LCD backlight replacement

monitor

Backlights are one of the most common failure points on LCD panels. Even though they usually say “no serviceable parts” on the back you might still be able to fix your monitor. Jared Bouck details the removal of the dead cold cathode and replacing it with a new tube and inverter. Not quite as dangerous as opening a CRT, but you still need to be careful with the mercury vapor filled tubes.

[thanks Tom]

Comments

  1. Kurtroedeger says:

    little hard core for my skills, but always good to know

  2. Loquax says:

    I’ve been thinking about converting my lcd 15″ to a transparency for projection, so this dissasembly has been very useful. Does it matter in making a transparency out of one of these LCD monitors if it is TFT or EFT(?)? The monitor itself is an older DELL lcd.

  3. flaunt_dzx says:

    I did this with a laptop. It’s not a good time.

  4. furtim says:

    Interesting. I recently had my 17″ LCD fail and have been keeping it around on the off-chance that I might be able to do something about it… Looks like now I can!

  5. COnfused fishcake says:

    I would definately try to make an lcd projector instead of this, as I am sure you will lose a bit of quality. Also, if your new CC tube is brighter, it may damage the screen by getting too hot. #2, I am unsure of what an eft is, but any flat screen is suitable for the lcd projector mod. Remove the invertor and CCFL, but keep them, they are good for case mods, general lights.

  6. bobstansalot says:

    That is why I read hackaday. You just can’t beat this stuff. Need to do some dumpster diving and find me a broken LCD.

  7. biznacho says:

    A customer of mine once asked me to attempt this. I had never done it before so I attempted it on a cracked LCD panel we had laying around. It wasn’t too difficult. The hardest part was keeping fingerprints off of the internals and remembering where all the screws went. I didn’t end up doing it for the guy. It was too hard for me to do without getting fingerprints all over and we were really busy anyway. If you have the time and can avoid touching the screens, I say give it a shot. Whats the worst that could happen? You break it?

  8. Tired2 says:

    I personally have replaced many many backlights that were not indeed bad. I have read that like 80% or something of backlight failure is the bulb, not the inverter. From my experiences, this is completely WRONG. a good way to test to see if you have a working inverter is to take a plastic bic ball point pen and while the computer is on touch it beween the red and white wires (on the molex). If your inverter is good, it will spark. If you shock yourself though, it feels like someone taking a needle and poking it all the way into your finger to the bone. Keep that in mind.

    My reccomendation, buy an inverter off ebay first. They are about 12 dollars, and you could always sell it if that does not fix the problem. If you try this method, you will probably break the old bulb you have trying to replace it, and manage to get some ghetto action goin once the new light is back in.

    good luck folks.

    -Tired2

  9. carpespasm says:

    anyone know of a decent place to score these dead backlight lcd panels?

  10. tom says:

    i replaced the inverter on a gateway 18″ lcd with no problems at all…a few screws, a couple of wires that plug in (no soldering), and it was good to go. i ordered a replacement inverter from a 3rd party vendor. i picked up the LCD for free since it was “broken”, and paid $85 for the inverter…not a bad deal.

    i also have a friend who built an LCD projector. the brightness is always a problem, even with a 400Watt high intensity discharge pulse-start bulb.

  11. flaunt_dzx says:

    Do you have any computer recyclers in your town?

    I had one by my old house that would let me dig through the piles of stuff, and would give me excellent deals on broken equipment. All it takes is making the right friends.

  12. Yorgle says:

    I got a 17″ IBM TFT flatpanel from the trash, and it was just the backlight that was bad. It had 4 CCFT’s in it. I left the CCFT’s and the backlight plane in place, and dropped in a $12 inverter made for a green glow tube for a PC case, and use that to drive one of the CCFTs. It’s bright enough for most uses. I need to get three more inverters and switch them off and on to be 4 levels of brightness.

    the inverter needed 12v, so i scrounged that from the line for the 12v fan in the monitor.

    The tubes in it were fine, the backlight assembly was fine (not that it can really break)… just the inverters/dimming circuit was bad.

    A cheap, quick fix, and it runs great! :D

  13. biznacho says:

    I should mention that it was a laptop LCD panel I worked on. I don’t know if there are any signifigant differences between an LCD panel designed for laptop and one designed for desktop monitor use.
    And it has been my experience as well that most of the time it’s the inverter that craps out and not the tube.

  14. weirdguy says:

    first, do cold cathodes really contain mercury? Second, the inverter thing is the same with computer ones (like for case modders). Third, you don’t have to dremel, most of the time glue is the only thing keeping it in the tube.

