ONN TV Backlight Not Working: Easy DIY Repair

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ONN TV backlight problems are very common on TVs even as new as two years old, particularly if you have been running your backlight too hot at 100% brightness since purchase.

Usually the problem is either with a single burned out LED which causes a voltage increase to the remaining LEDs on the strip and makes those pop too.

But there can also be power board issues that mean the backlight isn’t receiving power, or even T-Con issues that mean your ONN TV has a backlight but no picture, making it look like your ONN TV or ONN Roku TV backlight is not working.

I’ll cover every possible ONN backlight problem in this troubleshooting guide, and include tips on your ONN TV backlight replacement and repair.

onn tv backlight not working

Causes of an ONN TV Backlight Not Working

Backlight Failure Cause
Failed T-Con Board or Connection A poor connection of the LVDS cable connecting the T-Con to the main board or damage to the cable’s pins will result in no picture on your ONN TV.
Power Board Burned Out Component Overvoltage or wear over time can cause component burn out on the power board which can be identified by burn marks on the board itself, or by using a multimeter.
Dim Images Equal LED Failure When the individual LEDs in the backlight fail, you will see very faint images when you shine a light on your TV screen. To fix this, you need to replace the backlight LED strips.
Failed LED Diffusers Diffusers coming loose from the LEDs cause bright patches on your screen that look like backlight failure. You can simply glue these back on to fix your backlight.

Most ONN TV backlight problems can be fixed by replacing any failed components on your power board or by replacing your backlight strips where any individual LEDs have burned out.

1. ONN TV Backlight On Half the Screen

tv half screen dark

If you are seeing half black screen on your ONN TV, or you know that the backlight is working but you have no picture, then this is most likely not a backlight issue, but is instead a problem with the timing control or t-con board, and specifically is often a sign that there is a failure of the LVDS cable connecting the T-Con board to the display panel itself.

The t-con board is a small PCB board that drives your TV’s panel, sending the signal to each pixel row of your screen using internal clocks to keep each row in sync.

ONN tv t con board

Either the cable connectors themselves can come loose or get covered in grime or dust, preventing a clean contact, or components on the boards can fail, meaning they don’t power the backlight sufficiently or cannot provide a constant picture signal.

To access the boards, first remove the back panel. If you’re not confident doing this, then now is the time to get an expert in. Otherwise:

  1. Unplug your TV, hold down the power button and wait for at least 30 minutes. There are large capacitors in the power board for the backlight and these can hold charge for an extended period of time.
  2. Place your TV face down on a large table or workbench. Make sure there is nothing that can scratch the screen on your work surface.
  3. Ground yourself.
  4. Open your TV by unscrewing the screws in the backpanel. It should come apart in two pieces: front and back.
  5. Put the back panel somewhere out of the way and take a look at the circuit boards that have been revealed.
  6. You will see a T-Con panel for translating the signal into a TV picture, a power board and a main board.
tv internal boards

It’s a good idea to start your investigation with the T-Con board, as one or more of the internal clocks failing is a regular cause of TV screen problems.

The position of the boards will vary by model, but the T-Con board can be identified by the ribbon cables connecting it to the TV’s panel.

ONN tv t con ribbon cables

Start by giving everything a good clean, preferably with compressed air or a non-static brush. It’s possible that dust in the connections can block the signal.

Then, you should be able to remove the ribbon-like low voltage differential signaling (LVDS) cables on the T-Con board by pushing the locking cover down and they will then easily come away from the board. Don’t try to force them out without unlocking them first.

removing t con cable
Push the locking bar to remove the T-Con ribbon cables

After removing the LVDS cable, take a look at the individual connectors on the ends of the cables, and the connectors in the socket. You are looking for any signs of corrosion, damage or dust.

