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My TV has started drawing colors incorrectly

coderwalker

Jan 16, 2012
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Jan 16, 2012
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Make: Philips
Type: LCD TV
Model: 42PFL7403D.

For some reason the TV has started displaying color bars, it's like the timing of the colors is off. Like a printing press with the colors unaligned.

Here are LOTS of pictures: http://webstrand.comoj.com/tv/

It's like a printing press when the colors arn't aligned.

Has anyone seen this before?
Is there a name for this specific issue?
What could cause this?

I need to get this fixed badly. I do not have money to buy another TV.
Thanks in advance,
CoderWalker

Also,
Does anyone need to see pictures of the inside to diagnose this?

FILE0009.JPG
 

coderwalker

Jan 16, 2012
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Jan 16, 2012
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Capacitor?

Could this be a capacitor problem?

Also here's a video of the problem:
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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25,510
With some notable exceptions, asking "is it a capacitor problem" is like taking your car to the mechanic with an odd problem of (say) the engine surging and asking "Is it a bolt problem?"

It looks to me more like something to do with the controller for the LCD display.
 

coderwalker

Jan 16, 2012
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Jan 16, 2012
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With some notable exceptions, asking "is it a capacitor problem" is like taking your car to the mechanic with an odd problem of (say) the engine surging and asking "Is it a bolt problem?"

It looks to me more like something to do with the controller for the LCD display.

Thats a good point :p I'll try to be less broad.

The problem is very strange. I assume it has to do with an analog component going bad or some component that changes depending on temperature. The reason I say this is because when I first turn the TV on there is no problem works 100%. Then as time passes the lines start appearing like streaks. Then as time progresses farther the horizontal line of incorrect pixels gets larger, until finally the lines are going off the right side of the TV.

I hope this helps provide more information.

How should I begin diagnosing this problem?
If it is the LCD controller board, it has to either be a capacitor, transistor or a diode that has gone bad right?

Last of all, when you say controller board, do you mean the t-con board?

Thanks again,
coderwalker
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Let me first say that I sympathise. I have a TV with a different but equally weird and nasty display fault.

Like yours, mine seems to get worse the longer the TV is on, and a fan placed in the recess behind the TV seemed to cure the problem for quite a while.

My problem seemed thus to be triggered by temperature, but slowly getting worse :-(

Yours may be similar, and I would try providing better (perhaps forces) ventilation as a diagnostic aid.

If the problem takes longer to appear, then it is reasonable to expect that it has something to do with heat.

The next problem is finding it, a traditional approach is to use a "freeze spray" to cool components one at a time until you find the culprit. Then you (typically) replace it.

The component could be a transistor, a diode, an IC, a capacitor, a resistor, a connection, a solder joint, etc, etc.

I would normally be suspecting larger, more complex components (such as ICs) but it's not invariably one of these.

If you can find a service manual, it may provide some hints. I had a very brief look. There is a sticky post in the Datasheets section with a list of places to try, so you may have more luck if you do more than a cursory search.
 

coderwalker

Jan 16, 2012
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Jan 16, 2012
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I just noticed a few more things.

Tempature:
It is definitely temperature related, it gets worse as it's on. Also it's currently 66F in my house and the problem took longer to appear.

Spacing:
Looking very closely at the LCD TV, I noticed in every row, it's only every 5 pixels that have a problem.

Timing:
Also I think this may be very pertinent, however I'm not sure.
I connected a 480p source and I noticed that the video is first scaled and smoothed to fit the 1080p screen. However the horizontal pixel corruption problem does not occur before the image is resized but instead after because the corruption is a horizontal line of separated pixels. These pixels are the size of the individual LCD squares on the TV and not the source video. Also very importantly there seems to be a pattern. Maybe related to timing? I noticed that a bird flew by on the TV, while looking at the bird I noticed right of it there were incorrectly green lit pixels in the shape of the bird. Its almost like the colors are a few pixels off of the other colors sometimes.

Does this information also point to the t-con board?

Also, if it is the T-con board is that repairable or only replaceable?

*Look at picture 16 and 17 to see this in detail.

Accessing the T-con board:
I was going to look at it inside the TV however it has a metal plate in-front of it.
Almost like I have to lift off the back cover, disconnect the front cover, then lift the metal frame to access it.
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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I think your observation regarding the 480p source is relevant. Your observation that the problem is not affected by scaling or smoothing suggests that the problem is in the display of the image and not the decoding.

I can't help with specifics though, sorry (I just don't know)
 
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