MacBook Air A1466 820-00165-A (no power, no light)

[davidebeatrici]

I was brought the computer as it showed no sign of life. Upon opening it I immediately noticed liquid damage in at least one critical spot.



I got rid of J6100 and cleaned/reflowed the other spots. C5126 was broken and as a result it's now missing from the board (should I replace it before investigating further?).
I didn't take a picture of the bottom as there was nothing to see in particular aside from mild corrosion on R5100, which I cleaned and I also made sure that it measures ~100kΩ.

As far as I can tell, everything appears to be in order except for SMC_MANUAL_RST_L being ~0.8V and SMC_RESET_L being ~3.0V. The power adapter is original and I'm sure that it works, but unfortunately I don't have another DC board to test.
However, if I understood the power-up sequence correctly, there is either a problem on U5000 or U5110 depending on which of the two signals is supposed to be pulled up first.

Thanks in advance.

[mon2]

This is a very well documented model. Since the MagSafe light is missing, start with checking if you have the 3v42 power rail.

If it is absent, check the dual diode that powers the 3v42 regulator.

The dual diode must pass the higher of the 2 power sources to the 3v42 regulator.

[davidebeatrici]

PP3V42_G3H is 3.428V.

[reformatt]

Voltages for:

PPBUS_G3H
Voltage @ C5001
PP3V3_S5_AVREF_SMC
PP1V2_S5_SMC_VDDC
32khz on SMC_EXTAL/XTAL

Any corrosion around SMC?

[davidebeatrici]

While inspecting the SMC side I spotted some corrosion around U7400:



But the U5000 area looks good.

PPBUS_G3H: 8.65V
C5001: 3.428V
PP3V3_S5_AVREF_SMC: 3.322V
PP1V2_S5_SMC_VDDC: 1.224V
SMC_EXTAL: ~0.060V
SMC_XTAL: 0.000V

I took a look with my thermal camera and the SMC looks quite hot (~57°). Is it expected or a sign of malfunction?

[mon2]

Was the swamp juice around U7400 cleaned up with IPA?

The SMC, to me, is way too hot. Wait on other comments but I would at least consider to flux and reflow the component. Perhaps similar issues underneath the component. The SMC is available only from other donor boards.

[davidebeatrici]

The U7400 area is the only spot I haven't cleaned yet as I only noticed it while reporting back here. I will take care of that while reflowing U5000 later today.

[reformatt]

Bias for Xtal should be 1V. SMC is likely dead. You can swap from a 820-3437 board and reprogram it for 820-00165.

[davidebeatrici]

How's the reprogramming process? Because I can easily find the chip for sale at a good price online, if it's allowed I can leave links here.

[reformatt]

Donor board is best from eBay etc. Donor boards from China are a lottery, the SMC's pads are often corroded and need scraping, retinning with flux/paste prior to reballing.

Use Muerto's SMC tool from GitHub.

https://github.com/MuertoGB/SMCTool/releases/tag/v1.0.7

[davidebeatrici]

Thank you very much, I'll acquire a replacement SMC and report back here once I get it soldered on.

[davidebeatrici]

I cleaned the U7400 area with flux, solder and IPA. Unfortunately R7460 was too corroded to be salvageable, just like C5126.



SMC replacement:



SMC_XTAL: 1.145V
SMC_XTAL_R: 1.206V

But still no light on the charger and no fan spin... what should I check next?

[mon2]

Essentially need to revisit each voltage check again.

What is the voltage to ground of:

PP3V42_G3H
PPBUS_G3H

[davidebeatrici]

PP3V42_G3H: 3.427V
PPBUS_G3H: 8.23V

[mon2]

1) PPBUS_G3H has not been boosted by the SMC. Should be 8v6 after the SMC kicks in.

2) Confirm the voltage to ground of the SMBUS pins used by the PPBUS_G3H regulator.

Check:

SMBUS_SMC_5_G3_SCL
SMBUS_SMC_5_G3_SDA

3) Also review this flow chart:

G3 to S3 State for Ivy Bridge Haswell and Broadwell - LogiWiki

[davidebeatrici]

Thank your for the link.

Both SMBUS_SMC_5_G3_SCL and SMBUS_SMC_5_G3_SDA are oscillating between 3.396V and 3.415V. I'm assuming it's why the SMC is not boosting PPBUS_G3H, as according to the flow chart the voltage should be 3.42V.

Could U7100 be acting up?

[mon2]

Both are pulsing lines since they are communicating using this SMBUS / I2C interface. So SCL and SDA lines will be oscillating high / low to suit and the meter cannot capture the true movement of the signals. Suspecting this to be ok since close to 3v42. Continue to check the flow chart for other possible issues. Was the SMC a known good device? The part contains internal firmware.

[davidebeatrici]

Yeah, I expected the lines to be oscillating but didn't know whether the voltage range was acceptable.

I'm going to check the other steps in the flow chart and report back. The SMC was sold as "new"... no idea where it actually comes from.

[mon2]

What is the voltage to ground of SMC_RESET_L signal?

Also, review this thread:

Macbook A1466 820-00165 No Power. PPBUS_G3H is at 8.2V | Rossmanngroup Forums

[davidebeatrici]

I checked all steps of the flow chart until the one that "fails". Anomalies I found:

PP3V2_S5_AVREF_SMC: 3.322V
SMC_LSOC_RST_L: 3.226V
SMC_RESET_L: 3.062V

R5100 went out of spec: it now measures ~85kΩ. What I don't understand is how it's dropping voltage, I'm assuming I don't see it on the thermal camera because the passing current is very low.



That is, unless I misunderstood the circuit. The way I'm reading it is: SMC_RESET_L is connected to PP3V42_G3H through a resistor (R5100).