Macbook Air A1466 2015 no chime, no image (PP0V6_S0_DDRVTT)

Moss

New member
HI.
I replaced the BIOS firmware with a clean Me Region but no changes.
Could you tell me how to find that Me region is clean, I looked at the 400 and 2400 lines (I have it written that it starts with 2000 and this is true, but at 2400 I only have FF FF).
Thx
 

2informaticos

Administrator
Staff member
Is not BIOS then.
It should boot with working dump, even no clean ME.
BTW, we have posted links for clean BIOS on the forum, just search.

Probably bad CPU, in this case...
 

Moss

New member
Yes, I took the BIOS from this forum (but I also put 2 bios from donors). can you advise Post Card Testeur for macbook?
Removed 7462 and 7450 (0.6v appeared on it). replaced , i put it in its place C7450 and 0.6 disappears!!!!
thx
 
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Moss

New member
can i remove the 7462 and 7450 and connect them with a wire from one to the other? I don't know if there is a need if they do not touch GND?
 

2informaticos

Administrator
Staff member
Do not mix C7450/62, very different capacity.
Be sure all traces and solders are good there.

Do not tie together VTT and VTTREF.
Do you get high level at pin 17/U7400?
 

Moss

New member
Ok, thx
I just removed did not connect (C7450 / 62), now on C7450 0.6v!
pin 17/U7400 = 3.2v
maybe i need to press the chip when soldering (for xw7400)?
 

2informaticos

Administrator
Staff member
Be sure to put 0.22uF on V7450.
If you place higher value there, can block the reference power supply.
I hope both XW7400/60 bridges are good.
 

Moss

New member
Ok
I replaced the donor c7450 with the same one (0.22uF)!
(C7450 / 62) = but were good.
I can't find the XW7400 / 60 and how can I check them?
 
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2informaticos

Administrator
Staff member
About U7400:
VTTREF must be present at pin 5, when pin 16 is high.
Once pin 17 goes high, you should get 0.6V at pins 1 & 3.
 

Moss

New member
pin 16 have 3.3
when I put c7450 in place, 0.6 disappears!
I removed the C7415, which is not a good idea, but I saw that pin 6 became 2.5 instead of 1.8 and 0.8 appeared on pin 3.
I replaced the C7415 but the situation has not changed.
 

Moss

New member
when I remove something from the GND_DDRREG_SGND line, voltage immediately appears on 3 pin
 

Moss

New member
I noticed that constant cyclic reboots from the battery. I thought that by deleting 7462 I disabled the connection to the cpu but you are probably right, this is CPU
 
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