(Solved) Dead SMC? MBA 820-00165 No light, no fan, no PP5V_S5.

joshAU

Member
Hi all.
I have a Macbook Air that suffered water damage.
Very minimal amount, from the look of it.

Cleaned.
No Magsafe light, no fan.

Checked voltages and missing PP5V_S5.

CHGR_DCIN 20.5v
PPDCIN_G3H 20.5v
PPBUS_G3H 8.2v
PP3V42_G3H 3.42v
PPVRTC_G3H 3.42v
F7140 is 8.2v each side
SMC_RESET_L 3.3v
U7100 Looks OK

I'm suspecting the SMC, from reading a few other posts, but any suggestions appreciated.
Thanks.
 

Narek

Member
Where was the area liquid got on? Do you have other S5 rails present? Check the diode reading on PP5V_S5. Also if you have S5_PWR_EN. Are PP3V3_S5/SUS present? SMC_PM_G2_EN present?

If you have PP3V42_G3H present then you should have green light on charger, unless J9500 or I/O cable are corroded. Inspect them, also take a look at IPD flex connector (trackpad flex), area around U7501.

If water affected SMC area reflow it.
 
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2informaticos

Administrator
Staff member
SMC must be reballed, if has sign of corrosion close to its area.

Post voltage and diode mode to ground at SCL/SDA lines of battery bus.
If get 5V_S5, SMC_PM_G2_EN should be present too.
Check if 3V3_S5/SUS are present.
If yes, check also PM_DSW_PWRGD and PCH's RTC signals.
 
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joshAU

Member
Hi Narek.
Thanks for the prompt reply.
S5_PWR_EN and S5_PWRGD are both 0 volts.


Where was the area liquid got on?
There was very little water on the board...however I cannot remember exactly where, as I cleaned the board several weeks ago, and then had to wait ages for the customer to get back to me as to whether to attempt to repair it.
I should have taken a photo of it - I will from now on.

From memory, it was mainly around U7090, near the wireless card, and also near the SD card reader- especially around U4400.

Do you have other S5 rails present?

PP1V2_S5_SMC_VDDC : 1.23v

PP3V3_S5 : 0v
PP3V3_S5_AVREF_SMC : 3.3v
PP3V3_S5_DBGLED : 0v
PP3V3_S5_REG_R : 0v
PP3V3_S5_SMC_VDDA : 3.42v
PP3V3_S5RS3RS0_SYSCLKGEN : 0v

PPBUS_S5_HS_COMPUTING_ISNS : 8.17v
PPBUS_S5_HS_OTHER_ISNS : 8.17v

PP5V1_CHGR_VDD : 5.1v
PP5V1_CHGR_VDDP : 5.1v

PP5V_S5 0v

SMC_S5_PWRGD_VIN : 3.42v

Diode reading
with red on ground and black on L4820, PP5V_S5 reads 0.392.

Do you have S5_PWR_EN?
No...
0v

Are PP3V3_S5/SUS present?
No.
PP3V3_S5 : 0v
PP3V3_SUS : 0v

SMC_PM_G2_EN present?

No.
SMC_PM_G2_EN : 0v

If you have PP3V42_G3H present then you should have green light on charger, unless J9500 or I/O cable are corroded. Inspect them, also take a look at IPD flex connector (trackpad flex), area around U7501.

PP3V42_G3H : 3.42v
No green light

Tried with known good 821-1722-A cable that connects J9500 to the DC-in daughter board.
Tried with known good DC-in daughter board.
Tried with known good genuine Apple 85 Watt AC adaptor.
Also tried charger, DC-in daughter board and 821-1722-A cable in another MBA - it works fine, green light, fan comes on, etc
So charger, daughter board, and 821-1722-A cable are definitely working

I've inspected J9500 under a microscope, and it looks perfect.
The IPD flex connector also looks immaculate.

The area around U7501 looks fine, as well, with nothing obvious standing out.
 

joshAU

Member
Thanks 2informaticos.
Sorry, I posted the above to Narek before realising you had also posted.

I just checked SMC_RESET_L, on pin 2 of R5100, and I get 3.1v.

I'll try to reball the SMC.
Thank you.
 

2informaticos

Administrator
Staff member
I already saw that signal.
The thing is that SMC may not receive it, if corresponding ball is corroded.

You also need to check voltage and signals for U5000 (2 OF 2) at page 37.
 

joshAU

Member
Sorry for the lack of update.

I tried to reflow the SMC chip without reballing it, and surprisingly, the unit now works!
Surprising, as there was no evidence of any liquid having been near it.
Thank you both Narek and 2informaticos, I appreciate you help and advice.
 
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