LED Backlight Repair
A kind lady on Freegle gave me a load of broken electronic items including a 39-inch ISIS brand LCD television. It turned out this was another Vestel rebranded chassis. I rigged it up to a DVD player and used the bright torch trick to check that there was an active picture, but no backlight. There was about 120 volts being delivered to the backlight and a bit of research online suggested at least 1 of the LEDs might have gone open-circuit. I dismantled the entire set as carefully as possible and found 5 strips of 9 LEDs, all 45 wired in series. This requires a voltage of about 135 volts, but means the current can be kept low and constant. With the strips separated I was able to apply about 25 volts to each strip. 2 strips were fine, 2 were illuminating, but had a dead LED each (LEDs had shorted out) and the last was completely dead meaning an open-circuit LED. On the bench I was able to identify the open-circuit LED. I had some salvaged LED strips from a television that had suffer...