    And last, yo ucan do this same thing for scanners.

  15. nonobeez says:

    I once got 6 broken LCD flat panels from a dot.com in San Fran. I fugured I could mix and match to get some fixed, but it was not that easy. I later found out the units were notorious for blowing SMT micro fuses. I replaced them with copper wire…. they still wokr after 1 year!! the last 3 required replacing some transistors. Total cost of repair… $9.00 (mostly for shipping)

  16. furtim says:

    Some vital advice I haven’t seen would be how to tell a failed inverter from a failed backlight. What kind of failure pattern would you see from each one?

    The dead 17″ I mentioned above would flicker briefly and faintly, mostly in the lower-right, before going completely black. Could that be a bulb problem, or would a faulty bulb simply fail to light entirely?

  17. i started following the instructions to replace what I thought was a broken backlight. as i opened up the hp laptop screen, i found that a small connector near the bottom of the screen had come loose…so i plugged it in and it magically started working again. make sure not to overlook this possibility and end up buying a new backlight (like i did) before you’re sure of the problem.

  18. Vrogy says:

    http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=FL-122WH&type=store

    there’s a white cold cathode kit that’s probabaly suitable for hacking.

  19. benji says:

    Any one know how to just power up the CCF without usuing the computers PS or circuits?

    I have a few laptop CCF panels and id like to make a falt plane light or use it for under a light table for slides, I cant seem to get the CCF powered up though. I have connected it to the ballast or converter/inverter that was on the laptop but again cant seem to get the right startup volages..

    any one have any leads on this?

  20. Jason says:

    benji, there is an enable line and a brightness line on most inverters.
    the enable on mine was tied high and the brightness tied low for max bright. So there were 4 wires on the input to the inverter.
    you need to google the part number on your board to find the pin out.

  21. Adrian says:

    Hi guys, I have got a problem with my laptop lcd screen. The screen is purple (or pink) maybe because of the backlight, or the inverter, plus every second vertical line is missing. It just happend…when i shut the laptop down, was OK, but on the next boot it was like this. Have you any idea, what is wrong exactly, and what to do with it? Thank you for any help!

  22. tiuk says:

    #13, my guess is they contain mercury vapor.

  23. benji says:

    Alrighty, thansk for the lead jason!!

  24. biznacho says:

    #20 adrian, my guess would be that the inverter and backllight are OK. lines usually indicated a bad panel. backlight and inverter problems usually manifest as a very faint image on the screen. But I can’t see what you’re working with so I can’t tell for certain.

  25. Adrian says:

    Hi again, so the screen is bright enough, but when I change the wallpaper to a white one, it seems to be violet and sometimes red. The bigger problem is, that those lines are missing (maybe display controller failure?). Is it repairable (DIY)? Or better to buy a new screen (or laptop :-) )? Any experience? Thanks

  26. Washu_chan says:

    I’ve done a repair similiar to this but I used a DMM find the +12 and then looked for the line that changed state when the backlight was turned off and on use of an oscilloscope or logic probe can make this quicker work.
    On my display this was done by the controller board pulling a pin low which would turn on the backlight inverter a high signel also was avilible from the status LED since it was driven by a simple two transistor circuit that inverted the low signel off the same pin on the controller IC.
    I then simply soldered in the new connections use some plastic stand offs to mount the new BL inverter board.
    A little work with a DMM and a few parts was all it took to adapt the new inverter board and have all standby functions work.
    The display still works today better then new since the new inverter board runs cooler then the original.
    Though on someone posting the backlight color changing that sounds like the CF tubes themselves are dying or are not being driven properly.
    Another possible repair to a broken LCD might also include an array of surface mount white LEDs mounted to a long and thin PCB carrier which I might try if I have to fix another dead flat panel.

