820-00165 No Backlight But Has image

[peeka79]

Hi, I have a 820-00165 that has No Backlight but you can see the image with a Light flashed from Rear. There was Corrosion under the Backlight Driver Near A5 ball so I Replaced LP8550 and Backlight Fuse but still no Backlight. ANY help will be GREATLY APPRECIATED...Thank You

 

[2informaticos]

Check continuity from A5 to D7701.
Pay atention to XW7720; pictures available on the forum...

 

[peeka79]

Hi, 2informaticos Yes there is Continuity between A5 and D7701

 

[peeka79]

XW7720 Bridge looks new still...

 

[2informaticos]

What about BKL_EN/PWM?

 

[tlough75]

I know this may seem obvious, but did you check the fuse?

 

[tlough75]

I know this may seem obvious, but did you check the fuse?

nevermind, saw that you did.

 

[peeka79]

Thanks for your Help 2informaticos...Does the screen need to be plugged in And board powered up to check the voltage on BKL_EN and PMW ?

 

[peeka79]

Okay...With screen attached and power to board I’m getting 8.56V on both sides of F7701 but 0.001V at pin 1 and pin 2 of D7701 and L7701... Also I am getting 5V on pin 1 of C7710...

 

[peeka79]

Here are more measurements with screen attached and power to board C7704 Pin 1 0.001V

R7715 Pin 1 (BKL_EN) = 0.002V
R7731 pin 2 (BKL_EN) = 0.001V
R7704 Pin 2 BKL_PMW = 2.17V
C7704 Pin 1 BKL_PMW = 2.17V Pin 2 = 2.17V
R7714 Pin1 BKL_ISET = 0.001V
C7711 Pin 1 PP3V3_S0 = 3.30V
I Really Appreciate the Help

 

[peeka79]

Anyone have any ideas?

 

[2informaticos]

Check EDP_BKLT_EN if present.

BTW, no need to measure the same line in various points...

 

[peeka79]

Thanks Again informatics...With Screen attached and power to the board Q7707 Pin 5 EDP_BKLT_EN shows 3.31V

 

[2informaticos]

Post Q7706/07 voltages...

 

[peeka79]

With Screen attached and powered on?

 

[peeka79]

Thank You Informaticos2, I Noticed BKLT_PLT_RST_L did not have Continuity between Pin 2 Of Q7707 and TP(1) so ran a wire and all is good now Backlight Working Perfectly. Thank You So Much for all your Help

 

[2informaticos]

Glad to hear is soved.

BTW, when you diagnose internal video issues, LCD must be connected...