[SOLVED]820-3662 no backlight

[cobragfox]

Hello,

Have a 15in retina with no backlight. Replaced the lvds connector due to corrosion but still no backlight. PPVOUT_S0_LCDBKLT measures @ 54.76v, PP5VR3V3_SW_LCD @ 5.017v.

I've ohmed out the connection checking from the pads on the board to the other end of an lvds cable (not connected to the display). Also tried another display with the same outcome.

Any idea what else could be causing the backlight to not come on?

 

[JohnB8812]

54 volts means it doesn't see the screen. Have you tried a known good screen?

 

[cobragfox]

Yep tried a good screen. schematic says it should be 55v, isn't 55.76 close enough.

 

[JohnB8812]

Backlight should be around 30ish volts on these. 55 volts on backlight means it doesn't see a load or it doesn't see the light of the screen. Usually this is bad LCD connector, LCD cable, or screen. So in your case, inspect soldering on LCD connector and make sure it isn't burned.

 

[dukefawks]

I bet pin 1 on the LCD connector or cable is fucked. Nothing wrong with the actual backlight circuit for sure!

 

[cobragfox]

Gents you all are awesome. Since the backlight circuitry was working, looked into the display and found the backlight connector on the display was unplugged. Thanks a lot guys.