Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

[CyberNinja]

First, the black horizontal lines even overlay the TV's menu. Does this behavior indicate that it's the plasma panel that's defective? If not for the black lines, the TV works just fine. I've cleaned the 6 connectors between the panel and the Y-buffer board, causing no change in the black lines. Visually, the 12 ICs on the Y-buffer look brand new (no holes, etc.). I put my fluke meter in continuity mode and tried to perform the "short" test on the 6 panel ports and found many shorts. But I don't think I'm doing the "short" test correctly and I'm hoping someone can provide guidance. Searching for repair manuals on the net has been quite unsuccessful. Any advice would be greatly appreciated!!

p.s. Let me know if I can provide any pictures that may help.

[dick_barton]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

Pictures could prove usefull to more clearly see the problem.

[CyberNinja]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

Sorry for the delay. Here are 2 pics that shows how the TV menu options are overlaid by the horizontal black lines. As you can see, there are many black lines. At the bottom, they're dense enough to create a black rectangle. I would greatly appreciate if someone could tell me how to perform the "short test" with this models Y-buffer board. I get different readings/results when I swap the black/red leads. I know I have my meter in continuity mode, so getting different results is confusing. Thanks!

[CyberNinja]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

Doesn't anyone have experience with Samsung plasma TVs? From the 2 pictures above, is it possible to say it's a bad panel?

[dick_barton]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

Have you tried running the test pattern.
https://www.badcaps.net/forum/showth...t=test+pattern

[R_J]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

Sorry for the delay. Here are 2 pics that shows how the TV menu options are overlaid by the horizontal black lines. As you can see, there are many black lines. At the bottom, they're dense enough to create a black rectangle. I would greatly appreciate if someone could tell me how to perform the "short test" with this models Y-buffer board. I get different readings/results when I swap the black/red leads. I know I have my meter in continuity mode, so getting different results is confusing. Thanks!

Here is a video showing the testing of a similar buffer board https://www.youtube.com/watch?v=3Oq2MsU0XOQ
with a probe on the plug going to the Y-SUS, you should have aprox the same reading to each pin going to the plasma panel plug. If just using continuity the reading should be open circuit, if using diode test you might get a reading similar to a diode (.6xx) but each seperate pin on the panel plug should be aprox the same, if the ic is bad it will read close to a short. If an ic is bad it will be located where the black lines are located.
If there are no shorts, I suspect the panel could be bad. (I had a PN50A450 with black lines and it was the panel) to be 100% you need to scope the signal on the outputs of each buffer line going to the panel.

[CyberNinja]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

R J, Your advice is greatly appreciated! I've included a picture which is from a video showing a TV that is 99% like mine. I've labeled the 3 jacks/connectors between the Y-Buffer and Y-Sustain with red numbers (1,2,3). Can provide advice on which pin on which connector I should use to test for shorts? My Y-Buffer has hardly any labels around the connector pins, so it's not clear which pin I should use. Now a silly question: is it best to separate the Y-Sustain from the Y-Buffer before performing the short test? Even though it's a simple continuity/short test, I would think it shouldn't matter either way. But, just in case, I have to ask.

dick barton, using the picture I've attached, can you provide specifics on the "LVDS cable" and "jumpering pins 3 and 4 of logic board". I would love to generate the test pattern. Although, wouldn't the test pattern still have black horizontal lines if my Y-Buffer and/or Y-Sustain boards were defective?

[R_J]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

Without the board in front of me to test I don't know which plug to use. they are not all the same. You don't need to remove the buffers from the Ysus, Just try with one probe on one of the pins on plug one and check to the panel connector (like in the video)
You have pictures of the fault, so why not pictures of YOUR boards?
I doubt the test pictures would be any different.

[CyberNinja]

Re: Samsung plasma 50" TV, model PN50C540G3F, has black horizontal lines

I finally had a chance to re-attempt the "short test" on the Y-buffer board. This time I used 2 different meters and R_J's advice on the .6xx diode reading help me confirm with greater confidence the Y-Buffer board HAS NO shorts. My cheaper harbor fluke meter allowed me to set it to read continuity only and not once was I able to get a beep. At this point, I have to assume the Plasma Display Panel is the cause of the horizontal black lines. I've read an oscilloscope is needed to confirm the panel is bad, alas, I don't own one. When I find time, maybe I'll disconnect and clean all the thin ribbon cables to see if that makes any difference.
Based on the pictures attached here, I know all the boards are working great since the picture & sound is quite nice, minus the black lines.