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

[budwich]

I am trying to help out the neighbor. He has a Sharp LC-70LE757U that is flashing codes 2 - 5. The unit was working fine one day, he turned it off. Next evening, went to turn it on, nothing. Seems strange. Anyways, I am trying to keep in out of the "curb side dump". He got an "estimate" for fixing it that basically is replacing the panel and is pretty high so it isn't going to happen.

So I started looking at some of the service manuals for similar sets (ie.70le740, 70le835)... unfortunately there is no service manuals for this model on the nice "toms-service-manuals"... if it has common circuits to the other mentioned model, it would appear that the 12v supply to the t-con board is in "question" with this flash code. Supposedly, the estimate "analysis" checked some of the voltages and they were "correct" (relayed info from neighbor).

I further looked at this thread .... https://www.badcaps.net/forum/showth...rp+lc-70le732u... wow, great work all around.

Maybe, just maybe these are similar issues / "similar sets". This thread gave me hope that perhaps a similar solution can be found for our set.

Before I get my hope (and that of my neighbor) up too much, was hoping perhaps someone here might have access to the particular schematics for this set especially around the 12v pnl supply to help confirm similar operation and places to look.

Once I get the Tv back off, my checks would be to recheck that the 12v is being delivered to the t-con and that correspondingly that the det- pnl 12v is "high" (?).

Further to the above and based on the other thread, if the 12v is there at the power board and makes it way to the t-con board, but there is no "detect signal" being sent / set, then maybe I could try the same type of "trick" that the poster there and people on the forum helped with by "fooling" the system with a "diy signal". If this is the case, I am sure that the "estimator" would not have gone that far since it needs some "tender care" / "circuitry" for the "workaround". My fingers are crossed.

So can anyone provide me with any additional guidance and details to help lift a little of the "veil"? I have access to a scope and multimeter and some experience in general electronics troubleshooting but not alot in the TV area (more home audio and automotive).

I guess related to this, I can't believe that a 2 year old panel is the failure which I am sure they are quoting as the only solution. Do these failure that readily... yes I can see things like the back lighting, etc but the basic panel?

Lastly, no knowing alot about the inside design, am I correct in the understanding that the 12v supply is used to power the actual pnl LCD? If not, what? Thanks again for any help and guidance.

[budwich]

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

OK... found the service manual and parts manual for this specific set on "manual-archives". Quite a bit of difference (from the other sets that mentioned earlier) so at least now the "veil" is off "one eye"... :-) hopefully, the "principles" are the same.

PS. It appears that the lc70le757 (and related models) is quite a different "fish" than those models I thought might be similar.... so its back to square one to look at things.

[nicholas1110]

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

Hello,

You will want to power the tv on with one ribbon cable going from the tcon to the panel at a time. This will allow you to determine if the fault is panel related or tcon related. If the tv powers on with either side disconnected, that the tcon is likely good and the panel is at fault. Hope this helps you trouble shoot the tv further.

[budwich]

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

thanks.
Will do. I hope the ribbon cables are easily manipulated (ie. removed)... the connectors look rather fragile. There are four.

My take away from the Sharp tech tip (posted in the other reference thread) is that they check the panel via the cable removal to look for physical damage (ie. cracks) which for some "strange reason", they appear to suggest that those aren't legitimate. If there are no physical cracks, and the panel works in some form (with a cable removed), then that is a "legit thing", which I assume means they would have covered it under warranty but "nada" if its past that period.

[tom66]

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

To remove the cable you want to flip up the latch and gently slide out the cable.
Unfortunately if part of the picture comes back this is probably a panel issue and so not easy to repair.

[budwich]

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

I took off the "first" ribbon cable going from the "icon" board (right hand side of the 4 ribbons). Powered it up, interesting, the "perimeter" leds came on.... surprise as I haven't seen that happen in my brief "introduction" to the set (I own a samsung DLP rear projection set). Measured the 12v pin on the PD board (pin 1/2 at the connector leaving the board). It reads just under 12v (11.89). Then about say, 5-10 seconds, the lights went out on the perimeter and probably at about that time, the error code flash began with 2-5. The power reading dropped to below 1v so I assume the system shut down the panel.

