820-00165

[Neil250]

Green light
No fan spin
No water damage
Board just "suddenly would not turn on"

PP1V2_S3 = 0 V
U7400 with lots of white corrosion

L7430: 0.30 V on diode mode to ground

PP5V5_S5: 5.5V

change U7400?

 

[2informaticos]

Clean the corrosion, replace damaged components and rebuild traces.

Do you get 3V3_S5/SUS?

U7400 requires PM_SLP_S4_L to work, do not change it yet.

 

[Neil250]

PP3V3_SUS: 3.345V
PP3V3_S5: 3.346V at R2042

PM_SLP_S4_L measured at R8111 pin 1: 3.335

 

[2informaticos]

Post some of U7400 voltages; pins 12, 16, 17, 6,.
Be sure about R/C7425 and traces.

 

[Neil250]

I think this U7400 is f'd

12: 5.14 V
16: 0
17: 0
18: 0
19: 0
20: 0.029
12: 5.14

DIODE:

1: short
3: short
4: GND
16: SHORT
17: SHORT

There is hardly any solder (almost none) at 16 and 17, all corroded away.

 

[2informaticos]

"Clean the corrosion, replace damaged components and rebuild traces."
???
Resolder all U7400 pads also.

If still short somewhere, replace the chip.

 

[Neil250]

replaced U7400

fixed!