  27. Cristisphoto says:

    would thos cause a whit line across the screen
    Thanks all

    cristisphoto@yahoo.com

  28. jason says:

    I recently had my gateway laptop lcd died on me. I was able to connect to another monitor and i was able to see the screen when i have a flash light on it. What do you think i should get?? An inverter. Thanks

  29. jason says:

    I recently had my gateway laptop lcd died on me. I was able to connect to another monitor and i was able to see the screen when i have a flash light on it. What do you think i should get?? An inverter. Thanks

  30. Kandy06@sbcglobal.net says:

    Hey, I have an HP Pavilion ZV5000 with a cracked LCD screen. I’m not sure how it managed to crack… but if anyone is interested in the computer or the LCD screen ( I dont know why you would be interested in the screen, but hey.. who knows) email me at Kandy06@sbcglobal.net. I don’t want a $1,500 paperweight. :|

  31. Kandy06@sbcglobal.net says:

    Hey, I have an HP Pavilion ZV5000 with a cracked LCD screen. I’m not sure how it managed to crack… but if anyone is interested in the computer or the LCD screen ( I dont know why you would be interested in the screen, but hey.. who knows) email me at Kandy06@sbcglobal.net. I don’t want a $1,500 paperweight. :|

  32. elh says:

    Response to Jason (#29)

    Jason, I had the exact same problem with my Dell laptop. I’ve been using it with another monitor hooked up to it for the time being. The estimate I got for repair was almost $500. At that rate, it is worth it to me to try to fix it myself. Did you figure out anything yet or get any responses?

  33. melvyn says:

    hello everyone…

    I have ACER AL1511 BM 15″, it was send to me by friend of mine he was going to throw it away, the problem with this LCD is when you turn it on I could see ACER logo and than goes dark and than show something again but than back to darkness and stay like that but If I turn off the LCD and on again I see ACER logo, and Windows but back to darkness.. I open the LCD and I check with my multimeter to check if there any volt from PSU to lamp and only give me volts when I turn the LCD on and than when goes back to darkness than I get zero volt on my mulitmeter, I figure the lamp are fine or going dead or is the PSU… I read some of comment from other users, like “inverter”.. well let see what other people has to see about this LCD…
    thank you for your time.

  34. melvyn says:

    hello everyone…

    I have ACER AL1511 BM 15″, it was send to me by friend of mine he was going to throw it away, the problem with this LCD is when you turn it on I could see ACER logo and than goes dark and than show something again but than back to darkness and stay like that but If I turn off the LCD and on again I see ACER logo, and Windows but back to darkness.. I open the LCD and I check with my multimeter to check if there any volt from PSU to lamp and only give me volts when I turn the LCD on and than when goes back to darkness than I get zero volt on my mulitmeter, I figure the lamp are fine or going dead or is the PSU… I read some of comment from other users, like “inverter”.. well let see what other people has to see about this LCD…
    thank you for your time.

  35. edwin711 says:

    I have an Envision EN-7100e 17″ TFT LCD Monitor of about 3 years. When I turn the monitor on the picture looks normal but after a few minutes (somewhat random) the monitor screen blanks and the info led turns orange as though it is in power-saving, though it is not. Unplugging, then replugging the monitor and turning it back on will create the same situation… it turns on and them a few minutes later, image goes blank. Any ideas?

  36. Sheila says:

    My six year old Dell Inspirion 7500 LCD screen has developed a pink screen at startup. It clears up after about 10 to 15 minutes but seems to be getting progressively worse…worse meaning a more intense pink covering more of the screen. What to expect next and is this a problem worth fixing? Budget is tight and I am not a techie. Any suggestions?

  37. darc7 says:

    I’ve encountered a problem that so far has defied explanation – seems to be similar to what edwin711 describes. I took a bad Gateway 18″ LCD TV, replaced the inverter board, and it worked great – for two days. Now, it turns on fine but the lamps always wink out after a few minutes. I think there’s some type of grounding problem. When the lamps are OUT of the LCD chassis, they illuminate indefinitely. If I place them in the LCD frame (which is metal, so a circuit is formed), the backlight inverter emits a high-pitched whine and shuts off rapidly. If I ground the LCD frame to the main chassis super thoughly, it’ll stay on longer – but so far, I haven’t cinched it. Anyone with more technical knowledge than myself – HELP!! :)

  38. Keith Sandall says:

    Hi all.
    I purchased a used NEC 2010x 20″ lcd. When I power up the lcd there is a high pitched wine coming from the left rear of the monitor. When the lcd goes into power-saver mode the whine becomes lower pitch but is still there. When I adjust the size of a window with the mouse the whine also changes pitch! BTW Picture is awsome.Is my lcd about to blow up? I am far from an expert but don’t mind getting my hands dirty. Any suggestions will be appreciated.

