820-2877 Liquid Damage

[Djsp]

Hi i am practice on an old board a 820-2877-b, with damage from liquid, the board goes to S0, but no fan spin
PP5V_S0 = OK
PP3V3_S0 = OK
PP1V8_S0 = 0K
PP1V5_S0 = OK
CPUVCORE = 0
ONLY WITH RESET SMC STARTS

 

[2informaticos]

Do you really mean SMC reset, or just pressing power button?
Nvidia MCP platform boards don't start without pressing power button, as normal.

Post voltage for L7560, L7620 and L7710.

 

[Djsp]

you have to excuse me, I meant that if I do the reset procedure the smc starts with the fan at maximum.

L7560 = 0.022
L7620= 1.080
L7710= 0

 

[2informaticos]

"starts with the fan at maximum"
Do you mean SMC bypass maybe.
Board doesn't turn on in normal mode?

Post basic voltages for U7500; pins 14, 16, 22, 29.

 

[Djsp]

yes, in fact I said I am a beginner, then these are the measures of u 7500:
14 = 12.55
16 = 5.044
22 = 5.018
29 = 3.303

 

[2informaticos]

Post resistance to ground at L7560 (ohm scale).

 

[Djsp]

016.0 Ω
Is there low insulation?

 

[2informaticos]

Where did you find liquid spill?

 

[Djsp]

Yes, the part was affected by oxidation

 

[2informaticos]

Which areas have been affected by corrosion???

 

[Djsp]

Side A from the LVDS connector up to u7500 side B smc the circuit of the 3V42 etc. I removed it with some isopropyl alcohol, I rebuilt tracks on Q5315 and I also replaced it, and it works now I agree on U7500 I see if any capacitor pulls down, do you think I have to replace U7500?

 

[2informaticos]

Replace C7564 and R7565; check their traces too.
May need to replace U7500 and Q7560/65; better at same time.

 

[Djsp]

I replaced resistance and capacitor but nothing, I did a test with isopropyl alcohol on Q7560/65 and Q7565 heat evaporates fast I'm afraid it pulls down

 

[2informaticos]

16 ohm doesn't look low for MCP core voltage.
Post resistance to ground at L6995 (ohm scale).

 

[Djsp]

L6995= 47.20k

 

[2informaticos]

Check all the components related with U7500 area.
Pay atention to traces continuity.

 

[Djsp]

I removed the U7500 I realized that there is an interruption on pad 14 or the PPBUS_G3H pro pad to rebuild it and let's see what happens
But the question that arises is: did it stop by corrosion or why did the U 7500 go short?

 

[Djsp]

 

[2informaticos]

Where did you see short?

Looks like fault caused by corrosion...

 

[Djsp]

If I hadn't removed the U7500 I would never have noticed the interruption, I rebuilt the missing part now it works perfectly. It was very informative. Thank you!