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Agoraquest • View topic - KDL-55NX720 Problem

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View topic - KDL-55NX720 Problem

KDL-55NX720 Problem

This Forum is questions on any problems you could have with your Sony Televsion set (i.e. Sony Wega grainess problem, cable problems, so forth)

Moderator: jttar

by J_Palmer_Cass » Sun Nov 16, 2014 11:14 am

I determined the problem with the TV this morning. It is the LCD panel for sure. Looks like a bonding problem at the moment.

A new problem showed up today, or perhaps I just noticed it today. I noticed a single line near the top of the screen that was not responding all the way across the screen. The right top half of the screen had this single black line problem. After a bit of light tapping and squeezing, it is obvious that the top right corner of the LCD has a connection problem. If I squeeze the panel at the top right corner, the problems go away. I can make the problems (single line and original problem) come and go easily by squeezing the top right corner of the LCD panel.

I am going to take the balance of the frame off and see if I can get to the problem area. There is a potential temporary fix for this problem that I have seen on the internet.

Jehill, note that I also could make the picture look like every sixth line was missing (AKA black line) by squeezing the corner of the LCD panel in a certain way. Same single spot on the LCD panel makes things go bad in different ways.
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by jehill » Sun Nov 16, 2014 12:50 pm

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by J_Palmer_Cass » Sun Nov 16, 2014 1:18 pm

Well, I took apart the TV as far as I am going to go. The panel front is Gorilla Glass, and the LCD is part of that assembly. Clamps hold the Gorilla Glass LCD assembly to the main chassis frame / back light LED assembly.

First I removed the edge trim and various cables that were in the way..That took about 1 1/2 hours. I took pictures as I went so I could place the harness back where it belongs.

Next I removed all of the screws and clamps that hold the Gorilla Glass / LCD assembly to the main chassis frame / back light LED assembly.

After that I could lift the chassis frame / back light assembly far enough to see what is going on. Nothing that is obviously repairable can be seen.

However, I am going to try to place a rubber shim in the problem area. When I re-install the clamps that hold the Gorilla Glass / LCD assembly to the main frame / LED back light assembly, then perhaps there will be enough pressure in the right spot to keep the TV working.

Hopefully I broke nothing in the "repair" process that I have performed so far. I have to pretty much have to reverse the process to operate / test the TV again, so I better get the shim placed right the first time.

This is a non repairable problem if I took the TV to a repair shop. I guess I will see if the rubber shim works. The amount of pressure that was required to make the LCD work was not that great, and the pressure area is right under a clamp,
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by J_Palmer_Cass » Sun Nov 16, 2014 4:01 pm

Well I finished putting the Gorilla Glass LCD screen back onto the main chassis frame / back light LED assembly. I then installed the outside trim and reconnected the harness items that were disconnected. I have one extra screw that goes who knows where.

I used some self adhesive Anti Skid Pads that I had hanging around to place pressure on the upper right corner of the panel after the hold down clips were installed. I trimmed the pads up and stuck them on the back light assembly with the edge placed so it could not be seen from the viewing side of the screen. The stick on pads are very thin and look to be about 1/16" thick. They have a spongy like rubber, so they seem to be just right.

The TV works for the moment, so at least I did not damage anything during the repair.

As luck would have it, the used TCON board was shipped yesterday. So at this point, I am out $150 for the new and used boards that were not the cause of the problem. Not a bad price for what I learned. Let's see if this LCD panel "repair" holds up for any length of time.

It took about 5 or so hours to do the work today.
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by jehill » Mon Nov 17, 2014 1:30 pm

Good work! I sure hope that the repair lasts!
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by J_Palmer_Cass » Tue Nov 18, 2014 6:48 pm

I had to replace the location of the pads two more times.

The original placement worked for a while, then acted up as usual.

