A2251 820-01949-A

[hgoncalves]

Hello.

I have an A2251 820-01949-A with no power, and client said it stoped working overnight.

t has 20V on bench PSU, but took only 0.2A.

In DFU restore I get the error in attach.

Can you help?

 

[2informaticos]

Check SSD coils in diode mode to ground.

 

[hgoncalves]

HI,

L9020/21 = 0.388
L9030 = 0.362
L9080/81 = 0.151

 

[2informaticos]

"L9080/81 = 0.151"
Compare with good board; looks low...

 

[hgoncalves]

I don't have any other a2251board to compare it.

Is there any other way to be sure?

 

[2informaticos]

OpenBoardData Project

 

[hgoncalves]

Hi.

Thanks for the OpenBoardData Project.

I think I've made a mistake, and measured PP2V5_NAND_SSD0 when it was hot, because right now I have the correct value there : 0.410 on diode reading, and 2.5V.

Any other idea?

 

[2informaticos]

Erase SoC ROM and try again DFU restore.
Make a backup first.

 

[hgoncalves]

Hi.

After erasing SoC ROM U4770, the mac now stays at 5V and isn't recognized in DFU.

However, I have a strange behavier: now I only have again 0.136 diode reading on PP2V5_NAND_SSD0.

Sometimes I get the corrrect value, and other times I don't.

Any idea? Can I inject 2V there when I have a wrong reading there?

 

[2informaticos]

Always allow 10-15s after power is removed, before checking in diode mode, or ohm scale.

 

[hgoncalves]

OK. tks.

After erasing SoC ROM U4770, the mac now stays at 5V and isn't recognized in DFU.

Shall I restore it?

 

[2informaticos]

Erasing SoC ROM should put MLB directly into DFU.