View Full Version : Samsung pn51d450a2d horizontal lines on the screen


MRX37
02-03-2017, 07:50 PM
It's been awhile since I've done anything TV repair related. But this TV was a rescue. The guy threw it out carefully, meaning he made sure to set it some place out of the snow, and wrapped the cord around the base, the screen facing passers by on the street...

And well, I had to rescue it.

So the TV works, but it has horizontal lines running across the screen, a band of them that show up in menus. I could get pictures but really there's nothing more to say.

I did some googling and tried reseating all the ribbon cables but nothing changed. Now I'm trying to find out what went wrong and if it's worth my time to try and fix a 720p Plasma TV from 2011.

The good news is apart from the lines the display looked nice and bright, and taking the back off revealed clean looking parts with no obvious signs of heat damage or bad caps.

Findm-Keepm
02-03-2017, 08:26 PM
Have the manual and training guide? If not:

https://elektrotanya.com/samsung_pn51d450_pn51d450a2d_sm.zip/download.html

It's a Zip file, and the training guide shows several panel problems and their cures. It also details the SMPS voltages and other voltages to check. That would be my first step.

When downloading the manual, wait until "processing" becomes "Get Manual" - and click on the "get manual" - choose download, and then open it with WinZip or another ZIP archive tool to get the manual(s) and training guide.

Hope this helps.

MRX37
02-04-2017, 09:51 AM
Okay that's pretty useful, but of course it doesn't list the exact fault this TV has. It could be the Y buffer board. How coud I ascertain that before I decide whether or not to throw a part at this TV?

andy
02-04-2017, 01:38 PM
I recently worked on a Samsung plasma which black horizontal lines running through the picture (mostly in the top half of the screen). Unfortunately, it was caused by a bad plasma panel.

There seemed to be a manufacturing error where the ribbon cables were bonded to the glass. The ribbon cables connect to fine metal traces on the glass (possibly silver). The traces are covered with an insulating coating to protect them except for the area that is bonded to the ribbon cables.

Unfortunately, they left a gap between the edge of the ribbon cables and the insulating coating. The silver traces in this area are exposed to the air are erode over time (possibly electromigration, or oxidized from ozone generated by the high voltages). On my set you could hear and see arcing across some of the open traces.

It looks like Samsung had intended to seal the gaps with silicone, but it only covers the backs of the ribbon cables, and misses the gap.

MRX37
02-04-2017, 01:59 PM
I recently worked on a Samsung plasma which black horizontal lines running through the picture (mostly in the top half of the screen). Unfortunately, it was caused by a bad plasma panel.

There seemed to be a manufacturing error where the ribbon cables were bonded to the glass. The ribbon cables connect to fine metal traces on the glass (possibly silver). The traces are covered with an insulating coating to protect them except for the area that is bonded to the ribbon cables.

Unfortunately, they left a gap between the edge of the ribbon cables and the insulating coating. The silver traces in this area are exposed to the air are erode over time (possibly electromigration, or oxidized from ozone generated by the high voltages). On my set you could hear and see arcing across some of the open traces.

It looks like Samsung had intended to seal the gaps with silicone, but it only covers the backs of the ribbon cables, and misses the gap.

That seems to be what the issue here is. The Y buffer board tests good. Meaning the IC's don't have any shorts far as I can tell. On youtube there are videos showing how to test for shorts. I did that and found none.

Unless there's another simple test I can do then I'm just gonna assume it's the panel.

MRX37
02-04-2017, 04:18 PM
So I removed the panel from the frame, and perhaps because this is a later model (from 2011) it has silicone covering where the cable connects to the glass. I see no signs of arcing or damage. The cables themselves look fine.

So both suspects appear to be not guilty. Unless you guys can think of something else I'm just going to salvage the boards and scrap the rest. I have too many TV's as is.

andy
02-04-2017, 10:41 PM
The damage was very hard to see, even with strong magnification. The gap is only a fraction of a mm wide. There was silicone on my cables, there's just that tiny gap between the silicone and the insulating coating.

My set was from late 2009. I'm not sure which model years are affected.

MRX37
02-05-2017, 10:45 AM
Yeah. I'm just going to go with that. Well, it has a lot of good parts I'll salvage.