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820-00923 20V @ 200mA not turning on

A

AJay_Smoothie

New member
Thank you for the quick response. That gives me some hope that I can get this thing fixed.

L7270 is at 1V
L7900 is at 1.2V
L7960 is at 950mV
 
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2informaticos

2informaticos

Administrator
Staff member
Post basic voltages for U7100; pins 41, 42, 48.
Do NOT try to measure on its pins; use surrounding components as test points!
 
2informaticos

2informaticos

Administrator
Staff member
We have many threads about BIOS; just search and read the forum.

You have to reprogram U6100...

BTW, any reason to quote an entire post visible few centimeters above (no matters how long/short is)?
Please, maintain forum aesthetic...
 
2informaticos

2informaticos

Administrator
Staff member
You may need an USB BIOS programmer, like TL866, EZP2019, CH341, etc...
I suppose you don't have Medusa programmer, which makes the job easy (not cheap tool).
 
A

AJay_Smoothie

New member
I have several CH341 programmers from my Arduino days, I should be able to figure it out. I'll give it a go and see what happens!

What would be the reason for needing to re-program it? IC's aren't supposed to just "forget". I couldn't find a direct link back to the initial burned components so I was just curious for information's sake.
 
2informaticos

2informaticos

Administrator
Staff member
Do NOT throw the money.
You need BIOS with clean ME region; not a file read from other similar machine!

Medusa programmer can do all the job onboard; recommended if you plan to repair MacBooks in the future.

UEFITool can help you to change serial number and clean ME Region.
However, you need to desolder/resolder the SPI chip (U6100) in this case.
 
A

AJay_Smoothie

New member
Well this is sad sad end to my repair attempt. I can't spend 350$ on a programmer and nobody has even remotely clear instructions on how to do it otherwise.
 
E

Eduardo&Macs

New member
Hey Ajay,

You don't need to spend $350 on a programmer. There are dozens of programmers that you can use for this job. You can find some for around around $30-$50 that'll do the job.

The way I've done this sorta job is use a programmer that connects to the JTAG connector on the board. Read the BIOS 3 times to make sure they all match and ensure a good read. Use UEFITool to clean ME region.

It'll take a little bit of googling but you'll figure it out. You do NOT need to remove an EFI lock. This is to clean the ME region of the BIOS which are two different things. I personally use the Medusa programmer but I believe it's possible to use the CH341A programmers with an adapter that fits the JTAG connector on the board.
 
A

AJay_Smoothie

New member
Eduardo,

Are you saying the only thing that needs to be done is to "clean the ME region" without finding another BIOS to upload to it? Or do I still need to find another BIOS/bin/file to re-write the chip?

I also can find any pinouts as to actually hook up the programmer. I have about 4 of them and would rather desolder the chip(U6100) and quickly make some connections to my existing programmer than having to buy adapters that I'll use once.
 
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2informaticos

2informaticos

Administrator
Staff member
"copied over the mac ROM"
What did you copy over?
I was expecting to just clean ME region on your board.

BTW, always make a backup of original BIOS; before erase, or overwrite it!!!
 
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