820-00923 no power

[Kyle93]

This board has no power and just randomly died according to customer. No liquid damage.

Meter is at 20v 0.15 amps. PPBUS is 13v. Tried DFU but cannot get the machine into DFU mode.

What should be checked next??

 

[2informaticos]

This is not T2 machine.

Do you get 3V3_S5/SUS?
Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L (at same time).

 

[Kyle93]

Yes 3.2v on 3V3_S5/SUS

PM_PWRBTN_L is 3.3v and has a drop pulse when SMC_ONOFF_L is triggered.

PCH side of CPU is warm on thermal cam

 

[2informaticos]

Can you catch a pulse at PM_SLP_S4_L at same time?

If board stays in S5, PCH shouldn't heat at all.

 

[Kyle93]

PM_SLP_S4_L 3.4 but does not pulse when SMC_ONOFF_L is triggered

Board has constant S5 voltage and PCH is warm

 

[2informaticos]

If PM_SLP_S4_L is steady high, then power on sequence is started.
All S3 voltages should be present, like 1.2V for RAM.
If also PM_SLP_S3_L is high, then check S0 voltages.

 

[Kyle93]

PM_SLP_S3_L is high and all S0 rails appear to be present

 

[2informaticos]

Check for USB activity and external video.

What is CPU core voltage, after 10-15s?
PLT_RST_L goes high?

 

[Kyle93]

No usb activity or external video. Board is at 20v and a consistent 0.14amps

PLT_RST_L 0V

PPVCC_S0_CPU 0V

PPVCCIO_S0_CPU 0.950V

 

[2informaticos]

Also missing L7270 voltage?
You can try known good BIOS...

 

[Kyle93]

0V L7270

Bios from donar board did not make any differences

 

[2informaticos]

Do you get voltages from pages 73, 75 and 76?