Backlight on a Samsung TV...

[Externet]

Hi.
Received a free Samsung model UN65NU6900F television from ~2020 (4K) because has a dark column on screen.
I thought the newer TVs had all a wall of strips as background, and the edge strips were not the trend any more. Seems this one is using a single edge light strip only at bottom edge.
Can anyone confirm? Am preparing myself to the replacement of whatever is bad, will have to be very careful to not destroy something else.

The weird is the TV now in my hands has the dark column band at the left end of the screen, not near the centre as in the attached image taken by the donor. What is your opinion ? How can that be ?

[dyarker]

moving failure ...
exercise the connectors

[Janitor Tzap]

Hmmm.........

What have you done for testing?

I'd do a brightness test first.
Put it on a analog channel (3) and have just snow on the screen.
Turn up the Screen brightness to full.
See if the snow pattern is uniform across the screen.
If you still have a dark bar in the same area, it could be one of two things.

On LED Back Lit TV/Monitors, it can be burned out LED's.
Or it could be an issue with the T-CON Board.

Since your going to need to disassemble the set anyway, to fix the problem.

I'd first check connections from the T-CON Board first.
Sometimes it can be just a loose connection.

While you have the LCD Screen removed from the case.
Start looking at the Back Light LED Strips.
{On most sets, the Back Light LED Strips run Horizontally in the case.}

I'll see if I can find the tear down video on your set at ShopJimmy.com.

EDIT:
Here's a video on LED Failures.
https://www.youtube.com/watch?v=lzKQes3zb10
Here's the tear down video of your set.
https://www.youtube.com/watch?v=8mQw73l3oYU


Signed: Janitor Tzap

[Externet]

Thanks, Tzap
Not started diagnosing yet, perhaps by the next week weekend.
The second video link is the one I already watched before posting and seems to show the backlights are only on one long edge. Ordered them already, will take a week. Disassembling will be painful, on an unoccupied room bed.
So the T-con board can also fail with that same symptom, ha ! Will see...

[dacflyer]

ShopJimmy is a great website..
it's helped me a lot.. Altho i given up working on tvs any more.
too much of a hassle now..
Last one I had to use conference table at work.. Lol

[Janitor Tzap]

The big problem with repair of these sets, even if your going to DIY the repair yourself.
Is the price of the repair parts, verses the cost of a new set of the same type.

I had a 19" Insignia that burned out the back light LED's 18 months after it was purchased for around $95.
The exact same set, now was selling for $59.
The replacement back light strips for it, were selling for around $29 to $39 plus tax & shipping.
Making it not even worth the effort to even repair the set for myself.

As I said in an earlier post: "Anything 40" or under in screen size is not worth repairing."

Since this was given too you, Externet.
You have no money tied up in to the set.
Thus, the repair and the parts will be worth it.
Since new 65" sets sell for $800, or as little as $350 new.


Signed: Janitor Tzap

[Externet]

Hi Tzap. The backlight kit was $20 at ebay; should arrive later this week. Am into this repair just because this TV has ethernet jack and want to see if I can replace my dedicated ethernet-Chromebook-to-HDMI setup I use only for watching overseas programming for the last 3 years.
Yesterday I tried even with the screen dark section just to see if was doable. After trying several times with no success, cycled power to the modem and worked. But the Chromebook stopped working after that. Had to power cycle again and now both work connected to the internet. Damn modems and settings and digital garbage complexity am not familiar with.

But... Get tons of pop-ups advertisement and interruptions on the Samsung TV (not from the broadcaster) that I do not get any on the Chromebook. Pissed off. Would like to know if ADblock can be installed on the TV as an application. Teach me your tricks

If you know how to force lower the backlight current with a resistor in series (for longevity) let me know. I may have seen somewhere that light strips kit include a higher value resistor to replace one on the board (~0.47 to 4.7 ohm ?) TV is model UN65NU6900F I do not have the service manual or schematic.

