Replace LCD Backlight Inverter on Any Monitor For





Introduction: Replace LCD Backlight Inverter on Any Monitor For

About: I'm working on my Master's of Science in Mechanical Engineering, specializing in Engine Research at the University of Wisconsin - Madison. ***All Instructables Projects moved to my personal site, I didn't li...

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      27 Discussions

      Great turorial, i only have one question - Do the brightness controls still work with this method?

      1 reply

      Nope, the inverter that I used doesn't support brightness controls. The only way to retain brightness control would be to purchase and install an inverter with it, which would likely push the cost up towards what a replacement inverter or board would cost for your monitor.

      Is it possible to restore original brightness control through relays? How would you go about doing so?

      1 reply

      You can't restore the brightness with a relay, but you could replace the turn on switch with a relay. To restore brightness control you have to modulate the output to the backlights, that's why those inverters for the computer "neon" are so cheap because they have no brightness controls. Adding a relay is simple, just find the original turn on wire to the inverter and hook it up to a transistor, have the transistor power the relay coil and wire the +12V to the inverter through the relay. Adding brightness control isn't worth it, you'd be better off buying a replacement inverter board, or, with the prices of monitors, a new 19" monitor :-(

      I just did this for my 10.4" touchscreen in my car. Worked great, I only needed one inverter. I had all the wires backwards the first time and it didn't fry, after I got them right it was nice and bright. Thanks

      Very good job guys! With this guide a old dead monitor return to life! This is my experience So i find at only 9,90 EURO a kit for pc with neon cold cathode and inverter (just like I've seen in thi sguide) for a desktop pc. First for the power to inverter I use the original cable, go down insiede my desktop pc and work pretty well but...only for 5 hours! Damn, i retry with 2 inverter, one form a transparency adaptor of my old scanner and another from a fan with neon...and 12 hours later is functional! I assumed the problem of my first inverter is too cheap ad the eat on the monitor plastic chassis damage the inverter, already now my monitor as 1/2 pastic chassic and the eat is dissipate quiet good... :-)

      My HP Laptop's monitor is flickering intermittently. It's only 2 years old. I wonder if it's the backlight or the inverter. Can someone help me diagnose it? A new LCD part cost $120, the inverter, $15.

      1. If I use the function keys to dim the LCD brightness to about 50%, the monitor "usually" will not flicker. But it is very hard on the eyes since it is a bit dark.

      2. If I turn the monitor to full brightness, as I like to since it's easier on the eyes, the flickering is intermittent. When it does act up, first the sections of the screen flicker horizontally to black, on and off very quickly, then eventually goes black altogether. But I can still see the inprint of the page in the background.

      Any ideas? Thanks in advance for your help.

      1 reply

      Sounds like the inverter is dying. Usually if the backlight goes you'll get funky colors or an inconsistency in the light output, whereas if the inverter goes the light with flicker, not work or dim. Swapping an inverter is very simple, usually its nothing more than removing the trim bezel (screws usually under the rubber feet around the bezel), removing a screw or two and 3 electrical connections, and then plugging the new one back in.

      "found a labeled power wire running +12VDC to the main monitor board. I momentarily pulled that to ground and found about 3.5 amps"... I'm wondering (since the only electronics knowledge I have is coming from reading stuff), is this a good/correct/safe (for the powersupply) way to find out how much power a certain component can give? I'm doing the same thing as you did on the instructable and am in the process of looking where to tap power from as well.. It seems like a logical way of finding out, I'm just figuring it's pretty much the same a short circuiting a circuit, no? thanx for the instructable!

      2 replies


      The best way to do this is to:
      Find the 12V power regulator (should look like a 3 legged transistor bolted to a chunk of aluminum), write down the part number and look up the regulator on google or a datasheet website. On the datasheet someplace there will be a current output, that's what it can provide.

      Either that or grab a resistor and do what I did above, you could calculate the voltage drop/current and figure out what it's able to provide without dead shorting it.

      Let me know if I can help with anything else.

