Samsung LE40A656A1FXXU Display Problem

[dick_barton]

Hello all,
I have a Samsung LE40A656A1FXXU which has a problem displaying a picture. From cold the screen appears to be split into three sections. The leftmost third has some sort of refreshing problem and while watching everything is smeary and blurry as the picture being updated. The middle third of the screen is dark although you can still see the picture and the rightmost third appears as normal.

Taping around the edge of the screen does not have any effect. On several occasions after being on for 30 – 40 minutes the picture has returned to normal. Taping around the edge of the screen and on the circuit boards does not bring back the fault once it seems to clear. Only when the set has cooled down and is switched back on does it return to the faulty display.

Having replaced the TCON board I can rule that out as faulty but I have just noticed that bringing up the screen menu when the middle of the screen is dark has no effect on the menu colours which are as they should.

Would I be correct in thinking I have a video fault on the main AV board?
Any advice gratefully accepted.

CN801 readings with the set on.
P1 3.6v P2 1.95v
P3 5.01v P4 0.0v
P5 0.0v P6 0.0v
P7 12.7v P8 12.72v
P9 0.0v P10 0.0v
P11 0.0v P12 0.0V
P13 4.96v P14 4.96v
P15 4.96v P16 4.96v
P17 0.0v P18 0.0v
P19 12.75v P20 0.0v
P21 12.75v P22 12.75v
P23 0.0v P24 0.0v

CN803 readings with the set on.
P1 4.82V
P2 0.0v
P3 3.22V
P4 4.82V

Thanks

[CapLeaker]

Re: Samsung LE40A656A1FXXU Display Problem

my bet is on the tab bond. anywhere after the tcon and the actual LCD.

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Hello CapLeaker,
Thanks for your reply. I had seriously considered that may well be the problem but what is niggling me is why the OSD Menu appears nice and clean with no colour distortion in the middle of the screen even though the picture immediately behind it is faulty.
Regards

[CapLeaker]

Re: Samsung LE40A656A1FXXU Display Problem

maybe you can upload a picture with the fault?

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Hello CapLeaker.
When I try to upload a picture it comes up with a Timeout Error. I have tried several times but will try again. It must be possible because others are able to do it so I have to work out where I'm going wrong.
Regards

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Here's the message I keep getting. The pictures are 2Mbyes and jpg format so there shouldn't be a problem.


Request Time-out

Server timeout waiting for the HTTP request from the client.
Apache/2.2.22 (Debian) Server at venture.wssnoc.net Port 80

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Hello CapLeaker,
I have reduced the file size and finally uploaded two pictures. The screen is set to TV with no signal input and I think you can see the dark centre of the screen. The next picture is with the OSD and it appears to sit on top of the darker area of the screen and not be affected by the darker area of the screen behind it.
Regards

[mmartell]

Re: Samsung LE40A656A1FXXU Display Problem

Interesting almost looks like a led fault but I don't know how the leds are arranged in this set. Post a pic of the set with the back off and of each board.

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Hello,
Here are some more pictures of the back of the set.
Regards

[CapLeaker]

Re: Samsung LE40A656A1FXXU Display Problem

What happens if you put actual video on the screen? Is the left side sluggish in response? It's either tab bond or the panel.

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

The left hand side is extremely sluggish and smears as the picture content changes. The centre part of the screen is darkish and very red the right-hand side of the picture is pretty good.
Regards

[mmartell]

Re: Samsung LE40A656A1FXXU Display Problem

Oops I missed the part about the refresh problem. I concur with Capleaker about bad panel. Unplug one side of the tcon to panel ribbons and check the pic. Then unplug the other side and check pic again.

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Hello mmartell & CapLeaker,
Moving one of the ribbons on the Tcon board which go to the long narrow circuit board sat at the top of the screen panel does clear the fault and / or brings it back when wiggling.
I must admit that you were both spot on with your diagnosis for which I thank you.
Kind regards

[CapLeaker]

Re: Samsung LE40A656A1FXXU Display Problem

The left hand side is extremely sluggish and smears as the picture content changes. The centre part of the screen is darkish and very red the right-hand side of the picture is pretty good.
Regards

I see you got it fixed now, but when the screen is sluggish, that is surely a bad tab bond.

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Hello CapLeaker,
It's not fixed. As you say it's a tab problem so at least I no longer have any niggles. Now if I can find the poor connection point and arrange to pack something on top to maintain some pressure on it and keep it in place.
Thanks

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Unfortunately the puzzle continues. By opening up the tab on the leftmost Tcon connector looking at the rear of the set and wiggling it I can get a good picture. If I switch off, wait 30 seconds and switch back on the picture is dark again and will only return to normal when I open the tab and wiggle the (left-hand) connector once again.

Wiggling the other 3 in turn does not appear to return the picture to normal.

I have removed the frame from around the screen and have easy access to the screen panel tabs. Putting finger pressure on these 16 tabs in turn has no effect on the picture.

Any further ideas would be most welcome.
Regards

[CapLeaker]

Re: Samsung LE40A656A1FXXU Display Problem

try to rub an eraser followed by some Deoxid on the ribbon cable and clean the connector with alcohol?

[dick_barton]

Re: Samsung LE40A656A1FXXU Display Problem

Have finally accepted that it's a panel fault and split it down for spares.
Thanks to all for your assistance.