Dim Display for LCD Monitor -- Replacing Backlight Question - Page 1
Forum section: electronics / beginners

author: crosis
author_rank: Newbie
timestamp: November 03, 2018, 09:06:12 pm
content: I'm beginning my journey down the road to repairing a Dell E2210 LCD monitor. The screen is very dim but otherwise works.After searching for bad capacitors and failing i'm now taking the advice from this forum to explore replacing a possibly bad CCFL backlight tube. I opened up the backpanel (LGLM220WE1-TLP4) and located the 2 very small backlights -- one running horizontally along the top and another along the bottom. The entire backlight (from white end cap to end cap) measures about 490mm length (not sure the actual CCFL tube size since it enters the endcap) and 2.45mm diameter.Inspecting the tubes, one tube has a serious burnt stain at the endcap. When i plug the light in it does not turn on. For the other tube with no visible signs of problems, it turns on but only half of it lights up.Is there a way to open the endcaps to replace just he CCFL bulb or must i find a replacement backlight assembly complete with endcap and wiring?I assume the electrical requirement for a similar sized tube would all be the same as long as the wiring connector is similar.

author: Buriedcode
author_rank: Super Contributor
timestamp: November 03, 2018, 09:19:59 pm
content: I would try and find the assembly rather than just the tube, often (at least in my limited experience) there isn't much of a price difference between the two. I'm sure there is a way to open up the assembly, but often there are many layers of tape, reflector material, and sealant holding it in place. Try ebay for the assembly for your specific monitor, if that fails then search for the tube itself based on length and diameter.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2018, 09:23:36 pm
content: Sure, you can replace just the tube, those caps normally just pop out. It looks like they're in pretty bad shape though, the plastic is heavily discolored and it has melted due to the worn out cathodes running hot. You can also get LED retrofits that will work in many monitors though the quality varies.Something you should check though, I've scrapped old monitors and found that the rest of the optics in the backlight were also heavily yellowed from the UV, one was so bad that the plastic diffusers crumbled to bits when I touched them. If the light spreader and diffusers are yellowed the display will look icky and brownish no matter what.

author: floobydust
author_rank: Super Contributor
timestamp: November 03, 2018, 09:27:38 pm
content: ccfl warehousehas the silicone end-caps, and aliexpress etc.

author: crosis
author_rank: Newbie
timestamp: November 04, 2018, 05:47:32 am
content: Thanks guys. I will explore getting replacement assemblies.

author: mariush
author_rank: Super Contributor
timestamp: November 04, 2018, 06:00:46 am
content: You can find them but they're kind of expensive, and you should buy always in pairs and replace the one at the bottom as well.Also you risk them being damaged during transport.One alternative solution would be to replace everything with LED lightning, here's a kit :https://www.ebay.com/itm/Universal-Highlight-Dimmable-LED-LED-Light-For-LCD-Monitor-2-LED-Strips-C3W8/273267189421?epid=15020136190&hash=item3f9ffe66ad:g:UtwAAOSwO9RbGPc7:rk:5:pf:0It's 533mm long strips and 4mm wide (make sure your channel is wide enough) , but can be cut, they're made of 3 led segments, so after every 3 leds you can cut the strip.Also included is the circuit board so you can simply connect the voltage, ground, brightness adjust and enable wires to the right places on the power supply board (hook them to the connector going into the dsplay board)// why you may have to replace both tubes? In bigger monitors, usually there's 2 pairs of tubes, and the backlight inverter has some protections and if one pair uses more current than the other, it turns off. As these fluorescent tubes age, they use more current so if you replace just one tube, they may have uneven current consumption.

author: crosis
author_rank: Newbie
timestamp: November 05, 2018, 04:04:59 am
content: UPDATEJust to recap, the monitor was working fine however the display was very dim. I went ahead and opened it up to determine if the issue was with the backlight CCFL. On investigation the problem was in fact dead / partially illuminated CCFL tubes. GREAT.I decided to put everything back together again since whatever suggested replacement i do order will take a few weeks to arrive. Once back together i turned on the display to see a NEW PROBLEM -- see photos below. There is a white bar running vertically the entire length of the monitor. The left edge of the white bar begins exactly at center of the screen then expands toward the right for 2.75". In the photos i do not have a DVI-D cable attached so it is typically bouncing around the default multicolor informational window stating there is no signal. Once this "info window" crosses the white line it disappears. Bits of it can be seen in the black areas once the info window scrolls there. When the info window finally scrolls to the right side of the bar the text appears glitched until it scrolls beyond 2 inches past the white bar where it returns back to normal english text. When i have the DVI cable attached you can see the on-screen image distorted just after the white bar for 2 inches.So with that said what the heck did i mess up this time? Thanks for any suggestions.

author: mariush
author_rank: Super Contributor
timestamp: November 05, 2018, 05:36:48 am
content: If i were to guess, when you put the panel back together you either pressed too hard or moved the tiny circuit board on the back of the panel too hard and one of those flex strips that look like kaptop tape/plastic doesn't make proper contact with the lcd panel anymore, maybe it's partially unglued.If you don't know what I mean, it's these strips like the one in the attached picture. May be different on your monitor

author: james_s
author_rank: Super Contributor
timestamp: November 05, 2018, 06:20:01 am
content: You can occasionally fix it by putting a piece of paper or something over where the ribbon is bonded to the glass and rub a hot soldering iron across it. There's a good chance the monitor is scrap now though, those ribbons are really delicate and require extreme care when taking one of these apart.