820-00165 not booting ? dead cpu

[Neil250]

820-00165 A1466 MBA

Liquid spill
Corrosion around U7870, C7870,C7871

No fan spin
Replaced a terrible looking C7870---> fan spin
Orange light on charger

CPU VCORE: 1.8V
No backlight
No image
No chime
Fan is spinning
All G3H power rails are good

USB Mouse does not light up
USB SATA drive adapter spins up an old 2.5"HDD

I'm thinking this board is not even starting
Where to start?

PP5V_S4RS3: 5.15V
PP5V_S5: 5.14V

Q7706
4: 8.58V
3: 8.34V
2,5,6: 0 V

Thats with the LCD connected and without

On Q7706: I thought since voltage on 4 > 3 Q7706 should be open

In any case without real USB activity, the board is not turning on and thats the issue correct?

 

[2informaticos]

"I thought since voltage on 4 > 3 Q7706 should be open"
Do you think Vgs=-0.24V is sufficient???
However, no reason to check backlight, if no image, nor USB activity detected.

Post PLT_RESET_L and PLT_RST_BUF_L.
Check all SPI Bus Series termination resistors (page 46) and their traces.
Also clean J6100; remove it, if you do not use Medusa programmer.
Be sure to get all voltages from pages 57/58.

Try known good BIOS.

 

[Neil250]

OK that worked.

R6119 measured 200K
Changed it out and boom!
USB now works
Machine boots!

Can you tell me why you went to the SPI termination resistors?

THANKS!!!

 

[2informaticos]

R6119 is placed between PCH and BIOS chip...