Sanyo DP42849 LCD Half Screen 50 Cent..!

[smartjohn]

So now I am tackling my first LCD. I have raster (grey background) on 100% of screen with no signal applied. When I add a video signal, I only get half screen. I see on the other posts here that this model has t-con issues. Any other suggestions what to try first? Thanks for any input, I am in uncharted waters for me. Up until now I have been a plasma geek!

[smartjohn]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

My troubleshooting so far: Pulled the back and checked all ribbon cables. Checked the connections on the T-con board. All appear OK pulled the ribbons out and cleaned with clean cloth and contact cleaner. Still no dice, same thing only left half is working.

I read budm 's post on tab bond repair https://www.badcaps.net/forum/showthread.php?t=25371 but I must be missing something???

How do you trouble shoot the bonds to know if they are actually bad? Is there an easy test? Where exactly are the bonds that need repaired? The end of the tab that goes into the screen? or the end that connects to the long pc board that runs half of the screen width? I am just not getting what the magic is with these thermal pads and just where do they need to go? If someone can point me to another post or fill me in, much appreciated !! HaHa..

I may just go for getting another T-con board to test it first, before burning a lot more time on this one.... Thanks for any pointers!

[freakaftr8]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

Well I cannot guarantee that this is a tab bond issue. At least yet. Thus could be a tcon board fault but really the only way ro tell is a tcon board replacement. Looks as if no voltage is getting to right panel board. Check upper panel address board for bad solder connections. This board is only accessable if you pull off the frame of the panel unfortunately.

[smartjohn]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

Yes, I had the frame off the panel already. It's no big deal on this set only about 10 screws. I didn't see any bad IC's or anything that looked weird physically. I tried to feed the ribbon from the left side of the t-con board to the right half of the panel. I know it would be a screwed up image but it should prove that the panel was OK. When I did this I got all black no image. I went back to the normal hook up and it still works on the left side. I was trying to prove the t-con was OK. I guess I could try Right T-con to Left panel and see if this works.

Before i screw with that, what voltages should I be seeing in the panel address board? How do you "fix" the tab bonds???? I am lost here!! All I see is about 4 ribbons the run from the panel to the panel address board. From the name used, I am guessing it's the bond that connects the panel ribbon (tab) to the panel address board? I just need a little better explanation of how these are "bonded" together.

[tw2005]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

I don't think swapping the T-con ribbons will work, pin outs are most likely wrong. Tried that myself with a sanyo 37" AUO panel way back and it did not work and i remember seeing smoke coming out of the top of the panel from a resistor network. Lucky i didnot stuff it completely.

[splitcrete]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

I tried a left to right switch on a Toshiba. It burned the tab bonds beyond repair. DON'T DO IT. It taught me a lesson. I will never do that again. Good luck with your LCD

[martino]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

I have raster (grey background) on 100% of screen with no signal applied. When I add a video signal, I only get half screen.

He get's snow on the full screen with no signal,wouldn't that mean it can't be the t-con?

Or do you mean with grey background,that the back light is on all full screen?

[tom66]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

This fault is almost always tab bonds, I bet this TV uses AUO 42" panel, which has common fault with left or right tab bond. Just press on the bond with the frame off & picture should sort itself out. See video for similar fault/diagnosis/repair:
https://www.youtube.com/watch?v=purk_SyiT44

I have done LG 42" 42LH3000 with tab bond issue on left half of panel.

[freakaftr8]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

Im surprised the tab ics didnt go up in smoke when you fitted the tcon on the opposite side ribbon. Usually this sends reverse voltage into an area for the data bus as the ribbons work in opposite directions. We all learn the hard way sometimes. I did this once in my earlier days.

[smartjohn]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

martino, yes I meant gray background from backlight on the entire screen just before video signal fires up. Once video hits, right side goes totally black. I am going to try tom66's suggestion and press on the strips and see if i get anything. its rather difficult on this model to run with the set partially apart cause the plastic back is also the mounting place for the boards. I think if i "cradle" the set on its back i can take the bezel off to get access to the strips. Thanks guys for keeping me from going completely stupid on the ribbon swap!! no smoke so far ... I'm lucky (i think!). I'll try to get some better photo's as I have a new (to me) Canon Rebel XT that should improve over my iPhone shots.

[smartjohn]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

Finally got time to prop this set face up with the bezel pulled off. I left all but 4 screws holding the back to the bezel and flipped it on it's back. I pulled these 4 screws from below and then lifted the black bezel right off. I next had to pull the 12 screws that hold the metal LCD frame. And started to pull it off, but forgot about the tape that holds the tcon cover to the metal frame. After I pulled the tape off, the metal frame lifted strait up. I fired the set up and same as before, right side was black. I started pushing the ribbon tabs the way the video in tom66's post #8 explains. Bingo! the right half jumped around for a minute and then stayed lit!! Only issue is that the extreme right side has two large green and blue vertical bars running down the screen. Could this be a bad tcon board?? Your thoughts???

[tom66]

Re: Sanyo DP42849 LCD Half Screen 50 Cent..!

That could be a bad LCD panel, you just need to try pressing on all the tabs to see if it resolves itself. Not t-con issue.