Easy Laptop LCD Screen Diagnostics: Bad Backlight(?)

To Backlight or Not to Backlight? Is it Actually Broken, That is the Question:

So, you think you’ve got a bad backlight or a tech-savvy friend of yours turned on your laptop and said you have a bad backlight. .  . spoiler alert: there’s a big  (and important) difference between your laptop’s LCD backlight not coming on and the backlight actually being broken and unless you’ve fixed a LOT of  laptop LCD problems in your lifetime, this tends not to be something one knows.  A broken backlight means that the backlight is what needs to be replaced; a backlight simply not working, on the other hand, may have any of several sources, and a broken backlight is rarely the most probable cause.

Just one note before we get started: if your LCD screen comes (or used to) on somewhat (not entirely) dim or with a red discoloration or it comes on and flickers from the get-go, that’s usually a dying or dead backlight.  Proceed to our article on replacing your backlight the easy way!

First off, let’s cover some things that are not caused by a bad backlight

  • Garbled screen with weird ‘artifacts’ at random times
  • Laptop screen powering off or going wonky after a long period of use.
  • Lines on the screen
  • Screen appearing ‘shaky’ (weaving left to right or up and down at times)
  • Generally: If your screen stays bright, it’s not the backlight.

So, why wouldn’t your laptop’s backlight not come on, even though the machine seems to be powering up?  There are four reasons major reasons (and I’ve yet to come up with a fifth):

  1. Your laptop is not actually booting up (though part of it may be powering on, drives are spinning up, indicator lights flash, etc., it’s not actually doing any computing)
  2. Your laptop screen has a bad inverter.
  3. Your laptop’s motherboard has a damaged or bad video card.
  4. Your LCD’s backlight is actually bad.

To be a little more sure, the first thing you’ll want to do is to turn on your laptop and have a close look at the screen under decent lighting conditions.  Power on the machine.  If your laptop’s LCD screen is not ‘lighting up’ but is showing a faint image on the screen (if you look very closely under reasonable lighting conditions, you see a very faint image on your screen that looks like what ought to be there, but isn’t lit up), then we know at least that your laptop is booting.

If your laptop screen is not lighting up, you’ll want to have tried both of the following before attempting a backlight replacement:

  • replace the inverter with one of the exact same part number1 (no, not just one advertised as matching your model of laptop, really, you’ll thank me later).
  • inspect the LCD cable and found it in good condition and made sure it’s snugly in place.

If neither of those have fixed your problem, then attempting to replace your backlight is going to be the most cost effective next step in trying to fix your non-working screen.   Replacing your motherboard is the last thing to try.  We recommend you hold off on that until you’ve exhausted all other options.

 

1 I should note that Green Penguin Inc. does upon occasion advertise multiple compatibilities or even a part number as being compatible with most or all variations of a particular laptop.  In these cases, we have done extensive research into the matter, often having already tested and disassembled 30-40 different versions of the particular model of laptop in question.  I can’t guarantee it with anyone else and I want this information to be useful to you whether you purchase from us or not.   I want the result of your repair experience to be that if the part you’re replacing is faulty, the replacement fixes your problem, not makes it worse.

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5 Responses to “Easy Laptop LCD Screen Diagnostics: Bad Backlight(?)”

  1. Hawnrippa
    February 2, 2012 at 11:38 am #

    Penguin,

    Another thing you can try is to hook-up an external monitor to see if computer boots up and screen appears normally. However, that still does not pinpoint what the issue could be. Could still be the LCD screen, inverter or possibly the motherboard even though the the external monitor works.

  2. September 30, 2014 at 4:20 am #

    please i have a laptop with replaced lcd as a result of the smashed factory screen. The replaced screen worked for some time but now the backlight faulty but boots normally.i have checked the lcd on another laptop, it was okay but i dont know if the display cable is faulty or the motherboard.pleaese i need ur help on what step to take.thanks.

    • admin
      August 29, 2017 at 2:14 pm #

      @ahmad, obviously this is too late to resolve your issue, so this response is for others in the same boat:
      You don’t say here whether or not you tested just the LCD panel or the entire LCD assembly (cable, inverter, etc. included). Inverters are by far the most common culprit on the ccfl-lit LCDs. As a point of reference, ‘modern’ laptops no longer use an inverter to power the backlight on the screen as they are lit by lower-power AC-driven LED lights rather than the DC-driven compact fluorescent tubes that were once so prevalent. What brand / family / model of Laptop are you repairing? This would be something like Dell (brand) Latitude (family) C610 (model) or Acer Extensa E510.

  3. Chuck
    February 5, 2017 at 10:03 pm #

    Got into working on 2 Asus Eee PC 1015PX’s and decided to put the “Teal” m/b in to look
    at it some. Had earlier used an external monitor so now used the matte LCD in the opened one. New learning experience here… Within 15 minutes this m/b ate the LCD. Shut it down after it looked weird and the backlight even stayed On dim when turned Off. Plugged a diff glossy into it for a sec, not supposed to work on this m/b but lit up super bright. Turned it Off immediately. It had lost its original LCD to that m/b too and was all black with some backlight. Very freaky. So ordered another damaged case 1015PX just for the internal parts, m/b, LCD, etc. No more work on this one m/b, has some sort of short in it? It eats LCDs. Never thought that was possible but it burned out something and now LCD barely dim displays so m/b did something out of spec to the LCD. No idea m/b history. Result is another LCD & m/b needed.

    • admin
      August 29, 2017 at 2:12 pm #

      @Chuck —
      Sorry for the egregiously late reply!
      We’ve encountered this problem before as well, on more than one model. In fact, we’ve encountered this problem on an almost ‘viral’ level — motherboards that eat LCDs in a way that makes the LCDs eat motherboards in such a way that those motherboards will eat LCDs. . .and so on — imagine testing the parts from 50 laptops and running into a string of bad LCDs, so many that it can’t be coincidence (say, 7 in a row), so you use a known working LCD on the test base, it doesn’t work either, so, you think to yourself, must be the base, I’ll try this on a different known working base (motherboard), and it still doesn’t work. NOW what do you do?!? Unless you’ve encountered this horror before, you might cook another 2-3 bases. If you’re LUCKY, it’ll be a board between the LCD and the motherboard that’s cooked on the LCD end of things and when you test the LCD panel, it will work, but that’s definitely not a sure thing, and it’ll cost you another base and some time to find out. Yeah, that happened.

      For your case, it IS possible that you have / had a bad inverter. It is remotely possible that replacing the inverter will resolve the issue. All things told, it’s not a huge cost to test the ‘bad’ lcd and ‘bad’ motherboard against a new inverter to see if both can be fixed.

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