I have a 24 in Phillips tv/monitor that I suspect the backlights have stopped working. I did the flashlight test and I can see the image that is supposed to be on the screen. I origianlly thought the issue was going to be with the LED driver (which is part of the main board on this model), so I ordered a new board and it still isnt working. Following some advice I recieved, I opened up the tv to test the backlights. After testing each LED with a multimeter on the diode setting, I am pretty sure they need to be replaced, but am just looking for some confirmation from others on the site with more knowledge than me. Please refer to the attached photo. I used the testing points (denoted by TP1, TP2, and so on) on the LED strips to place the probes from the multimeter. Red lines indicate that the positve probe was placed at that testing point and black lines indicate the negative probe was placed at that testing point. Just from looking at the results, I would guess that the lights with a reading of 0.734V are ok and the rest are burnt. It certainly seems as though new strips are needed. Can someone please confirm this for me? Thanks for your time.

 

0.734V is suspect for an LED too unless they have a reverse diode across them and you measure them in he reverse direction. The LED forward voltage is around 3V depending on the colour. Try your test with the meter on a single "normal" LED to see how it goes, and your multi meter on the diode test should light the LED a little.
You may be able to use some of that stick on 12V led strip in place off the original LEDs and run them straight off a 12V supply, not the backlight driver board.

 

Try your test with the meter on a single "normal" LED to see how it goes, and your multi meter on the diode test should light the LED a little.

Thanks for your response. I tried the same test on some "normal" LED's and you were correct, they did light up a little but their voltage readings were 1.6V for red LED, and 1.7V for yellow and green LED's. The tv backlights do not light up at all when tested.

You may be able to use some of that stick on 12V led strip in place off the original LEDs and run them straight off a 12V supply, not the backlight driver board.

I'm not really sure I follow you here, but you did give me an idea. I have some longer strips of working LED backlights from a different tv. I think I am going to try to trim those to 2 strips of 4 lights each and, as you said, power them with a different power source and see how it goes. Do you think 12V per strip (so 24V for both strips) should be correct?

 

The TV LED strips will often be driven from a higher voltage constant current power supply. For example, one of the TVs I made into a work light has 24V or 32V. Some are even higher. See.....
http://www.sadarc.org/xenforo/upload/index.php?threads/old-tv-as-work-light.425/ Watch the Youtube video linked to in this first post. He is pretty good!
http://www.sadarc.org/xenforo/upload/index.php?threads/yet-another-tv-backlight.504/
The 12V LED strips I was referring to are these sticky backed things. Ebay has lots of them. Get the white ones, not coloured.

Each LED pack has its own current limiting resistor.