820-00426 Question about FDMF

820-00426, symptoms are all power rails are present, board alone takes a little over an amp, and slowly rises

CPU and GPU VCORE all present, as well as clean ME and reflashed BIOS chip, USB lights up but no activity.

Im leaning this towards a dead cpu, however I just want to be sure. R to G on CPU VCORE is around 13-14 Ohms, and I have a working 820-00426, and CPU VCORE there is around 19-20. So not too bad.

Board is relatively clean, but shows signs of age, just with chip discoloration and stuff like that. However I particularly noticed the FDMF chips looked a little old, just different, and the naming on them is also different then my working board. The chips name on the broken board is DG18AV FDMF 6808N. While the name on the working board is DF17BH FDMF 6808N.

I know these are for CPU phases, and were an issue with the 2013-2014 boards, but could this be related? I would just like a little more info in understanding this. Thank you!

EDIT: By the way, checking U6100 traces and connecting resistors is a little complicated because I am using schematic for 00163, because 00426 is not available, and for whatever reason apple changed the PCH and SPI resistor layouts so... this could also be the problem not too sure.


Staff member
All the boards with FDMF6808N suffer same problem.

Once board doesn't boot at all, dificult to revive it replacing the chips.
You can try, but hopeless project.
FDM6708/3030 can be get as real new.


Staff member
FDMF6808 was manufactured ONLY for Apple.
Probably a design problem was developed for that chip.
Fairchild manufactured FDMF6708 for large public; they solved that problem somehow on this and FDM3030 too.