1) Backlight Enable line between power supply and main logic board - always 3.7V (driver IC datasheet says it needs 1.7V for enable or higher and below 0.8V to disable) 2) Backlight dimming signal is 98% Duty cycle 4.7V (according to driver IC datasheet, should work). So pretty much stable 4.7V there. Turn off the TV. Disconnect all devices (including any external USB devices, hard drives, and all HDMI-connected devices) from the TV. Turn on the TV and check if the issue goes away (which means the TV is not the cause). If the TV is working, continue with the steps to help identify the cause. Dell G5 SE 5505 -- After latest update Alienware keyboard backlight not working. Help. Got my laptop in October. For the most part I'm a huge fan and would recommend. But this last update a few days ago has disabled the backlight on my keyboard. Starting Alienware center and reconfigure my zones does nothing. In case the hotkeys are not working, try it as a combination with the Fn key ( Fn + F7, Fn + F3, and Fn + F4 ). But if you have a gaming model, use Fn with the up and down arrow keys. Check the keyboard light icon to identify yours. Some ASUS laptops even allow locking the function keys using the Fn + Esc hotkey. This morning the set was working fine, but after being switched off for about two hours and switched back on this afternoon, there is only sound and completely black screen. So the questions are the usual. Is this a complete backlight failure resulting in the backlight LED's requiring replacement. after disconnecting the led from the power board the tv operated normally (on off button worked) . I put a flash light to the screen and could see picture and sound was working. When I reconnected the led to the power board it started blinking on and off again and the on off button stopped working. The first thing you can try if your onn TV turns black is to restart or power cycle the TV. This basically soft resets the TV by removing all power from its systems and powers it back up again. To do this: Turn the TV off. Unplug the TV from the wall. Wait at least 30 seconds before plugging it back in. Turn the TV on. Important - the dimmer strips appear to be working still, but they are just dimmer. If I use the "backlight" adjustment I can see them working but they remain about 50% DIMMER than the rest of the TV. When I look at the main power board I see there are 4 LED voltage control outputs (indicating four sections as I said). In this Video we have a Samsung model UN50J5200AFXZA that powers on with a flashing red standby light, but has a totally black screen with no picture. If yo If your backlight is working and you have sound, you most likely have a T-Con issue. If your backlight is working, but you do not have sound, you most likely have a main board issue. If your backlight IS working (but you DID NOT see images with the flashlight test) and you HAVE sound: Unplug your TV. rfiUI.