A1708 820-00840-A no boot

[hgoncalves]

Hi,

I have an A1708 820-00840-A, that has no boot.
It powers on, the backlight turns on, but it has no chime nither Apple logo. The display stays fully black.

Already tried with a known good display, and with just the board on the bench (external display), but with the same result.

Can you help?

 

[2informaticos]

Try known good BIOS.

 

[hgoncalves]

Hi,

I can't find a ME BIOS. Do you have any link to it?

 

[2informaticos]

820-00840 8HV22 Medusa clean ME + PRAM.rar

drive.google.com

 

[hgoncalves]

TKS!

 

[hgoncalves]

With the new BIOS, the result is the same. BL OK, but with black screen only.
Even on the external display, the screen turns on but stays black

 

[2informaticos]

What is CPU core voltage, after 10s?
Check for USB activity.
Also test starting in safe mode.

 

[hgoncalves]

PPVCCCPU_S0G starts at 0.947V and then stays at 0.645V.

I don't have USB activity

 

[2informaticos]

Looks like board really boots.
It gets stuck for some reason.
Did you test the board in safe mode?

 

[hgoncalves]

Hi,
Yes, I've tested it in safe mode, and even without disk (to see if the folder icon was showed on display), but nothing happends. Just a black screen, with backlight activated.

 

[2informaticos]

Then must be CPU internal problem...