Sharp Aquos PN-L703B With Horizontal Lines

[kebert]

Hi Everyone,

I'm the IT guy for a small school in rural northern California where money for technology is very limited. I talked our superintendent and board members into investing over $3,000 for a 70 inch Touch Screen TV for our 8th grade classroom. It's been great for the last 4 years but a month ago, a very thin horizontal line appeared near the bottom of the TV. Turning the TV off and on again would sometimes get rid of the line but it would come back after a short time.

Now the line is flickering, making the TV unusable. I read about the common tab drivers problem here and here and got excited by the possibility of being able to fix it. I took the TV apart looking for the tab drivers but they are not on the sides where I expected them to be. I assume this is because the TV is touch screen and is built differently.

Does anyone know where they are on the PN-L703B? Could my problem not be related to the tab drivers? Any advice is appreciated.

[budwich]

Re: Sharp Aquos PN-L703B With Horizontal Lines

the side drivers are there... you are looking on the "side"... you need to remove the front bezel to see how the set is laid out. If you are lucky, the "traditional save" of removing the faulty tabs on the bad side will likely get a working set again.

you can also confirm the existence of side edge boards by accessing the area at the bottom of the panel where the tcon ribbons go towards the panel (disappear). When you get to the bottom edge boards follow them over to the side / corner and you will likely find small ribbon cables that interconnect the bottom edge boards to side edge boards.

[kebert]

Re: Sharp Aquos PN-L703B With Horizontal Lines

Thanks Budwich. Sorry for the delay, I've been really busy with the end of the school year approaching.

I think I found the side drivers. Should I try disconnecting the blue ribbon cable from picture 3 or the brown ribbon cables from picture 2?

[budwich]

Re: Sharp Aquos PN-L703B With Horizontal Lines

OK... yes the third picture shows a cable that interconnects the bottom circuitry to the side circuitry. The good news is that those cables are "unclampable / unclipable" without destroying them... which means them can be put back and you will be back to "normal".

Anyway, the test (with power OFF) is to disconnect one corner cable (ie. on one side). Power up the tv and see what happens to the display (post a picture). Then power off again, reconnect the cable and disconnect the other corner one (opposite side)... and again check the display (post a picture). IF you are lucky, you may find that the set functions as it would "normally" with one or the other cable disconnected. This indicates where the problem lies... you can go from there.

[kebert]

Re: Sharp Aquos PN-L703B With Horizontal Lines

I disconnected the blue cable one at a time. Picture 1 is both connected. Picture 2 is left side connected. Picture 3 is right side connected.

I'll leave the set on tomorrow until the flickering occurs (it doesn't start right away) to see if disconnecting a side fixes it.

[budwich]

Re: Sharp Aquos PN-L703B With Horizontal Lines

OK!!! well if you notice the last picture, there doesn't appear to be any more horizontal lines which are in the other two. This is an indication that by disconnecting the little corner ribbon on that side, you have isolated / removed the "faulty tab" from the system / display path. Much like the information you referred to / read about in the first post, it is quite likely that the set can be "saved" by removing the tabs on the "bad side". What you need to do, leave the set in the configuration that you have for the 3rd picture and test that all the features of the set are functional.... just in case there are other signals going about that I / we aren't familiar with. IF everything seems to work, then you can proceed. NOTE!!!! the tab removal is a "ONE WAY street", once they are removed, they CANNOT be put back so proceed very carefully at this point until you are sure there is no other option.

[kebert]

Re: Sharp Aquos PN-L703B With Horizontal Lines

Thanks Budwich.

So disconnecting the cables aren't good enough, I need to remove the tab drivers? What exactly do I need to remove?

Do you know what the brown ribbon cables on the side are for?

[budwich]

Re: Sharp Aquos PN-L703B With Horizontal Lines

As you know from your reading (I assume that you did read those threads that you indicated in post 1), the disconnection of the cabling still leaves the tab drivers attached to the panel. This causes the darkness on the side that has "no powering" going to it and thus the tabs load down the working ones (and may eventually take those out... which would be bad as in dead tv).

Anyway, I would suggest you read a few threads about tab removal to get the idea but basically they are like tape and can be carefully peeled from the side of the panel (the bad side).

As for the brown ribbon cables... kind of like a "U"... interconnect the edge boards as on big sets the edge boards are multiple because of length considerations. you will find that the side likely has two edge boards connected with one "U" ribbon. For information, you will likely find the bottom has a couple of edge boards on each half of the panel.

Again, you need to check the set functions to see if everything works as expected with the corner cable disconnected. Otherwise, you might have a display but it might not be what you need / can use or than watching a picture. There may be a few other techniques (tape cutoff and track cutting) that might work (search on the forum) but I have no experience beyond what I have read in here. Those techniques are somewhat reversible if they don't achieve the desired results.