A1466 820-00165A Will not boot/turn on.

[FollowTheVoodoo]

Hi Everyone,

I'm trying to help a friend with their Macbook Air. She went to go plug it in and then she just heard a pop from around the area just above the keyboard.

I have removed the board from the chassis, I do not have a sacrificial power supply so unfortunately I can't tell you how much the current draw is. I will also mention that I made the rookie mistake of measure resistance with the system still powered up. I usually don't do that but I'm hoping I didn't damage anything (but I could be totally wrong).

There is no water damage that I can see, I can attach photos if need be.

Here are measurements and observations so far:

When first connecting the magsafe, it turns green, then turns orange. Sometimes I get fan-spin and sometimes I don't.

PPBUS_G3H = 8.6V
PPBUS_S5_HS_COMPUTING_ISNS = 8.6V
PPBUS_S5_HS_OTHER_ISNS_8.6V
PPDCIN_G3H_ISOL=15.03V
PPDCIN_G3H=15.03
PP3V42_G3H=3.417
PPVRTC_G3H=3.350V
PP5V_S5=5.024V
PP5V_S4RS3=0V
PP5V_S0=0V
PP3V3_S5=3.350V
PP3V3_S4=0V
PP3V3_SUS=3.490V
PP3V3_S3=0V
PP3V3_S4_S4SW_SNS=0V
PP1V8_S3=0V
PP1V05_SUS=1.059V
PP1V5_S0=0V
PM_SLP_S4_L=0V

I sort of lost track of what I have measured and what I haven't measured. but I do understand based on Louis' videos that in order to get S0, you need S3, and to get S3, you need S4. I know a lot of the S4 stuff comes from U0500 but I'm not really sure what makes U0500 happy to turn on PM_SLP_S4_L.

Any directional pointers?

 

[2informaticos]

First of all, welcome to the forum!

Did you test the board alone on the desk (no LIO flex connected)?
Try to start in SMC bypass mode.

If heard the pop and machine stopped at same time, there is something burnt for sure.
Check diode mode to ground on all secondary supplies, like in pages 57 & 58 and all big coils.

 

[FollowTheVoodoo]

Thank you thank you, there is some really good information here. Thanks for taking the time and fast responses.

Did not try without the LIO flex, I thought it was needed for power.

I will check all the secondary supplies on 57 & 58 and then try bypassing the SMC.

 

[FollowTheVoodoo]

So I reasked my friend what happened she said "she was using the computer, it was plugged in, fan starting going really fast and mouse started lagging and then the screen went black"

She then took it to the apple store and they came back and said power thing...will take a month to fix and gave her computer back because they were backed up.

Sorry for the redirect, I'm just trying to have all the information.

 

[FollowTheVoodoo]

First of all, welcome to the forum!

Did you test the board alone on the desk (no LIO flex connected)?
Try to start in SMC bypass mode.

If heard the pop and machine stopped at same time, there is something burnt for sure.
Check diode mode to ground on all secondary supplies, like in pages 57 & 58 and all big coils.

What is circled in blue is what you mean by LIO Flex? I tested with it connected for all measurements.

 

[2informaticos]

Yes, board must start without it (fan spins).

Please, do NOT quote an entire post...

 

[FollowTheVoodoo]

2informaticos,

I've been dead for a bit, works been busy. I notice that if I don't have the LIO Flex cable in, I don't get any lights on the magsafe connector.

 

[2informaticos]

That is correct.
SYS_ONEWIRE, as 3V42_G3H, SMC_BC_ACOK and many other lines go through J9500.

 

[FollowTheVoodoo]

Try to start in SMC bypass mode

How do I start in SMC bypass mode with the board on the bench?

Check diode mode to ground on all secondary supplies, like in pages 57 & 58 and all big coils.

Am I checking the outputs of the secondary supplies to ground in diode mode? I am actually pretty new to using diode mode (with voltage) I usually check continuity with resistance).

I checked the the following based on other posts:

SMC_RESET_L	3.387​
P3V3S3_EN	0​
P3V3S0_EN	0​
P3V3SUS_EN	3.348​
P1V8S3_EN	0​
S4_PWR_EN	0​
S5_PWR_EN	3.412​
P5VS0_EN	0

I also checked the big coils, L7310 and L7320 both showed 0V when I did diode mode as well as when I checked L7130. The rest showed 0.179, 0.379 and 0.538 roughly.

 

[FollowTheVoodoo]

Also I was able to hook up a DC power supply, 18.5V and the board is pulling on 0.02A

 

[2informaticos]

"How do I start in SMC bypass mode with the board on the bench?"
Use R5115/16 pads, instead of power button.
In fact, solder a wire to SMC_ONOFF_L and touch ground to simulate power button function.

"Am I checking the outputs of the secondary supplies to ground in diode mode?"
Yes, any secondary power supply, not only big coils.
Remember to disconnect power and put red probe at ground.

 

[FollowTheVoodoo]

"How do I start in SMC bypass mode with the board on the bench?"
Use R5115/16 pads, instead of power button.
In fact, solder a wire to SMC_ONOFF_L and touch ground to simulate power button function.

2informaticos,
So I see R5115/16 on the schematic, the output of that is SMC_ONOFF_L, I just need to solder to SMC_ONOFF_L (I'm guessing a TP is probably best) and touch ground and I should be able to get SMC bypass mode? I tried looking around on the forum but didn't find how to get into SMC bypass mode without being in the chassis. If SMC bypass mode is what I think it is (pressing the power button for 10-15 seconds and then connecting the magsafe) I tried that early on and wasn't able to get it to boot but I can put everything back and try again.

 

[2informaticos]

As mentioned, no need to use power button.
Tie SMC_ONOFF_L to ground, connect charger, wait 5-10s and release SMC_ONOFF_L.
Fan goes to max instantly, when start in SMC bypass succeed.

 

[FollowTheVoodoo]

Hi 2informaticos,

I was not able to get the board to go into SMC bypass mode. The first two attempts failed, and when I went for the third attempt the magsafe connection arc'd and messed up one of the balls on the magsafe connector of the DC-In Logic board, so I'm going to order a new one from the store.

Will recheck everything once I can safely power up the board again in the event I caused more damaged.