Samsung plasma tv pn50a450 issue

[XeroOmega]

Hi there everyone, this would be my First real post. Thanks to everyone who takes a look and anyone who has a suggestion.

To Clarify it is a Samsung Plasma, PN50A450P1DXZC, from 2008, with checkerboard 3D support

So i'lll give you a little rundown, i got this tv, free, broken(as i get alot of my stuff) and decided to give a crack to fixing it. My first plasma. Anyway i'm no stranger to repairing electronic devices, the first thing i did was crack it open, replace a few clearly bad caps (with mostly the same rating other than i used a 63v 100uF on the Y board in place of a 50v 100uF) and reset the voltages(Va, Vs, Vscan and another that i don't remember the designation of) i set them to spec, within a .1v range.

So i fired it up, the tv now turns on(bonus) and displays everything. Now the problem i'm having that i have been scratching my head about, i've looked around and tried to find answers as well. but i am stumped.

I am getting ALOT of red, in both white and black. this washes out other colors a bit too. (yellow is washed out, green is too dull, and blue is too dark, red is too vibrant, black has red all throughout, and white looks pinkish)
I have tried tweaking my video settings to no avail(also service menu settings).

Now i know this tv is from 2008, and it could be the panel dieing, but i also question that as it has less than 8000hrs running time, and surfers no burn-in.((the panel) is rated 100,000hrs half life, not the say the parts will last as long) I've been thinking of trying to tweak YSS and YA(have both on my board) but i do not know their default voltage ratings(nor can i find a probe spot for them)

If anyone has a suggestion it would be greatly appreciated. And keep in mind, this is one of many tv's to me, if i break it, meh i think i've spent a whopping 60 cent's on it(new caps). So feel free to through out your wildest idea's.

[tom66]

Re: Samsung plasma tv pn50a450 issue

Have you tried a factory reset from the service menu yet?

[XeroOmega]

Re: Samsung plasma tv pn50a450 issue

Indeed i did(factory reset from service menu), sorry i forgot to mention it. All of the tweaks i've done to the hardware/software of the tv, haven't seemed to help with the excessive red in the screen.
I should also note, i've noticed the red is the worst at the edges(both top and bottom left and right) of the screen, and seems to be less towards the center(but still there).

[tom66]

Re: Samsung plasma tv pn50a450 issue

It sounds like maldischarge. I would try tweaking the Yfr then Yrr pot on the Y-main board. Look closely at the screen while doing this. If that does not work, try decreasing -Vsc (making it more positive) and Vs.

[XeroOmega]

Re: Samsung plasma tv pn50a450 issue

Thanks for the suggestion Tom66, Mal-Discharge was definitely part of the puzzle.

(assuming up(clockwise) down (counterclockwise))
I tweaked Yrr down(quite a bit, 1/4 turn) and Yfr up (just a little bit)
-Vsc down to -187.2
I turned down Vs to 201.5
This resulted in Ve dropping to 97.4 (with no intervention from me) I turned it right back up to 100 without any negative effects

My Stock Values are
Vs 207
Va 56
Vsc -190
Ve 100

This has cleared up my picture alot, not as much red and white looks more white(not pink). There is still a little bit of red in black, but barely.

Now (after some tweaking with the picture options) it's much better, but i still have Green's and Blue's and Cyan too dark, any thoughts?
I have a sneaking suspicion that the color's on this tv were never true to begin with. If this is as good as it gets, i'm okay with it (people look like they have flesh now, before bright things looked almost poster-ized(cartoon-ish))

[tom66]

Re: Samsung plasma tv pn50a450 issue

Increase Vs to 205V to 210V to get rid of the pink tinge, the lower you can make it the better. Test on full white screen for a minute to ensure power supply does not shut down, if it does then decrease Vs until it does not. As for blue/green/cyan, I recommend tweaking Yrr. I also recommend you leave the picture settings at default after tweaking these, just so it makes it easier to compare the improvement.

-Vsc and Ve are cross-regulated using the same power supply circuit, so adjusting one changes the other on these panels.

[XeroOmega]

Re: Samsung plasma tv pn50a450 issue

Hey tom, i have taken alot of the red out of it. But i notice that when i ajust Yfr to get rid of the redish tinge it is very quick, on one end i flood it with red(i even see something burned in i can't normally see) on the other i can almost clear it up. But it seems i can either have no red and poor colour with great black, or, a little red, great white and good colour.

I have tried giving it a little more on Vs (up to 209V) it doesn't seem to effect the tinge at all.(only Yrr and Yfr effect it)

I've been having fun trying to tune it, but thats all for now as i have to go out, if you have anything else thanks, if not i will tinker away until i get it where i'm happy.

Lastly thanks for all your great help, i've read through your plasma repair thread and it was great and detailed. If this forum allows rep+ let me know and i'll throw some your way.