820-3437 Liquid Damage Pulsing S0


I have always interested in component level repair, so when the opportunity to get a liquid damaged Mac Book Air arrived, I was delighted. So bear with me, as this is my first attempt at this.

I get Green/Orange on the Mag Safe, but no fan spin.

Below are my voltages.

PPBUS G3H = 8.58




PPDCIN_G3 = 15.13

PP3V42_G3H = 3.44

PPVRTC_G3H = 3.33

PP5V_S5 = 5.2

PP5V_S4RS = 3.34 Pulse

PP5V_S0 = 3.14 pulse

PP3V3_S5 = 3.33

PP3V3_S4 = 0.33

PP3V3_SUS = 3

PP3V3_S3 = Pulse 2

PP3v3_S0 = Pulse 1

PP3V3_S4SW_SNS = Pulse 3

PP3V3_S0SW_SSD = 2.3

PP3V3_S4_TBTAPWR = Pulse 3

PP1V8_S3 = 1.7

PP1V2_S3 = Pulse .70

PP1V05_SUS = 1.06

PP1V5_S0 = 1.5

PP0V6_S0_DDRVTT = Pulse .34

PP1V05_S0SW_PCH_HSIO = 1.05

PP5V_S4RS3 = Pulse 3.34

The little corrosion I found was near U6100. I cleaned with with isopropyl alcohol. I measured all 16 terminator resistors and they are fine. The only issue I can find (besides the voltages) is Pin 2 on U6100 (SPI_MLB_MISO), does not have continuity with R6114, R6123 or it’s VIA (824). My questions are…

  1. Should I be getting continuity from those locations? If so, is re-soldering the chip/replacing is my next step? I know it’s a BIOS chip, so it’s not a simple rip and replace.
  2. Is 15.13 too far out of tolerance for PPDCIN_G3H_ISOL/PPDCIN_G3 which should be 18.5?
  3. Any other suggestions as to what I should look into.
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Have you reviewed Louis Rossmann’s vids? Louis’s YouTube stuff He gets into board level repairs.


Yep, he is the only reason why I made it this far, starting with no knowledge. :)


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