820-3330 No Bklt.

[Rford]

Hi,

I have a 3330 with no bklt. External Screen works with screen unplugged. No history. Older machine, very faint corrosion around the board, nothing major anywhere, especially along LCDBKLT circuit.
J9000
Pins 2,3=3.3V
Pins 38,39,40 (PPVOUT_SW_LCDBKLT) reads 25V. I believe this is supposed to be 50v for the 15"
Any idea what could cause the bklt to read low?

This is a mid 2012 model.

 

[2informaticos]

Do you get image for sure (on internal LCD), just missing backlight?
PRAM reset done?
C9797/99 both OK, good solders?
Post L9701 voltage.
Do you note any change at PPVOUT_SW_LCDBKLT pressing backlight control keys?

 

[JohnB8812]

25 is slightly low. If PRAM reset doesn't fix it, likely an issue with or around the LED driver.

 

[Rford]

As it turns out, its the LCD cable... and of course this is an "up behind the LCD" model so the whole screen has to be changed out.

 

[Rford]

You can make this "solved"