820-3476 - Always thinks magsafe adapter is connected

Joesipaq

New member
Hello all,
Received this one and it would not boot past the apple logo. Well, it seemed like it would loose power or reset just a second after the apple showed up. So, with no physical damage on the motherboard, i took a stab at the bios. Pulled it off and stuck another on. It ended up booting up, so I copied the original bios to another and stuck it on there.

Boots up fine ever time, but - now it believes there is a magsafe always connecetd
- with magsafe conneced
- without magsafe connected
- with dcin board unplugged from the board

Addapter_Sense always has 3.4v on it when the battery is connected.

I have preformed a SMC reset, PRAM reset, and replaced U7000 with no change.

Would the SMC be the next step?

Thanks all and have a great day!
 

dukefawks

Administrator
That means ACOK is being held high by something. Check if that really is the case and check J6100 for corrosion.
 

Joesipaq

New member
Ahhh, that makes more sense... So, Ill check that out tomorrow when I get into the shop. J6100 looked good from what I remember. I didn't see any sorts of liquid damage and I did go over the board 3 times or so, because I was at a loss. Jtag or similar looking connectors are normally ones i investigate first.

So, if not J6100. I should check out
R5187
Replace U7100
U7001
and if i get that far and still no luck it would be the SMC?
 

Joesipaq

New member
So, seems I have a 20ohm short between ppbus_g3h and acok. That was with R5187 removed. I replaced U7001 and its still there.
Causes could be could be
U7100 or the SMC at this point, Correct? As they both have a path to g3h. Most likely though, it would be U7100?
 

Joesipaq

New member
Update. I have now removed U7100, U7001 and R5187 and the 20ohm short is still there.
Before I pull the SMC i want to see if you have any ideas. Also, yes, J6100 has no corrosion. ACOK is being held high.
 

dukefawks

Administrator
A pull up to PPBUS would cause 12V on ACOK...weird. As the SMC has no connection to PPBUS I suspect the short will be inside the board. But SMC is the last component so pull it.
 

Joesipaq

New member
well, i sure messed that one up. I guess before my coffee. I said ppbus_g3H but i meant PP3v42_g3h. I have a 20ohm short between pp3v42_g3h and SMC_BC_ACOK. Still pull the smc?
 

Joesipaq

New member
SMC swapped out and now the ACOK is working fine. How odd.

Another random thing, The system reports that its SN is Not Available. What is that related to? It is running High Sierra
 

Joesipaq

New member
I did replace u6100 - but I copied the old one to the new one. I'll upload it tomorrow - or I guess I could stick the original one back on?
Now my question would be, why did my copy and verify not go how it was supposed to?
 

Joesipaq

New member
Here is the original dump I got. The system Serial is C02N55EYG3QH.

As a side note, why can I not upload the .bin using the Upload Attachments?
 

Joesipaq

New member
Alright! Thanks. If there is a good PM system here, could you point me in the right direction to modify certain parameters in the bios for the future? I have migrated the ME region before, if that's what it's correctly called, and this is the 2nd MacBook pro hat I've come across with no serial number in the os
 

Joesipaq

New member
Thanks Duke!
So, i wrote this bios, installed it and am getting a problem detecting the ssd (blinking folder icon)

I just installed the original bios chip with its programming (the dump i sent) and it boots up fine.

Can a bad bios value cause no ssd recognition? (i did not try a bootable disk to see if under disk manager it was recognized)
 

dukefawks

Administrator
Probably APFS problem only with 10.12/13. My BIOS is not APFS updated yet. Reinstall 10.13 over the existing install and it will update the EFI. Or if you don't want to take any risks install 10.11 on another SSD and then update that to 10.13. The old SSD should then work again.
 

Joesipaq

New member
I just I could make a time machine backup - they need their data data on this one, and it's already made me nervous a few times. Then try the reinstall
 
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