Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

This simply means that the address IC that is built into the panel that addresses that particular section that you are unplugging has either shorted out or has a bad connection to the panel itself in a way that is overloading the circuit and causing overload condition on the tcon board which is in turn shutting the set off. If you can run the TV with that connector unplugged with the picture condition that it has then let it go like that and the owner would just have to deal with it or chalk up to a new TV. Honestly I think you're pretty lucky with having it working in the condition its in right now. I definitely give you props for trying. Sharp panels in sharp television's are really finicky with voltage fluctuations they always shut down with the 2-5 code.

Especially cracked panels they hardly ever function and sharp TVs they always give a 2-5 code because of an internal short.

I should also note that the reason you still have a picture with that one unplugged is because the left side is now doing all the work so expect premature failure of the left side tab drivers sometime.

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

That's kind of what I figure (premature failure). I didn't / don't understand how the tv is getting basically a full picture with one side not powered / running. My neighbor was over today looking at the "progress" and was some what surprised. We are going to "suit it up" and see what it looks like. He has already replaced it with a samsung (disappointed with its performance compared to the sharp... but it is what it is). He will likely use the unit as a "third tv" until it completely fails. I guess one thing based on your comment about the "finicky with voltage fluctuations", leaving me wondering if the power supply has "aged" such that it just below "optimum" and hence the set is in this "limp mode" (with cable disconnected) as a result of "just enough" power to run like that but not enough to power a "full set". Do these power supplies have any current limiting capabilities inherent in their design to prevent catastrophic failure of the PD and any subtending boards? Thanks again for the guidance / comments as they have certainly been helpful in furthering my understanding of things.

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

In essence yes of course the power supply ages but its current limiting capabilities usually stay the same. I'll help clarify things the reason you still have a full picture with one side driver disconnected is because both drivers on the left and the right do medium duty cycle meaning they're both doing the same thing but one side takes the load off of the other side. With one side disconnected the side left connected is doing the full load. So in turn that driver is going to get hotter. Who knows how long it'll last. The side that you disconnected has a short circuit or is pulling more current than the power supply allowed so the t-con board is giving the signal to the power supply that there's an overcurrent and then the power supply shut the TV down with an overcurrent protection. Meaning that if the TV did not shut down and the power supply were to ignore the signal telling it that there's an overcurrent problem then damage eventually will rise to the t-con board or the panel or the power supply. Usually the power supplies are the least affected but the t-con board can eventually go bad if the signal is left unchecked. So once you remove that short there's no more problem the board doesn't recognize an overcurrent protection and the TV is left running with the picture that you have now.

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

That's great clarification. bad news for me / us :-(

I will be setting the tv upright shortly (once some more hands show up) and get a picture of a full screen with some test pattern on it just to provide this thread with some record.

I am thinking that once last attempt might be to access the edge panel and get at the lower bonded cable points just to see if there is any "debris" that might be causing some problems.

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

just be really careful flexing those tab drivers that are bonded to the side of the panel. Usually when you start messing with those things go south quickly and you may have line dropout in the TV where you have black areas or the TV may go double image meaning that all get really blurry looking vertically. I had a samsung in here that had a 60 inch Sharp panel and something happened similar to what you're describing except I found the problem first by messing with the side driver. When I started fussing around with that driver screen came back and it looked good except I had some line dropped out with black lines going across the screen in that area. So I tried my usual repair of putting a small shim or buffer against that driver pressing it into the panel. The next thing I know is the driver got hot overheated and destroyed the whole panel. I attempted to pull that driver off the panel and allow the other side to do its job but once you remove that driver and then it causes all sorts of problems. So just heed my warning with caution.

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

Got the tv upright so that we can view things.... :-( Picture wasn't as good as it looked as I thought (looking at flat and partial screen).

Basically, unplugging the corner cable results in a dim picture on that mid side.
Below are a few pictures of the results. The two lines are visible but would be ok if the picture across the screen was uniform. But alas it isn't so. :-(

The wow menu is readable, the two lines appear to have some "information elements", just not right... almost like they are stretched.

