Macbook A1278 820-2936B

[Instafixx]

Taking 800 amps and pulsing.
Fan spin. Green Light on MagSafe.

How to go about this ?

 

[2informaticos]

Any history available?
Tried SMC bypass?

 

[Instafixx]

SMC doesn't work.

 

[2informaticos]

CPU core voltages pulsing too?

Check R7402 solders and traces.

 

[Instafixx]

R7402 across pins 90k Ohms
Yes all voltages on the board are pulsing.

 

[2informaticos]

Still pulsing on SMC bypass?
PLT_RESET_L also pulsing?

"Any history available?"
???

 

[Instafixx]

It is turning on in SMC bypass mode. was doing it wrong.
Bad SMC ?

 

[2informaticos]

I don't think.
Check SMC I/V sensors; start with SMC_DCIN/PBUS_VSENSE and SMC_DCIN/BMON_ISENSE.

 

[Instafixx]

Diode Readings
SMC_DCIN_VSENSE is 0.709
SMC_PBUS_VSENSE is 0.740
SMC_DCIN_ISENSE is 0.740
SMC_BMON_ISENSE is 0.743

Voltage Readings

SMC_DCIN_VSENSE is 2.8V Stable
SMC_PBUS_VSENSE is 0V
SMC_DCIN_ISENSE is 0V
SMC_BMON_ISENSE is 0V

 

[2informaticos]

"SMC_DCIN_ISENSE is 0V"
Is wrong.
Check Q5310, its traces and adjacent components.

 

[Instafixx]

R5311/2 is 100k Ohms

Q5310 Diode Readings all are ok except
PPDCIN_G3H is 2.923 -
PPDCINVSENS_EN_L_DIV is OL
is it normal?

 

[2informaticos]

Did you check voltages on that area?

 

[Instafixx]

DCINVSENS_EN_L IS 0V
PPDCINVSENS_EN_L_DIV is 8.4V
PPDCIN_G3 is 17V
DCIN_S5_VSENSE is 17V
SMC_BC_ACOK is 0V

 

[2informaticos]

Sorry, I got confused bateween VSENSE and ISENSE...

What is AVREF_SMC voltage?

 

[Instafixx]

3.3V

 

[2informaticos]

"Green Light on MagSafe
...............................
SMC_BC_ACOK is 0V"
How is possible?

Check all I/V sensors.

 

[Instafixx]

Now there is no light on MagSafe. I got it previously .

 

[2informaticos]

Post U7000's basic voltages.

 

[Instafixx]

Now I find SMC_BC_ACOk is shorted.

 

[Instafixx]

all shorts removed. Still wont turn on.