TFT Backlight replacement

[Mark Carver]

I have a Benq 731 17 inch TFT screen, it's almost two years old. I'm away from home at the moment but my wife told me over the phone last night that, quote, "the screen has a dark strip two inches wide down the right hand side" She says that there's not a sharp line line dividing the dark patch from the rest of image, so I've discounted any faults with the individual pixel elements (?).

Doing some Googling it seems that TFT screens have a backlight tube ? I found this firm that do replacements,

but at 200 quid for a 17inch screen ! it's not worth the bother and expence (if that's the problem anyway).

Anybody got any experience or thoughts ?

TIA

[Tim Mitchell]

In article , Mark Carver writes

Yes, they have a backlight tube, but normally only one or two tubes with a reflector/diffuser arrangement to do the entire screen. So when the backlight fails you normally either lose the whole screen illumination or half of it. But maybe your screen has more.

I have tried to replace one in a laptop, and they are tiny (2mm diameter glass tube) and very fragile at the ends. Not to mention the problems of dismantling the panel in the first place. The other possibility is failure of the inverter module which generates the high voltage to drive the tube. This is easier to replace, being outside the LCD panel. If there's more than one driver you can test them by swapping them around.

[Mike Harrison]

Larger panels can have more than 2 tubes, especially on desktop monitors where thickness is not as limited as on a laptop. They are also probably not as thin as laptop ones.

Here are some tube sources :

[Steven Campbell]

Have you read that companies terms? "Note: We will supply backlights as a supply only with no warranty, we will not accept a return for any backlight that is broken, or faulty, under any circumstances, or if you find out that the backlight is not the problem "(they are extremely fragile, and easily damaged.) If you want a warranty, send the unit in for our fixed price repair service"

That sounds to me like they wouldn't even replace it if it was broke in transit!! Avoid.

At a cost of £200 for a tube is it worthwhile, considering you can get a 17" TFT from aria.co.uk for under £100 now?

details about BenQ warranties, If I'm reading it correct then you should have a 3 year warranty.

Steven.

[Mike Harrison]

thickness is not as

these people in the past :

[vortex2]

We recently purchased a stack of these

for the office and the image fidelity (for the price) is completely awesome....making previous generation TFT's look lousy.

Now I have to wait for my 4 year old home 17" TFT monitor to fail so I can upgrade.

D

[T i m]

I know we are wandering off topic a bit here but what 'realworld' difference is there between Analogue and Digital input to these TFT's please?

I ensured both the new video cards (my and my daughters machines) had DV outputs, just in case it went that way only in the future?

All the best ..

T i m

[vortex2]

These LG monitors we bought have no DVI...(none of our PC's have DVI anyhow)..I'm hard pressed to believe the image fidelity could be any better even with DVI though.

D

[Mike Harrison]

On an analogue interface, the image is converted to a voltage, then converted back to digital in the monitor, which will inevitably increase noise. Probably a more important issue however is that the monitor needs to re-generate an accurate and stable pixel clock timing signal from the analogue sync signal - if it doesn't get this quite right, resolution and sharpness will deteriorate rapidly as the LCD pixels will not 'line up' with the generated image. I must say that as an electronics engineer, I'm rather impressed at how well the monitors I've seen manage to do this, but it can never be as good as a digital link, and will sometimes be a lot worse. I would certainly not want to use anything above 1024x768 on an analogue interface.

[Tim Mitchell]

Mine is 1280x1024 on an analogue VGA interface and it is fine. However it seems to depend on the graphics card, another PC here blurs the pixels when some graphics operations occur (presumably due to the video timing changing slightly).

With DVI you are always sure of the pixels in the video being perfectly lined up with the physical pixels on the LCD panel.

[Mark Carver]

Indeed

Thanks for that, I'll pursue that avenue when I return home. I should still have the receipt, (I bought the monitor in a Tiny store !) but if not it seems from Benq's T+Cs that they can still accept claims based upon the manufacturing date. If all else fails that LG model mentioned by Vortex2 looks tempting !

Thanks again to all for you responces

[<me9]

I can compare both inputs on mine. (a Dell TFT) I can't see any difference.

[usenet]

I've been running 1600x1200 on analog for some years now, it's fine. I used to have an LG Flatron CRT screen which I have just upgraded to a Dell 2001FP which is really excellent. It has DVI and analog inputs. I recently ran it from another computer which happens to have a DVI output and, to be quite honest, I didn't see any immediate difference.

[Rob Morley]

My guess is that it will eventually make kit cheaper because fewer components are required with digital, but until it's the standard connection I don't think it will make much difference.

[Andy Hall]

It's substantially better at higher resolutions because the interfacing is done entirely digitally and not through digital to analogue and back again.

[fred]

In article , T i m writes

If you want to have the pc a long way from the monitor it should make for a better quality picture and cheaper cabling. Having your pcs in a (well ventilated) cupboard somewhere could save you a bit of space & keep the noise down, useful for anti-theft too.

[John Rumm]

Benq do a three year swap out warrenty on flat panel monitors. So give em a call and they will send you a new one! ;-)

[David Hearn]

A friend has a Dell 1920x1440 large widescreen display (like the large Apple Cinema displays) which has DVI and VGA inputs. He uses it with a Mac with DVI and a PC/laptop with VGA. He says there's a remarkable difference between the DVI and VGA inputs, with the VGA showing ghosting and blurriness which disappears when on DVI. I suspect this is partly due to the resolution, but also the physical size of the display (19"+ widescreen I think)

I use 1600x1200 on a 19" CRT with no problems.

D

[Alex (YMG)]

"John Rumm" wrote

Are you sure that backlight replacement won't specifically be an exclusion of this warranty? I saw something mentioning this on a Sony TFT I just purchased, but perhaps it was relating to them dying through wear and tear and not a malfunction.

Alex

[John Rumm]

I don't recall any restrictions, but then again it has been quit a while since I last sold Benq TFTs so can't remember with absolute cetainty. No harm is asking either way.