The overscan picture shows the dark band... maybe an unlit row of leds (caused by the unplugged cable possibly).

The smpte color bars show that the two lines have some information that appears to be shifted (mistimed).

It doesn't appear that any amount of "work around" will get the set up and running... :-( Might try one last thing, accessing the edge boards for visual inspection and maybe hitting them with some "freezing" strategically to see if it has any effect... but it doesn't look good.

[tom66]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

An LCD panel is row scanned, that means that data is programmed into each row using the source drivers (top most drivers) and the rows are selected individually by the gate driver ICs on the side of the panel.

What you're seeing is a failed gate driver IC which is keeping a row permanently selected. This driver is probably internally shorted between the VGH and VGL lines (+25V and -8V typically) at those particular rows that are lit up, causing the 2-5 error code.

Across the panel, there is a direct connection between the left and right gate drivers. The idea is these ICs work in parallel. The problem is, if the side is disconnected the internal body diodes in the gate driver outputs (which are just push-pull, totem-pole style outputs, using CMOS technology) will bias the internal supplies drawing current from the other driver and weakening the drive for the whole panel - hence the effect of half the panel being dark (although it starts further back than midway.)

There is one last thing you can try, I have never tried this myself, but essentially you want to physically disconnect ALL the side driver ICs from the LCD panel itself (not just the board, they need to be removed from the panel.) This will mean the left hand side ICs are doing all the driving. These ICs will now dissipate FOUR times as much power (P=I^2), so they will probably not last long even with improved heatsinking. However if you only kept this as a man-cave TV or bedroom TV it might work long enough to enjoy some years out of it. Obviously, this is physically changing the panel - it will never be possible to return it to the original condition - and it may well only work a few minutes... but if all else fails...

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

thanks for this tom66. Those "drive ics" are on the edge board, not actually "imbedded" in the physical side of the panel, right? Thus my question is if I do a "gambit" and remove one ic at a time, then power up and see the effect, could I have a "3/4" working panel if I get lucky ("do you feel lucky, puck... do ya?").... :-) In essence the panel would be "powered" by some completely but perhaps only a small section of a "one side powering".

PS. there are two edge boards joint by a small flex cable... I only have to deal with one, right? Are they "related" to the physically... meaning the lower board deals with the bottom half while the upper board is associated with upper... or is there some "translation" involved (eg. odd lines versus even, what ever)?

[tom66]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

The idea is to physically remove the driver from the panel glass. Each flex has an IC embedded, this is the failed component. For all intents and purposes they may as well be embedded in the panel, they cannot be replaced.

If the idea works you may well have a 100% functional panel, just one that won't run for long.

The edge boards work in parallel on most panels, driving the same lines in the same order. Depending on how the control logic works the drive signals may be split so each driver works on a 50% duty, so removing one set of drivers would make the panel flicker more (may not be noticeable) or may reduce the frame rate.

If there are drivers on both the top and bottom then they will drive their respective halves, which is different to the gate drivers. However this type of driving is very rare - I have only ever seen this once, coincidentally on a 52" Sharp, which was one of the first frame-interpolated (100/120Hz) TVs made. The extra drivers were required for the higher frame rate. (Similar to early "dual scan" plasma displays)

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

I will take a picture of the panel just to hopefully confirm what I am looking at for the "operation". I certainly like the idea / thought and it is certainly my only hope of saving the panel from the "landfill", even if its for a little while.
From your description of the operation, it would appear that I totally have to remove the frame to get access to the "front edge" of the panel and "troubled ic"... is this correct?

As for the "replace", I wasn't hoping or wanting to do any "replace", for sure this is a "cut out and hope operation" basically removing any short in the drive circuitry.

[tom66]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

Yes, the plastic bezel needs to come off, exposing the LCD module. The shielding on the LCD then needs to go, finally exposing the ribbons.

