How to power backlit LED's?

[Pioneerx01]

I was given several backit LED strips from TV's, but no other components (like these). I was told that they came from working TV (LG 49LB5550). I am trying to power them on. I tried 6V, 12V and 24V, but I can't get them to turn on. What are they running on 48VDC, 120VAC something else?

Thanks

[stj]

Re: How to power backlit LED's?

does it have connectors at both ends?

[Pioneerx01]

Re: How to power backlit LED's?

Yes the connectors are there, They are still technically in the metal back assembly of the TV.

[japlytic]

Re: How to power backlit LED's?

Although I cannot see the picture, the LED strip would most likely require a proper driver circuit.

[stj]

Re: How to power backlit LED's?

the led's are in series,
if the strip has connectors at both ends you first probably want to connect the pins together at one end to create a loop.
then you need to feed the other end with (led's x 3) v
so if it's 10 leds - 30v
that should get something.

[mariushm]

Re: How to power backlit LED's?

Look at the traces and see how many leds are connected in series. Each led requires about 3-4 volts, but it could be more, depends on how each led is manufactured.

It's common for such light strips to require about 60-80v to drive the leds, and usually there's 2 or 3 or more segments of leds each powered from voltages up to 60-80 volts.

Your strip may be made out of two segments, since you say there's a connector on each side. I wouldn't connect the pins together for a loop because you may just short the negative and positive leads that way, just look at the pcb and follow the traces first to figure out how the leds are connected.

Note that you can't just power the leds from a regular power supply (whatever voltage you decide on), you'll burn the leds due to too much current. You need to limit the current going into a reasonable value. Start with something like 20mA, then move on to 50, 75, 100mA etc

You can do that by putting a resistor in series with the power supply ... Use V = I x R and P = IxIxR formulas to figure out resistor... for example if you think the leds need 40v to work and you have a 48v power supply and you want to limit current to 20mA (0.02A) then
48v - 40v = 0.02 x R so
8 = 0.02 x R ===> R = 400 ohms and

P = 0.02x0.02x400 = 0.16w (so a 0.25-0.5w resistor should be used)

[ajshoe]

Re: How to power backlit LED's?

pics ??

[NeedsMoreFlux]

Re: How to power backlit LED's?

I am fixing a tv with led failure.

When you turn on the tv it spikes to 30 volts / 8 LED's = 3.75V each!!!(Probably too high-manufacturer programmed this tv to burn them!) Then it drops to 18.5 volts = 2.3V each!!!

I think your issue is that they are wired in series and ONE in the series failed!

Scrape away a tiny spot on the solder mask on each side of each LED then use a digital multimeter in "Diode mode" If the meter doesn't light up the led-reverse the probes.

I bet money you will find one bad one on each string. I bet these were given to you because they are bad!

Don't destroy them-They could be worth ALOT of MONEY!!11!!1!!!1!1!!

For 12 strips on this 60" vizio tv the sellers want $120-$240 for a set!!!!111!!1!!1!!!1!!11!!!!

So, I bought 20 LED's off Ebay for $14!!! Aliexpress or digikey sell them cheaper if you can find a match!

Let us know if you manage to fix them and sell them!

[NeedsMoreFlux]

Re: How to power backlit LED's?

$25 doll hairs per 2 strips!!! Check it out!

https://www.ebay.com/sch/i.html?_odk...0+led&_sacat=0