Macbook Air 820-3437B missing PP3V3_S5

[mrdefaultuser]

Hi all, I'm new here (thanks for having me). I've repaired some macbooks in the past, but never had to dig really deep, until now...

Got my hands on a Macbook Air that does not boot. Charger light goes from green to orange so there was some life in this thing.

Did some digging to find that I do not have a PP3V3_S5, also not pulsing in anyway. SMC_PM_G2_EN is also missing, no pulse.

Some voltages:
PPBUS_G3H 8.56V
PP3V42_G3H 3.42V
PPDCIN_G3H 16.5V
PP5V_S5 5V
PP3V3S5_EN_R 3.41V
PP3V3_S5_AVREF_SMC 3.24V
SMC_RESET_L 3.38V
SMC_ONOFF_L 3.42V

I don't have a donor board to check whether U7501 is causing the issues. But maybe someone has any tips on what I could check?

Did not notice any shorts so far.

[mon2]

Re: Macbook Air 820-3437B missing PP3V3_S5

Connect a known good battery and also the adapter and test again.

[Simplebeans]

Re: Macbook Air 820-3437B missing PP3V3_S5

Hi all, I'm new here (thanks for having me). I've repaired some macbooks in the past, but never had to dig really deep, until now...

Got my hands on a Macbook Air that does not boot. Charger light goes from green to orange so there was some life in this thing.

Did some digging to find that I do not have a PP3V3_S5, also not pulsing in anyway. SMC_PM_G2_EN is also missing, no pulse.

Some voltages:
PPBUS_G3H 8.56V
PP3V42_G3H 3.42V
PPDCIN_G3H 16.5V
PP5V_S5 5V
PP3V3S5_EN_R 3.41V
PP3V3_S5_AVREF_SMC 3.24V
SMC_RESET_L 3.38V
SMC_ONOFF_L 3.42V

I don't have a donor board to check whether U7501 is causing the issues. But maybe someone has any tips on what I could check?

Did not notice any shorts so far.

Can you also post/voltage measurements of these please:

PPBUS_S5_HS_COMPUTING_ISNS
PPBUS_S5_HS_OTHER_ISNS
PDCIN_G3H_ISOL
PPVRTC_G3H

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

can you also post/voltage measurements of these please:

Ppbus_s5_hs_computing_isns
ppbus_s5_hs_other_isns
pdcin_g3h_isol
ppvrtc_g3h

ppbus_s5_hs_computing_isns 8.57v
ppbus_s5_hs_other_isns 8.57v
pdcin_g3h_isol 17.09v
ppvrtc_g3h 3.42v

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

Connect a known good battery and also the adapter and test again.

Did not notice any change by doing that. Doing that is also more useful with newer macbooks if i recall correctly right?

[mon2]

Re: Macbook Air 820-3437B missing PP3V3_S5

To enable PP3V3_S5_REG_R, you must have P3V3S5_EN_R @ EN2 of U7501, which you do.

It is possible that something downstream is drawing excessive current and U7501 is shutting down this rail.

Remove all power, meter in resistance mode (start with the lowest scale and move up from there if required) -> measure the resistance to ground of P3V3_S5_REG_R.

What is the reading ?

If you measure a low resistance (ie. few hundred ohms or less as an example) -> then lift one leg of L7560 -> measure the resistance to ground @ L7560, pin # 2 (consumer side of this power rail).

Then measure the producer side of this rail @ L7560, pin # 1.

What is the measurement with the coil lifted (one leg) ?

If the resistance to ground is ok, then confirm that the current sense circuit @ pin 17 & 18 of U7501 indeed make to the current sense resistor. Use resistance checks without power. Perhaps a leg of this circuit is corroded.

Aside from the above, replace U7501 and test again.

Louis and others have reported failures of this component.

[Simplebeans]

Re: Macbook Air 820-3437B missing PP3V3_S5

ppbus_s5_hs_computing_isns 8.57v
ppbus_s5_hs_other_isns 8.57v
pdcin_g3h_isol 17.09v
ppvrtc_g3h 3.42v

Thanks also can you post voltages for

P5VS4RS3_EN - measure this at U7501 PIN # 4
PPBUS_S5_HS_OTHER_ISNS measure this at U7501 PIN # 23
and L7520 measure both PIN’s # 1/2

[piernov]

Re: Macbook Air 820-3437B missing PP3V3_S5

SMC_PM_G2_EN is also missing, no pulse.
PP3V3S5_EN_R 3.41V

.

