How to fix dimmed LCD PC Monitor? - Page 1
Forum section: electronics / repair

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 13, 2016, 11:41:15 am
content: hi. i have Acer X233H 23" pc lcd monitor. now its becoming dimmer and dimmer. its still functional it got nice picture etc, but i cranked the brightness to 100% but its still dimmer. where do i fix? or at least give me some clue of how the circuit section looks like. it must be somewhere on the board. thanks.

author: bktemp
author_rank: Super Contributor
timestamp: November 13, 2016, 12:36:08 pm
content: Most likely the CCFLs are worn out.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: November 13, 2016, 02:35:48 pm
content: I used to do CCFL retrofits using LED strips for my commercial touch screen customers. If you look around you may find a place to sell you the kit.But then why do it today when a normal consumer monitor can be gotten for nearly nothing?

author: wraper
author_rank: Unknown
timestamp: November 13, 2016, 03:25:00 pm
content: Quote from: Quarlo Klobrigney on November 13, 2016, 02:35:48 pmAnd color reproduction will go down the drain.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: November 13, 2016, 03:53:31 pm
content: Quote from: wraper on November 13, 2016, 03:25:00 pmFor POS customers it didn't matter to them. For the consumer, there's always color balancing in the monitor or the computer.

author: wraper
author_rank: Unknown
timestamp: November 13, 2016, 04:11:04 pm
content: Quote from: Quarlo Klobrigney on November 13, 2016, 03:53:31 pmWhich would not help much to correct color reproduction to a decent level.

author: wraper
author_rank: Unknown
timestamp: November 13, 2016, 04:21:25 pm
content: comparison.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 13, 2016, 07:38:35 pm
content: Quote from: bktemp on November 13, 2016, 12:36:08 pmthanks fellows but... can it be easily replacable? is it located in the LCD panel? or can i just increase the current through it by changing current limit resistor somewhere? and of course along with changing the current pass transistor elements?... in case getting CCFL supply is difficult or i dont have necesarry skill or tools to replace the CCFL...Quote from: wraper on November 13, 2016, 03:25:00 pmsince color reproduction is mentioned... fyi i have spyder monitor calibrator, so i think it may help in case my monitor color is off... no?Quote from: Quarlo Klobrigney on November 13, 2016, 02:35:48 pmi dont think 23" lcd and greater will cost me near nothing... and throwing away a still functional (just degraded light level) monitor is feel like blasphemy to me... :|

author: bktemp
author_rank: Super Contributor
timestamp: November 13, 2016, 08:05:26 pm
content: Quote from: Mechatrommer on November 13, 2016, 07:38:35 pmThat depends on your skills. It is doable but probably not worth it, because LED screens are cheap and draw much less power.QuoteYes.If you are lucky, you can access the CCFLs from the back, but sometimes you have to disassemble the complete panel to access the CCFLs.QuoteThis will probably damage the power supply. And it won't last long.QuoteCCFLs are fluorescent tubes running at up to 1kV (the ignition voltage is even higher).

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: November 13, 2016, 08:28:32 pm
content: Just like Fluorescent lamps in an overhead fixture that turn black on the ends, so do your CCFL's in the monitor. The LED kits I were using, were in the vicinity of $50 or so, and you have to know what you are doing not to bollocks-up the install (bloody fiddly fragile things).So is it all worth it, probably for the experience, definitely not for the money. I've seen many a large monitor on trash day go out only to find that the SMPS dongle power supply (redundant words I know) was bad. Cheap to fix. Buy another.Unless you live in the woods or Canada (same thing) (I don't know about Malaysia) just put out a roadside BOLO to your friends and family. Their reward will be cheap, a thank youUnfortunately you and I suffer from the same malady, "I hate to throw this out. Do you know how much this cost (me)?"

