820-00840 0.47A 20V no boot

[wgaca]

CPU gets hot, no USB activity, and no caps lock light.

EFI?

 

[2informaticos]

Is worth to try known good BIOS.
Any history available?

 

[wgaca]

No visible damage, no visible corrosion
I tried another EFI chip same behaviour

 

[2informaticos]

Monitor volttage at L7210/20.
Can you note any change in the first 10-15s?

 

[wgaca]

0.952/0.955 no change after time

 

[2informaticos]

PLT_RESET_L goes high?

 

[wgaca]

3.3v

 

[2informaticos]

Check R1320-25 resistors.
Compare diode mode and DC levels with good board.
An o-scope can help you to check the real activity there; pay atention to LPC_FRAME_L.