820-01958 no power

[Kyle93]

Arrived with water damage. After replacing affected components the board powers on to 20v at 0.12-0.14a

Strange, can hear a buzzing noise coming out of the board. Sounds like it either coming from the T2 chip or U7800

Tried DFU mode revive option which completed successfully but no changes.

What should be checked next??

 

[2informaticos]

So board turns on, but doesn't boot?
You may need to use restore option.
Ask the client if has data unsaved first.

 

[Kyle93]

Yes but no change after restore option.

When the board is on the bench if one of the screw holes to the left of CPU is just tapped with finger the buzzing noise goes away and the board jumps up to 0.24a for a few seconds. Once unplugged and plugged back in buzzing noise returns within a few seconds

 

[2informaticos]

Which voltages do you get on the board?
Do you note any drop on VCORE?

 

[Kyle93]

no, it stays at 1.8V

 

[Kyle93]

Looks like dead CPU. This board making same noise as the one in this video.

 

[2informaticos]

Audio board was also affected by liquid?
T2 data lines close to PPBUS_G3H and liquid spill damage it easy.
I suppose T2 chip got bad and doesn't work properly.

 

[Kyle93]

Yes, audio board had alot of liquid.

I assume you cant replace the T2 chips correct?

 

[2informaticos]

Already discussed few times on the forum, about such possibility:

820-01521 20v 0A

Hi, got this mac a1932 for repair. Board looks clean, never been repaired before, no corrosion or traces of liquid damage Bare board with no battery stays at 5v 0.09-0.1 amps When battery connected - switching to 20 volts, 0 amps Didn't find any short on board. F6700 was blown, changed with...

boards.rossmanngroup.com

Pretty hopeless...