820-3437 No Fan Spin

[fodelement]

Hello!

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 have a Green/Orange on the Mag Safe, but no fan spin.

Below are my voltages.

PPBUS G3H = 8.58

PPBUS_S5_HS_COMPUTING_ISN = 8.58

PPBUS_S5_HS_OTHER_ISNS = 8.58

PPDCIN_G3H_ISOL = 15.13

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. If I understood Louis's Rossmann Repair Training Guide correctly, should all of the rails be pulsing?
4. Any other suggestions as to what I should look into?

PS: PS:32 > IS:24 > Wagner 08

 

[2informaticos]

"PP5V_S4RS = 3.34 Pulse"
Never post DC voltage for a pulsing rail.
Only an o-scope can show you the peak voltage there.

"Is 15.13 too far out of tolerance for PPDCIN_G3H_ISOL/PPDCIN_G3 which should be 18.5?"
Don't bother with that; actual value depends of the charger used.
"PPBUS G3H = 8.58"
This is what you really need.

"Should I be getting continuity from those locations?"
YES, if you want to start the board.
Don't waste time in other thing, before solve tis issue first...

 

[fodelement]

YES, if you want to start the board.
Don't waste time in other thing, before solve tis issue first...

Hello,

Thank you for this information! I had a feeling this was an issue, but did not want to chase down something if it was not an issue.

Would removing U6100 an putting it back on/replacing it be the best way to resolve this issue? Or should I try something else?

I tested for continuity from

U6100 Pin 2 to via 824

U6100 Pin 2 to R6123 Pin 2

U6100 Pin 2 to R6114 Pin 2

via 824 to R6123 Pin 2

via 824 to R6114 Pin 2

None of which had continuity.

​​​​​​​R6114 Pin 2 to R6123 Pin 2 does have continuity.

 

[2informaticos]

Check the trace between U6100 and R6114/23 under microscope.
You can run a tiny wire to correct the issue.

 

[fodelement]

Check the trace between U6100 and R6114/23 under microscope.
You can run a tiny wire to correct the issue.

Would the wire have to come from U6100 Pin 2 then go to via 824, then to one of the resistors?

Or would I skip 824?

Thank you for all your help, I really do appreciate it.

 

[2informaticos]

What is "via 824"???

 

[fodelement]

No Title

What is "via 824"???

This

 

[2informaticos]

I was supposing that.
You mean TP[1]SPI_MLB_MISO.
Is just a test point and you can run wire from it to U6100, or R6114/23, depending where the trace is broken.

BTW, "Probe: 824" (maybe Via 824 in your boardviewer) appears for all the points of that trace...