Free TV- Repair Help Appreciated

[ShortCircuited]

They were throwing it away so i couldn't pass it up.
Model: LC-70LE550U

Problem Description:
-When powered on all indicator lights and backlights power on as expected.
-95% of the time the screen is black, but backlights are always on.
-About 5% (maybe even less) when powered on you will see the full picture for 1-2 seconds and then the screen quickly fades to black but backlights remain on.
- I disconnected the left ribbon cable (see photo) (as sitting facing front of TV) from the tcon board and the right side (as sitting facing front of TV) works fine while the left side is pure white (see images). When I disconnect right ribbon from tcon board the left side remains dark wile backlights remain on.
- Swapped ribbon cables on tcon board and the problem is exactly the same regardless of which ribbon cable.

Researching this exact TV here at badcaps points to a driver issue with some tabs. I would rather check with this forum before going further-at this point I have only removed the rear cover.

Appreciate any help/suggestions.

[Diah]

Re: Free TV- Repair Help Appreciated

1- could you play signal and show us the half screen which showing image how it look ?
2- can you record the 5% less option to show how the picture fades to black..?
3- if you play signal then you can tell if you hear sound or not when the set on with black screen

[neilc6]

Re: Free TV- Repair Help Appreciated

You have a panel problem on the bad side. You can try the tape cutoff method.

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

I did some more digging and found that a short-circuit is present momentarily when powering on. This occurs on the lower-left cable (see photo) which gets extremely hot-absolutely too hot to touch - for 1-2 second(s) then cools down. During a 5% boot where the picture showed for 1-2 seconds the heat was present until the picture faded and then the cable cooled down. During a typical boot (95% of the time) the heat burst is barely a second, BUT VERY HOT. Not sure how the trace and ribbon cable survives that burst of heat.

Appears as the left portion of the screen has a short and the tcon board detects this short and then powers off LCD output.

EDIT: If you look at my photo in the first post showing the white side on the left side of the screen and then again the lower-left quadrant of that half there are some bright white spots. Maybe this is what Neil is referring to?

Tape cutoff method? I'm all ears.

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

With this disconnected I can get this (crappy image). As soon as I close the ribbon latch (post 4 last photo) in this top photo (220268) The left portion of the screen is perfect for 1/2 second then fades away to no picture. Sure appears Neil is correct and the problem is with the LCD panel.



Crappy Image

[Clucas]

Re: Free TV- Repair Help Appreciated

most likely the panel and not repairable. Never heard of the tape cutoff method but doesn't sound legit. :-)

[DXseekerMO]

Re: Free TV- Repair Help Appreciated

This is a common problem with 70" Sharps. I have a LC-70C6600U with a similar problem.

The Gate Drive ICs embedded in the flex tabs off the left side drive boards are likely shorted. You basically proved that by detaching the connector from the source driver boards resulting in a better, albeit not perfect picture.

In the past I have detached that side drive board from the screen by heating up each of the flex tab bonds at the screen and slowly peeling them off. Too much heat will crack the panel...on the other hand not enough heat and they won't peel away cleanly.

I did this on the EXACT SAME MODEL SET you have. The picture was basically OK after that with some pixel stick at the bottom.

Peel the tabs as above and check the temperature of the same gate drive ICs on the right side. If one/some of the ICs is/are hotter than the others then this work-around should be considered a failure and the TV should be recycled.

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

This is a common problem with 70" Sharps. I have a LC-70C6600U with a similar problem.

The Gate Drive ICs embedded in the flex tabs off the left side drive boards are likely shorted. You basically proved that by detaching the connector from the source driver boards resulting in a better, albeit not perfect picture.

In the past I have detached that side drive board from the screen by heating up each of the flex tab bonds at the screen and slowly peeling them off. Too much heat will crack the panel...on the other hand not enough heat and they won't peel away cleanly.

I did this on the EXACT SAME MODEL SET you have. The picture was basically OK after that with some pixel stick at the bottom.

Peel the tabs as above and check the temperature of the same gate drive ICs on the right side. If one/some of the ICs is/are hotter than the others then this work-around should be considered a failure and the TV should be recycled.

Thanks for the suggestion. I will look into this some more.

