Sony XBR-65X750D Horizontal lines bottom of screen

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Hello howardc64, Well, I think we found the problem. While I was using the strips to mask the ribbon cables from the T-con board, I smelled a burning component smell. When I finished with the testing, the TV appeared unchanged from before. When I completed the disassembly to uncover the buffer boards I found 1 or 2 burned resistors on the buffer board. I took some pictures attached below and then tried to clean with a q-tip which resulted in the worst burnt resister crumbling and falling away. It must have still had some value because after checking the TV again, the picture is worse with more lines. I don't think the burnt resistors are the problem but rather a victim of another failed component somewhere else. Any suggestions? Thanks

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Label shows CLK1-8 with 5 being burnt the most. I believe these are the gate driver lines. Resistors might be 0 ohm (check others)

You might have damage/short in the COF (although the pic doesn't seem to show any damage).



Inspect COF (Chip On Flex) closely There is a bunch of logic in there and many lines run between buffer board and the panel. Sometime there are shorts on COF and will show some damage marks (compare with other COFs for appearance) I fixed one with COF damages. Pics here

https://www.badcaps.net/forum/showpo...72&postcount=7

Other people have posted worse looking burnt COF pics but I can't find any at the moment.

Pic also shows another flex cable below the flex COF is on (red arrow in my edit of your pic) I've never seen that before. Would be interesting to see if any damage in there if you can lift up the buffer boards and see.

You should have an identical bank of CLK1-8 resistors all the way on the other end of TV. Check those, take a pic, and measure resistance across each CLK1-8 resistor. We can use these as reference to compared with the ones around the burn mark

If you haven't already, look through my Samsung panel signal summary earlier to understand the general background on gate drivers.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Hi howardc64, The picture showing "another Flex Cable" is only a shadow from an extra light source to get a clear picture of the burnt "resistors". They are so small it is hard to get a good picture of them. I even took some pictures through a magnifying glass to try and get better pictures. I haven't checked the resistance of the "resistors" yet but if they're zero ohms, wouldn't that just be a fuse? These fuse/resistors are so small that I'm not sure how I am going to be able to replace them.
Howard, I really appreciate your help with this, thank you.

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Hi howardc64, The picture showing "another Flex Cable" is only a shadow from an extra light source to get a clear picture of the burnt "resistors". They are so small it is hard to get a good picture of them. I even took some pictures through a magnifying glass to try and get better pictures. I haven't checked the resistance of the "resistors" yet but if they're zero ohms, wouldn't that just be a fuse? These fuse/resistors are so small that I'm not sure how I am going to be able to replace them.
Howard, I really appreciate your help with this, thank you.

Yes, tiny and magnifying eye wear + microsoldering (or really thin tip) soldering iron necessary.

Thanks for confirmation the image below the flex was just shadow.

Start by checking the duplicate set of CLK1-8 on the buffer board on the other side of the TV for resistance (for reference). Driver signals goes up both side of the TV. Controls signals for which row to display. Only 1 side need to work for a perfect picture.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Thanks, I found that resisters R100 - R107 are 100 ohms and R11 - R15 are 300 ohms. I measured the resistors on both sides of the TV (buffer boards) and like you said, they were the same. The one next to the burned out one measured 103 ohms so I think they are still functional. With the on resister missing I noticed that there were more horizontal lines and they were extending half way up the screen now. I am guessing if I can successfully solder a 100 ohm resister in the burnt out spot, that I can at least reduce the lines to the bottom 6" again. I found a digital microscope at a store a little while back and tried it here, see attached photos.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Hello again, you said something that I needs more explaining for me. " Only 1 side need to work for a perfect picture." So are the lines generated on the TV because there is a fault on both sides of the buffer boards? Sorry, I'm a novice.

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Yes, tiny and magnifying eye wear + microsoldering (or really thin tip) soldering iron necessary.

Thanks for confirmation the image below the flex was just shadow.

Start by checking the duplicate set of CLK1-8 on the buffer board on the other side of the TV for resistance (for reference). Driver signals goes up both side of the TV. Controls signals for which row to display. Only 1 side need to work for a perfect picture.

you might check lines on R100-R107 against adjacent lines on good side to see their behavior (probably no continuity?) and see if same on the burnt side. Just in case burnt damage has shorting the lines against each other somewhere.

