WARNING: The plasma panels use fairly high voltages along with capacitors that store enough charge even when the TV is unplugged to give you a nasty shock that could result in serious injury/death! Please be extremely careful when taking off the back panel and working on the TV. Some suggestions/safety precautions to follow:
Originally Posted by tom669
To add a little data just recently got a 2011 D-series 720p (PS51D450) on my bench - AV board is bad but ran test patterns manually without it - full white had some pink tint around bottom edges and into middle of screen so upped Vs from 205V rated to 212V and that's gone, not a bad panel when it's working.
- Wear thick rubber soled sneakers while working on the TV and make sure not to provide an alternate path to ground by kneeling, etc.
- Use an insulated screwdriver to work on the potentiometer to prevent accidentally touching a capacitor or live element
- Preferably wear thick rubber gloves while working on the panel
- ALWAYS have someone else around to ensure that you are okay and to be prepared to provide emergency assistance/call for help if something does go wrong
- Patience is the key to safety. Take your time, work slowly and methodically and avoid sudden movements, etc.
- If you are not comfortable working a multimeter then you probably shouldn't be trying this.
I decided to take apart the TV again today to play around with voltages some more. I realized from the last time around, that I needed a better series of images to use as test images to determine if the red tint was improving or getting worse as I changed the Vs voltage. So I prepared a few images from B&W movies as well as some 1920x1080 black and white images via Google Search and loaded them on a USB Drive.
From running slides yesterday, it seemed almost like the red tint had gotten worse after I had set the Vs to 213V yesterday. When testing today, I dropped Vs down to 203V and to my surprise, I noticed that the red-tint seemed to have improved! A LOT of testing followed, and a lot of questioning my sanity and eyes. Fortunately, I had a bunch of great images to test the red-tint issue on and I was able to convince both myself, and my wife that the red-tint got a lot lighter when I dropped Vs. Ultimately, I ended up setting Vs at 197V, which is the lowest the potentiometer would let me set. This seemed to provide the best result, and so far, things do look much better.
This hasn't completely solved the red-tint issue, but it has brought it down to a level where a lot of people wouldn't even notice the red-tint anymore. I do still see it when browsing (white windows) and in some B&W scenes in movies, but I have to say that it has improved substantially and the red tint is easy to miss when I was watching Chaplin's Gold Rush.
I really don't understand why lowering the voltage improved the situation, especially because I am quite far away from the Panel spec for Vs of 208V. I did multiple tests, and both my wife and I could convincingly tell that the higher voltages 205-213V had more red tint issues, with the red tint getting stronger the higher I went in voltage. Should I be worried about any problems I might cause by setting Vs so much lower than the spec?
If things don't get any worse, I think I'll probably be satisfied with these improvements and will stick with this TV and panel. I'm still tempted to escalate with Samsung to see if they would come out and swap panels, etc till I was satisfied, but I have a feeling that my current panel performance will be deemed "within spec".
I also probed a couple of other voltages using the test points on the various boards. This is where I am at right now:
Vs = 197V (Spec: 208V)
Va = 55.5V (Spec: 57V)
Ve = 113.8V (Spec: 115V)
Vscan = -200V (Spec: -200V)
And now for the promised pictures!
I think most of the pics are self explanatory. The picture of the screws on the table is just to show how I placed them while unscrewing them so that it would be easy to match the screws back up with the back plate when putting everything back together. Be careful as some of the screws are of a different length than the others.
Also, for the VsBoard image, the Red circle highlights the potentiometer for adjusting Vs (Clockwise increases Vs) and the Green circle is the test point that you will need to probe with a multimeter to measure Vs. Note that there aren't any posts for test points on these boards, so alligator clips won't work when probing with a multimeter.