Info on LG TVs anyone?

[truman 10]

I have an LG 42LN613V TV..you can't see the display ,although it's there if you hold a torch up to the screen..I have disassembled it to investigate..the backlight (which I suspected was the problem) consists of 5 strips of LEDs (10 on each strip)..each strip is composed of 2 halves..when I power the chassis on the middle 3 strips flash on briefly..the top and bottom strips don't come on at all..there is power to the strips all the time (70v does this seem right?) does anyone know if the strips are independent of each other and if each half is independent of it's mate? ie have I got 4 faulty halves,1 faulty half or something in between?

[eHallam 10]

Hello

 

I would suspect faulty LED diode. Although the strips should be working even if there is faulty LED because LED's are soldered on strips or board on two continuously going + an - cables/copper rails. However it may be that LG just made the lED's differently to make repairs more difficult or pricier. I would test LED power supply by connecting any other LED strip, also I would check the power pull and capacitors if there is any. Maybe it's shorting somewhere on the strip. I had similar problem on my SONY TV, but it had faulty CCFL power supply, which was impossible to find so I simply upgraded it to LED's. Well as I said, best idea is to test power with some other LED strips first. 70V seems a bit high for LED's, to power up LED you don't need more than 12V but it safely operates up to 19V, even LED bulbs that operates on 220V has converters built it that turns 220V into 12V.

 

Have a great day!

Edited August 1, 2016 by eHallam

[truman 10]

Hello

 

I would suspect faulty LED diode. Although the strips should be working even if there is faulty LED because LED's are soldered on strips or board on two continuously going + an - cables/copper rails. However it may be that LG just made the lED's differently to make repairs more difficult or pricier. I would test LED power supply by connecting any other LED strip, also I would check the power pull and capacitors if there is any. Maybe it's shorting somewhere on the strip. I had similar problem on my SONY TV, but it had faulty CCFL power supply, which was impossible to find so I simply upgraded it to LED's. Well as I said, best idea is to test power with some other LED strips first. 70V seems a bit high for LED's, to power up LED you don't need more than 12V but it safely operates up to 19V, even LED bulbs that operates on 220V has converters built it that turns 220V into 12V.

 

Have a great day!

 

I've just watched a youtube of an engineer testing an LG display..the voltage for the LEDs was around 80V and he said that that is a good voltage for them...so 70V isn't far off.. I don't know what the range should be..

[steroc 10]

This thread here suggests it could be a bad LED that is shorting out and causing the LEDs PSU to shut down.

http://www.badcaps.net/forum/showthread.php?t=46713

One method it suggests to confirm this is to do a resistance test across each strip. As diodes only allow current to flow in one direction then you should get a high reading one way then if you reverse the tester leads you should get a low reading the other. If you get a low resistance reading both ways then it's faulty.

Edited August 1, 2016 by steroc

[punkin 10]

70v is plenty enough, you will have one LED in the strip that's not working and stopping the rest working because they are connected in series (just like Christmas tree lights how they work)

Shorting out one LED at a time will eventually make the rest of the strip work, that LED will be the faulty one and requires replacing.

[steroc 10]

https://www.ebay.co.uk/itm/282093073465

[truman 10]

https://www.ebay.co.uk/itm/282093073465

 

That's good. Ta

[acman 10]

Hi try the 'Bad caps', website, the forum on there is pretty good, you have to register to get the best from it, but it's free.