Chosen Solution
I recently purchased a second hand Toshiba 40L1533DB TV, when powered on initially all is fine, however the TV’s backlight turns off after some time. Interestingly, depending on the backlight mode, the time taken for the TV to turn of varies. On Low mode the TV’s backlight stays on for about an hour, but on medium or high this time is less. After turning the TV back on immediately after the failure, the backlight goes out again much sooner. I am wondering what area of the TV is at fault, perhaps the Power Supply board or the LED backlights themselves. Obviously if the LED strips were at fault themselves it would be a much more challenging repair.
@samhodgson Toshiba is another one of the black helicopter companies that think everybody wants to steal their products. There will be no support from them as well as only scarce information i.e. service manuals, schematics etc. They are guided by paranoia and DO NOT SUPPORT independent repair. Anyhow… This sound like it could be an issue with the “inverter” circuitry on your power board or the LED’s of the backlight strip. Measure the voltage on the LED connector of your boards while the backlight is on and again once it should turn off. IF the voltage does not get supplied you know the issue is not the backlight array. If the voltages stay essential the same, it is the backlight array. Another thing to check would be to see if the backlight has failed or if the main board turned it off. Once the screen is dark (you still have sound) shine a flashlight at an angle against the screen. If your can still make out shapes, silhouettes etc. you know it is the backlight if not then it could be the main board turning it off due to some overheating failure. My order of suspects are backlight array, power board, main board, others :-)Post some good pictures of your boards with your question so that we can see what you see. Adding images to an existing question Update (02/23/2020) This might just help you out to measure your power board
ive got very similar tv here Toshiba 40L1333B, when you turn it on, the backlight comes on for a split second and turns off/stays off. If you shine a torch at the screen you can see a picture. any idea’s. im an experienced electronics engineer, this is a relatives tv and i dont have time for look at it tbh. Thanks Col
