Replacing CCFL's - there must be a better way ?

[SAE140]

I've just changed the backlight CCFL's on two TP600 13.3" displays. The link to Dale's webpages was useful - thanks for that.

Luckily I dismantled one of the displays before ordering the tubes. Several Ebay sellers had told me I needed a 275mm tube - but not so - the ideal size would be 200-202 mm, but the nearest available stock size is 205mm - which is a pity - as a couple of millimetres less would make replacement easier (imho).

All-in-all I found dismantling the display to be more difficult than Dale implies - it certainly isn't a cakewalk: the front plastic bezel was well glued down, and eventually I found it necessary to remove the screen from the base unit before making any progress.
On Dale's site, he comments: "You have to wrangle the display under the two hook clips in the cover, then slide it up to the top. At that point, the part of the screen nearest the keyboard will lay flat in the cover."
Well, not quite. With some difficulty, the two hooks can be removed (by wiggling 'em downwards, and then pulling 'em out - see the Hardware Maintenance Manual) which makes removal and replacement of the LCD panel a lot easier.

Bearing in mind that the most challenging part of the job was extracting and re-fitting the gold-coloured ccfl reflector, and with one screen I even experienced problems with a few dirt particles dropping between backlight glass and LCD, if I tackled this job again I'd try not to dismantle or even open-up the LCD panel 'sandwich', but instead I'd remove some of the white plastic framing at either end of the reflector in order to slide the ccfl tube out, after desoldering the upper connection in situ. My guess would be that using a red-hot modelling knife blade would be the easiest way to remove the plastic to gain access without stressing the panel.

However, I don't plan on repairing any more screens right now - two is quite enough for one lifetime - but if anyone's got a scrap one to experiment with ...

Colin

[Harryc]

Colin, great idea on gaining access to the CCFL's by cutting or burning away the white plastic of the LCD frame at the CCFL end points. Never thought of that . The question is, would there be enough room in the reflector tray to slide the old CCFL out through the ends and install the new one the same way? If that part would work, you could even dremel the plastic away and replace it with white silicone after the job is done. The other problem is the wire routing, how would that work. IIRC, the wire runs internal to the frame as well, but outside of the reflector. I suppose if you got a long enough piece of wire you could just route it outside of the LCD frame. Flexview LCD's are much easier because you can just lift the LCD out of the metal frame on one end and the end caps are right there....so is the wire. My other thought is that if you can cut away enough plastic on both ends to be able to get a soldering iron to the CCFL terminals, you could just reuse the original wire. Now I wish I had an old LCD around here to play with ...

[jdhurst]

A different approach (because I have no skill in what you tried), is to replace the whole display (at least in the "T" series). I had a backlight go intermittent, purchased a display from eBay and replaced the whole unit. Much easier, and only a bit more expensive.

Now, some time later, I broke a hinge and salvaged a hinge from the old (intermittent) display unit. Replacing a hinge is not trivial either, but much easier than replacing a backlight.
... JDH

[Bookworm]

Tubes? ThinkPads use tubes? Wait 'till the antique radio guys hear about this.

I hope mine never need changing. If I tried what you guys are talking about...

I do have one suggestion though: If you know someone who is into scale model building, especialy model railroading, and they're better at it than I am, (my poor layout ) ask them for help. These guys build tiny models out of parts so tiny and delicate, that if they're really good at it, taking a whole thinkpad apart and putting it back together might be easy. Model railroaders not only deal with tiny plastic details (and enjoy it) but also tiny electric motors, gears, etc., so most of us can even solder.

[jdhurst]

@bookworm:

1. The backlight is a flourescent tube so far as I know (never seen one)
2. I just purchased a half-dozen 6CB6A tubes to fix my HP VTVM.
3. Have you checked my posts? I am deep into HO model railroading complete with Digital Command Control.
4. I purchased a repair kit from Tektronix once to fix a P6045 FET Probe. I blew up the front-end FET on a tube device (dumb on my part). The circuit board is the size of a cigarette roughly. A beggar to fix, but I did Under a magnifying glass) and it still works. 10Mohm input impedance at 1:1 voltage ratio at the scope end. Sweet.
5. As I noted in this thread, I replaced a hinge in my T41.

