820-3476 doesn't power on

[bighead]

Hi,

Another 820-3476.

Solid green light after 4-5sec goes to orange.
Customer said it was liquid damaged.
Only corrosion was around the JTAG connector.
I thought this gonna be an easy fix, but of course no.

Measurements:

PP3V3_S5 - 3.3V
PP5V_S5 5V
PPBUS_G3H 12.57V
PP3V3_SUS 3.3V
PP1V05_SUS - 1.05V

U1900
Pin 1 3.42V
Pin 12 nice wave form 32KHz

Checked R1300/3 and everything looks fine.

SMC crystal does not oscillate and no voltage on it.
Some with Y1905.

PM_SYSRST_L - 1.9V
PM_SLP_S5_L - 0V
PM_SLP_S4_L - 0V
PM_SLP_S3_L - 0V

What am I missing?

Thank you.

Edit: It was in the Ultra sonic cleaner too.

 

[dukefawks]

Did you remove the connector? Did you check the usually resistors in serie with U6100 data lines, R6110-31?

 

[bighead]

Yes, I did remove the connector.

I checked all the resistors in series on page 46. I can't find R6131.

I tried different BIOS too.

 

[dukefawks]

No idea, check traces to U6100 and resistors for corrosion. Is there a pulse on L7520 when connecting power.

 

[bighead]

When I checked the resistors I checked the traces to the EFI chip.

Yes, there is some pulse on L7520 when I connect the adapter.

 

[dukefawks]

Is there a pulse on other rails too? CPU Vcore also coming high for a moment?

 

[bighead]

There is no pulse on CPU Vcore.
However there is a weird looking 2V on PP3V3_S0. No pulse but 2V continuously.
Also I've 0.9V on PP3V3_S4SW_SNS_FET_R.
L7430 comes on for a sec.


I checked U8030 and the P3V3S0_EN is missing so I don't know how that is possible to have 2V on PP3V3_S0.
But looks like U8050 is burned. Could that be the problem?

 

[dukefawks]

If U8050 is really fried then you should replace it. Check for a short on R8050 to GND first though.