820-01949-A 20V @ 0.12-0.23amp down to 0.040a No Image/Boot

[CGid]

MacBook A2251
Brought in because the customer was not getting image for their machine anymore. Could hear sounds but no video. Another tech in my shop attempted a screen replacement. After the replacement the device no longer gives any power up sound or display still.

Current State:
Just the motherboard on the bench, the machine will boost to 20V @ 0.12-0.23amp draw before dropping down to 0.045a and staying there.
With the battery plugged in the machine boosts to 20V @ 0.9-1.5amp draw.

PPBUS_G3H - 12.62V
PP3V3_G3H - 3.366V
PP5V_G3S - 5.141V
PP3V3_G3S - 3.344V
PP3V3_S5 - 3.366V
PP2V5_NAND_SSD0 - 2.519V

Attempted to connect to AC2 but the machine does not appear in DFU.

 

[CGid]

Here is the T2 under thermal imaging as it's plugged in. Draws 0.12-0.23 amps then drops to 0.040a

https://imgur.com/a/eXBtkkG

 

[2informaticos]

Try to force it into DFU with external switch method.

 

[CGid]

Attempted external switch with no change. After powering off the machine with PMU_ONOFF_L amperage drops to 0. Then pressing the DFU button for 3-5 seconds does nothing. I did measure to make the sure button press is connecting the 2 points and continuity shows it is.
0V on DFU_STATUS.

 

[CGid]

Played around more and got it into DFU. Attempting to revive now.

 

[CGid]

So Revive worked or so it says. I get the Lock icon after revive but I still have no display.

 

[2informaticos]

Do you get G3S and SSD voltages?

If DFU revive worked, then data should be saved in DFU mode by Apple authorized service, if needed.

 

[CGid]

PP5V_G3S - 5.141V
PP3V3_G3S - 3.344V
PP2V5_NAND_SSD0 - 2.519V

Those are my voltages while it's connected to the other Mac still post revive.
Attached is what my main mac displays.

https://imgur.com/a/1FiDEf7

 

[2informaticos]

There should be more SSD power rails.
Also 1V8_G3S...

 

[CGid]

I'll check 1V8_G3S tomorrow. Sorry I don't know what ssd rails are significant as when I lookup "SSD" I'm software there are numerous SSD rails and I didn't know which ones you'd want to know and which weren't significant.

 

[2informaticos]

Usually we have 3 power rails for SSD; you've found one already.
Look at U9000's coils for more.

 

[it-solve]

Might not be related but had similar issue where connected screen which had a fault was interfering with DFU restore and after a restore was coming back to lock icon and no internal or external.

If you haven't tried already, attempt with button method and internal screen disconnected. I used USBc screen instead or you can use the original broken spare.


What works for me consistently for entering into DFU are these steps:

> Disconnect all cables and battery
> Connect battery
> Connect left port closer to touchpad. And make sure you run never OS than faulty macs'.
> DFU_FORCE via a switch or soldered push button
> Disconnect and connect the USBc on the faulty mac
> Should appear as DFU on the Apple Configurator

> If you are running Sonoma and higher it should appear in your Finder and will give you revive and restore options. If you run it via there, You will see the logs in Console which are verbose and can point to why its failing (if its failing)