Samsung Plasma PN50B450B1D Dim picture, black pixels

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Does the PSU generate Ve or does the X-main? I realized that there aren't any connections that are labeled Ve. The only way I measure it was from the Test point that was labeled Ve.

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Y-main generates unregulated Ve (probably 10~20% higher than regulated Ve), this is then regulated by X-main.

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Is it possible for a bad component on the Y-main to cause a bad Ve reading? (Ie, The little dips in Ve voltage when looking at the oscope)

This set is known for usually a bad y-main from what ive been reading.

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Do the glitches stop when the X-main is completely isolated?

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

From disconnecting the X-main from the control board and having a steady correct Ve voltage from my multimeter. However looking through the Oscope (with xmain off of crtl board) the little dips are still there.

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Didn't consider that but it's possible, try checking -Vsc too.

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Heres photos:

1 X-main with crtl board
2 X-main with crtl board unplugged

3 Y-main normal with crtl board
4 Y-main with crtl board unplugged

Anything look out of the ordinary?

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Might be me but I can't see any SET UP wave only SET DN. (Y-main ramp pulse about 2xVs to initialise plasma panel.)

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

For some reason, While I was measuring the Y-main I heard a pop noise and the set went off and wouldn't turn back on....

I checked the X-main and Y-main (unplugging each) and found if I unplugged the x-main board the set would come on but now theres just no picture.

But I checked all the fets on it again and found that 4 FETs were shorted.

RJH3044

Either the x-main just finally gave out right there or something touched and arc'ed and shorted it. I wasn't even touching the set when this happened though so I'm sure what happened.

Searching up RJH3044 lead me to this datasheet. I'm not sure if its the same part but if it is I noticed it actually has a Built-in Fast Recovery Diode between the collector and emitter.

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

This is reading exactly the same as my thread on the PS42B450.

Mine had dark pic and after some playing around eventually no pic at all and wouldn't power up. Isolated X-main and it worked fine with original symptom of dim/incomplete image.

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

I can't even get the original symptom to return now.

Where is the thread about your PS42B450?

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

https://www.badcaps.net/forum/showthread.php?t=16773

Swear it was a B450 but IIRC both B450 and C450 are basically identical with only minor changes to the case (same parts and panel.) Different model year 2009 vs 2010. You can interchange the 42" parts that I know of, not sure about 50".

I made that a long, long time ago -- a lot of the comments I made in that thread are now known to be wrong to myself.

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Decided to buy another x-main since I can't find a reasonable price for the FETs. Replaced with the new X-main and same problem as the beginning. Just as my gut feeling told me.

I tested all the FETs on the y-main and they all tested good as well. Stilling thinking its the control board, They're cheap from $18 so ill give it a shot.

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Do not rule out your new X-main as being defective though.

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Ok this set is really starting to annoy me...
Just got the new control board today but it's defective... Doesn't even give a picture. I put back the old crtl board and the original symptom is back, so im returning the new one.

I checked EVERY component on my old x-main and did not find anything bad with it. There are about 150 parts total including the smd components. And I really doubt the second x-main would have the exact same problem as the first... especially ruling out every part on the x-main already.

Heres some photos of the the x-main with the new defective crtl board. Maybe itll give a clue of how the crtl board works with the x-main? Well I guess ill try another control board...

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

1st looks good, what is up with 2nd?

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

So the 1st one indicates the x-main is working normally?

2nd photo was just a zoom in. It was set on 0.1V per line but with 10x probe thatll be 1V each instead of the 50v in the 1st photo.

[tom66]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Only thing I can't see is the Ve portion of the wave it looks to be around Vs but if anything that would cause oversaturated pic, not no pic. Check all power connectors, Y-main connections, LVDS, etc.

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

I checked all the connections, it was the first thing I did.

I think there's a chance I might of bought the wrong control board... I noticed small slight differences.

Here's my original control board, What numbers exactly do I have to match?

[Glitcher]

Re: Samsung Plasma PN50B450B1D Dim picture, black pixels

Well just bought another control board. If this one doesn't work I'm giving up on this set unless anyone has any other ideas.