MBP A1286 820-2915 green light only, no start

[blazzelia]

Not yet, will do it and report back. Thanks

[piernov]

C9560 failure is a problem on 820-2850 not 820-2915.

[dellxps15]

be very carefull that the psu is in perfect working condition as some charger give green light but fail to power on the board. also bad battery can lead to this problem too.
try smc bypass if it start:
short the 2 pins on board, then connect psu while keeping the two pads shorted, then release the pin and short them again. check if pc start with full fan spin and give post and screen.

[blazzelia]

Have you replaced C9560 BTW?

I've checked its value - it has 300uF (the schematic says it should be 220uF). In any case, it seems to be ok. The voltage levels are unchanged without this capacitor.

[blazzelia]

try smc bypass if it start:
short the 2 pins on board, then connect psu while keeping the two pads shorted, then release the pin and short them again. check if pc start with full fan spin and give post and screen.

I did that, the fans won't start, the voltage levels are unchanged, the pulsing rails still pulsing.

[blazzelia]

Any other idea?

[dellxps15]

read voltage on C7205 pin N° 1
check voltage of r7940 both side,
post u7201 voltage.

[blazzelia]

Sorry for the delay ... long working hours ...

So, ping 1 on C7205 - oscillating
Same for both sides of R7940.

Regarding U7201, do you mean the voltage on all pins?

[dellxps15]

voltage on c7200,
resistance on c7205 ?

[blazzelia]

voltage on c7200,... ?

Very confusing ... the board was sitting on my desk since my last reply, so about 3 weeks away. At first the voltmeter showed 3.7-5V, then up to 12.4, then down again, then 12,4 for minutes until I got bored waiting for a change. Powered off, tried again - 12.4V. I put the MB away and check it the next day - 12.4V. At some point I just left the MB powered on, decided to get back to it in about half hour. After a few minutes the green light from the magsafe went off. I reconnected it - green light and 12.4V, and the magsafe did not go off. Not sure if that tells anything...

The resistance on C7205 starts at around 20 Mohms going down to 4 MOhms.

[dellxps15]

your macbook has some problem with ppbus and smd. 12,4 volt going down could be bad 10omh resistor r7021, r7022. check if they are 10omh.

[blazzelia]

R7021 and R7022 are both intact and have 10 Ohms.

[dellxps15]

board should not power on on 12,4 volt unless u do smcbypass. ppbus must be 12,57 volt (12,6) not 12,4 as smc is not boosting. if u connect fan, and connect psu, fan start spinning or they dont ?

[blazzelia]

No fans spinning...

[blazzelia]

No fans spinning...

What does it means?

[blazzelia]

Any other idea?

[mon2]

Measure the voltage to ground of:

SMBUS_SMC_BSA_SCL
SMBUS_SMC_BSA_SDA

on J6950 (battery connector). Post the voltage measurements.