If I'm right, the left side is working OK, and the right side has shorts. The right side ribbons would therefore be cut in this operation (think of it like a "hemispherectomy" - try to isolate the bad portion!) The ribbons need to be cut close to the glass, most likely they can simply be peeled off without a cutting tool. It's important that there are no shorts where the ribbon is cut.

The disclaimer is that I have *no* idea that this will work. If it does not work then the panel will be irrevocably dead, so use it only as a last ditch attempt!

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

ok... but yikes... this is a 70 in monster, so removing the bezel is going to be an significant issue. Question on experience of removing lcd set stuff. I have done things on dlp rear projection tv that the bezel at on in a "pop off fashion" without taking off the back. Do lcd bezels get removed from the front leaving the backs intact? It does look like that but I can't recall seeing anything dealing with the bezel when I had the back off.

[tom66]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

Usually the LCD panel is screwed to the bezel from the back via accessible mount points - the screws are easily accessible. Sometimes there are also clips (smaller panels may only use clips)

Once the bezel is off the LCD casing is easily removed, it's fixed on with smaller screws.

It's certainly quite an operation - no lie! You'll need a large flat surface to work on as the panel glass will not be fixed in place when you take the metal shield off.

Be very careful when putting the metal shields back on. It is easy to misalign them and damage the LCD panel by applying too much pressure to the wrong point. The panel can be briefly tested with the metal off.

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

I took the back off with the set standing upright (on its stand). Attached picture shows the edge board (lower side) that I have been referring to.
Tom66, there are two flex cables that go under the board to the screen. Are the "gate drive" ICs connected on the reverse side of that board or do I have follow those cables around to the panel by taking the bezel off some how to find the corresponding gate drive ICs??? Note: this is the opposite side of the panel in terms of the trouble but its not easy for me to get at the other side right now.
thanks again for your help on this "operation".


PS. I see we clashed with our posted... :-)

[budwich]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

Based on your comments, do I only have to remove the one side bezel as opposed to the whole bezel?

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

Guys and Tom it's amazing that you guys are talking about this right now because I just repaired a Vizio width 70 inch with a sharp LCD panel and it's the dreaded e701i- that I was talking about in an earlier post that kept blowing t-con boards. Anyways I repair the t-con board and did the one side at a time and realize the right side was having a problem where it was dark and it would lock the t-con board up. I realize that one of the gate drivers were shorting out because in that section and had a perfect picture and when I press on the gate driver it would get them like the rest of the screen the only way to tell would be to disconnect the gate drivers from the bottom driver board on the panel. With nothing to lose I removed all the gate drivers off of the panel very carefully peeling them off. What I have now is a perfect picture with no problems. There are no more right hand gate drivers but the picture does work perfect. I shouldn't say perfect on a full grey screen the very bottom middle is just a little bit darker. This is probably because the left-hand get drivers cannot pull the current that are required when both the gate drivers on the left and right were there before for the dual duty cycle like you were talking about. But it is worth a shot removing those gate drivers from the field side of the TV screen.

So in essence yes it does work. My question is how long?

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

Here are some pictures of my Repair just to give you an idea of what your up againt

The last.pic is what you will end up with when the job is complete.

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

End result.

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

To recap the side of the screen that is having problems is most likely the gate driver is on that side and those are what I carefully peeled off of the LCD panel. You cannot remove just one you have to remove all of them so therefore the boards are no longer connected to the bottom flat ribbon cable that goes from the bottom of the panel to those boards. You can leave the ribbon cable in there if you like but there will be no more ribbons and no more boards on that side of the panel that has the defect to recap the side of the screen that is having problems is most likely the gate drivers on that side and those are what I carefully peel off of the lcd panel. You cannot remove just wanted you have to remove all of them so therefore the boards are no longer connected to the bottom flat ribbon cable that goes from the bottom of the panel to those boards. You can leave the ribbon cable in there if you like but there will be no more ribbons and no more boards on that side of the panel that has the problem. For me it was the right side first tab on the lower right side board of the panel..


Before and after

[freakaftr8]

Re: Sharp LC-70LE757U Flashing 2-5 :-( can it be saved economically?

4 hours still running