A1278 820-2936-B Reboots

[hgoncalves]

Hi,

I have an A1278 820-2936-B that is on continous loop (rebooting).

Even with just the board on the bench, it has the same behavier.

The only things the get hot are U4100 and U3900.

I can't see any obvius oxidation, and I don't know where to start.

Can you help?

 

[2informaticos]

Did you try SMC bypass and safe mode?
Run EFI ASD and see if any error pops up.

Also test trying one RAM module at a time.

 

[hgoncalves]

Hi,

The mac don't even boot to macos. It's just powering on / off bettwen a few seconds (2 or 3 seconds) interval.

Even without ram modules, fan or anything else connected it has the same behavier.

On the lab PSU it goes from 0A to 0.4A to 0.8A to 0A, fan spins for a while, and then stops. It seams that it tries to power on, but then powers off.

 

[2informaticos]

SMC bypass is first to try.

BTW, can you catch voltage on PCH and CPU coils?
Also check ALL_SYS_PWRGD and PLT_RESET_L.