820-4924-A not turning on (draws 350mA)

c0dix

New member
Hello everyone,

I have a board (820-4924-A) without any signs of corrosion and no liquid spilled on it. From one day to another it didn't turn on.
The light of the Magsafe connector turns green and then orange. The board draws 350mA with a disconnected battery.
I have measured the following signals so far:

PPBUS_G3H 12.5V
PP5V_S0 5V
PP3V3_S0 3.3V
PP3V3_S4 3.3V
PP5V_S4 5V
PM_SLP_S4_L 3.3V
PM_SLP_S3_L 3.3V
PM_SLP_S5_L 3.3V
PP3V3_S5 3.3V
PP5V_S5 5V
PP5V_S3 5V
PP3V3_S3 3.3V
S4_PWR_EN 3.3V
PPVCC_S0_CPU 1.86V
CHGR_RST_L 3.3V
PM_SLP_SUS_L 3.3V
PCH_PM_SLP_S0_L 3.3V
ALL_SYS_PWRGD 3.3V
CPU_PWRGD 1.048V
PPVRTC_G3H 3.3V


What should I test next?
 

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

Check for 3V presence at pin 3/U1950 and PLT_RESET_L.
If yes, then try new full BIOS.

Did you test USB activity?
 

c0dix

New member
Thank you for welcoming me!

Okay, I measured the following:

SYS_PWROK_R 3.419V (pin 3/U1950)
PLT_RESET_L 3.333V


What exactly do you mean by USB activity? I just connected a USB mouse and the lights turn on, so power seems to be delivered.
 

2informaticos

Administrator
Staff member
Mouse gets steady light if connected when board is turned on?
In such case, should be activity.
Always better to confirm with an OSX pendrive/HDD; if Link LED flashes, that is.

You still have to test LIO board/flex to finish the repair.
 
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c0dix

New member
You're right, no steady light on the mouse and I also tested with an OSX pendrive and the Link LED is not blinking, so it seems its not communicating...
For testing i've been using the USB port on the side of the magsafe connector.
 

2informaticos

Administrator
Staff member
Aaaa, this 4924 board, no LIO board there.
I mixed the threads somehow; to much heat here...

Try new BIOS file now.
 

c0dix

New member
As I'm just a normal guy trying to repair his macbook I do not have all the accessories that a macbook repair shop has.
What would be the cheapest way for me to flash the bios chip? The "CMIzapper Medusa 2" would cost me around 300€...
 

c0dix

New member
I don't understand what could have happened to the bios chip, that it needs to be flashed a new firmware.
 

c0dix

New member
I just connected the display and the OSX pendrive and an apple logo is showing up! Yay!
Can I stay with that BIOS or do I need a customized one with my serial number?
 

2informaticos

Administrator
Staff member
Is better to preserve original serial number.
Swap Fsys region with the one from your backup; Fsys --> $SVS.
 

c0dix

New member
Did it and booted once from OSX pendrive. Then I shut it down via GUI and now it's not turning on again..... it draws again 350mA then restart after a few seconds and again draws 350mA... No apple logo no boot sound...
 
Last edited:

c0dix

New member
I just flashed the BIOS again. This time the "original" version from the other thread (without changing serial). And it happend again. Started once and then not more.
 

c0dix

New member
Heating up the chip did not help... I've read out the contents of the BIOS chip after booting and it changed. Is this normal behavior?

So the current situation is, that flashing the BIOS makes the system boot, but only once. Then it's broken again and drawing 350mA
 
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