Sony Bravia KDL - 46EX650 top part of screen blank or lines

[dicky96]

This problem apparently started intermittently then gradually became permanent.

I tried reseating the LVDS and T-Con cables at the Tcon board but it didn't help. I suppose I could strip it down further and try reseating the cables at the other end but I thought Tcon cable problems cause vertical lines?

Or is this tab bonds / chip on flex problem yet again!

Rich

[CapLeaker]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

seems like on the first picture is a bar, on the second picture there are lines, probably sluggish to respond. My bet are on the tab bonds.

[attainteddragon]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

since i have seen lots of sony tab issues, i would look there first.

give the bezel a twist and see if it alters the issue.

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

Trying to twist the bezel had no effect.

I got the bezel removed and also the metal shield or cover around the edge of the LCD panel. There are six tab bonds at the bottom, pressing on each of these make absolutely no difference to the picture at all

There seems to be a plastic cover or edging all around the LCD panel and I can not see any evidence of tab bonds on the sides of the panel unless they are under the plastic but I am not sure how I could remove that as it passes behind the six flexes at the bottom of the panel

See pics
Rich

[attainteddragon]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

if you disconnect one side of the t-con at a time, is the fault still present on either half?

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

OK mate.

With the right hand of the screen disconnected, the left hand side still has the flickering horizontal lines same as before (actually I didn't check closely if the height of the flickering area is the same but think it was)

With the left hand side disconnected, the right hand side now shows more of the image than before (compare the attached pic with the one on post #4 - you can now see the icon above the Audio icon) and there are no flickering horizontal lines, just a blank grey area at the very top of the screen

Rich

[attainteddragon]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

it's hard to see, but is there a matching grey bar on the top and bottom of the screen in that pic. maybe feeding it a source can make things look a little clearer.

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

Sorry mate the photo wasn't good. What you see on the screen is a menu from a MAG250 box connected to HDMI on the TV.

There is no grey bar at the bottom and it seems the grey bar at the top is a 'red herring' just part of the menu screen from the MAG250 because when I attached another video source I actually get a perfectly good picture full screen height with just the one TCON cable attached.

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

With just the other TCON cable attached or with both I get those horrible flickering yellow lines at the top of the screen,

Is this indicating i have a TCON fault and not a panel fault?

I suppose I could arrange to connect the 'good' TCON cable to the other side of the panel, the leads are too short but if I let the mainboard and Tcon board hang free I could do this though it may be a bit awkward to see the screen at the same time. If I went to that effort would that prove anything we don't already know?

Rich

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

Oh here is a photo with just the other Tcon cable attached. Different video image because I could not navigate to the calendar icon as i could no longer see it! but that is not really relevant.

I did try connecting the 'bad' side of the screen to the 'good' Tcon cable

At first I got vertical lines all down the 'bad' side of the screen but interestingly there were no flickering horizontal bars. Of course I had not seated the tcon cable properly. After fixing that I just got a completely blank screen with no flickering lines or anything else. So I guess it is not as simple as that, ahh well...

Anyway it doesn't appear to have done any harm when I put the cables back how they were I was back to square one.

[attainteddragon]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

looks to me that you have another bad panel. it may even be a side cof chip but not totally sure about that.

you know which side is playing up, you can have a prod and play to see if you can isolate the fault a bit better. you might get lucky and find something getting hot on the panel driver board, but i would not hold my breath on this one unfortunately.

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

OK thanks mate. I can only see tab bonds at the bottom of the panel, not on the sides

Will check for something getting hot.

[dicky96]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

Nothing getting particularly hot on the narrow boards that the tab bond cables connect to though it's a bit hard it tell as any IC components are on the underside of the boards.

I definitely can't see any side tabs on this panel.

I also tried swapping the Tcon cables around to eliminate a possible bad one - it makes no difference so they are both OK.

I seem to have something missing in my knowledge here. I am really confused how I am supposed to diagnose a TCon fault from a panel fault.

I am also puzzled by the results of disconnecting one TCon cable at a time, and how you interpret them.

To be clear, I have the following situation.

Left cable only attached = left half screen image with lines at top
Right cable only attached = right half screen image with good picture
Both cables attached = full screen image with lines at top on both halves

It seems to me, if with both cables attached I get lines on at the top of the right hand side of the screen, but with just right hand Tcon cable I get a good image on that side.... then it suggests some signal coming from the left hand TCon cable is making the right hand side go bad - yet you say these results prove it's a panel fault.

So why am I misunderstanding this?


I am not questioning your knowledge here Mr Dragon, you obviously know more than me, I am a learner. I just can't get my head around the logic of the diagnosis and I really want to understand this.

Is there some explanation or tutorial somewhere of the method and reasoning to correctly diagnose a faulty panel from a faulty Tcon?

Thanks
Rich

[attainteddragon]

Re: Sony Bravia KDL - 46EX650 top part of screen blank or lines

To be clear, I have the following situation.

Left cable only attached = left half screen image with lines at top
Right cable only attached = right half screen image with good picture
Both cables attached = full screen image with lines at top on both halves



Rich

i am only a learner too, so my knowledge is very minor compared to some others around here.

think of it this way, when you only have your right hand side hooked up all is great in the world, but at any time when you have your left hand side hooked up, your panel no longer wants to play with anyone else. when you get a signal through the bad chip on that side of the board, whether it is something short or open, it ends up taking priority over the rest of the panel. guessing it is really due to the needs of the failed part, so the panel as a whole suffers. that is why one side works properly without the bad half in play. nothing getting dragged down.

the only way to really tell what is exactly wrong would to be to put your boards into a known good panel, or scope the lvds signals that go into and out of the t-con.

i believe that last time you were able to locate the offending tab chip that was playing up. this time not so lucky, there is always a chance that there is a component on the panel driver board that has failed, but outside of a ceramic cap going open, i have seen very little in the way of anyone doing much in repairs on these boards.

there is also lots of cases of water damage on these boards due to cleaning with an overly wet sponge when the driver board is on the bottom of the screen.

hope this is coherent enough, havn't finished my first coffee yet! my bad.