(347) 552-2258 [email protected]

Macbook pro A1990 (820-01814-A) Stuck on 5V

A

air_chair256

New member
Hi everyone ,

I have a Macbook pro A1990 (820-01814-A) it doesn’t turn on and it’s a data recovery case.

When charger connected it shows 5V on all 4 ports.

When connected to another MAC using Apple Configurator it’s already in DFU and when try to revive it tries then shows error 4042.

Voltages on board.

PPBUS_G3H = 12.32V

PP1V2_AWAKE = 1.2V

PP1V8_AWAKE = 1.8V

PP3V3_AWAKE = 3.3V

PPVDDCPUSRAM_AWAKE = 0.8V

PPVDDCPU_AWAKE = 0.75V

PVDDCPUAWAKE_SW0 = 0.75V

PP1V8_SLPS2R = 1.8V

PP0V8_SLPS2R = 0.8V

P1V1_SLPS2R = 1.1V

PPV2V5_NAND_SSD0 = 0V

PP0V9_SSD0 = 0V

PP1V8_SSD0 = 0V


Can’t see any corrosions or water damage signs.

Nothing gets hot.



Any idea where should I look next?


Thanks
 
A

air_chair256

New member
Thank you for your reply,

The device is not liquid damaged or physically damaged, client said the device was working and next day it didn’t turn on.
Tried with charged battery and trackpad connected, same result.
When I connect the Macbook to another Mac it connects in DFU mode straight away, without me trying to sending it into DFU mode.
 
2informaticos

2informaticos

Administrator
Staff member
If you can complete DFU revive (without errors), then data can be recovered in DFU mode.
But this can be done only by Apple authorized service; connection to Apple server is required.
 
A

air_chair256

New member
Thanks for the clarification. Just to confirm — I read that anyone can perform a DFU revive using Apple Configurator 2, even without being an AASP. In my case, the revive fails with error 4042.

Are you saying the revive fails because it needs to connect to Apple's server and only Apple authorized service can do that? Or are you suggesting that the failure is likely due to a hardware issue (which I suspect, given the SSD power rails are 0V)?

Just trying to understand whether this is purely a software/server limitation — or a hardware fault preventing the revive.
 
2informaticos

2informaticos

Administrator
Staff member
Anyone can do DFU revive/restore.
If revive completes without errors, very likely SSD is good.
Then authorized service can retrive the data in DFU mode.
Failing revive can also be caused by other hardware issue, not SSD itself.

Be aware, restore will erase SSD, if succeed!
 
A

air_chair256

New member
Thanks again for the info

Since I don’t have access to Apple authorized service and the revive fails with error 4042, I’m trying to troubleshoot the hardware side to possibly get the machine working again.

Given that all the SSD-related power rails are showing 0V (PPV2V5_NAND_SSD0, PP0V9_SSD0, PP1V8_SSD0), would you suggest focusing on the power supply section for the SSD?

Is there a known buck converter or PMIC section on the 820-01814-A board responsible for these SSD rails that commonly fails?

Appreciate any advice on where to look next.
 
2informaticos

2informaticos

Administrator
Staff member
Power on sequence for T2 machines is very complex.
Sometime SSD voltages can come back after DFU.

Check diode mode to ground on SSD power rails; compare with good board.
Do the same for all secondary power rails.
 
A

air_chair256

New member
I've done some additional testing as advised:

Diode Mode Readings:

PP0V9_SSD0:

  • Black on GND: 0.048
  • Red on GND: 0.133

PP1V8_SSD0:

  • Black on GND: 0.665
  • Red on GND: 0.317

I also removed L9020 and L9021 to isolate the fault. The short appears to be on the SSD side, not on the U9000 side.

I injected 0.8V into L9020 (PP0V9_SSD0) and there's no current draw — completely flat.

At the moment I don't have a donor board to compare readings but I'm in the process of sourcing one.
 
A

air_chair256

New member
Diode mode With Red on ground and black on PP0V9_SSD0 I get 0.133 in the chart you sent it shows the value as 0.399

Does this mean there is a short on this line? Or is it normal?
 
2informaticos

2informaticos

Administrator
Staff member
Not a short, but very low value.
Injecting voltage will not heat anything; unless thermal avalanche occurs, which is very low probable.
Lift L9020/21 and R9020.
Check where the low reading remains.
 
A

air_chair256

New member
Lifted L9020, L9021 and R9020 and the low reading is on the SSD side ( L9020 has two legs 1 and 2 and the low reading is on pad 2 which is the side that connects to SSD) pad 1 which connects to U9000 shows normal reading.

Update: When L9020 and L9021 are lifted and I connect the motherboard to charger I get 0.9V on L9021 leg 1 which is on U9000 side.
 
Last edited:
You must log in or register to reply here.
Top