LCD Problem (Obvious in Pictures)

[metalbird44]

Model: Sharp LC-70LE757U

Problem: Dark Area in Middle of Screen, HOWEVER OPC meter displays perfectly in that area

Steps Tried So Far: Disconnected the Left-of-Screen-Side Tabs from the T-Con board

[budwich]

Re: LCD Problem (Obvious in Pictures)

Model: Sharp LC-70LE757U

Problem: Dark Area in Middle of Screen, HOWEVER OPC meter displays perfectly in that area

Steps Tried So Far: Disconnected the Left-of-Screen-Side Tabs from the T-Con board

don't understand what you mean by "disconnected the ... from the tcon board"

why or how did you decide on this. what was happening before they were disconnected?

try posting a picture of a known test pattern (color bars). Maybe post a picture of the area where you "disconnected" the tabs.
IF you are talking about the tabs drivers on side of the panel, they are usually removed along with any side edge boards on the side.

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

I saved the TV from being dumpstered.

I found it was having the exact same problem as described here:
(buzzing T-Con board, isolated to left-side-most ribbon)

https://www.badcaps.net/forum/showthread.php?t=50060

So I disconnected the side ribbon:



Now I'm here.

[budwich]

Re: LCD Problem (Obvious in Pictures)

ok... that helps. I didn't read the other thread that you referenced but if you put the corner ribbon back and disconnect the one on the other side, what happens?

Further, the disconnecting of the corner ribbon only isolates the side tabs, it does not completely "remove" them which is the final step IF indeed that's the problem. Hence, you need to clarify all your steps to ensure that the forum understands exactly where you have been and what is happening so that you don't end up with a "bad set" or worse.

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

Okay, I replaced in the right-of-screen side ribbon and removed out the left-of-screen side. (The TV is upside down in pictures.)

The whirring sound coming from the T-Con board has returned, as has the flickering, but the spot is still there, although it seems to have changed shape slightly.

[budwich]

Re: LCD Problem (Obvious in Pictures)

hmmmm.... so it appears that there is a potential issue with the side that causes "tcon noise" since powering / signalling to the other side is disconnected.

The problem, that I see, (not a good picture to determine display issue... not a known test pattern) is there app is there appears to be a vertical line. This is usually not a good sign. Since the history of the "dumpster dive" is unknown, you need to carefully look at the connections / edge boards along the bottom of the panel. Someone may have did some "window washing" and caused some "contamination" therein.... look at the tabs near the area of the vertical line. possibly look at cleaning / reseating clampable cables that exist between the tcon and the edge boards.

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

What would be a good test pattern? Is there a name for one I can look up?

Thanks for your help.

[budwich]

Re: LCD Problem (Obvious in Pictures)

smpte color bars. Its possible that the vertical line that I see is a reflection on the screen as opposed to a display line... maybe

[chrismurphy]

Re: LCD Problem (Obvious in Pictures)

LED array fault
This TV has local dimming , suggest obtain new power/driver board to see if the symptom is still there. If it is then panel fault LEDS

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

Here's the test color bars:



I couldn't get rid of the glare. The room's not very bright but there was still some residual daylight.

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

Here's some angled shots to reduce glare:

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

One more sample, this is what the set looks like with both side driver tabs connected:

[budwich]

Re: LCD Problem (Obvious in Pictures)

ok... thanks for the extra "test pictures". First, just for info / clarification, the small corner cables at the bottom of the panel are NOT "tabs". They are interconnection cables connecting the bottom edge boards to the side edge boards. The "tabs" are "flex ribbons" connecting the edge boards to the panels. They are bonded to the panel.

Anyway, the pictures provide a "clearer" display of what is happening (your pictures are upside down, I know). The pictures show a left side (properly seen) of the display as good. The darkness is evenly distributed top to bottom in basically the middle of the screen. The right side of the picture has color issues. Normally (as in the failure case), they may be horizontal lines running from the right side towards the left side. They don't appear to be so. This potentially indicates that there may not be a problem with the tabs / tab drivers on the right side. There might be more of a problem with the interconnection between the side board and bottom edge board on the right side... either the cable itself or at the clampable connector on the boards. It might even be a problem with the tcon on the right side... maybe.

As in quite a few threads (including the one that you linked), the panel is likely saveable by removing the tabs along the "bad side".... BUT WAIT. As this "operation" (ie. removal of tabs) is a one time operation and CANNOT be reversed, you should try a couple of more tests.

One, try switching around the corner cables from one side to the other (ie. swap) and see if the problem / display changes. Go from there. Still further, the side has two edge boards that are interconnected with unclampable / clampable interconnection ribbon (brownish). you can also try disconnecting the "u" cable and see if this changes anything (ie. leave the corner cables at the bottom connected). This "test" isolates half the side tab drivers to see if there is some other issue that might be addressable in another fashion besides tab removal. Go slow and always de-power before moving / removing cables.

At this point, I wouldn't do any "tab removal" just yet.

[Diah]

Re: LCD Problem (Obvious in Pictures)

i would suggest don't do any things with tabs or ribbon any more, just try to take the LCD in parts carefully so we see what we have behind it which make this dark., i tips on burn smoke

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

Okay, switching the corner ribbons had no effect.

However, removing the brown "U" ribbon connecting the two side board on the problem side eliminated the buzzing and moving horizontal lines, but the dark area returned.

[Diah]

Re: LCD Problem (Obvious in Pictures)

did you try turn OPC to off from setting , then reboot it and see any effect
https://www.youtube.com/watch?v=xXNTKYDLD5M

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

did you try turn OPC to off from setting , then reboot it and see any effect

Yes, the most recent pictures were taken with OPC turned off.

[budwich]

Re: LCD Problem (Obvious in Pictures)

the dark area is the result of the side drivers being "undriven". Basically, even though you have disconnected the cabling at various points (and tests), the tabs / tab drivers are still connected to the panel. The result is that they "load down" the drivers on the opposite side. This causes the "dark area" in the screen (normally about "half screen") and the "color shift" on the bad side as the "timing" of the signals flowing across the screen is impacted.

Can you post a picture that you see with the "half side" edge board. I would like to see what happens with the color bars in the bottom half of the screen.... for information purposes. Still looks like a side driver issue.... possibly on the upper half side edge board.... maybe

[metalbird44]

Re: LCD Problem (Obvious in Pictures)

Here is the display with the second board of side tabs disconnected (via the brown U ribbon):



Also, I believe I've determined the source of the buzzing noise on the T-Con board:

[Davi.p]

Re: LCD Problem (Obvious in Pictures)



This is the problem now... is it a cut?? It's a burnt trace?
Seriously, i think this huge tv needs a professional, too many things in the field here.. do you have any experience in electronics repair??