Often, when my readers talk to me about problems like seeing a black screen or no picture on their TV, I usually suggest they start by checking the LED backlight.
But some of you might not understand why a TV’s LED backlight stops working or what actually causes it.
In this article, I’ll walk you through what makes a TV’s LED backlight stop working and how you can check it.
Let’s move on…
What is Actually TV Backlight?
LED TV backlight is the light source that illuminates the LCD panel of your TV.
LCD stands for liquid crystal display, which is a thin layer of liquid crystals that can change their orientation when an electric current is applied.
LCD panels do not emit light by themselves, so they need a backlight to make the images visible.
How Does LED TV Backlight Work?
LED TV backlights come in various types, with the most common being the edge-lit backlight.
In this kind of backlight, LEDs are positioned along the TV’s edges. A thin sheet of plastic, known as a light guide plate (LGP), spreads the light evenly across the screen.
Now there’s a shiny film behind this plastic that makes sure no light escapes from the edges.
To control how bright the light is and what color it shows, there’s a special board inside the TV. This board listens to commands from the main board and changes how much power the LEDs get.
What Causes LED TV Backlight Failure?
- Sudden power surges.
- LED driver board issues.
- Power board/main board issues.
- Physical or water damage.
Here is a detailed explanation:
Reason 1: Power Problems
If the electricity going to your TV suddenly becomes too strong or too weak, it can harm the lights at the back.
Things like lightning hitting, bad wires, or the power suddenly going out can cause this.
Reason 2: Broken Lights
If any of the lights at the back of your TV get broken or stop working, they can stop the other lights from working too.
This can happen if the lights are not made well, get too hot, or get physically damaged.
Reason 3: Issues with the Part That Controls the Lights
There’s a part in your TV that makes sure the lights work correctly.
If this part is broken or not working, the lights can become less bright, blink, or turn off.
This can happen if the electricity becomes too strong, the parts inside break, or they get physically damaged.
Reason 4: Problems with the TV’s Brain
Your TV has a kind of brain (Firmware) that tells it what to do.
If this brain part is not working right, it can’t tell the light part what to do, so the lights can stop working.
This can happen if the electricity becomes too strong, the parts inside break, or they get physically damaged.
Reason 5: Getting Hurt or Wet
If something hits your TV really hard, like if it falls, or if it gets wet like if you spill a drink on it, the lights can get hurt and stop working.
This is because anything that hurts the TV can hurt the lights too.
How to Diagnose LED TV Backlight Failure?
If you suspect that your TV backlight has failed, you can use some simple methods to diagnose it.
Usually, the following two methods I use whenever I test the TV backlight.
Method 1: Flashlight test
This is a quick and easy way to check if your LCD panel is still working.
To perform this test, you need a flashlight and a dark room. Turn on your TV and play some sound. Then turn off the lights and shine the flashlight at different angles on your screen.
If you can see some images or text on your screen, it means that your LCD panel is working, but your backlight is not.
But If you cannot see anything on your screen, it means that your LCD panel is also damaged or not receiving signals from the main board.
Method 2: Multimeter test
This is a more accurate way to check the voltage and current of your backlight circuit.
To perform this test, you need a multimeter, a screwdriver, and some safety precautions.
Turn off and unplug your TV and remove the back cover.
Then locate the connector where the backlight cable connects to the LED driver board or the power board.
Set your multimeter to DC volts and touch the probes to the corresponding points.
Turn on your TV and check the reading on your multimeter.
If you get a stable reading that matches the expected voltage of your backlight circuit, it means that your backlight circuit is working, but your LED strips or bulbs are faulty.
On the other hand, If you get a zero or fluctuating reading, it means that your backlight circuit is not working, and you need to check the LED driver board or the power board.
F.A.Q.s
Q: Can voltage fluctuations really affect the LED backlight?
Yes, voltage fluctuations can have a significant impact on LED TV backlights.
Higher or lower voltages than the recommended levels can stress the components, causing them to fail prematurely.
Power surges, spikes, or inconsistent power supply can lead to backlight issues.
Q: Can LED TV backlights be repaired, or do they need complete replacement?
It depends on the extent of the damage.
In some cases, backlight issues can be repaired by replacing individual faulty LEDs or addressing minor wiring problems. However, extensive failures might necessitate the replacement of the entire backlight unit.
Q: Is it cost-effective to repair a failed LED TV backlight?
The cost-effectiveness of repairing a failed LED TV backlight depends on the model, the age of the TV, and the nature of the issue.
In some cases, repairing the backlight might be more expensive than purchasing a new TV, so it’s wise to consider these factors before making a decision.
Abdul Kader, a handy guy and experienced founder of a TV repair shop in Gulshan, Dhaka, Bangladesh. He is mainly an expert in understanding and repairing different types of issues with Smart TVs and providing helpful insights on how to keep them in good working order. Read his Full Story.