820-2330 No Backlight

[Bouba148]

Hi Team,

I Have a 820-2330 that has no backlight:

F9800 is OK
at Q9807:
Pin 2 BKLT_PLT_RST_L, I have 3.298V
pin 5 LVDS_BKL_ON I have 0V that's why it can't provide a gnd for the Div bridge to be able to close Q9806.....

Now the LVDS_BKL_ON line is directly provided by U9600, I've checked for eventual broken trace, but no........

So what would be the next step please? replace the U9600 or there is something else to check before doing that replacement as I'm not sure to have an U9600 is stock / donor board.....

Question: should I plug the screen for the U9600 to send that signal?

Thanks, Gracias

 

[Bouba148]

Hi
OK I plugged the screen and I have LVDS_BKL_ON , Q9706 is closing to send the enable signal to U9701.
R9730 is 61KOhms but should be 0.1 Ohms
Will replace it and let you know

 

[2informaticos]

Backlight and LVDS/eDP circuitries always need LCD to be connected!!!

If R9730 is bad, check for any short on PPVOUT_S0_LCDBKLT_SW and PPVOUT_S0_LCDBKLT.
Probably nothing, if R9730 is only corroded.
If is burnt, that will point to a short somewhere...

 

[Bouba148]

Hi,
I replaced R9730, but Honnestly i'm suspecting the lcd screen that kills the backlight because it' does not have the locking latch, also the client reported backlight issue after replacing the original screen with this one (used one)
​​I will check for any short Last week i've already replaced F9800 and tested the board with another screen and it was OK.
But this time i don't have that spare screen to test the board and as i'm suspecting the client used screen i will not plug it to test it.
At least i'll have a look for any short and wait next week to get a known good screen.
Gracias

 

[2informaticos]

Don't close the LCD connector, or at least check if the closing latch has the plastic protector in good condition.
Compare resistance to ground from backlight rail w/ and w/o screen connected...