820-2796 not start after liquid damage

[thomamagic]

hello,
please need help for mainboard 820-2796 a1370 model
i have ppbus good and led charging
fan no turn
bios flash ok same problem
All big coil have good diode value
When plug power, i have 0.217A without battery
thanks for help

 

[2informaticos]

This MCP platform requires pressing power button to turn on.

Trigger SMC_ONOFF_L and check for pulse at PM_SLP_S4_L.
I supposed that SMC_ONOFF_L stays high normally.

Do you get C7755 correct voltage?

 

[thomamagic]

yes i have already test to trigger SMC_ONOFF_L it's for that i have 0.217A, before press i have 0A
on PM_SLP_S4_L i have 3.3V when push power and on C7755 yes i have 0.9V

 

[2informaticos]

on PM_SLP_S4_L i have 3.3V when push power"
Drops to 0V after power button is released?
Check L7330 voltage, at same time.
What about PM_SLP_S3L?

 

[thomamagic]

no, i push power button and PM_SLP_S4_L have 3.3V always
on L7330 i have 1.35V
PM_SLP_S3_L : 3.3V always when push

 

[thomamagic]

i have lot damage around U7500
i have clean all pad and solder, you think this chip is dead and can make this problem?
Thanks

 

[thomamagic]

i have remove U7500 and fan turn
i have 0.310A
think i have found the problem, need found ic on donor board tomorrow and check if it's better or if i have line defect to this chip

 

[2informaticos]

"i have remove U7500 and fan turn"
If you've turned on the board without U7500, you are really lucky if Q7560 didn't blow out.

Do NOT do this ever again.
Never ever let high-side MOSFET (in buck converter) with Gate pin "on air".