Hello again, you said something that I needs more explaining for me. " Only 1 side need to work for a perfect picture." So are the lines generated on the TV because there is a fault on both sides of the buffer boards? Sorry, I'm a novice.

Yes, theoretically if R100-R107 are for gate driver lines, it can be unsoldered on one side of the panel and will still work perfect. But thats theoretical and we unfortunately don't have schematic OR know the complete damage (Just R104 or also other areas...)

Note the ohm readings taken are all in circuit. if resistor was 0 ohm, then in circuit test maybe can conclude its 0 ohm. Since you read 100ohms, don't really know if its the resistor or another circuit path. Surest way is to remove a good one (or unsolder one side only) to test. But this is quite challenging of course without all the microsoldering tools. I suppose can try 100ohm first and measure after soldering.

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

I have a few salvaged buffer boards. Can look and pull 100 ohm resistor and send it to you via USPS letter. Need to know dimensions of these SMD resistors. Maybe 0603? Just measure with a caliper.

https://eepower.com/resistor-guide/r...and-packages/#

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Thanks for the offer on the resistors but I have a buffer board that I got from a LG 70 inch with a broken screen I got for free a while back and in circuit, they measure 100 ohms so that might be a standard but like you say, that is in circuit so I will have to check. Those resistors are sure small. Like a friend of mine from Mississippi would say, those resistors are smaller than gnat poop! Anyway, I will test the resistance of one removed from the board to confirm the value. I did test ALL of the burnt resistors and they did test around 100 ohms but that was in circuit. Regards, Gil

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Good morning Howard, hope you had a great weekend. I have a digital caliper and to the best of my ability the length measured 1.25 MM so with soldering I would guess that it is a 0402? I also tried to check resistance across the span of the burnt out resistor and got infinity reading. I will try to remove a resistor from the LG 70 buffer board and measure the resistance and let you know. Regards,

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Good morning Howard, hope you had a great weekend. I have a digital caliper and to the best of my ability the length measured 1.25 MM so with soldering I would guess that it is a 0402? I also tried to check resistance across the span of the burnt out resistor and got infinity reading. I will try to remove a resistor from the LG 70 buffer board and measure the resistance and let you know. Regards,

Try measuring burnt out resister circuit with nearby other resister circuits. You'd want to make damage didn't create any additional shorts. Use the identical circuit on other side of the panel for reference on correct measurements.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Looks like 100 ohms are right. I didn't find any short circuits with the burnt resistor. I tried using a soldering iron to remove the resistor on the LG buffer board but it didn't work so I used my hot air station and achieved success. I decided to pull a second resister just in case and I took my eyes off of the resister for a second and it was gone so I de-soldered another one. I stumbled across the lost resister about 10 inches away. Didn't think the hot air gun would blow it that far away. I feel over my head because everything is so small. Those resistors are not much larger than the period at the end of this sentence. Regards,

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Looks like 100 ohms are right. I didn't find any short circuits with the burnt resistor. I tried using a soldering iron to remove the resistor on the LG buffer board but it didn't work so I used my hot air station and achieved success. I decided to pull a second resister just in case and I took my eyes off of the resister for a second and it was gone so I de-soldered another one. I stumbled across the lost resister about 10 inches away. Didn't think the hot air gun would blow it that far away. I feel over my head because everything is so small. Those resistors are not much larger than the period at the end of this sentence. Regards,

Some magnification aid and steady hands are necessary. Hot air on these tiny components probably need require some experience to not send it flying.

If don't have hot tweezer, a wider knife tip soldering iron ti can heat both ends of the resistor simultaneously for removal. Board traces are also tiny and easy to lift so require care when soldering it on.