[Janitor Tzap]

But... Get tons of pop-ups advertisement and interruptions on the Samsung TV (not from the broadcaster) that I do not get any on the Chromebook. Pissed off. Would like to know if ADblock can be installed on the TV as an application. Teach me your tricks

Here's ADblock website: https://adguard.com/en/adguard-android-tv/overview.html

If you know how to force lower the backlight current with a resistor in series (for longevity) let me know. I may have seen somewhere that light strips kit include a higher value resistor to replace one on the board (~0.47 to 4.7 ohm ?) TV is model UN65NU6900F I do not have the service manual or schematic.

Hmmm..........

I don't know if that will have much of a difference.
But in the set Menu, you will have brightness levels for viewing.
You can adjust the light level.
Thus, lowering the light levels will extend the time on the LED Back Lights.

Note:
Some white light LED's are rated for around 50,000 hours.
So, you watch maybe 7 hours a day.
Now multiply that by 365 days = 2555 hours per year.
So they should last almost 20 years.
Now there are different grades of White LEDs, and they are rated for 30,000 or 20,000 hours.
Sacrificing the longevity for higher brightness.

Meanwhile.......
I'll do some searching for Back light modifications.


Signed: Janitor Tzap

[Externet]

Done. Works. Happy.

Ordered the $20 backlight strips and arrived and replaced them today.
Did the opposite procedure shown by youtube experts. Did not have to handle such huge glass fragility, have no glass suction cups to move it either. Left the display face down on a bed and detached / lifted the metal chassis instead, did not have to remove filters and shuffle difussers nor risked sandwiching hairs or lint this way. Very difficult and tricky with enough pauses to slowly examine details.

[CeaSaR]

65" tv for $20. Sounds like it could almost be the script for a DealDash ad.

Nice going!

[Janitor Tzap]

Nice.

Leaving it face down on the bed, is probably easier than removing the glass panel with suction cups.

But, yeah..........
About 80 percent of TV/monitor repairs, are burned out LEDs on the Back Light Strips.

I haven't found anything about modifying the Back Light Strips with a current limiter resistor.
Thou, I found LED's that have built-in current limiter resistor in them.

One thing I hope you did, before installing the new Back Light Strips.
That Is to clean any old glue off those areas that the old Back Light Strips were on, in the metal chassis.
Because the metal backing strip, on the LED Light Strips acts as part of the heatsink.
If the metal backing strip is not making good contact with the metal chassis.
It will cause the LED(s) to run to hot.
Thus, burning them out sooner then they're normal life span.

Thou.....
I've looked at vid's, where some people installed 12Vdc muffin fans, to help cool down the set.


Signed: Janitor Tzap

[dacflyer]

Last tv I replaced the leds, i applied heat sink grease to the stripes,,
Hoping that, that will help keep em a tad cooler..

[Janitor Tzap]

Last tv I replaced the leds, i applied heat sink grease to the stripes,,
Hoping that, that will help keep em a tad cooler..

Ahhh..........
That isn't a good idea

The glue backing on the LED Light Strips is to keep them in place.
By putting the thermal grease on it.
The grease will slowly work itself in to the glue, causing the strip to come loose.
In this diagram, you see how transistors are held in place on the Heatsink with screws and a bracket.

I haven't come across any TV/Monitor back light strips that have holes in them for mounting to the back metal chassis.
Or a fan(s) to increase air flow in the case to lower the temperature.
Thou, that would up the cost of the set, and make them last a lot longer then 2 or 3 years.


Signed: Janitor Tzap

[Externet]

The removal of old strips adhesive done with

Screenshot from 2024-08-11 09-02-40.png (149.92 KiB) Viewed 3353 times

[Janitor Tzap]

The removal of old strips adhesive done with

Yeah, that'll work.

I used 3M General Propose Adhesive Cleaner.

And 99% Isopropyl Alcohol to remove any residue left by the cleaner.

Note: Don't use Rubbing Alcohol, or Isopropyl Alcohol that isn't 99% pure.
These contain oils in them that will leave an oily film on the metal.


Signed: Janitor Tzap