You are saying carefully heat this up where it connects to the LCD panel and peel it away disconnecting from the LCD? This one is the only one getting hot when booting. I used a piece of plastic and applied some light pressure to this cable and was able to get it to stay on for several seconds, so i think all the others are fine. LCD panel has 10 of these LCD connections in total and the one with the arrow (left-lowest) is the one causing the problem.

[DXseekerMO]

Re: Free TV- Repair Help Appreciated

Thanks for the suggestion. I will look into this some more.

You are saying carefully heat this up where it connects to the LCD panel and peel it away disconnecting from the LCD? This one is the only one getting hot when booting. I used a piece of plastic and applied some light pressure to this cable and was able to get it to stay on for several seconds, so i think all the others are fine. LCD panel has 10 of these LCD connections in total and the one with the arrow (left-lowest) is the one causing the problem.

Yes, this is what I am saying. There are several threads in here describing the problem and the procedure. There's one of these that's particularly good, I can't remember the username but he's in the NW US. Maybe someone will chime in here with a name.

I'm not very happy with myself forgetting the username....this guy helped me out a lot.

[DXseekerMO]

Re: Free TV- Repair Help Appreciated

Thanks for the suggestion. I will look into this some more.

You are saying carefully heat this up where it connects to the LCD panel and peel it away disconnecting from the LCD? This one is the only one getting hot when booting. I used a piece of plastic and applied some light pressure to this cable and was able to get it to stay on for several seconds, so i think all the others are fine. LCD panel has 10 of these LCD connections in total and the one with the arrow (left-lowest) is the one causing the problem.

His username is "freakaftr8". The Vizio 70" TVs use a Sharp panel so also check out similar repairs on model e701i-a3(e)

Shame on me for forgetting his name

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

His username is "freakaftr8". The Vizio 70" TVs use a Sharp panel so also check out similar repairs on model e701i-a3(e)

Shame on me for forgetting his name

TY for the help...will look em up for sure!

[mmartell]

Re: Free TV- Repair Help Appreciated

Don't use heat - these will peel off like tape. There's a small chance afterward that some residue is shorting some of the address lines you can then go over the pads with a magnifying glass to spot it and rectify it.

[jjanssen7]

Re: Free TV- Repair Help Appreciated

Don't use heat - these will peel off like tape. There's a small chance afterward that some residue is shorting some of the address lines you can then go over the pads with a magnifying glass to spot it and rectify it.

X2 No heat, not necessary. And too much risk of damage.

[DXseekerMO]

Re: Free TV- Repair Help Appreciated

Don't use heat - these will peel off like tape. There's a small chance afterward that some residue is shorting some of the address lines you can then go over the pads with a magnifying glass to spot it and rectify it.

X2 No heat, not necessary. And too much risk of damage.

Guys I've always used heat with no damage...then again I don't go overboard with it either. The tabs seem to peel off a lot cleaner.

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

I used a hair dryer to warm the adhesive with my hand as a temp gauge-too hot for me too hot for TV. Regardless the cable tore. Initially, it was much improved after removing that one driver cable (bottom-left), so I flipped TV for testing and now the entire upper-left region is very dark. I think I did something to another cable messing with that front trim/bezel. Will have a closer look with my chinese microscope to ensure the contacts and adhesion are not causing a problem. TV boots most of the time now. Either way, I think she is destined for the can.

Will have another go at it soon.

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

The bottom-left sector looks much better with the cable removed. This tcon board is not shutting down anymore. Should I remove the next LCD ribbon cable up from the bottom?

EDIT: I measured the light strip at the bottom at 18cm high, which equals 5 horizontal section for the LCD height- this is the exact number of ribbon cables on each side (5). With this and the TV's probable fate I am thinking remove another LCD ribbon cable. Any votes on this?
Here are a few shots with the lower-left LCD ribbon cable removed/cleaned:

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

I removed all 5 driver cables to the left side and it appears fine now. Did find one thin vertical line (blue) on right half of screen, BUT I can live with that for free. Used a cigarette lighter to heat the tabs on the PCB side, The LCD side removes easy enough.

Thanks for the help everyone.

[ShortCircuited]

Re: Free TV- Repair Help Appreciated

TV is still working. It did have a blue vertical line, but that is now gone.

[nomoresonys]

Re: Free TV- Repair Help Appreciated

most likely the panel and not repairable. Never heard of the tape cutoff method but doesn't sound legit. :-)

It's LEGIT...try a little research before popping off.