820-00165A SMC dead after defective G3Hot supply

[Beeldbuisje]

The owner of this Macbook air tried to install Windows on this machine. During his work the macbook crashed, he tried to restart, but didn't come on anymore.

3,425V G3Hot was just 2,7V. Two bad resistors in the G3Hot supply: R7095 & R7096. After that 3,42V; but no charger LED etc.

PPBUSG3H is 8,1V, so this proofs no communication between SMC and "battery charger" U7100.
What I checked:

PP1V2_S5_SMC_VDDC: 1,2V
SMC_ONOFF_L: 3,3V
SMC_RESET_L:3,3V
SMC_ONOFF_L:3,3V
SMC_BC_ACOK: 3,3V
SMBUS_SMC_5_G3_SDA: no signal measured with scope.

No liquid damage etc.
The only thing I can imagine is a short rise up of G3Hot. Because one of the defective resistors had a bad contact in it. Because they're used to control the G3Hot power chip, I'm afraid of a temporary too high G3hot. Not sure, it could be.

Does somebody has another clue as changing the SMC chip? (hard to find )

tnx
Gert

[bekirsalman]

Re: 820-00165A SMC dead after defective G3Hot supply

If you shared the photo of the area where the problem is

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

I don't know how this can help you, but here are the pictures.

Don't bother about the spot with dirt. It's some residue from cleaning the flux away. I already tried to reflow the SMC chip.
It's heavier on the picture as it is in real.

[piernov]

Re: 820-00165A SMC dead after defective G3Hot supply

Voltage on SMC_VDDA? SMC can easily be found on same model donor board.

[dellxps15]

Re: 820-00165A SMC dead after defective G3Hot supply

keep in mind that 3.42 volts, comes also without smc chip.
i see flux on smc zone so was it reflowed ?

people trend to give smc the tate of dead too often. reflowing , reballing can kill it. when pa c dont power on we need to figure out why. no just head some chip here and there.

if u dont have green light: psu original and working ? dc-in board is ok? power on dcin pins ? u have the 3.4 volt for green light ? do u have 3.3 5 volt ? ppbus is 8.1 instead of 8.5 8.6 ? resistor across ppbug33h (10omh reisistor) and others are ok ?

no fan spin ? nothing ?

[piernov]

Re: 820-00165A SMC dead after defective G3Hot supply

No light on Magsafe, not turning or and SMC not communicating with charger IC to increase voltage to 8.4V/8.6V/12.6V (depending on the machine) usually points to the SMC not booting.
It could be held in reset (not the case here), have a missing power rail (PP3V3_S5_SMC which is PP3V42_G3H, present here, or PP3V3_S5_SMC_VDDA which is taken from the previous rail with an inductor inbetween), have an issue with the crystal oscillator, or have an issue with the SMC itself (like liquid damage or just dead).

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

@dellxps: one thing I didn't mention: also no fan spin. If there's no 5VS5, there's no possibility to have fan spin... All the rest of your questions are readable in my first post

For beeing sure, I checked again the SMC_VDDA voltage. Present! 3,4V

Is there an easy way to check the crystal oscillator? Probably using an oscilloscope and measuring the frequency?

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

edit: measured on pin 1 & 3 of the oscillator, nothing, but nothing visible on the scope.

[piernov]

Re: 820-00165A SMC dead after defective G3Hot supply

If the crystal and the resistors/caps connected to it aren't visibly damaged, then it's most likely the SMC anyway.

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

Indeed nothing to see. Even measured were possible and no defective components found.

Looking for a new SMC I guess. Hopefully I can find a cheap donorboard. Don't know what else will happen with this MacBook.

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

Does someone had some experiences where to order a good SMC chip for such a board.
It has to be taken from a donor board.
You can find lots of donor boards on AliExpress and Ebay, but those people aren't sure about the condition of the SMC chip.

No experience with ordering those chips, so if someone has a little advice...

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

Ordered a defective donorboard in China. Well working SMC chip, replaced it, machine fixed now. Thanks for the tips!

[mcplslg123]

Re: 820-00165A SMC dead after defective G3Hot supply

Ordered a defective donorboard in China. Well working SMC chip, replaced it, machine fixed now. Thanks for the tips!

Defective board on aliexpress with smc working-sounds unbeleivable. You seems to be lucky. can you give the link from which store you buyed the donor board??

[Beeldbuisje]

Re: 820-00165A SMC dead after defective G3Hot supply

Not ordered on Aliexpress, but on Ebay.
see-ic was the shop.

He confirmed me his SMC on the donor board should be OK. And he was right :-)