820-00923-A Not Powering Up After BIOS Flash

[imperialboard89]

Yes, on PPVCC_S0_CPU after some seconds the Voltage drops from 1.15V to 0.64V and remains stable on 0.64V, but I still don't see the Apple logo on screen.
There is also not audio when it boot up. What else could I test?

 

[2informaticos]

"USB activity works because I connected a keyboard with backlight ant it works."
Don't make confusion between USB power and activity!

Internal Caps Lock LED reacts?

 

[imperialboard89]

No, internal caps lock led does not react at all

 

[2informaticos]

Really strange, if you get correct CPU core behavior.
Try another BIOS file...

820-00923-05 OK clean.BIN

drive.google.com

 

[imperialboard89]

Thanks, I flashed the BIOS you sent me.
Now the tension of PPVCC_S0_CPU on C10G1 start from 0V up to 0.785V and remain stable at 0.785V. If it can help, I noticed also that the tension on PPVCCGT_S0_CPU is now present with 1.05V.

I still don't see the Apple logo on screen. I'am thinking that maybe the right BIOS file could resolve the issue... or what else?

P.s.: However, I noticed that with the previous BIOS the board absorbed 0.900A while now it reaches a maximum of 0.450A. The voltage however remains at 20V. (See here)

 

[2informaticos]

Search for other dumps on Internet.
And remember to make ALWAYS backup when you touch the BIOS...

 

[imperialboard89]

I initially did not inform you that I had two similar BIOS chips. What I did was desolder the original BIOS, program the second BIOS (the non-original one), and then solder the second BIOS onto the board. Meanwhile, the original BIOS still contained its original bin file. After soldering the second BIOS onto the board, the computer no longer booted. I then resoldered the original BIOS chip, but the computer didn't boot with that chip either. From that point, I started flashing the original BIOS as well, forgetting to backup the original BIOS.

However, I want to highlight that after this process, the computer didn't boot even with the original BIOS, whereas before soldering the second flashed BIOS, it worked fine.


For this reason, I have a slight doubt that no BIOS file may resolve the issue. I'm considering two other scenarios: overheating of the board (due to all these soldering and desoldering operations in the BIOS area) or it might require an ultrasonic cleaning. What do you think?

 

[2informaticos]

Board overheated, or knocked of components is expected in this case.

 

[imperialboard89]

I've tested 5 different BIOS files (2 sent by you + 3 found on the internet), but none of them allows the MacBook to start up.

I compared the area near the BIOS with an identical non-functional board, and all the components are present; there is no missing component in the area surrounding the BIOS.

If there are no further tests to conduct, I would even be willing to send you the board for analysis. My curiosity about this issue has grown to the point where I'm eager to understand why the board isn't booting. I am genuinely willing to invest money in resolving this problem, all in the pursuit of learning and gaining insight into the issue.