The contacts should be a shiny gold or silver color. If they are dull and appear to have a rough, copper-like layer over them, this would indicate oxidation and therefore a new cable is recommended.

t con cable
A T-Con LVDS cable in good condition

Get your TV back into an upright position, and with one of the LVDS cables connecting the T-Con to the Main Board disconnected, switch your TV back on and see if any picture is there. Disconnect that cable and re-connect the opposite cable.

If your TV is now working with either of the cables connected, then you know the problem is either with your T-Con or Main Boards.

Both T-Con and Main Boards can be replaced for around $30 from eBay.

To get the correct board, note the T-Con / Main Board model number written on the label on the board, and put this into eBay.

See how to replace a T-Con on a ONN TV in the video below.

If the screen still has dark bands, then you can check the boards themselves for failure, but the most likely cause is a backlight failure, which we will look at below.

ONN roku tv power board

2. Look for Internal Component Damage

Because the backlights themselves are tucked away underneath the other internal components of the TV, it’s generally a good idea to take a quick look at the power board before completely disassembling your TV.

The power board is often the problem if your backlight is flickering or your ONN TV won’t come on at all.

You need to open up your TV as before and identify the main board and power board, which will be in addition to the t-con board that we have already looked at.

The Main Board is a larger PCB where you plug your HDMI and other connectors into. This does a lot of the work of translating the input into signal, which then goes to the T-Con board.

ONN tv main board

The Power Board is where you plug in your power cable, and which converts your home electricity supply into a voltage and current that your TV can use.

ONN tv power board

You will then need to find the ribbon cable which powers your backlight (either via a voltage inverter or directly to the backlight), which will be connected to your power board.

Look for any signs of damage or burning, and check that the connector is firmly in place.

Take a look at the video below for a good look at how to troubleshoot your power board using a multimeter.

If you need to, it’s much easier to replace the entire power board rather than any individual components (unless you happen to have those components lying around).

You can get new power boards for between $30 – $50 from eBay. Just put in your model number and then simply replace the power board in your TV in one go, as in the video below.

3. Dark Areas Indicate Failed LEDs in the Backlight

The backlight inverter powers the backlight of your TV by uprating the standard voltage and current of your home supply to the higher levels required by the backlight.

It’s a very small board in most TV models (although in some is integrated onto the power board). Check this board with your voltmeter, and don’t forget to also look at the cable. These boards are only around $10-15 on eBay, so are very cheap to replace if they have failed.

An error message relating to a burned out LED in the backlight, which is sent from the voltage inverter to your main board will often cause your TV to turn on and off repeatedly.

tv inverter board

To check for backlight failure:

  1. Follow your normal process for switching on your TV.
  2. Get right up close to the screen and point the light on your phone or a flashlight directly at the screen.
  3. Try changing channels with your remote, or going into the menu.
  4. If the backlight is the only part not working, you will see very faint images on your TV screen.

You can see this process in the video below.

If you see faint images, you can be sure that either the backlight inverter or the backlights themselves are the failure point in your TV.

Confirm that the inverter is properly supplying power, then you will need to completely disassemble your TV to access the backlights.

Backlights on modern ONN TVs come in LED strips of varying lengths. Older models used lengths that spanned the entire frame of the TV, but due to cost savings, more recent TVs use a set 16″ LED strip which is connected in series for each row to span your TV.

ONN tv led backlight

These cold soldered connectors are a notorious failure point on ONN TVs, but can be easily fixed if you are willing to re-solder a joint yourself.

Equally commonly, the LED backlights themselves can fail. This is due to repeated current over powering, which over time causes thermal degradation of the LEDs leading to burnout.

You can replace any failed LEDs by just removing the entire strip and replacing it.

The problem with fixing the LEDs is that they are located in the most difficult to access part of your TV. So if you are not comfortable with a larger repair job, then now is a good time to seek help from a professional.

You need to remove the back panel, remove all of the circuit boards and connectors, then another layer of screws for the front panel, and only when you have fully removed the LCD panel can you get to the backlights.

You will also need a multimeter or TV backlight tester to test the backlight strips to find out where the problem lies.

