A1398 - 820-00138-A no power

[hgoncalves]

Hi.

I have an A1398 - 820-00138-A with no power.

It pulls 100 mA from bench PSU, has fan spin and green light on charger.

I have all major voltages, except:

PPVCC_S0_CPU = 0V (0.018 on diode reading, and 18 ohm to ground)

PP1V05_SUS = 0.744V

No big coil seams to be shorted.

Can it be BIOS?

 

[2informaticos]

1V05_SUS looks bad; what is diode mode there?
Try changing U7840.

 

[hgoncalves]

Hi.

1V05_SUS has 0.357 in diode reading.

My board doesn't have U7840, but my schematic says it should have. However, I can only find it on 820-00163-04 boards.

Can you please confirm if this board model (820-00138-A) should have it?

 

[2informaticos]

That voltage may be created with a simple resistors divider; as per schematic note.
You are probably in this case.

First you must get 3V3_SUS; it also requires 3V3_S5.

 

[hgoncalves]

Hi have 3.3V on both 3V3_SUS and 3V3_S5

 

[2informaticos]

Possibly bad PCH.
It sinks too much current from 1V05_SUS.