42" Samsung pn42c450b1d Pink lines/pixels

[Glitcher]

So I've been working on this set for a week with no luck..
The original problem was once I turn it on, the screen only displays pink lines and pixels but there's no picture. Initially went with replacing the X-main first, but no luck, same problem.

I found that the Y-buffer had a shorted IC. I replaced the IC and the set turns on now with a picture however the pink pixels are still there (See photos)

I also already replaced the main board.

What do you guys think the problem is? Since I had already replaced the X-main board. Could this be a Y-main problem?

[tom66]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

Have you checked the Vs, Va, -Vsc and Ve voltages?
Do those match sticker within 1V?
Any Yrr/Yfr adjustment pots?
How do the test patterns of 100% white and bar of white / block of white look?

[Glitcher]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

All the Voltages are in exact spec.
Ve is measuring 101V

The Y-main does have Yfr and Yrr pots. I haven't tried adjusting those yet.

I'm not sure how to get into the test patterns. But when playing a picture with a full white screen, the entire screen is covered in pink pixels and then each pixel fades away until the entire screen is white. (however it still has a very slight pink hue to it.)

[tom66]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

Test patterns in service menu. From standby press Info Menu Mute Power.
I would try adjusting the Yfr pot until the pink fade disappears on image change.
In addition I would apply latest Samsung firmware update.

[tom66]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

I've noticed you replaced one buffer IC.
Make sure you re do the silicone on the IC. It's not just for holding it on, it's electrical isolation - each one of those pins is selectively energised with 140V wrt the other pins so it's pretty critical no dirt/dust/particles of metal impringe on it.

[Glitcher]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

Turned out the Yrr pot was extremely off causing the pink pixels. I gave it a twist and all the pink pixels are now gone! The whites still look like it has a slight pink hue but I think its just my eyes or the lighting in my room...

So I guess the initial problem was just a bad buffer IC on this one. I went through 3 buffers on ebay.. first one was the wrong model # and the other two had shorted IC's since I guess they were taken from cracked screens.. So I just replaced it on my original board.

I've never actually seen a bad IC on these newer Samsung models though.


Also: where can I get the silicone for the IC?

[tom66]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

You can use HV epoxy or any epoxy which seals without air bubbles.

If there's a pink tinge on full white, I'd tweak the Vs up to 210~212V, common fault on these Samsung panels. That usually gets rid of pink tinge.

I think the buffer ICs fail randomly - luckily Y-main failure doesn't kill them, and yes, most buffers from eBay appear to be bad unfortunately .

[cliff_hootarski]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

This might work:

MG Chemicals 1035 Non Corrosive Translucent 1-Part RTV Silione Adhesive Sealant

Can be found on Amazon.com

[Glitcher]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

Will this work? I can get it at an auto store. I read that someone else
On the forum has used it also.

http://www.permatex.com/products-2/p...r-82194-detail

[tom66]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

Looks good - is that for ignition coils/spark plugs? If so it should work.

[cliff_hootarski]

Re: 42" Samsung pn42c450b1d Pink lines/pixels

Or maybe this:

MG Chemicals 4226 Super Corona Dope - High Voltage Insulating Varnish