820-2915 turn on 20 seconds, then turn off and no more on

[Salvatore951]

I replaced the gpu in 820-2915, I tested many hours with valley benchmark, shipped it back to customer. Customer went to Apple Store to mount HDD and then called me the same day because macbook doesn't turn on.
I received macbook back:

No visible damage on the board, if I try to turn it on multiple times plugging magsafe to board, sometimes it turns on and I get video on lcd, after 20 second it shut down.
I thinks there are no short in power rails because sometimes it turn on. Could be SMC o u9600 or gpu? what can cause shut down after 20 seconds?

 

[Salvatore951]

i reflowed SMC and now it works. My question now is? Is reflow of SMC a temporary fix like gpu Or is SMC a real solder problem?

 

[dukefawks]

This could have been anything. It could really have been an SMC issue or something else got heated up and works again. Expect another return on this....