Problem Determination: DMD vs PCB


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DaveC
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Problem Determination: DMD vs PCB

Postby DaveC » Tue May 12, 2009 2:50 am

I have a previous post where I described the dark lines I have acorss my screen that were fading away as the set warmed up, but now change in width and intensity only, but never go away any longer. Anyway, the DMD (BP96-00249A) was replaced last July, so I was hoping that was not the problem again. After getting some advice here, I called the Samsung Auth repair guy and described the symptoms after trying a couple of things for him. He came back a few days later and said it is the Digital PCB board (BP94-00385A).

I am really confused because what I have read on this forum seems to point back to the DMD and not the PCB, unless I am just getting turned around?????

Here are the "tests" I tried and the results. Can someone in the know technically explain how these tests rule out one or the other if they do please?

Problem/Analysis

P1) After the set is started dark lines (shadow, interference like) span the screen from end to end. I have a big set (HLN567/WX/XAA) and there are probably a couple dozen lines. The lines are horizontal but at a slight angle, not vertical. They reduce in intensity and width as the set warms up, but are always there and create a very poor picture to watch.

A1) I think this points to either the DMD or PCB failing (not the Analog board), but does not isolate one or the other?

P2) Using the Samsung remote (not the cable company remote) I hit the menu button. The menu is superimposed over the channel feed but the lines remain.

A2) I read that if after hitting the Menu button the lines remain, then it is the DMD but don't know why? This is contrary to the Service Tech diagnosis!

P3) I put in a DVD in the player and used the Samsung TV/Video button to Connect to S-Video 2. The movie appears along with the lines. No change in the horizontal line interference.

A3) Clearly it is a problem that affects all three of these tests, but I am still confused as to which component these tests point to as the failing one? Is it clear to anyone out there? Are there any other tests I can do? Given that the DMD is a $500 part and the PCB is a $200-$300 part I do not want to make a mistake and order the wrong part.

If I can't be sure, I'll have no alternative but to pay the Service Tech $500 to $700 and let him figure it out, which I rather not do since I was laid off and don't want to spend the green if I can avoid it.

Thanks, Dave

DaveC
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Re: Problem Determination: DMD vs PCB

Postby DaveC » Sun May 17, 2009 6:49 am

Okay. I now believe IT IS the Digital PCB board. I sought another opinion that had me look at Menu display again. As you know, the display is transparent which was making me think the lines were still there. But after looking closely at the icons and lettering, I could see that the lines did not affect the menu display. Therefore, the digital PCB is the culprit I believe, which leads me to another question and another post.


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