Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

[sattech200]

I guess I assumed that back-light failures would be a thing of the past with LED display's. And I was just proved wrong! This is acting exactly like a failing back-light/inverter. Seems to get worse the longer the laptop is powered on and happens mostly coming out of sleep mode.

I have the unit tore down sitting on the bench. Have reset and wiggled all cables and connections. Think the lid switch is fine, I have watched it go to sleep about a dozen times and wake up from standby just fine. My gut is telling me motherboard but I'd like to troubleshoot this further to be sure.

I really haven't given any thought to diagnostic procedures for this type of issue and wondering if anyone has any tricks, tips, suggestions, or similar experiences?

Thanks a ton!

Laptop: Dell Inspiron 15 (M5030)
Display: Innolux BT156GW01 V.4
AB1560001

[sattech200]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

And I just found this very interesting article explaining the issue and possible solutions....

http://nwapchelp.wordpress.com/2011/...ard-connector/

[MisterD]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

pull screen and leave it connected, apply heat to the printed circuit board from hair dryer or heat gun but don't get it too hot, then you may have to spray some cold spray to get it to just the right temp. I did this on the same Model Dell M5030 and found it to be the Circuit Board that's part of the LED Screen, upon close inspection I found 3 resistors in a row that had poor looking solder connections on one side, I re-soldered and now I have continuous Backlight, before it was hard to get any backlight at all, I had to keep powering it off and on several times and it would flicker just before it would go back out.

[sattech200]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

Excellent! I did what the link above suggested and that didn't help. Will try your suggestion in just a little while.

Thank you very much!

[MisterD]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

I gave this Laptop back to my friend and she said it started flickering again, I'm not sure if the backlight went completely out this time but I'm sure I was in the right location, it could be thermal intermittent component on the LED Board (integrated with the screen) and maybe it started working for several hours after I heated and cooled it a few times. so now I'm going to just replace the screen if she's willing to spend the $55. by the way I was able to see the video on the screen with a flashlight when the backlight was out and it also worked fine with an external monitor.

[MisterD]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

Excellent! I did what the link above suggested and that didn't help. Will try your suggestion in just a little while.

Thank you very much!

The area I heated and cooled was on the left side of the Circuit Board with the screen facing away from you, there is a small potentiometer near that area, you will see the 3 resistors in the same row
my soldering iron tip is not the best, it is a small 25 watt weller iron but a new tip would probably helped me solder better.
so at this point I'm not sure if it's poor soldering or just a thermal intermittent component on that board. Good luck. please keep us posted.

Thanks.

[MisterD]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

I just realized your display is different, the one I was working on is as follows:

AU Optronics B156XW02 V.2
01JC2N

[sattech200]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

Gotchya! I pulled my assembly apart to access the board while powered up and now I can't get backlight to come on at all. Had a millisecond flicker at one point. I'm reading horror stories of people having this type of issue on these but not able to isolate the issue. screen, cable, mainboard, etc...

I do have a hot air rework station so not worried about that part, also just picked up the schematic on the unit. Will be tracking this down more in the next day but I am still green at finding the source of the problem at the board level.

Damn I thought these problems were a thing of the past. Was so nice to just plug in my spare/test CCFL lamp to determine where the problem was.

Thank you for all of the information you have given so far. It helps greatly! I will update as I dive deeper into this.

[sattech200]

Re: Dell Inspiron 15 LED - Intermittent back-light failure?!?!? (Scratching my head)

Well, after fiddling with it for about 20 minutes the backlight mysteriously started working again. My gut is telling me it was something to do with the cable going to the LED's from the board mounted on the screen.

I documented the pinouts and voltages for the power and control coming from the motherboard under normal working circumstances....and it's been working fine for several hours now. Going to let it run for a few more hours and then probably reassemble the screen and check the pinouts on the motherboard if it messes up again to determine if it's a display, motherboard, or cable issue.