I checked the "mass" of mur260 diodes on the power board. They bias at about .54v and reverse at just under 3v (2.9ish).

Further, additional power up attempts (ie. power at outlet switched off, then back on), no more "perimeter leds" come on. The 12v power comes up and about 3-5 seconds there after, drops when the error code start flashing.

I don't see any display (not easy as the panel is laying flat with some over hang) as there is nothing connected to any inputs.

I haven't checked PS-on signal as it is hard to get at and likely needs to have the board flipped to get there (pin 14 which is on the bottom of the connector).

Looking at the main board block diagram, of course, the "det 12v" pin has to be on pin 12 which is on the bottom of the connector and again difficult to get at.

[budwich]

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

Did some more "on/off" (at power outlet). Held the meter on the 12v pin (ground on board mount screws). The panel perimeter lights came on, flashed off then on again and stayed on. The panel itself lit up (back lighting) for about 2-3 seconds and then went out but error light no longer is flashing and the perimeter lights seem to stay on... at least for the "one minute" that I kept powered. This is with the one ribbon cable from the Tcon board disconnected.

I don't see any cracks on the panel (during the brief light up period), I can't see the whole panel. I wouldn't expect there to be physical damage as the set hasn't been "travelling".

I guess this means the panel is no good... :-(

[budwich]

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

I no longer have the 2-5 error code flashing with one cable removed from the TCON board. I turned the set on with the remote and went to menu. Set stays on and displays a menu of sorts. There are some lines running thru it and the "lettering" is a bit "jagged".

I guess I have a couple of questions.
Is the 12v supply sufficient at the 11.93v? I was expecting to be above 12v.... maybe a panel load (failure) on the supply?

[tom66]

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

11.93V is fine for a 12V supply. Generally a 5% tolerance either way is acceptable. For a 12V rail this might be extended to 10%. (10.8-13.2V)

[budwich]

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

OK Tom. Now we did some more playing (neighbor came over to help). He said he never saw the perimeter lighting come on when the "shop guy" came over to do the "first look". So the neighbor was excited and dismayed at the same time.

Then we did some more "testing". We replaced the right most tcon cable and removed the left most one. The panel behaved the same way.... basically, perimeter lights come on, flash, then stay on. Panel turns "blue" in color while it searches for the input and then goes dark cause nothing is connect. If we hit menu, the screen comes on, but this time we can't see the menu, because the side of the tcon that we disconnect, I assume serves that side of the screen which is where the menu would.

Great we thought. Let's pull all Tcon cables back in. :-( as soon as we do that, the power up sequence "changes" in some form and the perimeter lights never come on, eventually, the code flashing 2-5 shows up and the 12v drops. :-(

Now we can't get it out of this mode, even when unplugging the tcon cable on the right side. :-(

So there appears to be some form of "diagnostic"/check that prevents the system from coming up and even lighting the perimeter lighting. I am think that maybe that perhaps the 12v det line is never getting pulled up and after a bit, the system "says", that's it, don't both doing anything and shuts down in error. So I am conjecturing that perhaps the 12v level is not sufficient to "trigger" the detect circuit (where ever that is... have to look). Does this open a possibility that perhaps the panel is actually good but some sub circuit / check is failing during some startup sequence?

[jetadm123]

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

I don't know if this reset procedure will work (works on some of the other sharp 70" models) on your model, but you can try it. With all boards connected:

1) unplug AC cord.

2) press and hold down both the "input" and "volume V (that's volume down)" buttons while plugging in the ac cord. You can release the buttons after you plugged in the cord.

3) If the panel isn't damaged, you will see the letter "K" followed by the model number.

