820-3115 Green Light Cycles On / Off

[computercaverva]

I suspect this unit is the victim of a cheap Chinese charger, bad dorm room wiring, etc. Came in with no green light / no power. R7051 was blown, replaced the resistor and ISL. Got green light back, however after a few seconds it cuts off, and then a few seconds letter will come back on. SMC_BC_ACOK, Adapter Sense, PPBUS, 3V42, are all normal and they do not seem to fluctuate whether the green light is on or not. The computer will not turn on when the light is green or off. I replaced the SMC_RESET_L chip as the Manual SMC Reset rail was only 2.887v as the regular SMC_Reset was 3.4ish along with SMC_ONOFF. Could this be an issue when the computer tries to change power states or is it more likely an SMC issue?

 

[aprendiz]

Try another magsafe, what is the voltaje on PPBUS_G3H??

 

[computercaverva]

Tried a second charger and DC in board. PPBUS is 12.57v

 

[dukefawks]

Green light must first be stable. I hope you tried a known good magsafe board....

 

[computercaverva]

Yup the light cycles with several known good DC In Boards, and with 60W / 80W / and Magsafe 1 cable connected to DC Power Supply

 

[dukefawks]

PPBUS staying stable if green light goes out? Does this power on from a charged battery?

 

[computercaverva]

PPBUS stays stable with or without green light, as does PP3V42. It does not power on with a charged battery.

 

[dukefawks]

Seems like a dead SMC to me