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sh33pz

New member
It powers on, green/orange light ok

- Missing EDP_BKLT_EN to Q7707
- v1.745 CPU vcore
- USB mouse does light up



I have nothing but the DC in-board, no flex cable, below is the boot patterns.


90% of the time, the fan stops and starts about every 12 seconds and this cycle don't stop and CPU heatsink gets hot.

The other 10%, the fan starts, stops and starts and revs up fast and the CPU heatsink is cool to the touch.

No liquid damage, don't see any corrosion. But a few things to note when I got this board.

- The BIOS seems to have been replaced, same chip type but a different package.
- A jumper wire ran from the D7701 to pin 5 on the backlight driver.
- J8300 connector where the backlight power, is blueish in color on top of the connector.
- Backlight fuse is jumpered - I removed this.

I checked around u6100 and u1900, traces are fine and y1905 connection to u1900 are fine.
u1950 pin 8 has the 3.4v and I did replace it anyways and no corrosion was under it.

I think I went down a rabbit hole.

Any direction or is the CPU/PCH is dead?

Any check else I should check or do?

Thanks
 
S

sh33pz

New member
This worked and the MacBook air now boots, but I need to update the serial number to the correct one.

I made 3 copies of the old bios before updating it with the clean ME bios found on this forum.

Now the issue I have is, I want to update the clean ME bios with the serial number from my old bios but I can't seem to find it. Maybe I am looking in the wrong area? I did a text search for ssn and override-version and I can't find anything in the old bios. maybe I am missing something simple, any ideas? I can't use the case as a reference and this is a board from a local shop in town that parts out macbooks for non working logic boards.


As for a chip reader, I am using a raspberry pi with flashrom to do the reading and writing of chips.
 
S

sh33pz

New member
ok, just making sure, I ended up using the SN from a donor from China I had that matched the board I had, seems to boot, I'll try installing an OS later on.

thanks!
 
S

sh33pz

New member
Update on this.

I can not complete an OS update from Mavericks (OS that came with the device) or install High Serria. I would assume it is the BIOS, wondering where I messed up.

I can do an internet recovery and install the OS ( which is Mavericks ) however when I try to install an EFI update, it downloads, runs the install, reboots and this is where it will get stuck on a black screen.

The Fan is turning on for 2 seconds and turning off and never breaks out of this cycle until I pull the battery and power. When I reconnect the power, the MacBook boots as normal but the Firmware never gets updated.


I tried with my updated serial bios and I also tried with a clean BIOS (3437clean.bin file) and made no changes to that file that duke had posted on the forum and both do the same thing.

I went and check the resistors and they all seem to be within spec and the traces aren't broken. I tried a different BIOS chip as well, just in case it was messed up.


Right now, my mind is stuck on the idea the BIOS information isn't programmed right or missing something. Does anyone have any ideas? Possible I am looking at this wrong and overlooking something dumb.

Thanks.
 
2informaticos

2informaticos

Administrator
Staff member
Did you try fresh install on other HDD?
Tried external drive with preinstalled OSX?
Can you install El Capitan?
 
S

sh33pz

New member
I have tried another SSD, again, while installing, I get the black screen with a white apple logo and the install bar which makes it just a little past the starting point, the screen goes blank and the fan gets stuck in the start stop start stop and never comes out of it.

For kicks, (Battery is disconnected) I tried a SMC reset while in this boot loop (holding options, command, shift and power key for about 10 secs and releasing it) charger light goes green then back to orange and then I have to press the power button to turn the MacBook on again and it goes right back to start stop start stop loop upon turning on, I would have thought it would have tried to boot from scratch again but didn't. Only when I remove the charger completely it will boot and resuming installing and then gets an error "installer resources have expired"


I don't have an external drive but I'll get one and I haven't tried El Capitan but will look for an installer and try it.

Also, the newest MacOS Mojave does the same thing while installing it.

I wonder if there is a way to manually push an EFI update via terminal or something...
 
S

sh33pz

New member
UPDATE on this and how it was SOLVED.

Short version, swapped SMC, firmware now updates and running on the newest OS with no issues.


Long version:

I found a way to manually push firmware updates to the BIOS.


You can get the firmware from unpackaging (Program such as unpkg) the install files. In my case, I used MBA61_0099_B20_LOCKED.scap and copied it to my Downloads on the MacBook.

Open a terminal window and run:

You need to install the firmware to SSD/Harddrive EFI partition:

sudo bless -mount / -firmware ~/Downloads/MBA61_0099_B20_LOCKED.scap --recovery --setBoot --nextonly --verbose

You need to verify the firmware got copied over and you do this by:

diskutil mount /dev/disk0s1 ; ls -l /Volumes/EFI/EFI/APPLE/FIRMWARE/ ; diskutil unmount /dev/disk0s1


If you see the firmware file: MBA61_0099_B20_LOCKED.scap you should be good to reboot.

Type: sudo reboot and the MacBook should reboot and update. In my case, it would get stuck and never get past this.


Anyhow, since I know 100% for certain it is the firmware updating causing it to get stuck in a loop, I checked all traces again and measured every resistor (may have been fruitless to do so but I figure what the hell, why not) and it all matched up.

The BIOS has lines to the JTAG, CPU, and SMC.

JTAG has been removed already as it was destroyed before I got the board. I can't swap the CPU but, I can check the lines to the BIOS under the SMC.

So, I removed the SMC and checked the path to the BIOS and it was fine. Since I had the SMC off, I figure, just as well swap it out. I couldn't see anything else other than the CPU or the SMC causing the issue.

Booted the system with a donor SMC and re-ran my manual firmware update and BOOM it worked. At this point, I am assuming the SMC was the reason the BIOS was corrupted in the first place.



Sources I used for Manual Firmware updates:
https://forums.macrumors.com/threads/did-yosemite-update-boot-firmware.1818849/page-2
https://apple.stackexchange.com/que...date-latest-macbook-pro-efi-firmware-manually
 
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