The Samsung NU series has a high rate of backlight failures causing dark vertical bands or dark sections of the screen. See post here. The one repaired here has the right side dark. The backlights are edge lit from the bottom and running in Dynamic mode and at maximum level will tend to burn these out pretty quickly.
This model has two strips with each wired in left and right banks. Though only one side was bad, I replaced both with new strips. Part number is AOT_55_NU7300_NU7100_2X40_3030C There are a few sellers on ebay.
I was lucky and the light spreading inner panel was not burnt by the hot LEDs.
Edge lits are very finicky and any imperfection will cause an uneven backlight or bright spots.
This TV had a fan error displayed on the TV. Removing the back cover showed the fan caked in dust. I vacuumed and sprayed duster on it and it was spinning when I turned the TV on. You can see the location above the VGA port so you may be able to clean it without removing the back.
If your apps are running slow or giving errors, you should try a factory reset.
1. With TV off. Press Mute-1-8-2-Power and TV should come on with the service menu. Hit OK on OPTION, OK on Factory Reset and OK again on Factory Reset. You should just press OK three times in a row. TV should reset. Be very careful in the service menu since you can brick your TV changing things.
2. Go through the setup wizard and complete it to the end
Backlight failure is common in LED TVs. Keeping the backlight level at around 55% will make them last. I would also recommend turning off eco sensor which automatically adjusts the backlight level based on the ambient light.
3. Turn off Eco Sensor: Menu ->System->Eco Solution – Turn Eco Sensor OFF 4. Turn down the Backlight: Menu -> Picture Set Backlight level to between 10-12. It should apply to all sources by default.
Motion smoothing will sharpen images for fast actions like sports but will make movies too sharp and look like soap operas. 5. Menu -> Picture ->Picture Options Turn OFF LED Clear Motion
This 2017 model Sony TV wouldn’t turn on but gave a 6 blink error code. 6 blinks according to the service manual is a backlight problem. Luckily, new strips are relatively cheap. This model uses the style of LEDs that also turn blue. With a new set of backlights, the TV turned on with a picture. With this model, backlight appears can be turned down in the BRIGHTNESS picture mode setting. I would recommend setting to about 50% to prevent future failure.
This TV would attempt to turn on but didn’t with no backlight and no video. Unplugging the cable from the power supply to the main board, the backlights came on. This test indicates that both the backlights and power supply were likely good.
Next test was to power up only one side of the panel at a time between the tcon and the panel. I got a picture and the TV was on with the right side disconnected. There appeared to be a short in the panel on the bad side so I blocked a few pins on the outermost edge with tape and this allowed the TV to turn on with a clean image. I used the procedure explained in this post.
There are lots of reports on the reddit tvrepair subreddit of NU series TVs with failed backlights. NU is a 2018 model year and backlights are failing after 2 years. These models are edge lit from the bottom so LEDs that have burnt out will cause dark vertical bands or sections.
Some model numbers include
UN50NU6900F UN55NU6900F UN55NU6950F
With the screwless back cover and edge lit design, replacement can be pretty difficult especially on a large screen.
It is always recommended to never run your backlights at maximum which shortens their life.
Another reddit post shows that the LEDs can melt the clear plastic panel that spreads the light behind the panel.
Here is what edge lit LEDS look like behind the panel. In the NU series design, there are fewer LEDs and they are spaced further apart. They run both brighter and hotter.
Model UN50H5203 UN50H5203AF UN50H5203AFXZC AH01 UN50H5203AFXZA
This TV had no power and didn’t turn on. The standby voltage was low indicating a damaged power supply. This model year does suffer from backlight failures and probing the connector to the LEDs indicated a lot of shorted ones. I suspected the bad backlights had damaged the power supply though the FET and diode for the LED driver tested good. With the LED connector unplugged, the standby voltage was normal again and the TV could power up. I confirmed the screen was good and I was getting video. I ordered replacement strips and a new power supply board since I suspected the LED controller was damaged.
Panel part number DF500BGA-B1 Power supply BN44-00772A LED strips (4 rows) LM41-00001Q LM41-00001Z 2013SVS50
Flickering and double images and horizontal lines are symptoms of a bad panel and typically not repairable. However there may be a workaround by blocking pins to the panel.
To determine if this workaround will work, first make sure your TV has a separate Tcon board. Newer TVs may have integrated Tcon boards so you will be out of luck in this case. Next, you will need to power up the TV with one side of the TV connected at a time to see if one side will display a good picture. With the TV unplugged, disconnect the ribbon from the tcon to the panel one side at a time. It is locked in place by a flip lock that will need to be lifted up to unlock.
If one side shows a good picture, you can try the technique in these youtube videos and block connections on the bad side. When inserting and removing the ribbon cable, it will be safer to UNPLUG the TV between attempts.
If the tape cutoff method doesn’t work, the very last resort is to look for side tabs on the bad side (if there) and rip them completely off.
Why Does This Work?
The panel is driven by drivers which drive both the left and right side and if one side has failed, blocking the connection to them will block the faulty drivers but the other side can maintain the picture. The analogy would be if one kidney was causing you pain so we remove it but you still have a second kidney.
How Long Does This Last
This workaround could last years or until the other side fails.
Troubleshooting TCon or Panel Issues
The Sony T-Con training manual linked here shows examples of both tcon and panel failures.
Update: Some new youtube videos from Frugalrepair about this fix
The Vizio M series has a common issue with the BGA connections on the main processor. Over time and repeated temperature cycling, the leadfree solder balls will crack and loose connection to the board. This problem is also found in Xboxes, PS3 and some laptops.
Diagnosing The Failure
Typically the TV will turn on but with no backlight. With the back cover removed, you should measure the 12V , PS_ON (pin 14) and ON/OFF (pin 15) pins with the ground on the chassis on CN9101. 12V should measure 19V and be stable. If it isn’t, the power supply also has a common failure. With the TV on, PS_ON should go logic high (> 2.5V) as well as the ON/OFF (BL_ON backlight ON) pin. ON/OFF not going high is a sign of failure.
With the TV unplugged, you can try heating the processor up with a hair dryer before plugging in. This test is equivalent to wrapping a game console or laptop in a blanket to get the processor hot and expand the solder ball joints enough to make contact to turn on.
Baking the board (or heat gun). There are a lot of guides for baking boards but I have found that results are temporary and only last weeks or months
Purchasing a new main board. Since this is a common failure, a brand new board may only last 3-5 years before this problem occurs. The processor on these models run very hot.
Reballing. If you search ebay, there should be repair services offered on ebay. Reballing will replace the solder balls with leaded ones which should last longer. Reballing is an expensive repair and should be over $100 USD and have a 1 year warranty. Beware of services that may just reheat the processor (lower price and short warranty).
This TV turned on but the backlights flickered and didn’t stay on and there was no video. I found out afterwards from the owner that the panel had been hit. Usually cracked screens still display video.
Unplugging the main cable from the power supply to force the backlights on showed a 2 inch crack on the edge of the screen. This model does not have a tcon board and the function are integrated into the panel which may have caused the no video situation. With nothing to lose, I ripped off the tab bond at the location of the crack and was able to get the TV to turn on and display video. The L shaped crack had also caused horizontal lines to emanate from that point.