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820-3115 B No green light on Magsafe

N

Neil250

Member
I cannot see an image on the screen (used a flashlight behind apple logo)
No backlight

I watched Louis' videos on this and started checking the following:


LCD_BKLT_EN: 0V with display connected
Diode mode reading on LCD_BKLT_EN: 0.60V
LCDBKLT_EN: 12 V
LCD_BKLT_EN: 0 V
F9700 is good

Q9706
4: 12.4 V
1,2,5,6: 0 V
3: 12 V

Since Q9706 is a P type MOSFET that will only open when the voltage on the gate is much lower than the voltage on the source it seems like this is major issue.

C9782 diode mode is 0.4 V
R9788: 300KO
R9789: 146kO


I think Q9707 is not opening. No path to ground.
Q9706 never opens.

I think this LCD is never recognized to begin with.

Resistors on LVDS_DDC_DATA and LVDS_DDC_CLK are good (exactly on spec).
R9008 - 3.2kohms
R9009 - 3.15kohms

J9000 connector looks good.
No corrosion.
NO Liquid damage evidence.
All pins look good.
LVDS PINS:
pin 2,3: 0 V
pin 6 - 0.560 diode mode
pin 7 - 0.643 diode mode

If LCD_PWR_EN on U9000: 0V

SMC_LID: 3.45 V



I followed:

https://boards.rossmanngroup.com/for..._bklt_en/page2


I will check with another LCD assembly.

Please remember that I am totally new to this.


R1981: 100K (LVDS_IG_BKL_ON = LCD_BKLT_EN)

LVDS_IG_BKL_ON is coming from U1800 so I think I may be screwed.
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
Why do you insist on video???
Can you confirm USB activity first?
If not, there is no reason to expect video.
Post exact voltage at L7510/20...
 
2informaticos

2informaticos

Administrator
Staff member
I asked about EXACT VCORE voltage in case you cannot confirm USB activity.
No idea if you tested that yet...
 
2informaticos

2informaticos

Administrator
Staff member
I asked about USB activity, not only power!

Your board doesn't even boot.
When it does, VCORE drops to 0.75V from initially 1.15V.
And you have a fix searching for video; instead of doing mentioned tests at their time :(.

Try known good DDR module, one slot at a time.
If still the same, try known good working BIOS.
 
N

Neil250

Member
I don't believe USB ports are working.
No sustained significant current draw on any of them with connected devices



CPUVCORE

Measured at
R7510 PIN 2: 1.117 V PPVCORE_S0_REG
 
2informaticos

2informaticos

Administrator
Staff member
Just for test.
It should boot, even with dirty ME region.
In fact, see (at least) if you note mentioned drop on VCORE...
 
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