4) you can shut the set off and turn it back on to see if you get video.

Good Luck

[budwich]

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

thanks... will give it a try.
When we were able to get a screen "up" doing the "unplug on tcon connector" (left one in this case), on the side of the screen that was functional so to speak (right side looking from the back), a large "PH01" was coming up when we were trying to select an "input" on the remote because we want to see if the panel was seeing any video conversion from the main board. I don't I have seen any reference to the kind of "code". Does it ring any bells?

[tucocaps]

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

You can check some of my other threads, but I just went through a bunch of similar sharp models. The five short blinks (pretty sure that was the count) was the dreaded panel short/error. Only way it could be alleviated was to connect the boards to another panel/chassis that wasn't damaged in such a way to throw that fault.

These Sharp sets are different from most other LCD's in that they have some kind of protection feature that kicks in as a result of an error on the panel circuit. It is especially aggravating when trying to make sure the mainboards and such are working.

I have another completely different Sharp set that is doing something similar with a cracked screen. It powers on, but doesn't appear to allow video/sound. I'm assuming/hoping it's only the panel, because when it comes down to it, you never really know for sure with these Sharps.

[tucocaps]

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

OK Tom. Now we did some more playing (neighbor came over to help). He said he never saw the perimeter lighting come on when the "shop guy" came over to do the "first look". So the neighbor was excited and dismayed at the same time.

Then we did some more "testing". We replaced the right most tcon cable and removed the left most one. The panel behaved the same way.... basically, perimeter lights come on, flash, then stay on. Panel turns "blue" in color while it searches for the input and then goes dark cause nothing is connect. If we hit menu, the screen comes on, but this time we can't see the menu, because the side of the tcon that we disconnect, I assume serves that side of the screen which is where the menu would.

Great we thought. Let's pull all Tcon cables back in. :-( as soon as we do that, the power up sequence "changes" in some form and the perimeter lights never come on, eventually, the code flashing 2-5 shows up and the 12v drops. :-(

Now we can't get it out of this mode, even when unplugging the tcon cable on the right side. :-(

So there appears to be some form of "diagnostic"/check that prevents the system from coming up and even lighting the perimeter lighting. I am think that maybe that perhaps the 12v det line is never getting pulled up and after a bit, the system "says", that's it, don't both doing anything and shuts down in error. So I am conjecturing that perhaps the 12v level is not sufficient to "trigger" the detect circuit (where ever that is... have to look). Does this open a possibility that perhaps the panel is actually good but some sub circuit / check is failing during some startup sequence?

If you connect the TCON cable to the panel, and it throws the error, then my bet is the panel is shot. My panels were very damaged, so that may be why you got past the 5 blinks with just one panel connect connected?

You could try this. If you disconnect both/all ribbons from tcon to panel, do you then get the 5 blinks? That's how I see them behave. Disconnect both ribbons, and five blinks happens. If so, then connect the one you did before. If you get past the 5 blinks, then connect the other. If 5 blinks then, that's gotta be the panel. These codes are listed in one or more of the manuals you can find on tanya. I believe it does say "panel fault" or something to that effect, but you should double check.

[budwich]

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

great insight.... thanks. I guess I am still having a hard time swallowing that there is a "range of damage" that affects the panel... from "very damaged" (physical cracks / "mistreatment") to "something damaged" that causes the "end result", panel shut down and basically :-(. Because of the "startling observations" that we could move disconnected cables back and forth (at least for a bit) seemed to me to be more of a timing issue than "outright failure". Not knowing the amount of "buffering" and such going on near the panel end, it just seemed strange. Anyways, I wish I knew a little bit more about the "timing events" that goes on during the initialization / starting up. To me, that would give one a better clue as to where things begin to fall down. Its kind of like the "blue screen of death" in the microsoft days... where the "standard course" of action was "just reboot" without much around what's was actually failing to start the "cascade". To me, I would think that sort of "failure analysis" could lead to higher potential of saving the panel... maybe. Although, if it is basically some form of "design robustness" or lack thereof at the panel itself, it is certainly majorly disappointing given the cost of the product.