The second pad placement I thought would work was totally opposite of the correct placement. I placed the pad at the defect spot. The pressure was opposite of what corrects the problem with finger pressure. The pressure should be into the LCD panel from the outside, and I was squeezing the pad with the clamp to place pressure toward the panel front. Just as bad or perhaps worse than no pads at all.

The third and latest pad location is right in the top right corner next to the defect point. The pressure into the bad LCD point should now be created by the backlight frame clamp where it screws into the LED panel. The defect point is right under the clamp location which makes me wonder if the clamp created the problem.

I do not think that this repair is going to work, but at least I can now dismantle the TV quickly by memory. I am going to watch E-bay once a week and see if a defective KDL-55NX720 comes up for sale with a good LCD screen. A bad backlight or bad boards will be OK if I can get one fairly cheap and fairly local.

Kind of interesting that the back light assembly is the main TV chassis. The full LCD screen can be removed from the chassis / back light frame fairly easily now that I know how to do it. If someone has a backlight failure with a good LCD screen, my main chassis and boards will work just fine in a swap out.

Let's see if the TV as is will now pass the 2 hour failure test. If not, it goes into storage in the original box.
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by J_Palmer_Cass » Thu Nov 20, 2014 9:37 am

Well, the TV operation is stable with the single corner pad in place. There is one horizontal "dead" line about 5 lines down from the top of the screen that goes almost all the way across the screen. The problem line can be seen with a red screen more than with other colors (AKA missing red). The problem horizontal line can not be seen watching a black and white picture. Solid white looks good, but various color combinations look worse than others.

At normal watching distance, the problem line is not really that bad. If I watch the TV in a normal manner, I really do not notice the defect. However, I know it is there so it is an irritant at times. All I need to do is stop staring at the top of the screen and watch the picture!

I guess that is the best that I can do with this bad LCD screen. Maybe if a KDL-55NX720 comes up on E-bay with bad back light assembly I will place a bid on it and swap out the LCD screen.

Anyhow, I hope the TV works until next year. I don't like any TV in particular that is for sale this model year.

I still have to test my "new" used TCON board. If it works properly, I will probably sell it on E-bay. Same goes for my new BATL board.
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by jehill » Thu Nov 20, 2014 5:12 pm

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by J_Palmer_Cass » Fri Nov 21, 2014 11:01 am

Well, the TV is still working. I can force the LCD screen to go bad by pressing on the upper right corner, but the TV behaves well if I leave things alone.

As far as returning purchased boards is concerned, a few of these specific BATL boards have recently sold on E-bay for $30 more (plus shipping) than I paid for the board (with free shipping). It is not available anywhere else. The TCON board sells for about what I paid for it. The TCON board is non returnable. Why return the hard to find BATL board for a loss when I can sell it on E-bay?

When you recycle a TV these days, they strip out the boards and resell them. You should list your boards on E-bay and then strip them out of your TV is they sell. Then recycle the remainder of the TV. US mail will pickup the package at your home. You do have to buy some anti static sleeves for the boards.

Anyhow, I will report back in a week or so on the status of my LCD screen "repair".
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by J_Palmer_Cass » Sat Nov 29, 2014 3:52 pm

Well, I tested the new "used" TCON board and ran it for a few days, and the new TCON board is fine. The new main BATL board also works fine.

Today I installed the original BATL and TCON boards, tested, and then assembled the TV. I am glad that I stored the individual sets of screws in separate plastic bins so I could assemble the TV with the various screws in the proper locations. No "extra" or missing screws.

The TV works fine with the rubber pad in place in the upper right corner of the LCD screen. There is small problem with one line of the red right near the upper top of the screen, but it is really not noticeable unless you focus on the upper part of the screen when there is a red screen requirement at the top of the screen.

Now to determine what to do with my service boards. I will probably keep them for a month, and then sell them on E-bay for a modest loss.

I will post back every few months to report the status of this TV. It will be interesting to see how long this LCD screen "repair" lasts.
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