Panasonic TH-42PX50U

[keico]

Ok picked this TV up for twenty bucks, knowing full well there was a problem.

Seems like the same problem I had with a Phillips 42 plasma. Replaced upper & lower buffer boards on the Philips 42 plasma and has been playing well ever since.

The only difference is that this Panasonic when I first turn on, and this is after it is unplugged for awhile, will play perfect, then as time goes on the lower half of the screen starts to get real static.

Was wondering if these buffer boards can be repaired or should I just order lower & upper buffer boards.

[keico]

Anyone ??

[tom66]

Yeah, looks like lower buffer.

Before you replace the buffer, check the video cable on the D board, although it's unlikely to cause this problem. The D board is under the A board, so you'll need to remove that first.

[keico]

Finally got around to replacing the lower buffer board.

Played good for over an hour then I went to hook it up.

All of a sudden it would display the symptoms in the pics I posted. Then it would go away.

It will play fine for awhile then it will start to do it again.

Do you think this could be the sc board.

I have actually ordered one, but also wondered is there a way i could fix this board also so that I could have a back up.

[tom66]

Sounds a lot like a loose or dodgy connection or a sustain board that's killing buffers.

[keico]

Here are some pics so you can see how it looks went I first turn it on then you can see how after awhile normally anywhere from 30 minutes to more before it starts to show problems.

[tom66]

Does it occur suddenly? Or happen slowly?

[keico]

Originally Posted by tom66

Does it occur suddenly? Or happen slowly?

I would say all of a sudden

It will start then stop. Each start it last longer until it just stays that way

[tom66]

Originally Posted by keico

I would say all of a sudden

It will start then stop. Each start it last longer until it just stays that way

Sounds a lot like a cold solder joint to me. If you have a hairdryer, try heating up the buffer board and see if it goes wrong.

If you turn off the TV when the fault occurs then turn it on, does it occur immediately or shortly afterwards?

[keico]

Originally Posted by tom66

Sounds a lot like a cold solder joint to me. If you have a hairdryer, try heating up the buffer board and see if it goes wrong.

If you turn off the TV when the fault occurs then turn it on, does it occur immediately or shortly afterwards?

If I turn the tv off then on it is still there. I have to let the TV sit overnight

for it to play normal

[tom66]

Originally Posted by keico

If I turn the tv off then on it is still there. I have to let the TV sit overnight

for it to play normal

Okay, that does sound like a thermal problem - try the hairdryer trick.

[keico]

Originally Posted by tom66

Okay, that does sound like a thermal problem - try the hairdryer trick.

Here is what I did. On the back of this TV there are lots of vent holes. I took a very strong 12 volt fan and used metal tape to secure it in place where the SC board is.

At first I had it at the top and it seemed like it made no difference, maybe just took longer before it started displaying symptoms. I noticed it is always the bottom half that starts to go crazy, and then a short while later the top half will follow, so I added a second 12 volt fan.

Both were held in place with metal tape. Now when I did this the top half stayed normal, where as eventually the bottom half would start to act up.

Now this morning I decided to just leave the bottom fan on and guess what all day it has showed a perfect picture.

Go figure. Also I have attached a picture to show what I did.

Oh and the SC board finally came in the mail, so later I will be installing that.

[DavidOH]

I'd say your on the right track.

http://www.scribd.com/doc/50676393/p...ning-course-ET

[keico]

Ok have to give an update. Put SC card in and it has been 8 hours and it has been running like a new tv will see for rest of the night and into tomorrow

[keico]

Ok I believe the problem has been solved. Since I have replaced the SC card it has been perfect.

[vinceroger69]

whats the sc card?

[selldoor]

@VR69 - see scribd.com a couple of posts up
SC Board Explanation
Figure 29
The SC Board consists of buffers and drivers used to generate the scan signals for thePDP panel. The buffers provide isolation between the D board and the drivers.Connector SC20 provides the drive voltages (140V, 100V and 18V) as well as thetrigger signals to switch the FET transistors. The D board switches the FETs on and offto create the distinctive scan signal. Each trigger signal switches a drive FET creating aportion of the waveform. For example, applying the CPH signal to the 140V FET createsthe peak portion of the waveform, see figure 29.
34

[vinceroger69]

cheers selldoor.