SONY Bravia 40" LCD - 40W4500 - Interesting Picture Problem.....

[markie76]

Hi Guys,

Was looking for a tv for mum and came across this one being sold as faulty with a picture problem so I thought I'd give it a go as suspected Tcon problem.

When you switch it on the picture comes up as follows;
1. The far rhs of the screen is fine - motion, brightness & colours ok.
2. The middle of the screen is dark - colours undefined and motion seems ok.
3. The lhs of the screen is dark & suffers from motion blur and image retention; movement has a trail and the previous image on the screen takes about 2-3 minutes to fade out. IE going from tv picture to a menu/epg fragments of the tv picture are left behind. Going from the epg to tv picture and fragments of the epg are left behind - see pictures below.

BUT.
After 20-30 minutes, if you give the back of the unit a slap on the lhs/middle the picture can go back to normal and works ok from then on. You can switch it off and back on and its ok. After leaving it for an extended period of time the symptoms return.

I originally thought this was a faulty Tcon until I slapped it and it went normal - dry joints somewhere?

Anyone experienced this before? Any pointers greatly appreciated  

Thanks,

Mark.

PICTURES






Close-up of the blurred/retained area

After 20 mins & a slap

[Ohm Supplies]

it looks to me as though the screen tabs have lifted slightly, its more common on one of the 42" panels that LG use (made by AUO) but it does happen on Samsung panels too.
the tabs need to be reattached/reseated, its a difficult job to do but its a common enough job and not impossible

regards
Andy

[markie76]

it looks to me as though the screen tabs have lifted slightly, its more common on one of the 42" panels that LG use (made by AUO) but it does happen on Samsung panels too.
the tabs need to be reattached/reseated, its a difficult job to do but its a common enough job and not impossible

regards
Andy

Thx for your reply. I was hoping no-one would say that :(
The panel in this is a Samsung lty400hc02 - the 'tabs' in question - do you mean the ones in the panel which go from the pcb along the edge onto the LCD layer?
What equipment is needed? Do you need new tabs?

Thanks,

Mark.

[Ohm Supplies]

the only way to test for sure is to strip down to the tabs and press them, see if the set changes, although the picture changes with a knock when its warm, I cant see it being anything else.

Andy

[markie76]

the only way to test for sure is to strip down to the tabs and press them, see if the set changes, although the picture changes with a knock when its warm, I cant see it being anything else.

Andy

OK, took it apart and removed the LCD panel outer shield to reveal the tabs and hey presto - the first tab on the top left when pressed in various positions the picture goes from bad to normal/flickers/bad/normal. I think its more in the middle of the tab where the rectangular block of something (chip?) is attached on the other side. Previously I've only seen this problem result in a complete coloured (red, green) line running down the screen.



Right how to repair?

These look like they are 'heat melted' onto the LCD layer and as I don't have any formal LCD panel manufacturing/repair equipment, what would be the best way to repair/extend its life...

Any suggestions?

Thanks,

Mark.

[Ohm Supplies]

If you press the top of the tab, what happends?

[markie76]

If you press the top of the tab, what happends?

Pressing hard along the top edge of the tab, where it is fixed to the pcb, make the picture flicker between normal and interlaced. Then pressing the front middle of the tab seems to have the most response where it goes between the symptoms in the picture and normal. At the moment the picture is normal - I'll leave it off for a while and try again.

[Kilroys]

Try this it says how to repair it.
Sony or Samsung, same panel, same problem

http://www.tv.quuq.org/forum/index.php?topic=5128.msg14299#msg14299

[markie76]

I packed it with some amalgamating tape and foam cut from a pipe-jacket - held in place by the metal panel frame.

For first few days when powred from cold the picture was ok.
Then it went again - but after 5 minutes or so with a tap/press would return and stay.

Looking closely at the plastic strip and surface chip - I'm wondering whether these fail because of gravity.
The chip is mounted on the underneath of the strip and given its subject to heating up/cooling anyway - gravity also pulling it away from the strip can't be helping.

I figure the solution requires some engineering - two thin strips of rigid metal, some rubber tape, two small nuts & bolts, a drill & some foul language. But the aim is to sandwich the chip to the strip between the rubber tape (piece top and bottom) which is then held in place with pressure from the metal strips (top and bottom).

Watch this space :)