A1398 U7310 820-00163-A

[hgoncalves]

Hi,

I have an A1398 820-00163-A, with a burnt U7310, and I have no other equal board to use other one. Only have 820-3332-A boards...

Can I use one from any other board?

 

[2informaticos]

Why would you want to solder FDMF6808N?
Didn't read many threads on the forum about its problems???
Get FDMF6708/3030 from reliable store; avoid any chinese seller!

First be sure CPU core power rail is not shorted to ground.
High chance U7310 killed CPU.

 

[hgoncalves]

OK. Tks. Better to use FDMF6708.

 

[hgoncalves]

Hi,

PPVCC_S0_CPU = 0.0018 in diode reading
I've replaced U7310 with a new FDMF6708, but I have no power. It pulls 0.24A from bench PSU, but no power.

 

[2informaticos]

Resistance to ground looks good.
But this doesn't mean CPU was not damaged...

 

[hgoncalves]

Hi,
In the morning the behavior was a bit different.
It puls 0.284 A in bench PSU, and i get 0.670V on L7310, but still no power on and no fan spin.

 

[2informaticos]

Power on YES, if you got even CPU core voltage.
Don't make confusion between boot and power on!

What is the CPU core behavior, drops to 0.67V from higer voltage (after 5-10s)?
Did you check USB activity?

 

[hgoncalves]

Hi,
on PPVCC_S0_CPU it only has 0.68V from start. I starts and stays steady with 0.68V

 

[2informaticos]

Compare coils voltage with good board.

 

[hgoncalves]

Hi,
I don't have any known good board to compare it. Is there any other way?

 

[2informaticos]

Do you have any other A1398 working board?

 

[hgoncalves]

HI,

I don't have any other working board or working A1398 mac...

 

[2informaticos]

I suspect bad CPU, damaged by overvoltage...

 

[hgoncalves]

OK. Tks

 

[GfilipeZ]

Hi,

I don't know if it is better opening a new thread...

I have a 820-00138-A board, with similar original problem. U7320 was shorted.

After read various threads, i know i shouldn't use FDMF6808N from Aliexpress.
But just in case, and because i don't have the other IC versions, i replaced U7320 with one IC i bough on Aliexpress. Now fans are spinning, but no image and all 3 cpu phase are at 1.7V steady.

Caps lock doesn't turn on a green light, so i suppose, no CPU activity. And like we talked about yesterday in the other thread, cpu core should drop to 0.6V .

So, this could mean CPU damaged by shorted U7320? Or should i try with 3 new FDMF3030?

 

[2informaticos]

The CPU core drop doesn't apply here; only valid for newer machines.
Very likely damaged CPU.

Please, open new thread when needed...

 

[GfilipeZ]

Yes, i should started a new thread. Sorry!

Thanks!