strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

[slimmy182]

Hi All,

I have purchased this Macbook as not working, seller says it "simply does not turn on anymore". It's in really mint condition and I didn't see any external damage or liquid spill. So I decided to try as first an DFU restore but it was not responding nor detected at all. So I lefted with the charger plugged in for few hours (no charging sound or image on display). When I got back home, I open the lid and login display image from the prevously owner was there! I did not touch anything to make it start. Then i proceeded to a complete wipe of data and install of MacOs Monterey with no problem at all. Except one. It was draining the battery even if it was plugged to charger!
I just changed 2/3 charger and all the USB-C ports, nothing changed.

Usb-c multimeter says it's taking 20.57V and 0.000A.

Not charging at all. This is the same for all 4 usb-c ports, except for the lower in the left side where I can't get any reading.

Then I cheked whit usb-c to HDMI adapter, but no video output at all. I also check if there is any usb activity plugging and external hard drive, but it does not even got any voltage (led of external HDD remains off). Same for all the usb ports.

Now I have 35% of battery charge left. I didn't try DFU restore, it my be worth give a try? Even if there is no usb communication?.

Anyway I'm ready to open it and check for problems inside, my multimeter microscope and soldering station are ready
Any advice or help it's really, really appriciated!

[mon2]

Re: strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

Follow the circuit and locate the battery pack connector.

Locate in this section the SMBUS lines (SCL and SDA). These lines will have a single package ESD protection device (D6950 ?? - confirm it with the schematic).

Check the voltage on each of these lines. The part is quite small but is a show stopper and if damaged, resulting with the same symptoms as yours of not charging.

You can flux it and remove it but I recall more than one case where this part was the root cause on the logic board.

[slimmy182]

Re: strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

Hi mon2, thank you for the advice!

SMBUS lines (SCL and SDA) both 3.36V, measured on J6951 pin 2 and 3 (it's the flat battery connector)

After disconnecting battery and reconnect it when I plugged in dc charger it was being detected (just say dc in connected but not in charging). If I unplug and replug dc in it's not detected anymore.

Should I remove single package ESD protection device D6950?

Thank you very, very much!

[mon2]

Re: strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

Yes, you can try - it is a very small device so proceed with low air pressure so it is not lost.

TBH - the voltage readings look ok as for our repair which consumed too many hours to locate this bad boy - the voltage was very low on the SCL or SDA line but ok on the other.

Nevertheless, it is worth a quick try and you can place it back if it does not resolve the fault.

Other areas to explore after the above is to check the charging circuit but the detection is often linked to this area / physical connector faults.

The charging circuit will have a current loop that must function properly. If the loop is broken, the charging circuit will shut down.

See attached - check the voltage at the green arrow points to confirm there is a minor or now voltage differential on the 2 legs.

Post the voltage readings on each side. You can also remove all power -> meter in resistance mode -> check the resistance on each leg to confirm the series resistors are as per the schematic values.

The ISL is a WLCSP (BGA) device so you will not be able to probe the underside.

[slimmy182]

Re: strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

TBH - the voltage readings look ok as for our repair which consumed too many hours to locate this bad boy - the voltage was very low on the SCL or SDA line but ok on the other.

I think in this case D6950 was not the problem of this machine.
Yesterday, before taking it apart, I tried a DFU revive/restore. None of them would complete, stuck on step 4 and then error. Results was Mac always in "recovery" mode not booting anymore.

Then I toke it a part.

The charging circuit will have a current loop that must function properly. If the loop is broken, the charging circuit will shut down.

See attached - check the voltage at the green arrow points to confirm there is a minor or now voltage differential on the 2 legs.

R7061 & R7061 shows no difference in voltage, and resistance value looks good as the schematic ones.

But then.. inspeting under the microscope other areas, I found this little corrosion around U3100:


R3103 (UPC_XA_R_OSC) and R3105 (UPC_XA_UART_RX) were mainly affected.

I cant really figure out how liquid reached that parts, there is really no other evidences of how could it be penetrated.

Then I start cleaning it using IPA and toothbrush to gently remove the corrosion. After that amtech FLUX and reflow the whole area, including U3100.

This is the result:


Then re assemble, plug in DC in and now it was taking 20v and more than 1A, finally charging! I was able to finish DFU revive and get it back to work. Now it seems that all usb-c funtionality are back (charging, video out, data exchange and so on.)

Thank you for your preciuos contribution mon2. There is always something to learn.

[DanielDacko]

Re: strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

Change this two resistors just to be sure that it won't happen again. I see that the first one still has damage from corrosion.

[slimmy182]

Re: strange MacBook pro 2018 A1989 820-00850-A not charging or any usb activity

Yep, already ordered, waiting for delivery! Thank you for your suggestion