But I would not want to try a backlight repair. ... JDH

[SAE140]

Colin, great idea on gaining access to the CCFL's by cutting or burning away the white plastic of the LCD frame at the CCFL end points. Never thought of that :). The question is, would there be enough room in the reflector tray to slide the old CCFL out through the ends and install the new one the same way? If that part would work, you could even dremel the plastic away and replace it with white silicone after the job is done. The other problem is the wire routing, how would that work. IIRC, the wire runs internal to the frame as well, but outside of the reflector. I suppose if you got a long enough piece of wire you could just route it outside of the LCD frame. Flexview LCD's are much easier because you can just lift the LCD out of the metal frame on one end and the end caps are right there....so is the wire. My other thought is that if you can cut away enough plastic on both ends to be able to get a soldering iron to the CCFL terminals, you could just reuse the original wire. Now I wish I had an old LCD around here to play with ...

Ok - bearing in mind that this is only armchair engineering at this stage ...

To remind you about the 600 TFT screens (can't comment on any others):
the ccfl is powered via two wires running from a connector, through a short length of spiral wrap, with the pink wire (silicone insulation) passing through one leg of an inverted-Y access slot in the white plastic frame, and then soldered to the lower end of the ccfl tube. The black return wire passes through the other leg of the Y-shaped access slot, and then is routed (externally to the reflector) up to the top end of the ccfl tube where the solder joint is covered by a tiny right-angle rubber boot. Along it's route, this black wire is secured to the back of the white casing by 2 white plastic 'tabs' which are held in place by tiny x-head screws.

Ok - so my thinking is this:
1) prepare a flat work surface (kitchen worktop would be ideal), and cover with a tea-towel or similar soft material.
2) remove the LCD module from the lid plastics, then remove the aluminium surround band by bending back the tabs, etc.
3) taking care not to distort the unprotected module 'sandwich', lie it face down onto the soft cloth. It will not be lifted up again until the job is completed.
4) remove the 2 tabs holding the black return wire in place
5) taking care not to burn the wires, with a red-hot blade make two cuts in the form of a 'V' to remove enough white plastic casing to enable access to the ccfl tube at either end. It won't need to be a big V - just enough to pass a 2.5mm tube through. Personally I wouldn't use a Dremel, as although this would normally be good engineering practice, in this case I'd want to avoid any vibration or dust.
A red-hot blade may sound barbaric - but it's the kindest option I can think of. If you're working in the kitchen, there'll be a stink, so wait until 'her indoors' is out shopping (!).
6) push the pink silicone wire UP into the reflector housing, which of course will push the tube out of the other end. Ideally some 10 mm or so of tube should stick out, as you'll need to hold the tube between finger and thumb in order to lift-away the right-angle rubber boot. Then de-solder the exposed joint.
7) pull the ccfl tube out of the reflector, then de-solder the remaining connection.
8) re-fitting would be a reversal of the above.
9) as you suggest, some silicone or even a dab of 5 min epoxy would be useful to repair the damage.

Two things I'm not happy about: one is the weakening of the frame by the 2 'V' cuts - but, bearing in mind that the major strength of the module comes from the backlight glass itself, maybe this isn't an issue, especially if repaired before lifting the panel up. The second concern is the removal of the inverted-Y slot, which 'grips' the wires as they leave the module. I don't know how important that is. Again, silicone or epoxy might be the answer here.

The bottom-line is that I'd really like to try this method, so I'm now on the hunt for a busted screen to play with.


(bookworm) Tubes? ThinkPads use tubes? Wait 'till the antique radio guys hear about this.

Ah - in Britain we call those little central heating devices used in old radios "valves" (which is what they actually DO - if you think about it (?)) - so I claim exemption. The other 'Tube' we have is London's underground train system.

(Yup - divided by a common language ...)


(jdhurst) The backlight is a flourescent tube so far as I know (never seen one)

Spot on - they are glass tubes, thinner than a wire coathanger and extremely fragile, so I was a tad worried about 'em being shipped halfway across the world. But they arrived ok inside bent plastic straws inside a short length of plastic plumbing pipe - the bent straws pressing the 'tubes' against the side of the pipe, thus preventing movement in transit. Ingenious.

'best, Colin

[Harryc]

If you try this, take pictures please .