Assuming you have followed the steps to check the T-Con, Power and Main Boards, you now need to:

  1. Any wires or ribbons that are near the edge of the TV should be disconnected.
  2. Then remove the screws around the edge that hold the bezel of the TV.
  3. With some care, you should be able to remove the bezel, panel and reveal the TV backlight underneath, which will be in strips of LED lights.
  4. Use a voltmeter or TV backlight tester to check whether they are working, and replace any failures.

It’s also possible that one of the connectors linking the LED strips as they span the width of your TV has failed. This can be fixed by checking the connectors with a multimeter and re-soldering and broken connections. This article has a good study on this.

4. LED Diffuser Failure Gives White Spots

ONN tv led backlight problems

Bright spots are very common on ONN TVs older than two or three years. This is because of the design of the LEDs used in the backlight and the fact that the glue holding the reflector over the LED can burn off over time, causing the reflector to fall to the bottom of the panel.

The basic design of these backlight LEDs is that they come in strips of LEDs with a lens over each LED to diffuse the light and make sure there are no hot-spots, but just a general glow.

tv led reflector

You can see a set of working LEDs with reflectors in the image below, and you can see the circular reflector covering the LED diffusing the light.

tv backlights

With ONN LEDs specifically, the glue holding the reflector on can fail, usually caused by thermal degradation from the LED itself.

This means that the light from the LED is no longer being spread out, and creates a hot-spot of white light on your TV.

You can tell if this is a problem if you can hear something rattling inside the bottom of your TV’s case when you move it.

This rattling is the fallen reflectors.

The easiest way to deal with this is to open your TV up, carefully removing the back panel and internal components until you uncover the backlight LED strips.

You should see one or more LEDs without reflectors which correspond to the position of the white spots on your screen.

tv backlight led without reflector

The reflectors/diffusers themselves should be in the bottom of the TV’s case, and they most likely would fall out when taking your TV apart.

tv led backlight reflector

Most ONN TV backlight diffusers will be connected by three points to the LED strip.

Simply glue the fallen diffuser lenses back over their LEDs using a clear epoxy, and the hot spots on your TV display will be fixed.

  1. Get some toothpicks and clear epoxy. Superglue is not recommended as it is not heat stable.
  2. Put a small amount of epoxy onto a some waste card or paper if it is pre-mixed, or if not pre-mixed, put each component onto separate parts of your card.
  3. Use the toothpick to pick up some of this epoxy (mixing both components if necessary) and carefully apply to the three points on the LED strip where the diffuser connects.
  4. Carefully place the diffuser back into place on the LED strip and hold it until the epoxy has set.

ONN TV Support & Warranty

It goes without saying that if your TV is under one year old, then you should contact ONN / Walmart customer support to get it replaced under warranty.

You can call ONN directly on:

  • 1-844-334-2355 (9am – 9pm EST daily)

Or contact them via email on customerservice@onntvsupport.com.

Even if Walmart won’t fix your TV, they might still offer you a discount off a future model if you pester them hard enough! This is always worth a try in my experience.

ONN TV Backlight Fix

In summary, to fix ONN Roku or ONN TV backlight problems:

  • If you have lost picture but not the backlight, then clean the T-Con’s cables and connections.
  • Look for failed components on the power board if the entire backlight has stopped working.
  • If there’s dark areas in your backlight, then replace any individual failed LEDs.
  • For bright spots in your backlight, glue any fallen diffusers back over the LEDs.

If you are still having trouble, then I would suggest contacting ONN support or leave a comment and I’ll see what I can do to help.

To prevent backlight issues in the future, remember the reduce the brightness of your backlight, as high brightness and therefore high LED temperature is a common cause of failure.

If you’re struggling to fix your TV, then you might find it easier to upgrade instead and get one of the most highly rated new TVs.

Read More:

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ONN Roku TV keeps restarting?

ONN Roku TV black screen?

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