820-4924-A no Display - missing PP5V_S0_LCD

dudipupan

Member
Hi everyone,

I stuck in a MacBook Pro repair (820-4924-A).
The MacBook is powering on (fanspin, CPU gets warm) but i get no display.
So i started checking the LCD power rails and noticed that PP5VR3V3_SW_LCD is missing (0V) (LCD connector pins 28,29,30).
Here I stuck because of missing experience.
Can anybody give me some hints how to detect why this rail is missing?

Thank you!
Best regards
dudipupan
 

2informaticos

Administrator
Staff member
Did you check PP5VR3V3_SW_LCD in the first few seconds?

Be aware, there is no reason to search for internal image/backlight if no external video, nor USB activity; check first.
 

dudipupan

Member
Thank you again for your reply :)

I dont't get PP5VR3V3_SW_LCD in the first few seconds - just checked it with an oscilloscope.

I get the 5V suplly on USB but no activity. And no external display. So the problem is not the missing lcd rail - it's another S0 that holds off the board from booting completely?
 

dudipupan

Member
The previous owner changed the battery. Before the battery change it worked well without any issues. That's all i know about this board - no signs of liquid or anything else...
Ah and he sent it to me with two PUS - onw of them with too high output voltage (20V) - i don't know if he used the 20V PSU...

How can i flash new BIOS on a MAC? Already did it with a programmer on other Notebooks but never did it with an apple product...

Thank you!
 

2informaticos

Administrator
Staff member
You can remove the chip and use a classic USB programmer.
Or get Medusa programmer and do the job onboard.

All necessary information can be found on the forum.
 
Last edited:

dudipupan

Member
Thank you!! Bios flash solved the problem. How is that possible that Bios breaks by changing the battery? 😃

Now i really got a problem with missing PP5VR3V3_SW_LCD on another board (booting with chimes, external display and 3.3V for few seconds). Should I create a new thread or can I ask you directly in this thread?

Thank you! 🙂
 
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