Question about LG DU-52SZ61D TV
This is a 52" DLP HDTV. The picture is clear but very dim, only visible at all when close up, except for an approximately 1" vertical strip on the right side, which is brighter but still not bright enough. The bulb is good, as I can see it lighting up through the lamp cover and I even tried a new bulb with same results.
The edge of the brighter strip is not clean and sharp but rather blurred and somewhat uneven. It looks like what you might imagine the picture might look like if a piece of cardboard or something was mostly blocking the light path. Could it be some sort of obstruction? Though dim, the picture is clear and the colors seem even, and the sound and everything else works fine on the set.
If it matters, this set is only about 3 years old, and the previous owner told me he had the light engine replaced once while it was under warranty. It was then working fine until recently when the cleaning lady supposedly "bumped" it. Whoever worked on it did a poor job, since one of the two screws in the lamp door was replaced with a sheet metal screw instead of the correct machine thread screw, and the phillips head of the other screw was badly rounded. Perhaps the owner did this replacing or checking the bulb or something. I'm hoping the repairman just did a poor job on reassembly and the "bumb" knocked something loose which is now blocking the optical path. I have no experience repairing DLP TV's so I'd like to know for sure or at least know what to look for before I tear into the set. Thanks in advance for any advice or information.
With all of this bumping and knocking, still the problem you are having should not be occurring. This is due to the fact that the light engine is basically protected from that kind of activity. Now I feel that I have to explain how the light engine works, because there are a few things I am going to ask you and I want you to know why I am asking you these specific questions.
First of all a light engine works in the following manner:
A digitized video signal is sent into the signal and control bus of a DLP processor the signal is used to activate the transistors that control the mirrors that reflect light from the light source (the bulb) to the screen (more explained in next sentence) of the TV. The light from the mirrors then is reflected into a color wheel which spins at a rate which allows the individual monochromatic lights from the mirrors to be reflected with its proper color sequence (this is what creates the color picture from the monochromatic light from the DLP processor). This is a high level description, yet it is accurate for the questions I am about to ask.
1) Is the color wheel moving? (you can tell because it will make a fan like noise when it is turning)
2) Is the bulb at its proper luminance? (you can tell by using a light meter)
3) Are all the lenses in place? (you can tell by opening the light engine and inspecting the lenses)
4) Is the light from the bulb striking the DLP processor mirrors? (This sounds like what is not happening in your case, this or the processor is bad, being blocked by an obstruction, or out of alignment)
I believe that the last question is what is happening in your case, please correct me if you think that my assessment might be incorrect.
As for doing any of the work yourself, I would advise against this because this is what may have happened in the first place with the first owner. (who knows for sure). I would suggest getting this repaired by a qualified TV repair shop since the placement of these parts and the handling is very critical. If you do plan on doing this yourself you will need the following items:
1) voltmeter (to measure the voltage levels on the DLP processor, and the other points on the circuit board)
2) schematic diagram with service manual (To see where parts are located and to indicate where test points are)
3) light level power meter or you can use a temperature meter and do the conversion formula for watts to lumens (heat energy to light energy) 4) Ohmmeter (to measure resistances of components and circuit devices)
5) Signal generator (to create/generate a reference signal source with which to test against)
Now, if you know what these pieces of test equipment are and how to use them great have at it, if not, my original statement hold true: get a qualified TV repair person to take care of this issue.
I hope this helps,
Posted on Jul 23, 2008
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Posted on Jan 02, 2017
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