What LEDs to buy for Backlight?

[Southerner1959]

I will soon be dismantling the screen on my LG 47 inch TV to replace the faulty LEDs . . .

Can somebody give me an idea of what I should be looking to buy? (I want to order some, BEFORE I start dismantling the screen)

I can see in the Video the are rectangular surface-mount types . . .

Firstly, what size are they?  I'm guessing about 3mm square, or maybe bigger ? (I see that many are just 1mm square, but about 3mm long altogether, due to the solder connections either side)

Are the tops flat, or do they have a dome?

I see all the cheap ones on ebay are just normal LED spec, ie about 3V and 20mA max current . . . are the ones used in the TV much higher current? (I can see that RS Components sell some rated up to 400 mA . . . however most of them listed don't mention the current rating in the spec)

And what about the colour?  I see you can get various different types of white, like Cool White, Bright White, etc etc.

Hope somebody can advise !

[Southerner1959]

I'm guessing these might be about right . . . they are 6mm square (is that the right size?) and rated at 350mA:

http://uk.farnell.com/vishay-semiconductor/vlmw712t2t3qn-gs08/led-smd-warm-white-1-4w-87-4lm/dp/2082791

But they do them in Neutral White, Cool White, Warm White etc !

[Turnip]

Another thought is a local council tip looking for led screen smashes, maybe even Ebay, as might be the cheapest way of getting a whole heap of 'em.

Guess excess heat is the main problem even though strips are sort'a stuck to the backplate - Chris.

[zomikula]

Plus people will not know to set it up on low to medium brightness

the vivid mode etc.. do not help

[Turnip]

Well said Zom,

Seems unreasonable that folks have to try sort LED issues with no information.

CCFL's didn't mind the heat but LEDs hate it.

Trouble is that current LED back panels are near thin as foil and with no fan in sight - Chris.

[watteau]

Hi,
CHS do the backlight kit for some LG models,
This is one part number: 23013ZP, but they are not cheap.
see below:
http://www.chsinteractive.co.uk/electrical-components/special-offers/led-array-screen-assy-47-x12-strips-television-lg-47ln613vzbbekyljg-click-here-for-more-info.htm
Regards
John.

[Southerner1959]

I haven't been on here for a couple of weeks, as the Forum has been down.

Many thanks for that link John . . . that looks right, as each of the 6 rows consists of a strip of 5 LEDs and a strip of 4, connected in series.  So that kit is to replace ALL the LEDs.

It's silly that they don't sell individual strips, as to buy the whole lot for £63 is ridiculously expensive! (might phone them out of curiosity tomorrow)

However, I have had the screen apart a couple of times, and replaced the faulty LEDs.

They are just 3mm square . . . and high current (now I have got them working I was able to measure the current - it's 400mA.)

I found some similar ones from RS . . . but they look a bit yellowish compared to the existing ones . . . so I have now ordered the highest white temperature they do - 7500K. They're all about £1 each.  Part number 835-3034

One TV repair company I phoned said I'd never be able to solder new ones in . . . but didn't find that too hard!

However, the biggest problem is getting the little plastic lenses to go back on properly - I had to remove lots of these to find which LEDs were faulty (just 3 of them) . . . . you need to drill out where the little locating pins go into the mounting strips. Getting them seated correctly is very critical or you get bright patches or shadows, despite all the diffuser sheets!

[zomikula]

With the lenses do them one at a time, i just pop them off with a spugder (metal)
And place it how you take it off so you know which way round it goes.
use gel super glue

Tape down with tape to help it set remove tape after about 15 mins once glue is set.
Use a suitable tape so as not to leave residue.


How have you got on with the rs led ?

[Southerner1959]

Well the 7500K LEDs arrived today . . . but they still look yellow compared to the rest! (I've changed just one)

I think the problem is the fact that the voltage these ones are getting is lower than the original ones (having done some online research, it appears the colour of the light LEDs emit is very dependent on the voltage)

And there's no way of changing that, as there are 27 in series in each chain (two separate chains fed from separate PSU feeds) . . . and the voltage they get will depend on their effective resistance, compared to the original ones.

It's a real nuisance LG not giving info about the ACTUAL LEDs they use!

I rang CHS, but they won't sell individual strips, just the whole pack of 12 ! (I just need 1 complete row, which is a strip of 5 and a strip of 4)

I don't suppose anyone on here has any they would sell me?

Or alternatively 3 LEDs from a duff TV?

[fix2003]

try one of the set dismantlers like EMOS they would sell single strips as the must disassemble sets were 1 or more would be faulty so have some odd sets

[downunder]

I successfully restored a LED strip to operation a couple of weeks ago by substituting a 4.7V zener in place of a deceased LED.

Problem was when I went to see if it created any unevenness of light on the screen I discovered the panel was cracked. Ah well, another day will come.

Bruce

[old tvman]

Whats the part number on your led strip? Ihave a few spare.
davy.