820-2879 switching off

[iClub]

Good morning, I identified oxidized components on the top of the board and replaced the SMC, in the tests the mac turns on and after a while it turns off and on again, there are times that it doesn't turn on.

Voltage: PPbus_g3h 12.57V; PP3V42_G3H 3.4v; ALL 3.3V; PP3V_S0 3.3v; VCORE 0.91V;

I tried to do ASD TEST, but it turned off

 

[2informaticos]

Did you try SMC bypass mode?
Does it turn off w/ and w/o battery connected?

Post exact resistance (ohm scale) to ground at L6995.

 

[iClub]

L6995 3.630K in reference to the ground.

SMC bypass works, but the mac keeps turning off unexpectedly both on the ASD TEST screen and when initializing the system.

It shuts down without the battery connected? yes.

 

[2informaticos]

3.6K at L6995 to ground can mean bad MCP.
Normal value is more than 30K.

 

[iClub]

Sorry I don't know what "MCP" means.
Isn't it worth it?

 

[2informaticos]

"I don't know what "MCP" means"
Look at U1400 in page 2.
MCP stands from Multi Chip Package (embedded south, north, graphics, DDR control functions).

BTW, Intel also noted its chips like MCP and SOC (System On Chip) for newer ones.

MCP89 is an old chip, very tired really.
You can find working boards on Aliexpress very cheap.
But keep in mind, the MCP can die in any moment.