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 13, 2016, 10:56:14 pm
content: Quote from: bktemp on November 13, 2016, 08:05:26 pmyup maybe. but i can buy some more time of the lcd life, instead of just throw it to the bin today... i'll see what i can do when i have free time, at least now i have a slight clue on where to tinker later. if the step up transformer is the culprit (like my earlier monitor) then it deserve its place in the bin due to difficulty of getting the part. thanks to all you guys for suggestions.. my latest24"27" samsung S27E310 led monitor priced somewhere $300 few months ago from local shop iirc, unlikely to get scammed because the shop is reputable and well known. although i can see some 22" led monitor priced just $100+ in the net, but i believe the models are not available locally. so $300 is not quite cheap, but well, its an investment if i have to. fwiw...edit: sorry S27E310 is a 27" led monitor, no wonder its price...

author: Rasz
author_rank: Super Contributor
timestamp: November 15, 2016, 10:18:53 am
content: first thing you should do is open it up, make clear pictures of PCBs and upload here, we are not magicians with crystal balls of clairvoyancesometimes you get lucky and its just a faulty connection to the lamp, but that mostly results in flickerfaulty lamps usually manifest in weird colors on the edges, replacing lamps is where I draw a lineyou might have a dying ccfl inverter, does your monitor whine?you are ~1.5K km from the manufacturing center of the world, you should have zero problem sourcing cheap electronicsif you are cheap and in need of a bargain look for used one on second hand market

author: eugenenine
author_rank: Frequent Contributor
timestamp: November 15, 2016, 12:41:22 pm
content: Most of the time getting dim over time is the ccfl tube. They are ~$10-$20 from digikey last time I bought one. I've replaced them in a few laptops over the years. Newer monitors/TV's are getting to where they have more than 1 (well were having more than one before they switched to led's).Its a pretty easy fix but a little time consuming since you are disassembling the lcd panel to get to the tube.

author: mariush
author_rank: Super Contributor
timestamp: November 15, 2016, 01:06:38 pm
content: LCD monitors usually have four CFFL tubes , two on top and two on bottom, and they work in pairs.As they age, they turn from white to darker whites with a bit of yellowish tint.To replace them, you would have to open the monitor completely, get the whole lcd panel out, turn it around and remove the metal case, then remove the protective glass, the actual lcd panel, and you gain access to the cffl tubes.After replacement, you also have to be careful to not put too much pressure on the lcd panel or to crack the glass when putting the whole stack back.See here pictures of how the CFFL tubes look inside, and you can see in other folders on the site various failure modes of cffl tubes :http://s807.photobucket.com/user/budm/library/Bad%20backlight%20lamp?sort=3&page=1You can separate cffl tubes from stores or eBay but they're expensive and you'd need at least pairs, and ideally you'd replace all 4 at a time.. the boards have current sensors on the two separate outputs ( 2 backlight inverter outputs, two cffl tubes in series per inverter output) and sometimes if a pair uses much more current than the other the backlight is turned off (it's meant to protect the high frequency transformers from overheating when there's too much current used by aging cffl tubes).So it gets kind of expensive.You can also buy from eBay LED strips and install two led strips instead of the cffl tubes and there's inverter replacement boards (you just put the board inside the monitor, power it from 12-20v the inverter uses normally and just connect the backlight on/off and adjust light intensity wires from inverter to the new board, basically you're taking the inverter on the power supply completely out of the equation.With led strips you may get wrong colors as other said above, but it should be cheaper than four cffl tubes.

author: CJay
author_rank: Super Contributor
timestamp: November 15, 2016, 03:06:37 pm
content: Plenty of repair kits out there for CCFL tubes, they're not too expensive either, googling your screen model number and ccfl repair kit throws up quite a few results.I've salvaged the LED strips from smashed laptop displays which I intend to fit to the screen in my spectrum analyser but I'm now really interested to know if the original laptop screens were in some way different to compensate for the LED spectrum or if the LEDs in the screens were 'matched'.I've also managed to find a pair of CCFLs which I think are suitable.