Hi,
I might apply to Guinness for a world record in how often one TV backlight has been repaired...let's say, I foolishly thought that replacement LED strips must be available for my 55UE76GQ (probably quite similar to OPs) - but they aren't.
So I replaced individual LEDs on the strips as they failed - bad idea.
Or at least, bad idea to only replace the failed ones, over a period of 3-4 months I have dis/reassembled the TV 13 times...each time fixing 1 or max 2 LEDs.
Works better now than ever, but only after I changed my approach - if you do go for just changing out the LED strips, this will only partially be applicable to you.
In any case, should you want to replace individual LEDs, make sure you get yourself some sort of Lab PSU, something that lets you adjust voltage and current of your power source. Set it at 3V per LED, power capped at about .5A. They are rated for 1A, so .5 will not hurt them, 3V is most LEDs forward voltage (some regions have 6V LEDs, check online listings).
Then test each individual LED with your PSU, note down the amperage or wattage for each LED. Test a new LED as well (if you want to replace individual ones I will assume you have some).
Usually, at ~3V, the 1W LEDs will pull ~0.20A/0.6W. Weak ones will pull less, mark these on the strips. There are test points on the strips for each LED. Replace any that pull less than say 80% of that rating. They are on their last legs. They may still look bright, but they aren't.
Test LEDs again1 before reassembly, of course :)
Result will be drastically improved picture quality, you don't notice the slowly degrading LEDs as they start getting dimmer, but when you replace the whole strip or fix all weak LEDs, the difference is night and day.
In any case, procedure is:
1) Find a large flat surface, cover it with soft but thin cloth (I use a mattress cover, large and cheap)
2) make sure there is NOTHING on the surface that sticks out!! It WILL brea the panel.
3) put the TV on it face down, remove legs if mounted
4) Remove upper plastic shell covering PSU and electronics
5) Remove lower plastic shell covering speakers and display ribbon cables
6) carefully open ribbon cable sockets and stick them under the adapter PCBs fixed to the panel
7) remove the lower bar holding the bottom of the panel in place (7 screws for me), will have to lift the sides up because it has some tabs keeping it in place - I just slide it to the edge of my table, easily done with the cloth under it
8) either turn the TV around on its back or slide it to the edge of your table and use a credit card sized pick to disconnect the sticky tape holding your panel in, just be gentle with the panel so it doesn't flex much, there are zero things you can hurt under it except for on the bottom side, where there is no glue anyway (that's where the flexible PCBs are that the person above damaged...flimsy stuff)
9) pull the flexible PCBs out of their black plastic holders (they will reach, much easier than removing said holders) and either tape them to the panel or be very careful with them, see above
10) gently remove the panel, pro tip: hold it in the MIDDLE on top and bottom! it will hardly flex this way. If you try holding it on the corners, it will flex a lot and may break. Try it...for whatever reason, the panel flexes way less if you grip it in the middle.
11) put the panel down somewhere flat and soft (a second table helps :)), ideally on its outer side, which is usually surface treated and scratches less easily
12) remove/unclip plastic holder at the bottom
13) remove polariser (thin film, reflective on the inside, has tabs on top)
14) remove diffuser (thick plate, dotted on inside) - you can put both on the panel to cover it/prevent dust gathering
15) aaaaalmost there....remove reflective screen, first unhook it from the sides using a spudger or other tool to get behind it, then pull it upwards, start at one side and work over to the other, take care not to rip off LED diffusers, go slow
16) Eureka! We have arrived at the LED strips...find the one not working (easiest again with a lab PSU, set at 3V * LEDs per half-strip, say 21V for a 7+7 strip, or for the brave: reconnect IR receiver if disconnected, plug in and use your remote...you will see immediately which one fails. Don't electrocute yourself...a Lab PSU is recommended! Common sense saves...
To reassemble: make sure you remove ALL remnants of old sticky tape...this is a very annoying job, but has to be done. Try using a blow dryer or the like to warm it up, easier to remove that way, but still sucks. Reapply suitable tape (i.e. 3M PT1100), my advice is to put it on the frame, not the panel, for assembly. Cut out the spaces where the polariser tabs are but take care to cover the area above them, or you WILL have annoying light leaks!
Reassemble in reverse order...good luck, and don't think you will be done in an hour :D
Have some help handy, handling a large panel on your own is...interesting...definitely not recommended above ~55", your arms are just not long enough if you're not an NBA player. And let's face it, if you are, you would just buy another TV :D
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