  39. Esfires says:

    I have an Envision En-7100si monitor that has recently gone out on me. I’ve done some research and everything points to me needing to replace my inverter board. Ok, I can do that. I read through numerous online guides and tutorials (including this one, or course) to familiarize myself with the process. When I opened up my monitor, lo and behold I couldn’t even find an inverter board. I can see the AD board, but attached to it by two multi-pin clips is another larger board. This board is where my power cord runs to. It has a section on it that looks like all the examples of inverter boards that I’ve seen, even with the clipped on wires that lead to my backlight, but it is just a section on this larger board. These are the only two boards it has, besides the circuitry that is part of the LCD display. Is this just some variation on inverter boards that I haven’t found yet or am I just missing something?

  40. Rahul Rathod says:

    Yes it is hard to figure out Inverter in LCD Monitor. On laptops is easy. Mostly it is in back of the LCD or under power button bezel . Why dont you give search of monintor inverter in google. You migh find many pictures you can match with.

  41. Nathan Araujo says:

    Hi my Dell Inspiron 8100 has a backlight issue. The backlight shuts off after about 20 minutes, then when I restart it shuts off after about 3 minutes and less and less after that. The screen also has a pink illumination to it. I tried replacing the Inverter, but still the same problem. The screen shuts off even faster when I turn the brightness up all the way. SOME PLEASE HELP? It sounds like the backlight is bad or there’s some bad wiring or bad voltage going in. It doesn’t matter whether it’s plugged in or not either.

  42. rickgaribay@yahoo.com says:

    Hello,

    In an effort to find the backlight for a Dell E151FP monitor, I mistakenly cut 3 plastic strips that go from a circuit board to the LCD. At first I thought these were just adhesives, keeping the LCD secured to the frame.

    I am wondering if I have permanently damaged the unit or if I can somehow glue or tape this back together. Any ideas or comments appreciated.

    I am attaching a picture of the image as well. I would very much appreciate you advice so that I know if I should continue with my backlight replacement project or if I have ruined the LCD.

    Thanks,

    Please see pictures here:

    Sincrerely,

    Am I screwed?

  43. rickgaribay@yahoo.com says:

    Hello,

    In an effort to find the backlight for a Dell E151FP monitor, I mistakenly cut 3 plastic strips that go from a circuit board to the LCD. At first I thought these were just adhesives, keeping the LCD secured to the frame.

    I am wondering if I have permanently damaged the unit or if I can somehow glue or tape this back together. Any ideas or comments appreciated.

    I am attaching a picture of the image as well. I would very much appreciate you advice so that I know if I should continue with my backlight replacement project or if I have ruined the LCD.

    Thanks,

    Please see pictures here:

    Sincrerely,

    Am I screwed?

  44. Seems you have lamp issue. I have seens lot of CCFL . Laptop LCD backlight issues ( Lamp issues
    Dell inspiron 8100 / 8200 / 8000 series . Mosly SXGA Tx38d99vc1caa LCD comes up with reddish tint and lamp blows up. But as laptop model it self is old now i will always suggest to check inverter voltage. Here is some more information about back light issues

    http://www.247laptoplcd.com/faq.html

  45. Beverly Avery says:

    My husband has a Gateway laptop. He recently purchased a 19″flat screen monitor. He wants to connect them together so he can see the data on a large screen. So far he can’t get connectivity. What does he do?

  46. Beverly Avery says:

    My husband has a Gateway Laptop. He recently purchased a 19″ Flat Screen Monitor. He is trying to connect the two together, and use the flat screen exclusivly. So far, no connectivity. How does he do this? It’s not working!

  47. bOB says:

    Regarding plastic strip cutting , ( 42 )These are ribbon strip connectors,that connect to the matrix array inside liquid crystal display,cutting them has rendered the screen unrepairable ,sorry to say.

    Bob

  48. paul says:

    Inverter of Display (Bulb?)

    I have a flickering backlight that has some other consistent symptoms of note.

    Physically tapping (and perhaps banging after a second cup of coffee) does affect the backlight. It will flicker

  49. Aeo says:

    I just finished a successful application of this hack to a Dell E152FPc LCD monitor except I just used the Xoxide inverter and powered the exising Dell CCFL tubes since they were okay: http://forums.inventgeek.com/viewtopic.php?t=33

  50. gdelator@uag.mx says:

    have HP Pavilion zv5267la 15.4″ LCD, it was send to me by friend of mine he was going to throw it away, the problem with this LCD is when you turn it on I could see HP logo and than goes dark and than show something again but than back to darkness and stay like that but If I turn off the LCD and on again I see HP logo, and Windows but back to darkness.. Lamps ok, Buy a new inverter result is same back to darkness, Help…
    thank you for your time.

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