LED & LCD TV How to Diagnose Symptom of No Image on the Screen
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This flashlight test will show how to identify if you have any video appearing on the screen and whether or not you have backlights. Within this test, we will show how to determine if the problem is a bad t-con board, bad main board or bad backlight inverters for LCD TVs or LED driver for LED TVs.
Most LCD TVs are made up of a main board, a t-con board, power supply board and backlight inverters. Some TVs have one backlight inverter, some TVs have two backlight inverters and some have the backlight inverter built into the power supply board.
Most LED TVs will have a t-con board, a power supply board, a main board and an LED Driver board. Some LED TVs will have the LED driver board built into the power supply board.
If you have no picture on your screen, the first thing we will want to look at is to see if we have backlights or not. You can do this in a few different ways. The first is by looking through the back of your TV and seeing if you can see white lights shinning through holes on the panel.
You can do this a few different ways. The first is by looking through the vent holes on the back cover of your TV and seeing if you can see white lights shinning through the holes on the panel. Be sure to turn off all the lights in the room. As you can see on the screen, we can see the backlight is on through the top vent on the TV.
If it is too difficult to notice if your backlights are on or not, with the back cover still on, you will need to remove the back cover of your TV and look for the light shining through the panel.
Here is what the chassis looks like with the back cover removed and the backlights working. Once you have determined if you have backlights or not, you can then move on to the next steps.
If your backlights are working, but you have no image on the screen, that means the problem is either the t-con board or the main board. Next, you will want to see if you can hear audio. If you cannot hear audio, try and remember if you had audio immediately after the TV image went away on the screen the original time. Or you can also cycle through the inputs to see if you can hear any audio on any of the inputs. For example you could connect your cable box to your TV and try to find the input for that cable box knowing that it would be sending audio to the TV.
If you do have audio and you do have backlights, I recommend starting by replacing the t-con board as that will be the fix, the majority of the time. If you definitely have no audio and you do have backlights, then the problem could either be the t-con board or the main board. You will need to replace each board individually to see which one fixes the problem.
If you do not have backlights, you will want to turn all of the lights off in the room and get a flashlight. Apply power to your TV and press the menu button on your remote to pull up the menu on the screen. You will not be able to see the menu until you shine a flashlight on the screen.
You may need to twist the flashlight and try different angles to be able to see the menu. As you can see on our screen, the menu shows up and you can even read the AV1 on the screen.
This shows that the TV has no backlights, but the image is showing up on the screen, thus our inverter and LED driver is bad and our T-con and main board are good.
You can see on our screen that I can turn the menu on and off and the image appears and then disappears. At this point you will want to replace the inverter or LED driver or the power supply if it has the inverter or LED driver on it.
So as a brief overview, if your TV does have backlights and has audio, I recommend replacing the t-con board first. If your TV does have backlights but does not have audio, then it is either a bad t-con board or main board, and each board will need to be replaced individually to see which one fixes the problem. If you don’t have backlights, but you see an image on the screen with the flashlight, that means that your main board and t-con board are good and that you will need to replace the backlight inverter or backlight inverters on your LCD TV and the LED Driver on your LED TV.
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