Help with Magnavox 42MF321D/17 problem. Sound but no picture.

[William42]

I don't know much about the problem but what I do know is this:
A friend gave me this plasma TV. He got it from his friend. The initial owner said that it would just “go out” sometimes and apparently it got so bad that he gave it away. My friend didn't want to deal with it so he gave it to me. I brought it home, hooked it up and turned it on. I got nothing so I took off the back and had a look around. I saw nor smelled nothing unusual. After probing around awhile I pushed the menu button and the menu screen appeared so I put the back back on, hooked it up again, attached the speakers and I got a good picture and sound. Everything seemed good and I smiled for my luck.

After the set was on for about an hour the picture started acting funny. It looked as if it wanted to go blank. About 25% of the picture, in various places, started fading in and out of black but before it went out completely I turned the TV off then back on again and the picture was fine again. Then I fell asleep for 4 hours and awoke to a black screen but I still had sound and I was able to change channels but only had sound, no picture. That was two days ago. I've tried several times turning it on since then but only get sound, no picture. I had unplugged the TV for a day but that didn't help any. That's all the information that I can provide.

Now, if there's anything anyone can do to help me with this problem, even with the limited information provided, I would be most grateful. I'm pretty handy with things and can diagnose problems if I knew where to look but I don't have a clue where to start. From my research I found that this problem might be related to the YSUS circuit or PC board. But maybe from my limited description of the problem y'all might think it could be something else?

Are there any tests I could do, i.e, voltage outputs, etc. that would tell me anything? And by the way, I don't know what a YSUS board is or what it looks like so you would have to be pretty specific in your description of things. If photos would help I could provide them.

Again, any help with this problem would be greatly appreciated.
Thanks in advance,
Bill

[William42]

Re: Help with Magnavox 42MF321D/17 problem. Sound but no picture.

I thought I'd have another look at my tv's guts and while I was at it, snap a few photos. I assume that this is the YSUS board?



After looking it over a little better I noticed that one of the caps has a bulge on it's top.



Is this enough to cause the problem that I described above? Again, thanks for any input...

[CoppellTVRepair]

Re: Help with Magnavox 42MF321D/17 problem. Sound but no picture.

Ss I told you earlier in our email communication I have a fixed over of thousand of those and sure enough I have walked down the troubleshooting path you are trying to lead me into at least 100 times.

TO do this right is more complex than you think.

It is possible you may be lucky and all the required checks may turn out to be not needed as they may all happen to pass; then it may look like the repair is fairly easy and seamless.

Then again if one of the possible failures on the YSUS has materialized then there's a good chance that you'd fry the buffer board; and that's not even considering the quality of repair you may do on the buffer board itself, which you can't quite verify or confirm without having a working Y-main; and the other way around – without a working buffer you can't be 100% certain (although you can get close) to knowing that you have a working Y-main.

Long story short, it is WAY easier to have this fixed by someone who does have a complete set and knows how to test boards one by one.

Again, that does not mean you could not possibly do it yourself; what it means is that after having fixed 1000 of those I would have taken a chance by doing certain things in certain order, but I would have preferred to have a working set where I can work on boards one by one and know what I am getting, not just hope it is all right.

I do not expect you to believe me, frankly, since I do this for living and it is natural for you to assume that I just want money. I would not blame you for doing so - I have a general contractor currently working on a building of mine and even though I know the guy for several years nothing in the world could convince me that he's doing a good job and not cutting quality and effort at my cost…such is the human nature 

Nothing teaches you better than personal experience.

As I said if you're lucky you may decide it was really easy and all the above was just a marketing pitch.

Then again I know that if you do 10 or 100 boards you'll think differently…just as I do.

Resources:

http://blog.coppelltvrepair.com/2010...according.html

http://www.coppelltvrepair.com/p/165...ew-oem-buffers

http://www.coppelltvrepair.com/p/360...repair-service

Note: the above articles do not say nearly all of what we know about the boards and I am not ashamed to admit it. I have personally stayed late not one and two nights at the time , reverse engineering and experimenting with the Y-Main.