I will give the suggestion a try but am now leaning to the fact that its is a lost cause. My "resignation" might have one "star" still blinking, and might try a tcon board replacement as a "hail mary" but the star is "very dim"... :-)

As for the "panel fault" failure description, the service manual in most of sharp's models that I have scan all just indicate "PANEL_POW Panel 12V failure" which potentially reflects more on the powering as opposed to the "destination" (ie. the panel)... at least, that's my read. Of course, as part of the checks with this failure, is to look at the 12v source and delivery point on the tcon. But to me that still leaves a large "greyness" especially with way 12volts DC is delivered via a "small heavy cable" to the tcon board but there after is send via a very "small thin" ribbon based cable. My guess would be that perhaps the ribbon cable could be an issue but since it is "bonded" at the panel, all is lost if for any reason there is an "inherent issue" in the cable itself. :-( Coming from some experience with automotive 12vdc "delivery", its very easy to have "path issues" as opposed to "component failure" (they appear often too) because the component are normally more robust and less exposed.

[budwich]

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

Out of the 4 ribbon cables going from the tcon to the panel, I now can "run" with the two "outter most" disconnected (ie. right and left most 80 pin ribbons). The two inner 64 pin ribbons are connected. Replacing either 80 pin ribbons results in a 2-5 code thereafter. The "failure" appears to be "worsening" since the "run scenario" started with just one disconnected. But maybe its just random. Looking at the ribbon cables at both ends, I don't see much out of place / unusual. :-(

Will "chew on" perhaps throwing one last $ at a replacement Tcon board.

Does anyone know the actual start check sequence that the system uses? It appears that when things are kind of running, the perimeter lights come up pretty fast where as when things are not "happy", no perimeter lighting is even attempted so some early checks fail, well before (at least chrono wise), lighting happens stopping the initialization process.

[budwich]

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

Maybe my last gasp at this. The "det_pnl 12v" coming to the main board from the tcon board is on a 40 ribbon connector. Pretty small pins to get at. Looking around the board, both at the main and tcon, there doesn't appear to be any places that are easy access since they are SMD populated / laid out. Are there any "safe tricks" that I can use to connect to this line... shaking aside... :-)

[tucocaps]

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

I probably worked on at least 10 of these, and I have one more giant 75 inch to tackle, which will very likely have the same fault. I think your panel is shorted, and I think that's the "power failure" indicator. If I remember right, I had at least one or two panels that seemed perfect from the outside, and others that were badly cracked but didn't fault out. It's probably due to a short in your case, as opposed to physical damage. Either way, I believe the net result is a bad panel. Others may have some deeper insight on this fault and why it's connected to the panel....

I wouldn't, but if you do buy a T-CON, please don't stick the ebay seller with a return Instead , just resell it if it doesn't fix. Just spreading the good karma...

[tucocaps]

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

Oh, one thing I forgot. I remember reading something when googling this fault about the LED array causing it. Unfortunately, the post was short and rather vague that I had found. All I remember is that the suggestion was that there could be a short in the LED array, and in some cases that could somehow be repaired. I'm not sure if that is even correct, or if it is, feasible to be able to take apart the panel and fix.

If you do try this, make sure to post back and let us know!

[budwich]

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

I probably worked on at least 10 of these, and I ......ve some deeper insight on this fault and why it's connected to the panel....

I wouldn't, but if you do buy a T-CON, please don't stick the ebay seller with a return Instead , just resell it if it doesn't fix. Just spreading the good karma...

I am not one of those kind of people. Its my risk / gamble, not the seller's.... so "I buy, its mine". I probably wouldn't even try to resell it if it doesn't fix things as then I have no way of determining that the board is "certified good". Same with the existing boards if this set finds it way to the "curb".