back cover causing Plasma display issue.

[eszentric]

I have a Samsung PN64F5300AF that has been casting the (not so uncommon) pinkish/green tint on white areas of the image. I recently R&R'd the Ys and Xs boards to test the caps, check the Vs and Va, and Caig cleaned all the connectors, including the scan board ribbon cables.
Before reinstalling the back cover, I ran the TV for an hour, and was happy to see the display problem was gone. So back on went the rear cover, and in less than a minute, the display problem was back.
I checked the inside of the cover, and the back of the TV, to make sure there was nothing out of place.
I have since tested the back-cover theory three times this past month, running the TV a couple days with the cover on, and a couple days with it on, and I get the same results every time. I have now been running the TV for over two weeks without the back cover, and the picture has never looked better. I'm thinking the cover may be causing some kind of electrical resonance, or oscillation.
Has anybody ever experienced this? Is there something I can line the inside of the cover with, that will provide insulation between the circuitry and the metal cover?
Thank you, Rob

[aaronwt6]

Re: back cover causing Plasma display issue.

My guess would be that you have a heat related issue. Running it with the cover off is keeping the failing part just cool enough to work properly. Again, this is just a hunch for personal experience.

[jetadm123]

Re: back cover causing Plasma display issue.

Agree with aaronwt6 that it's a heat related problem. You can try re-seating the ribbon cables, but with the cover off, try heating up the boards with a hair dryer to see if you can re-create the problem.

[eszentric]

Re: back cover causing Plasma display issue.

Thanks for your suggestions... I've thought about heat being the issue, and at one point I had actually installed a couple computer cooling fans (externally powered) on the inside top of the cover (plenty of room away from components) above the the hottest boards, but did not help at all.
Still I will try the hair dryer test to hopefully duplicate the problem, and better yet isolate it down to a specific board. If I find that it is a specific board that is overheating, I would imagine it would be one or more mosfets under the heat sinks that may not be transferring heat to the heat sinks properly. Would it be advisable to remove the heat sinks to reapply some Arctic silver?

[ReeceyBurger123]

Re: back cover causing Plasma display issue.

You could possibly have some sort of weird ground loop when the back cover is installed it connects the loop. Make sure that all screws on the boards are tightened properly.

[eszentric]

Re: back cover causing Plasma display issue.

Thanks Reeceyburger, I will double-check that. I also wanted to mention that while all the caps checked out okay on both the Ys and Xs boards, I did notice that the Xs pwb was warped, and had dark (burn?) area running down the middle of it. If this pwb is in fact running hot enough to burn and warp the board, then is it safe to say, the heat sinks may need to be R&R'd to clean and regrease them? And maybe add some fans for additional cooling? I have no confidence with Samsung's design for not installing fans in this TV.

[eszentric]

Re: back cover causing Plasma display issue.

Thanks to you all for the great tips; It turns out this problem was in fact due to the Ys board overheating. The hair dryer test did the trick with duplicating the symptom, and narrowing it down to the exact board. I was extremely fortunate to have found the last Ys board on the planet, and for just $100 on Ebay. I also installed a couple 120 mm cooling fans inside the back cover... Something Samsung should have put in all of their plasma units.
This makes me wonder how many other people out there with fan-less plasma sets, are having similar display issues. I would suggest to anyone out there with a fan-less plasma, to retrofit it with fans immediately after the warranty ends. The additional airflow the fans provide will definitely serve to prolong the life of your set.