820-3536 No Power

[tlough75]

Got an 820-3536 with no power, no MS2 light. No obvious signs of liquid damage. PP3V42_G3H is 3.42v but PPBUS is 12.26v. Checked pins 10 and 11 on U7100 and got .521 and .524 diode mode and 3.42V present on both pins. Looked around U1950 but didn't see anything crazy. I reballed the SMC becuse I thought it may have had corrosion. the board itself is drawing 13mA.

 

[2informaticos]

Did you check SMC_RESET_L?

 

[tlough75]

Yup, 3.42v

 

[tlough75]

SMC_ONOFF_L is 1.6v

 

[2informaticos]

Bad enough.
Disconnect keyboard and check again.

 

[tlough75]

that is with board on bench

 

[2informaticos]

First check R5170 value.
If OK, remove C4810 and check again.
If still low, remoce R4810, to discard keyboard connector corrosion.
After all, remain only U5110 and SMC...

 

[tlough75]

Removed C4810 and the board is now running. I take it C4810 was leaking to GND. Got a MS2 light and fan spin. put board into chassis just hear that glorious chime and got that as well as a flashing "?" folder.