Magnavox 42MF230A/37 intermitent and Red horizontal lines

[chancho]

High, new member here. I love to tinker before I throw out my electronics.
I have saved many a washer/dryer/dishwasher and computer with an inexpensive component change instead of the junk heap.
When I found you guys, my spirits lifted because I have never tried to fix a plasma TV before.

I have a 2006 Magnavox 42MF230A/37 Plasma TV. I think I have two separate problems:

1) There is a red/green/blue horizontal pixel band on the top 5" of the TV. Below it the TV picture is fine. This has been going on for a few weeks now.

2) Using an HDMI/DVI cable from my cable box to DVI input on the Plasma, the picture including the pixel band with completely cut out for 5-10 seconds and come back on and appear normal.
I switched inputs to the side yellow RCA, and the picture no longer cuts out. I haven't had a chance to try the component inputs yet.

I opened up the back to expose the boards. The is no burnt smell or components that I can see; neither are there any puffed capacitors.
Any help would be appreciated.

I know it's 7 years old, but if it could be fixed for ~$150, the tinker factor would be priceless.

[tom66]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

Can we see a picture of the fault? I have suspicion that it is a Y-buffer fault.

[chancho]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

Can we see a picture of the fault? I have suspicion that it is a Y-buffer fault.

I'll takes some and get back... thanks

[chancho]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

Here is a shot of the back, full screen and close up.

[tom66]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

Definitely a Y-buffer fault then. How's your soldering, or would you prefer to replace the faulty board instead?

[chancho]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

I've done plenty of component level repairs.
How easy is it to diagnose?

[tom66]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

Along the left hand side of that picture, you have a long board which connects to the orange/brown connectors which ultimately go to the plasma panel's glass. There is an IC under each heatsink next to the connectors. Replace the top two ICs (~TQFP128 soldering.)

No diagnosis necessary -- unless you want to narrow down exactly which chip is causing the fault (only one is failed, but due to how they are interlaced, it is hard to tell which.)

[chancho]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

I think things went from bad to worse. I turned it on to check some voltages, and there was a loud pop and the whole screen went black. Any ideas before I throw in the towel?

[tom66]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

It's quite possible that Y-buffer chip that was failing has failed completely. Unplug the top Y-buffer and see if you get an image on the lower half of the display.

[chancho]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

I tried disconnecting the top 2, 3, and 4 buffer connectors...nothing changed.
I tried HDMI input on main board and RCA input on side board...only black screen.
I cycled through all the source inputs, but nothing showed up on the screen, not even the no source box that usually appears when I have the wrong input selected.
The only thing different is that the lines that were on top of the screen are now flashing on the bottom 5" of the screen.
I looked again, and I couldn't find any burn marks of puffed caps.

I'm going for a new TV today, but I will keep trying to fix this one until you:
1) either say that we found it and it's fixable
2) the parts cost more than $150
3) you've had enough
I appreciate your help no matter what. Either way, let me know where the beer fund button is, so I can contribute...

[tom66]

Re: Magnavox 42MF230A/37 intermitent and Red horizontal lines

I meant the whole board should come out of the set. Do you have screen glow in a dark room?
Re. New TV, avoid Samsung :P. (This is basically a Samsung PDP inside.)