      Oh OK, I thought you actually meant you shorted the wires - without a resistor in between and a current meter in series...<br/>So what you do is put in a resistor, measure the voltage drop over it and calculate I = U / R the current going over it? Would that be the maximum a certain point in a system can provide? Sometimes there simply isn't a datasheet to be found :)<br/><br/>I'm now looking at an old inverter from another lcd (laptop), and mine. Both have more then just ground and positive going to them, need to find out which is which (probably an enable line and light control, which would need either +3.3 or +5V)... Some of the wires are doubled (like ground and positive), the others need some more investigation. Or I might end up just buying new inverters, like in the Instructable...<br/>Maybe I'll first start off building a bench power supply off an old ATX power supply to get started, think it might come in handy after all :)<br/><br/>But thanx again for the instructable!<br/>

      Thanks Waterppk, My monitor is stating to flicker and is dimmer...looks like it's time to replace some ccfl's....thanks for the info.

      very good tutorial. i'll definately be using this tutorial soon. one question: is it the same for every monitor? do i absolutely need 2 inverters every time? theres no way i could screw up and blow the bulbs is there?

      2 replies

      Each monitor will vary. The only differences will be where to get power to run the inverter from and also how many backlight bulbs are in each monitor. You will need an inverter for each pair of bulbs in the monitor, in this case I had 4 bulbs so I needed 2 inverters, if you have 6 bulbs you'll need 3 inverters. There isn't any way to screw up unless you short the leads out of the inverter - they're running in the thousands of volts and very little current, so if you screw up it'll just make a big spark and pop a fuse :P There is no way to blow the bulbs unless you had a 2" LCD and tried powering it with this inverter, then you would damage something as the inverter would not like having a bulb that short on the output - as long as you have some reasonably sized screen you should be fine!

      ok awesome :) im looking at something within the 19" to 22" range to do this with. so they'll probably have quite a few more bulbs the higher you get up there dont you think? nice to know i cant damage anything also. im usually pretty good with electronics, so i doubt i'll screw it up, but just in case ;) thanks for the fast reply, hopefully i'll be able to follow these instructions in a few days and see if i can fix some monitors! PS: i cant believe that the cathode kit is only $3 but the shipping is $7 :P

      I have an old toshiba satelite that had a broken screen. I used it for a while hooked up to a external monitor. I recently got a new satelite that had a fried board from a friend. The wires are a little different but is there a way to swap the screen to the one that works. Is there a color code for what wires are what.

      i recently bought 5 defunkt 17" lcd's from my local computer recycle store. they are CTX business models, nice ones to, i think there only about 2 years old. they each had "no power" written with crayon on the top of the bezel just above the screen. So i thought they don't actually open them up and check, so, i assumed it was the inverters. (each has two bulbs) So they let me plug each one up and check for myself, i could see the on-screen menu on each one, but no light, so i knew it was the inverters. he let me have all 5 for $40 (8 bucks apiece, what a deal!) I've got one to work, witch im currently using now, by swapping the inverter out of a REALLY old lcd (1999) he let me have about 3 months ago. ironically, the plugs were the same and it's worked for a week now, the other four, i will use this instructable and get them all working. (i have dual nvidia cards, up to four monitors)! This will save me a ton of money.

      Nice instructable but in step 4, the distance between the primary and secondary side should not be made smaller by putting screws there. I'd rather fix the supplies with double sided tape (3M red) or hot glue. Otherwise really good idea.

      Great instructable, very insightful, but didn't work for me when I did the same thing last month (to repair 6 CCFL 20" monitor) . It worked for a few minutes, but later the LCD flickered and smoke came out from back of the monitor. It may be because there was a short somewhere since I didn't have the proper connectors to go with HV bulb ends. BTW, I think LCD monitor CCFLs run at about 900V, but computer case CCFLs run at about 690V. I may be wrong, but this may be another reason that my experiment ended with smoke and stink. Good luck! Koray.

      1 reply

      Sounds like something shorted out ;) Usually if the inverter isn't enough to get the tube illuminated it just won't light up, but the inverter typically doesn't melt down or anything. I ended up soldering and hot gluing the leads on the inverter to make sure they weren't going anyplace because I didn't have the proper connectors.