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DIY LCD Backlight Repair
Bill Nye (not the science guy) writes to tell us that InventGeek has an interesting article on do it yourself LCD backlight repair. From the overview: "Those of us that have used LCD monitors for a while know that over time the backlight starts to dim and will eventually completely fail. Leaving you with some electronic scrap that you could sell on eBay for 35 bucks or so. Well for less than $20.00 and about a half hour of your time you can replace the backlight and rejuvenate that monitor to as good as new condition."
Just FYI Fry's carries everything you need, from those special power modulators to mini flourescent tubes to repair your LCD's.
I have an old HP craptop, about three years old now. I was able to get a new inverter for the screen backlight for about 40 bucks from them... took off the front panel, put in the inverter (simple plugs), and it all worked fine. Ask your laptop maker if they can sell you the part without the service. It is an easy DIY fix.
Whoever stated that signature sizes should be limited to one hundred and twenty characters can just go ahead and kiss my
Actually there aren't any large capacitors in the backlight of TFTs. I've worked with some invertors and they don't peak at more than 1000V and normally operate at 600V.
The key trick with this jazz is to find the part number and buy a new one. Much quicker.
Yes, I've been able to fix multiple different laptop screens this same way as well. IBM T21's T41's etc... Most laptop lcd are relativly easy to dismantale is you've got a sharp set of #000, #00, and #0 phillips screwdrivers. I found almost all my bulbs from http://lcdpart.com/. I found there prices to be really affordable as well, $10 for the 14"-14.5" bulb! You'd be surprised how easy this whole procedure is if you can solder a few wires. ;-)
I've replaced backlights in powerbooks, both with official Apple parts (it has been
some years since THAT was available) and with generic lamps from third-party
suppliers.
Firstly, remember the lighting uniformity is HARD TO ENSURE. For the thinnest
displays (like modern Powerbooks) it's unlikely you can even FIND a source for the
lamp (2mm tubes are common, the available units are usually 4mm or the wrong length
or both), and if you do find it, getting the foam/mylar/backplate sandwiched
after replacement is going to be a chore. Expect a splotchy result.
The most recent display I had any good luck with was one of the Powerbook 500 series
(about 1995 vintage). That required a little work with a Dremel tool to fit the
available lamp (which was about 5mm too long), and took a bit of care during
disassembly. The plastic display bezel got brittle with age by the time
the unit was both out of warranty and failing to light up.
The 'supported' solution is to ship the unit to the manufacturer for
rebuild. Presumably, they DO have the right parts and a lot of patience.
My advice: pay the $400 (or whatever).
There's a lot less toxin in the lamp than in your last filling. More worrisome is the
wiring to the tube, which wants about 2000V to start. The wires are funny, rubbery
things, possibly a hightech silicone.
One very useful tool was a spare power supply; if your backlight was on a connector,
you can test it on known-good power that way, and an inverter replacement is a LOT
easier than lamp rebuild.
Ok, some comments from somebody who works with cold-cathode lamps.
First the mercury is pretty much a non-issue, it only escapes if you break the lamp and the ammount is miniscule anyway. As long as you are in a well ventilated area don't worry at all.
Second the manufacturer fits high-performance cold cathode lamps, subsituting hobby grade lamps is going to give you terrible colour rendering (I've seen cheap lamps that were more pink than white), and also the light output will be _considerably_ lower.
And last if you use the original inverter you are going to be overdriving the new lamp horribly. So the colour will suffer and the life will be affected (plus the lamps will run very hot indeed).
These are not at all like incandesent lamps, the inverters are tuned to the lamp parameters and cheaper/different lamps are likely to not match the inverter very well at all.
I get a kick out of the seemingly sarcastic sounding "how do I fix this" things that I see here, and have seen in many other places. Fact is that with "tech" moving at such a pace these days, people (those with lots of ready-cash) are more likely to just dump this stuff into the trash (and landfills) and just go buy something new, rather than fix it.
I have been doing this sort of thing now since something like 1998 with relative ease. The only hassle has been scrounging up the cold cathode tubes that are large enough to cover the screens like the originals. Some will note that these have been conspicuously absent from the after-market parts shelves up until a couple years ago when it became fashionable to "light up" your box with colored lights. You quite literally had to know how to find them prior to this because they did not want them to be found. Any technician worth his salt knew that if you could replace the tube (and it wasn't hard at all to do), you could revive a computer or screen and make some money rather than having the user tossing this item into the landfills and spending whopping amounts of cash on "new models". (Yea, thats an accusation about the major OEM players; NEC, Toshiba and Sanyo; IMO)
As for the brightness issue... If you've replaced the tube and it's still dim, it's nothing more than the capacitors failing on your DC to AC converter boards. The caps are rated so close to tolarance in manufacture that with heat buildup and time, they fail prematurely. I've successfully pulled the boards and replaced the caps to bring them back to life assuming the transistors and IC have not failed. The brightness issue is nothing more than deviating the PWM (pulse width modulation) of the AC out to the tube. This change in PWM changes the resonance for the tube's circuit and hence it's brightness level is related to the PWM circuit efficiency. When the caps become leaky and dry, the circuit can no longer approach its normal or calculated PWM value or resonance, and hence your screen no longer can get as bright as it used to. Color temperature changed screens are the same issue. The cc tube is just more sensative to the current PWM and is lighting up in a particular color temperature; usually a brown or reddish hue.
Theoretically these LCD screens can last for many, many years if you want to simply replace these tubes and fix their circuits when they fail. Based on past history and my direct attempts to get these cc tubes and parts from several OEM's directly; replacing the entire LCD screen as a complete part; at a hefty price I might add; is generally your ONLY choice. More often than not, the replacement LCD panel cost more than the whole monitor did new!!!
I expect however that replacing the cc tubes as a standard repair will not be available because the folks manufacturing the LCD screens seem to control the access and if there is limited or no access to the parts, you only have access to "NEW" screens... or obviously new monitors!
Your market... you decide!!
Cheers;
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I work in the fluorescent tube recycling industry. The hazard from the tiny 2mm-4mm back light is negligible. I've done tests with a Jerome type meter, and they read way below (almost non-existent readings) OSHA limits for airborne exposure. OSHA states that you need a respirator for a time weighted average exposure above .1mg Hg/cubic meter. You need to break a lot of tubes to get close to this, probably hundreds of the tiny back light kind. Mercury does vaporize at room temperatures! It doesn't need to be heated!
The type of mercury used in fluorescents is the inorganic kind, which is a hell of a lot less dangerous than organic mercury. Inorganic mercury will be filtered out of your blood and come out in your urine, just like most toxins, but organic mercury is small enough to find it's way into your body fats and stay there for good. Organic mercury is usually what you find in fish.
Mercury Vapor
NIOSH/OSHA Mercury Vapor Health Guideline
Cthulhu Saves.