I never advise that a TV owner repair their own equipment and counsel against opening or otherwise attempting repair of any electronic equipment, as it will expose you to dangerous voltages, could result in death, a nasty shock, a broken screen, or all three. You may even drop your cocktail.

Modern LCD televisions have become less complicated but at the same time, more complex in their design. You might ask how this is possible. There appear to be fewer parts and they seem to be easier to repair, so much so that you might attempt the fix one yourself. In some cases you may have even been successful. The technology has become denser and this can open the door to the smallest failure resulting in an irreparable TV.

The process of troubleshooting and correcting the actual flaw requires a thorough knowledge of the theory and technology which makes a television work.

Besides broken and shorted screens, the most common failure I see these days is one which involves a failed backlight.

Backlight? What the heck is that?

The simplest analog that I can use when I describe how a modern television works is that of an old time doctor’s X-Ray reader. Even if you aren’t old enough to have seen one in person you’ve probably watched an old movie where the Doc has a sheet of X-Ray film that he places on a box that glows brightly. The actual LCD is equivalent to the X-Ray film and the box is the backlight.

The first LCD TVs used fluorescent tubes like those in most utility lights. Around 2008~10 the industry began to migrate away from fluorescents, which contain mercury to LEDs, which are cheaper and much more energy efficient.

At first, television manufacturers did their best to build sets with sufficiently hardy materials. But as televisions have became cheaper and cheaper, cost cutting resulted in flimsy construction and poor quality designs.

LCD television backlights fall into two categories. The first and most common is the “direct lit” design. This uses a series of metal or composite strips which have a row of LEDs attached. They are typically connected in series, like old Christmas tree lights so if one fails, the string stops working and sometimes the entire backlight is prevented from starting up.

The second type is called an “edge lit” design. This design is used in very thin TVs. Here, the LEDs are placed in a string and mounted along a vertical or horizontal edge of the screen.

What makes this work is a large sheet of plastic which looks like Plexiglas. But it is actually a custom designed lens called a “light guide”. The guide takes light that is shone into its edge and distributes it evenly across its face. The LCD is placed on top and the picture is illuminated from the back. This design tends to run much hotter, because it usually requires many more individual LEDs than the “direct lit” design.

Edge lit designs are subject to catastrophic failures which damage the plastic light guide and can make repairs impossible due to unavailable parts.

An LED is a solid state device, and as a result there some who believe that they run cool because of this. This is wrong. The average LED used in television backlights can run as hot as 130*F at full brightness. Most burn around 100*F. If you own a thin TV you probably noticed that if you place your hand along the bottom or side of the screen you will feel heat radiating. My cat likes to sleep there when we are watching TV.

Manufacturers sacrifice heavy or expensive materials which would normally be used to dissipate heat and extend the life of their products. The cheaper the TV, the less there is. Some attach their LEDs to cardboard.

Things to Know

Modern TVs have multiple picture settings. Standard, Computer, Vivid, Sport etc… These are primarily changed by adjusting the backlight level.

The first and most important thing you should be aware of about your new LED TV is that running it with the backlight turned all the way up WILL reduce the life of the backlight. And the life of the TV itself.

You should also be aware that manufacturers consider backlight failure to be “End of Life” for a device and do not normally support this repair, even under warranty, and do not supply replacement parts for this failure.

Once the backlight fails, the technician who fixes it can use one of a couple methods to perform the repair.

 They can isolate the individual LED(s) which have failed and replace them. This method is fiddly and requires a lot of time and special equipment. It can also result in artifacts and color spots in the picture due to misalignment of diffusion filters or inability to source the correct color LED (yes, they do come in different shades of white) . It also leaves you with a large number of old LEDs that are probably ready to fail, leaving you back where you started. My experience replacing individual LEDs has been mixed and I do not recommend it.

Second, the tech may be able to find “good” used strips. Not recommended for obvious reasons.

Finally, the tech can attempt to find new aftermarket strips. These are usually purchased from China and the quality can vary a lot. It is best to do business with a supplier who has working relationships with off shore vendors and who offer reasonably long warranties.

Replacement of LED strips requires the technician to disassemble and remove the LCD panel to access the backlight. This can be a straight forward process, but since manufacturers do not design TVs with repair in mind, it can place a number of pit falls in our way. Some go as far as gluing the screens down or other ways of inhibiting removal. This can lead to a broken screen and cause the LCD panel to be damaged beyond repair.

For this reason most shops will require a disclaimer that shows that you understand the risks of this job and will hold the shop harmless in the event that the screen is broken.

How Do I Know If My Backlight Has Failed?

To troubleshoot a failed backlight can be a simple process. First confirm that your TV seems to be completely starting up. Sometimes you will hear program audio but see no picture. Look to see if the screen glows in a dark room, if it does then your backlight is working and there is something else wrong with your TV.

Using a bright flashlight, shine into the screen at an angle and look in different places where you would expect to see an image. Sometimes it helps to hit the menu button on the remote and look where you would expect to see the graphic.

If you do see an image odds are pretty good that the backlight is at fault.
There are other backlight failures which appear as:

·         A blue over all tint to the picture

·         A dark cloud that extends from the edge of the screen

·         White golfball sized circles randomly scattered across the screen

·         Half the screen appears to be dark and gradually lightens as it reaches the center

·         The TV comes on and shows the “splash” screen which disappears and then the TV restarts

Most of these symptoms can indicate other problems but a backlight must be ruled out.
Is it Worth it?

Whether it is worth the money to replace a backlight depends on the replacement cost of the actual TV. TCL, ELEMENT, SHARP, HIGHSENSE and other ROKU type sets have a high failure rate and are usually cheap to replace. The average out the door cost to replace a backlight with parts and labor is between $150 and $250 depending on the size of the TV, value and cost of parts.  But in the end the decision is yours.