[lotas]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Installing a new resistor will most likely not help here (it will burn out again), the problem is in the panel itself, you just need to remove all the remaining ones (CLK1-CLK8), the image may more or less be restored.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Thanks Howard, will give it a try. Lotas, you may be right but I would rather try soldering 1 resistor in place first before de-soldering 8. Thanks for your help.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Well, after 3 hours of trying to solder that microscopic resistor to replace the burnt one, I have found at least 8 ways that it won't work. The “pads” for the resistor have burnt up with the resistor so I have to try to solder a thin wire from the test point to the resistor or to the space where the “new” resistor will sit. What I found is when I have successfully soldered a wire to one side of the resistor the resistor is so small that when I try to solder the other side wire, the first one un-solders and falls off. That and being so small that the wires stick to the soldering iron, also, the resistor sticks to the soldering iron do to capillary effect of the molten solder. Trying to maneuver that tiny wire into position so that it won't short the very small distance to the other side of the resistor takes the hands of a neurosurgeon. I had finally soldered looped wire to both sides with the thought of cutting the wire when in place but when gently pulling the wire to ensure a good solder joint, the soldered end of the resistor came off. Like the Hee Haw song goes, “if it weren't for bad luck, I'd have no luck at all.” Anyway, I am going to step away from this for a few days so that my frustration can drain away and maybe figure out another way to do this that could work. Thanks for the help. Regards,

[howardc64]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Well, after 3 hours of trying to solder that microscopic resistor to replace the burnt one, I have found at least 8 ways that it won't work. The “pads” for the resistor have burnt up with the resistor so I have to try to solder a thin wire from the test point to the resistor or to the space where the “new” resistor will sit. What I found is when I have successfully soldered a wire to one side of the resistor the resistor is so small that when I try to solder the other side wire, the first one un-solders and falls off. That and being so small that the wires stick to the soldering iron, also, the resistor sticks to the soldering iron do to capillary effect of the molten solder. Trying to maneuver that tiny wire into position so that it won't short the very small distance to the other side of the resistor takes the hands of a neurosurgeon. I had finally soldered looped wire to both sides with the thought of cutting the wire when in place but when gently pulling the wire to ensure a good solder joint, the soldered end of the resistor came off. Like the Hee Haw song goes, “if it weren't for bad luck, I'd have no luck at all.” Anyway, I am going to step away from this for a few days so that my frustration can drain away and maybe figure out another way to do this that could work. Thanks for the help. Regards,

yeah, microsoldering tools + technique. magnifying eye wear + tweezers etc..

But I agree with lotus on post #34. CLK1-8 are gate driver lines. Theoretically disconnecting these on 1 side is no harm since other side of the screen has a duplicate set of circuit. Its interesting disconnecting 1 by removing the burnt resistor made picture worse. This might suggest there is a failure somewhere the burnt up that resistor. Could be the in the COF/panel.

Theoretically removing CLK1-8 from the burnt up side should allow the TV to work properly. But of course we don't know where the damage is and how it changed the circuit. Of course this is a bit scary because if pictures got worse, you currently don't have the tooling+skills to put back the resistors.

Another way to disconnect CLK1-8 (sent from t-con) on the failed buffer board is to find which pins on the t-con connector they are and block it out. The way to do this is to do continuity checks between CLK1-8 resistors and t-con connector to find the correct pins to block them out. This doesn't require irreversible desoldering but requires a bit of probing effort with fine OHM meter probe tips.

On design theory, one might ask "why have duplicated circuit on both side?" I think perhaps has to do with voltage drop if one side has to drive the voltage all the way across the screen to the other side via long distance. But this repair technique seems to work for LCD panels. Its the principle behind the "masking tape" fix.

[lotas]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Why such torment, you need to clean the heels for verification and tin them and solder the usual low-wattage resistor (0.25w) 100 Om to them and that's it.

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Thanks for the advice howardc64 and lotas. I am looking at ordering a 1/4 watt 100 Ohm resister from eBay. (They're cheap, under $3). As for the masking, I tried that and the best I could do is get a picture I already have which kind of gives me the impression that the problem is in the panel itself. I hope not so that is why I am willing to try relatively inexpensive fixes in hopes that it can be fixed. Again, Thank you for your help. Regards

[ggil44]

Re: Sony XBR-65X750D Horizontal lines bottom of screen

Hi, While I am waiting for the 110ohm ¼ watt resistors to show up in the mail, I decided to “tin” the resister contact points with the most pointed soldering iron I have. In the process, I de-soldered the resister next to it but it did appear to have one end broken already. Anyway, I am posting the picture as it shows on the TV now in hopes that it might give a clue to a possible cause of the problem(s). Originally, I was experiencing horizontal lines only 6 inches up from the bottom, now I have horizontal lines over the entire display. Please see attached pictures of the TV (upside down). The first picture shows where the horizontal lines used to stop. Thank you again for the help.