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

... measure the resistance to ground of P3V3_S5_REG_R.

What is the reading ?

2.5kOhms, if I remember correctly. At least high

If the resistance to ground is ok, then confirm that the current sense circuit @ pin 17 & 18 of U7501 indeed make to the current sense resistor. Use resistance checks without power. Perhaps a leg of this circuit is corroded.

Aside from the above, replace U7501 and test again.

Paths are ok, almost zero resistance on the paths.

Already ordered a U7501 some days ago. Will take some time for it to arrive. Thanks for the help so far!

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

Thanks also can you post voltages for

P5VS4RS3_EN - measure this at U7501 PIN # 4
PPBUS_S5_HS_OTHER_ISNS measure this at U7501 PIN # 23
and L7520 measure both PIN's # 1/2

P5VS4RS3_EN 0V
PPBUS_S5_HS_OTHER_ISNS 8.57V
L7520 1/2 0V

Thanks for thinking along!

[mon2]

Re: Macbook Air 820-3437B missing PP3V3_S5

Remove all power. Meter in resistance mode.

What is the resistance to ground of SMC_PM_G2_EN ?

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

Remove all power. Meter in resistance mode.

What is the resistance to ground of SMC_PM_G2_EN ?

Ohno! 1 Ohm!

[mon2]

Re: Macbook Air 820-3437B missing PP3V3_S5

Remove R8140 and check the resistance to ground again of this signal on both sides of R8140 pads.

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

Remove R8140 and check the resistance to ground again of this signal on both sides of R8140 pads.

Removed the resistor and checked resistance afterwards, but no shorts on both sides now. I don't get it...

Fan spins 3 times with the resistor removed so thats looking promising, will use some equipment at work tomorrow to look at it a little better.

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

So changed the resistor, macbook boots now! Though not completely there yet:

• Power button and keys are not working.
• Trackpad not working
• Fan at 100%

Something to work on this weekend, anyway progress has been made

[Simplebeans]

Re: Macbook Air 820-3437B missing PP3V3_S5

P5VS4RS3_EN 0V
PPBUS_S5_HS_OTHER_ISNS 8.57V
L7520 1/2 0V

Thanks for thinking along!

No problems sir. Thats the thing i like about the Macbook Air A1466, the logic board is easy to repair, so keep it up your nearly there. With the fan spinning 100% thats always almost synonymous with the trackpad not working, i would be suprised if it is not, check your trackpad and trackpad/keyboard flex cables etc.

[mrdefaultuser]

Re: Macbook Air 820-3437B missing PP3V3_S5

No problems sir. Thats the thing i like about the Macbook Air A1466, the logic board is easy to repair, so keep it up your nearly there. With the fan spinning 100% thats always almost synonymous with the trackpad not working, i would be suprised if it is not, check your trackpad and trackpad/keyboard flex cables etc.

It was the ribbon cable indeed. Had a lot of fun diagnosing and repairing this macbook

[vinifera]

Re: Macbook Air 820-3437B missing PP3V3_S5

Hi all i have a a1466 and i have PP3V3S5_EN_R = 0,52V ?

[vinifera]

Re: Macbook Air 820-3437B missing PP3V3_S5

.

I have the same board and i measure 0,52V on PP3V3S5_EN_R?
When i remove L7560 then i measure 2,78V ?
No short on PP3V3S5_EN_R.
Can someone help me ?

[mon2]

Re: Macbook Air 820-3437B missing PP3V3_S5

When i remove L7560 then i measure 2,78V ?

If you have a voltage on PP3V3S5_EN_R (EN2), then this enable pin is OK since that part of the regulator is attempting to output a voltage @ PP3V3_S5_REG_R.

The concern is more with that the output voltage is not @ 3v3 (rather is 2v78).

The voltage is dialed up using the FB (feedback) resistors on pin # 16.

With NO power to the board -> meter in resistance mode -> confirm the resistor values present on pin # 16 from the large inductor @ L7560. Check that each resistor is matching the values shown in the schematic. These resistors will impact the true output voltage value.

Also, check the resistance to ground of L7560, pin # 2.