Macbook Air 820-000165 - liquid damage repair - getting trolled & getting no where!

[Maxibon]

Macbook Air 820-000165 - liquid damage repair - getting trolled & getting no where!

Hey guys!

Hoping I can get some help with this one.

I received a Macbook Air A1466 820-000165 in from a customer for repair with the reported fault as an intermittent boot issue.

The customer said the Macbook wont boot, which has been happening intermittently, but getting worse and worse over time, and now wont boot at all

I got one boot out of it as soon as I received it then nothing.

Opened her up to find liquid damage on U3510, C3510 & on U7600 TPS51916 resistors R7612, R7611 & C7615.

Cleaned up those areas & replaced R7612, R7611 & C7615 - got a boot, right after, did a restart and then no boot, back to 20 - 30 seconds on fan spin then nothing.

Here is where I'm stuck - during boot I have all rails present, for about 20 - 30 seconds then nothing no boot.

These are the following measurements that I hope can help point towards a resolution or help me understand what's happening!

P3V3_S5_VFB2_R = 3.3v
P3V3_s5_VFB2 = 1v
P3V3_S5_COMP2_R = 1.9v
P3V3_S5_LL = 3.4v
P3V3_S5_VBST_R = 8.45v
P5VP3V3_VREF2 = 2v
SMC_PM_G2_EN = 3.4v during boot, drops to 1 volt after
P5V_S4S3_FUNC = missing
P5V_S4RS3_COMP1 = 2v
P5V_S4S3_VFB1 = missing
PP5V_S4RS3 = missing
P5VS4RS3_EN_R = missing
P3V3_S5_RF = 1.25v
P5V_S4S3_DRVH = missing
PP5V_S5 = 5.04v
PP3V3_S4 = 3.3 during boot, then jumps to 340.00v
PM_SLP_S4_L = 2.7v during boot then missing after

I also have a short on PP1V05_SO which I find odd, because it measures fine during boot - I really hope this helps shed light on how I'm not able to solve this one!

Thanks for any of your time and help in advance!

Max

 

[2informaticos]

First of all, welcome to the forum!

"SMC_PM_G2_EN = 3.4v during boot, drops to 1 volt after"
Do you mean, it drops after 20-30s?
SMC_PM_G2_EN MUST stay always high, once charger is coneccted; even in S5 state, when board is off.
I'm wonder why didn't mention drop voltage on 3V3/5V_S5 at same time; both controlled by above mentioned signal.

"PP3V3_S4 = 3.3 during boot, then jumps to 340.00v"
You may want to say "mV", isn't?

You've posted many unneded signals; try to post something more usefull please.
Like 3V3_S5/SUS, PM_BATLOW_L, SMC_RESET_L, PM_DSWPWRGD, S5_PWRGD and all RTC signals.
Specify if any is not stable and time for drop, if is the case.
Also check 3V42_G3H and PPBUS_G3H, if stable.

 

[Maxibon]

Thanks so much! I'm excited to be a part of it, and hopefully become a better repairer as well

Thanks for your prompt reply as well.

To be clear, I've just timed it, I get fan spin for 10 seconds, and during this time is what I'm talking about when I say during boot, and then after.

In saying that I've just checked again, and SMC_PM_G2_EN is 3.4v during fan spin (10 seconds) then stay on after - I must have measured incorrectly
PM_SLP_S4_L = 2.7v during boot then missing after the fan spin (10 seconds)

You're correct about my measurement on PP3V3_S4 - didn't realise my multi meter was changing mode on it's own :/ how embarrassing LOL

PP3V3_S4 is 3.3v during fan spin, then 340.00mV after.

PP3V3_S5 = 3.3v
P3V3SUS_EN = 3.3v
PM_BATLOW_L = 3.3v
SMC_RESET_L = 3.3v (odd when I measured this just now it caused fan spin for the 10 seconds again)
PM_DSW_PWRGD = 1v
S5_PWRGD = 3.3v
3V42_G3H = 3.4v
PPBUS_G3H = 8.6v

With the RTC (real time clock) do you mean U1900 SLG3NB148CV.

Thanks again for your time, I clearly have a lot to learn.

Max

 

[2informaticos]

"PM_DSW_PWRGD = 1v"
All the time, or just when fan goes off?
Check SMC_S5_PWRGD_VIN too.
If is OK, then reball SMC.

 

[Maxibon]

Doubled checked everything.

PM_DSW_PWRGD = 3.3V
SMC_S5_PWRGD_VIN = 3.2V

Would you still recommend reball SMC?

May I ask either way how you came to that so I know for next time??

Max

 

[2informaticos]

You've posted lower value for PM_DSW_PWRGD before.
That was the reason of my previous post; check the note from page 59.

Check if SMC_RESET_L is stable high.
Also test if board stays on removing U1930.
Inspect U1950 for corrosion.

 

[Maxibon]

I see.

I've checked SMC_RESET_L and it's 3.3v - stable however if I moved my positive probe on the pad, the board would fan spin for 10 seconds again.
I removed U1930 and board still fan spins for 10 seconds then nothing
After removing U1930 moving positive probes on SMC_RESET_L does not cause fan to spin for 10 seconds again
U1950 has no corrosion

I hope this helps :/

Max