[SOLVED]820-3437 pp5v_s4rs3

[LearningMan]

Hi, I have this 820-3437 MBA board not powering.
Every couple seconds PP5V_S4RS3 and PP5V_SO gets a DC voltage and then cut's back to 0v. Every time it does this, the voltage is lower by 1v increments.
It ranges from roughly 3.8V down to below 2.5 and then loops back to 3.8V.

 

[dukefawks]

Was this liquid? Is CPU Vcore pulsing also?

 

[LearningMan]

Hi. Yes liquid damage.

PPVCC_S0_CPU pulsing
PP5V_S4RS3 pulsing
PP5V_S4RS3_EN pulsing

 

[dukefawks]

Was corrosion around clock chip U1900? Check resistors in the data lines from SPI ROM.

 

[LearningMan]

No Title

Check resistors in the data lines from SPI ROM.

Legendary! Thank you.

It was SPI_MLB_CS_L, athough not obvious because it was a corroded via quite close to R6101. The via / test pad does not show up net in boardView. Definately connected directly to CE pin on U6100.
This one (see attached).
And bad R6116 & C6100.

Thanks again.