LCD screen wont light up

19 inch lcd tv set . I can see the picture in there very dark just like the backlights are not working . I took the screen apart and hooked up the lights and they were very bright . So the lights and screen are working . Why wont it light up ?
Reply to
Ken G.
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Ken G. ha scritto:

Inverter broken. Slang

Reply to
Slang

Read the whole post . I said the lights are working

Reply to
Ken G.

Huh? Why should I re-read what post?

I think we all know somewhere that the lights _aren't_ working.

Reply to
Spam Trap

I decided to hold off commenting, because I felt ignorant. But since you don't seem to be getting any useful answers, maybe I should throw in my two cents...

If the light is working, but the image is extremely dark, that suggests there's something seriously wrong with the driver circuitry. That would not be a quick 'n easy fix.

Reply to
William Sommerwerck

If the lights are working and the display is dark, this is normaly a fault with the panel driver, or part of the supply to the panel itself. This is serviced with board substitution.

The main drivers for the panel are embedded in to the rear surface of the display itself. This type of fix is to change the panel. The driver and power supply board should be tried first.

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JANA
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Reply to
JANA

From having repaired laptops with dark displays by replacing the inverter, the inverter was always a small circuit card separate from the lights. I don't know if LCD TV's are similar. But, if they are similar, then Slang would seem to have a point in suggesting the inverter may be broken...the inverter, not the lights.

Reply to
Fabian Fuller

Having repaired a few thousand IBM Thinkpads over the last five or six years, I agree that it is probably the inverter. On an IBM, and probably many if not most other brands, it is a small narrow card mounted under the LCD Panel. It is also relatively inexpensive.

Henry Mydlarz

Reply to
hemyd

I think by "lights are working", he means they light up from the inverter in the normal manner but somehow the LCD panel is still very dark.

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Reply to
Sam Goldwasser

Maybe the lights are lighting up but only dimly? We need more information.

Reply to
James Sweet

Ok i didnt want to get to long winded .

First i have worked on around 40 or 50 LCD monitor/tv and little portable DVD players and have seen many different problems . That said The subject tv when turned on has a picture exactly like a monitor with no backights , you can hardly see it at all .

I took the screen apart meaning i took the LCD glass panel off of the frame and away from the backlights . I hooked the now no LCD glass backlight frame up to the tv set and turned it on and watched the tiny thin bulbs light up bright .. just like any other i have tried this on .

I know what the inverter is , it`s working because the bulbs are very bright . So bright it was hard on my eyes . So ... the screen is showing a picture ( as above ) and the lights and inverter are all working but the light is not shining through the LCD glass screen .

Screen drivers were mentioned . I would guess this is the problem .

Reply to
Ken G.

Are your brightness and contrast buttons working? I had a sony TFT which had a burned transistor in the interface of the control buttons causing no button pressing at all and in my case the screen was on maximum brightness. Replacing the transistor fixed the monitor.

Cheetah

Reply to
CheetahHugger

I was beginning to think it was just me. The OP did indeed say that the lamps were alight and were "very bright".

That would certainly seem to rule out a problem with either the lamps, or the inverter driving them. If there is a visible image - even though it is of course very dark - from just the ambient room lighting, again as the OP says there is in his first post, that would suggest that the panel drivers are working. That makes it a bit of a mystery as to why the light from the lamps is not correctly backlighting the panel to produce a 'normal' picture. About the only thing that I can think of is that someone has had it apart before, and assembled it somehow wrongly such that the light is being blocked from getting into the lightguides behind the panel. The only other possibility that I can think of is that there is a problem with the wiring to the inverter, or a bad joint or crack on the inverter board, such that it does not work and the lamps do not light, when it is all sandwiched back together.

Arfa

Reply to
Arfa Daily

That's a good thought - I hadn't considered that it might in fact be stuck at absolute minimum brightness. If you shine a light at the front of the panel, and alter the contrast / brightness settings, can you perceive any difference in the dark picture that is there ?

Arfa

Reply to
Arfa Daily

Well, I'd have appreciated 'some' sort of reply myself when I posted a similar problem with a laptop [subject: Gateway M305 -- 10/18] this week. I guess ya'll figured I had it in hand. I'm still waiting for my eBayed inverter, and I leave town today....

Inverters 'can be' cheap. Cheaper than a new laptop, at least. But they're expensive enough that it's worth shopping around. I found inverters for this one ranging from the $20 'pull' I ordered, up to almost $100.

On a laptop more than a couple years old, it would only be worth fixing if one can find a deal....

jak

Reply to
jakdedert

Sorry. I don't visit this newsgroup regularly, and I just didn't scroll back far enough to see your post on the 18th. No intention of ignoring your post...just didn't see it.

This thread got me to remember this one time when a laptop display would not light up. It turned out to be a jammed plastic pin (like an on/off switch) that normally got pushed down when the laptop was closed (thus opening the circuit), and got released when the laptop was opened (thus closing the circuit). Since it was jammed it never fully released to close the circuit.

Fabian

Reply to
Fabian Fuller

I am able to see the menues and did try the brightness settings . Its hard to see anything but i did see the bright bar move . I was the first one to take the screen apart , their was some of that aluminum tape they like to use in these that was never touched . This screen uses 2 very thin bulbs , A set at top & bottom . The rest is a real thick platic diffuser and a couple thin sheets of stuff in there too . The display assembly has enough of a hole at each end of the bulbs to see them lit when everything is back together . This set looked used .. finger prints & slight soilage . It has its original box & all papers . It was a store return situation . I was given another LCD tv set today , a Zenith 13`` with the exact same symptom .. real dark screen . I found a blown fuse to the inverter and fixed it right up .

Reply to
Ken G.

You are quite correct, Fabian. I also repaired many laptops where the sleep mode switch (operated by a lug near the pivot of the top cover) was jammed. It makes the display go dark by shutting off the backlight.

Henry

Reply to
hemyd

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