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No backlight on LCD - 820-3437 Macbook Air

patrickribbsaeter

patrickribbsaeter

New member
Gmorb said:
check if you get an image or backlight. if you still dont get an image either an apple logo or flashing folder by flashing light onto the apple logo on the back of the screen then check continuity on pin 18/19 of lvds connector and pin 2 of L8304 and check voltages on pin 18/19 of lvds as well.
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- LVDS connector Pin 18/19 i get on both 000.2v (schematic says should be 3.3v) (in continuity mode I get: OL. on both pins 18/19. NO BEEP!
- pin 2 of L830: I get NO beep in continuity mode. and voltage I get the same 000.2v
- pin 1 of L830: also shows 000.2v and NO beep!
 
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Gmorb

Gmorb

Member
Ok means the traces are blown between 18/19 and l830 solder a wire from 18/19 to pin 2 of l830 and verify that there is continuity also make sure you are checking voltages while screen is plugged in.

u8300 could be bad but since traces are blown its possible reattaching will fix it and let voltage flow again. Make sure you measure l8304 to see if its good.
 
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patrickribbsaeter

patrickribbsaeter

New member
Gmorb said:
Ok means the traces are blown between 18/19 and l830 solder a wire from 18/19 to pin 2 of l830 and verify that there is continuity also make sure you are checking voltages while screen is plugged in.
Click to expand...

How much heat do u recommend for the Solder iron? celcius?
 
patrickribbsaeter

patrickribbsaeter

New member
Gmorb said:
Ok means the traces are blown between 18/19 and l830 solder a wire from 18/19 to pin 2 of l830 and verify that there is continuity also make sure you are checking voltages while screen is plugged in.

u8300 could be bad but since traces are blown its possible reattaching will fix it and let voltage flow again. Make sure you measure l8304 to see if its good.
Click to expand...

Pin 18/19 shows now 3.3v both och them(with screen). Even L830 shows 3.3v.. But no logo, no light on screen still.. ?
 
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Gmorb

Gmorb

Member
Check continuity between pin 2 of l8304 and the capacitor right below it. should connect to it through pin 2 as well. Check the boardview to verify.
 
patrickribbsaeter

patrickribbsaeter

New member
Gmorb said:
Check continuity between pin 2 of l8304 and the capacitor right below it. should connect to it through pin 2 as well. Check the boardview to verify.
Click to expand...

Yes, there is Continity now.. :) between pin 2 of l8304 and the capacitor right below it.

But no light still..
 
J

JohnB8812

New member
Lets start over...Do you have 3.3 volts on pin 18/19 of the LCD connector? If so, you should have image meaning if your screen doesn’t have image, try another known good test screen. If you DON’T have 3.3 volts on pin 18/19, check to see if it makes its way to L8304 pin 1. If yes, possibly blown inductor or bad trace from inductor to screen. If NOT getting voltage on pin 1, check if EDP_PANEL_PWR is present at pin 1 of U8300
 
patrickribbsaeter

patrickribbsaeter

New member
JohnB8812 said:
Lets start over...Do you have 3.3 volts on pin 18/19 of the LCD connector? If so, you should have image meaning if your screen doesn’t have image, try another known good test screen. If you DON’T have 3.3 volts on pin 18/19, check to see if it makes its way to L8304 pin 1. If yes, possibly blown inductor or bad trace from inductor to screen. If NOT getting voltage on pin 1, check if EDP_PANEL_PWR is present at pin 1 of U8300
Click to expand...

Thanks. Im going to check exactly what u described and get back to you here shortly.. meantime.. Do you know if this Backlightdriver works for this motherboard? https://www.mouser.se/ProductDetail...=sGAEpiMZZMsE420DPIasPlogyTiw5Lxrbcr5vzVG7Qo=
 
turbo

turbo

Member
patrickribbsaeter said:
1. No apple logo when adding light to the screen. The screen is pitch black still.
2. I get chime when pushing start button. And the apple logo on the back of the LCD is lit. But not front.
3. L7701 (I have 8,5 Voltage). On Diode mode I have 0.384.
4. C7710 (resistance mode I get 0.428) and Voltage mode 5.12V)
Click to expand...

change led driver
 
2informaticos

2informaticos

Administrator
Staff member
Locate XW7720, between L7701 and D7701; check if is not corroded.
If board is luquid damaged in the backlight area, change U7701...
 
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