dead macbook 820-2936-B

[ukRich]

Need help with diagnosing this problem
820-2936 no power,magsafe green, fan spins for a second then stops then repeats. Board is liquid damaged and when I got it I was not getting any ppv5_s5. Replaced u7200 and c7273 that was shorted

All rails ok until I get to pp5v_s3. if I watch the MM, it jumps to 5v then straight to 0v. In diode mode does not show any short to ground but Im obviosly missing something

Thanks

[vinifera]

Re: dead macbook 820-2936-B

i have the same problem ? What did you find ? PP5V_S3 go on and off

[piernov]

Re: dead macbook 820-2936-B

Liquid damage? History of the board?
Green light on Magsafe? Fan spinning?
ALL_SYS_PWRGD and CPU VCore present?

Almost every board issue is different so you have to give the most information possible to be able to troubleshoot it properly.

[vinifera]

Re: dead macbook 820-2936-B

after reflow the gpu, the fans goes on and off for 1 seconde.
After check of the power lines ; PP5V_S3 and PP5V_S0 ;
PP5V_S3 0-5-0-5-0V 5V "ON/OFF
short check = 0,422 as a good board"
PP5V_S0 0-5-0-5-0V 5V "ON/OFF and goes to 5V and 0,18V
short check = 0,395 = as a good board"
green light on magsafe and orange when connecting a battery

This problem is occured after reflow the GPU, because before it works.
I think of a current sense problem ? but where to look further ?

[vinifera]

Re: dead macbook 820-2936-B

I have done a reflow , because the boot line doesn't go further. I think that i damaged something , but which further steps to find ?

[vinifera]

Re: dead macbook 820-2936-B

Which current sense problem ?

[piernov]

Re: dead macbook 820-2936-B

Cannot help you if a GPU that doesn't even exist was randomly reflowed for no reason, sorry.