Why my Toshiba TV was blank and bling with every 5 second, but still h

@indaeyo Having sound and a black screen, but shining a flashlight in a dark room and seeing shapes / shadows, means the backlight is gone. Backlight can come and go for a short period, but it will inevitably fail totally.

There are two main reasons for backlight failure:

1. Power board / inverter board has component failure, and not providing enough power
2. LED strips have failed themselves

The second one is because the manufacturers use poor quality LED strips. The first one is much of the same, but they’re using poor quality components on the board(s), in particular electrolytic capacitors.

You need to determine if it’s the strips or driver that has decided to take a dirt nap. You can use a DMM (digital multimeter) to measure the output for the LED strips, or you can try to power the strips with an adequately rated power supply.

Are you sure about the model number you wrote in the comment? I can’t seem to find anything really on a Toshiba with that model number. Also, if you pop off the back of the TV to get access to the boards (unplug and be careful as there is high voltage in there!), could you take good quality and up close pictures of the boards in there, and update your question? Adding images to existing questions.

The main board could be branded Vestel, as they’re (at least was) a big manufacturer.