

Do you get PM_SLP_SUS_L?
If not, check all PCH's RTC signals.
 

EsteTron

New member
It took a while to revisit this board but I am back at it. I have not replaced the SMC yet.

Using both orginal 85 watt magsafe 2 and DCPS with genuine 85 watt magsafe 2 connector attached.
PM_PWRBTN_L drops from 3.4v to .04v when triggering SMC_ONOFF_L
PM_RSMRST_L = 3.3v
PM_SLP_SUS_L = 3.3v

BATLOW = 0.037v

PM_SLP_S5_L is missing.

I see that BATLOW comes from SMC.
 

2informaticos

Administrator
Staff member
"PM_PWRBTN_L drops from 3.4v to .04v when triggering SMC_ONOFF_L"
Check if any PM_SLP_Sx_L signal reacts at same time.
 

EsteTron

New member
PM_SLP_SUS_L = Stays at 3.3v
PM_SLP_S5_L = stays at 0v
PM_SLP_S4_L = stays at 0v
PM_SLP_S3_L = stays at 0v
PM_SLP_S0_L = stays at 0v
 
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