MacBook Air 2018 A1932 820-01521 Not turning on.

[sikocan]

MODEL: MacBook Air 2018 A1932 820-01521

Problem: 5.12V / 0.60Amps

History: Unknown but I can see slight liquid spill on IC U8201/74aup1t97gm

Things tried: I've cleaned the liquid area, removed the IC U8201/check pads, good/ chip looks good, put back. Replaced CD3215C x 2 times, so 4 new chips just in case. I've attached photo readings of V/resistance and signals as per logi wiki website. Please advise what I can check next. Schematics available upon request.

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Each CD3215 controller (U3100 / U3200) must be working before the 20V can be enabled.

https://repair.wiki/w/A1932_2018_-_2019_MacBook_Air

* voltages on the CD3215 look ok - the BMC rail will be enabled for the port used to power the logic board.

1) Check the voltage of PPBUS_G3H.

2) Check the voltages of the I2C bus lines that mate with the U3100 & U3200 via the TBT bridge.

[MobileXT]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

0.60Amps looks like there's a short on the board somewhere. check all the power rails one by one. If you have infrared camera make it easier to locate the shorted caps.

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Each CD3215 controller (U3100 / U3200) must be working before the 20V can be enabled.

https://repair.wiki/w/A1932_2018_-_2019_MacBook_Air

* voltages on the CD3215 look ok - the BMC rail will be enabled for the port used to power the logic board.

1) Check the voltage of PPBUS_G3H.

2) Check the voltages of the I2C bus lines that mate with the U3100 & U3200 via the TBT bridge.

1) PPBUS_G3H 12.17V.
2. All are 0V. Resistance of them for your refence:
I2C_TBT_X_SDA 32K Ohms increasing
I2C_TBT_X_SCL 32K Ohms increasing
I2C_TBT_XA_INT_L 3.63M Ohms
I2C_TBT_XB_INT_L 3.63M Ohms


I have reflashed the TBT ROM. No change.
Voltages on TBT ROM CHIP:
1. 3.26
2. 3.26
3. 3.26
4. Ground
5. Clock
6. 1.18
7. 3.26
8. 3.26

[ugamazing]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

I haven't read *every* detail in your posts, but I will mention: Make sure you try several USB-C port assemblies. We had an A1932 unit this past week that was cracked/severed on one of the bends. Just noting this in case you hadn't.

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Your ppbus_g3h rail is low. SMC has not yet boosted it.

Can you attach the battery to see if it helps?

Check the I2C lines on the isl device for the ppbus_g3h rail. Check the voltage of SCL and SDA.

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Hi mate,

Thanks for your help so far.

From the IC U7000 ISL9240HI
PIN:
SDA & SCL is 1.8V
ppbus_g3h 12.269

Thanks

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

With the battery it was the same situation.

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Voltage of PP3v3_G3H_RTC ?

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

PP3v3_G3H_RTC is 3.14V

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

The last measurement is considered to be too low.

Is the meter being used accurate?

From repair wiki...

The most common reason for PP3v3_G3H_RTC to be missing or low, is a short to ground, usually on a capacitor around one of the CD3215s.

Locate where this rail travels on the CD3215.

Remove all power and check the resistance to ground of this rail. What is the resistance?

As a test, remove the cap(s) on this rail near the CD3215. Then check the voltage again. It should be higher to allow the cd3215 to function properly.

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

PP3v3_G3H_RTC goes to pin 62 of u3200, pin 62 on u3100
Both readings are hard to focus on, but resistance mode is varies between 5kohms to 1.5M ohms between.

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Removed caps on both c3100 and c3200
Same result

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

PP3v3_G3H_RTC is now 3.2928

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Good. Now this is the expected voltage. One of the removed caps must have been bad.

What is the voltage now of ppbus_g3h ?

Check voltage of PPDCIN_G3H on each of the ports (cd3215).

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

I'll now replace both caps and test again

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

ppbus_g3h 12.268v
PPDCIN_G3H 5.122v

I've replaced both caps.

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Measure the voltage of:

PP3v3_UPC_XA_LDO
PP3v3_UPC_XB_LDO

[sikocan]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

PP3v3_UPC_XA_LDO 3.33
PP3v3_UPC_XB_LDO 3.26

[mon2]

Re: MacBook Air 2018 A1932 820-01521 Not turning on.

Good voltage.

Attempt the following:

Revive T2 firmware via Apple Configurator 2

Reference:

https://repair.wiki/w/A1932_2018_-_2019_MacBook_Air