Dell TFT turns on and off repeatedly.

Posted on 2005-03-24
Medium Priority
Last Modified: 2008-03-17
Hi I've had a strange problem, I had a TFT that worked fine all the time on its system. I hooked it up to another system all seamed good but then it started to randomly turn off then on again. The system itself was stable everything still running. There doesnt apear to be a pattern to it ether. I plugged in a CRT and everything is fine. I plugged the TFT into another pc and it does the same. Is there anything else that could be causing this or is the TFT on its last legs?
Question by:Drefsabuk
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Accepted Solution

Purple_Tidder earned 750 total points
ID: 13626501
Probably bad TFT.  I had same problem with Dell 15" monitor, about 2 years old.  It started to do what you talk about, then instead of flashing off, started turning white.  If I powered it off then back on, it would be ok for a few minutes, then turn white again.  Probably need a new monitor.

Quite possibly it could be the backlight inverter.  Does the screen just darken and you can still see things on the screen, or is it dead, power light and all?
LVL 13

Expert Comment

ID: 13627170

Are you SURE that you are not just going into a "power save" mode?  You didn't say if this happens right when you are using the system -- moving the mouse or typing -- or if it only happens when the system is idle (even if it's only been idle for as few as a couple of minutes).

Give us a better description of both what happens -- exactly what happens -- and also when it happens (what was going on with the comptuer to which it was connected at the moment of the incident).

Author Comment

ID: 13627415
Ahh sorry for the vauge description. It happens regardless of activity I could be playone an online game them it goes black the led goes yellow then green again as if I have just turned the thing on and off manually. All cables are in tight no shorts etc.. its getting worse as well happening more and more often now. I think its a bad TFT to be honist at this rate, its only 3 months old though so its in warrently. Its just really annoying as it was fine and its just happened all of a sudden.
LVL 13

Expert Comment

ID: 13627781

Well, it's not a bad TFT, if by "TFT" you mean the actual LCD panel.  A bad panel could not -- would not -- cause the light to change from green to yellow.  Now, if by "TFT" you mean the entire display, and not just the actual TFT panel, the you could be right (but "bad monitor" would be a better description than "bad TFT").

Inside the monitor there are two major components -- the LCD panel (TFT), and a video card that accepts the incomming signal and converts it to the drive signals required by the TFT LCD panel  [the video card is complex for an analog VGA-input monitor, but simple for a digital input (DVI) monitor (except that almost all monitors that have DVI inputs ALSO have analog inputs).  [If your monitor has an internal power supply, that's a 3rd major component).

The fact that the light is changing from green to yellow (or orange) indicates explicilty that the monitor is either going into a standby mode or an "off" state.  This is a function of the video card, based on what it detects on the incoming video line from the computer.  So, in your case, we can conclude a few things:

-The LCD panel iitself -- 80% of the cost of the display -- is almost certainly not bad
-The video card in the LCD monitor could be bad OR
-There could be a problem in the host computer (it's video card, or software settings) OR
-There could be a problem in the cable between the display and the computer
-[very slim chance] there could be a problem in the monitor power supply [internal or external]

Current PC standards allow for several mechanisms by which a computer can signal it's attached monitor to go into standby mode (there are at least 3 mechanisms).  One thing that you might want to explore is changing these settings, which can exist in several different places.  There are settings in Windows, there may be settings in the bios of the computer, and the monitor may have it's own settings in it's own setup menus.  It might be worth exploring whether any of these will help to alleviate the problem.


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