LG 47LN578V - Brief Backlight flash on power up.

[newtothis]

Re: LG 47LN578V - Brief Backlight flash on power up.

Most LED strips are outsourced

The LEDs are manufactured and even if not readily available they are available somehow... It is a case of lots of emails and talks with the manufacturers until a supply chain is achieved. There are as far as I know no repair services for bad strips... I think it is about time there was one!

My post made me think.... Ok so if strips are not available.... Make them... It cannot be that hard to do and with sets being scrapped due to strips going it sure is economically viable to do it.

Replacing an LED on a bad strip can be a pain as to finding out what LED is needed... Doing it from scratch gives us all the ability to use existing documentation for available LEDs

[JeffJ]

Re: LG 47LN578V - Brief Backlight flash on power up.

Most LED strips are outsourced

The LEDs are manufactured and even if not readily available they are available somehow... It is a case of lots of emails and talks with the manufacturers until a supply chain is achieved. There are as far as I know no repair services for bad strips... I think it is about time there was one!

I agree, i have the skills with SMD and the tools. Its just a matter of a good process to identify the proper led, Vf, brightness, Amperage, and color....

My post made me think.... Ok so if strips are not available.... Make them... It cannot be that hard to do and with sets being scrapped due to strips going it sure is economically viable to do it.

Replacing an LED on a bad strip can be a pain as to finding out what LED is needed... Doing it from scratch gives us all the ability to use existing documentation for available LEDs

I have a box with a fair amount of tested strips that i have been hoarding, i feel bad for not making them available to the used market at a decent price but the fact is if i do and i need them getting them back at a decent price is another story. Making our own strips. Now we're talking. But the issue is i'm a self taught man with limited skills (don't tell my wife that lol) we would need a hand from our gurus Budum and Tom.

Edit: after thought. If we make our own strips. We would need to know A) how the supply circuit works what ti provides voltage and amperage wise. and B) they should all be replaced at once. no mixing custom with factory that's just a nightmare waiting to happen.

[newtothis]

Re: LG 47LN578V - Brief Backlight flash on power up.

I work a lot on BGA faults and have IR equipment, HA equipment and all my thermosensors etc ... I can etch boards and have my own etching kit... I have tonnes of SMD components, wires etc etc... Simply a case of working out the current draw for the LED strip and making one up. Really can't be that hard. LED's hate heat as we know... So quick soldering is needed... Advantage of IR is that plastics etc don't melt with it (Unless you have the component too close to the plates and the heat rather than the radiation hits them)

So if it is possible to create them I can make them pretty quickly

[JeffJ]

Re: LG 47LN578V - Brief Backlight flash on power up.

Your equipment is far superior to mine i have a simple small BGA rework station one IR and one Hot air. I have done BGA re-balls and what not. I have fixed some pretty obscure problems. For example an A board with a BGA issue that needed a proper re-flow. I didn't bother re-balling it as i assumed i wouldn't have the stencil for the chip. But its working strong still. almost 3 years now "Knocks on wood" I work in Computer IT and i do not know how many laptop mainboards and printer formatter boards i have saved with my rework stations but its easily in the 500+ range, and throw in a bout 10 dozen game consoles.

[newtothis]

Re: LG 47LN578V - Brief Backlight flash on power up.

Your equipment is far superior to mine i have a simple small BGA rework station one IR and one Hot air. I have done BGA re-balls and what not. I have fixed some pretty obscure problems. For example an A board with a BGA issue that needed a proper re-flow. I didn't bother re-balling it as i assumed i wouldn't have the stencil for the chip. But its working strong still. almost 3 years now "Knocks on wood" I work in Computer IT and i do not know how many laptop mainboards and printer formatter boards i have saved with my rework stations but its easily in the 500+ range, and throw in a bout 10 dozen game consoles.

Tip : If you don't have a stencil for what you need get a universal one and place it over the BGA chip... Get a tea candle (Ones in the metal case) and let it melt... Using a cocktail stick/toothpick fill the holes that are not needed in the stencil with wax. Make sure you skim over the stencil afterwards to make sure its flush. VOILA custom stencil. Easy to clean off with boiling water too

[JeffJ]

Re: LG 47LN578V - Brief Backlight flash on power up.

Tip : If you don't have a stencil for what you need get a universal one and place it over the BGA chip... Get a tea candle (Ones in the metal case) and let it melt... Using a cocktail stick/toothpick fill the holes that are not needed in the stencil with wax. Make sure you skim over the stencil afterwards to make sure its flush. VOILA custom stencil. Easy to clean off with boiling water too

I can't even comprehend how simple but awesome this suggestion is! thanks a lot! I will try this next time for sure. I am also ashamed i didnt think of such a solution. I pondered the fact of trying to use a "like" or universal stencil but the problem was re-flowing was a good gamble of fixing where a "screw up" trying to re-ball could be game over. I always chose the high ground.

[budm]

Re: LG 47LN578V - Brief Backlight flash on power up.

@tezzanator, Can you please tell me how LEDs it uses?

[tezzanator]

Re: LG 47LN578V - Brief Backlight flash on power up.

Apologies for the delay, University Today

I'm going to rip these strips out to test the leds individually and then De-Cap any that won't light up to see how they are constructed. It appears the lens assembly is held on by 3 dabs of what appears to be epoxy, I will try a couple of methods for de-capping them and see which is the least destructive whilst getting some high resolution photos in the process

What I know so far:
There are 54 LEDs on boards labelled ROW2.1 Rev 0.7 L1 and ROW2.1 Rev 0.7 L2 corresponding to the relative spacing of the LEDs for, I'm guessing, uniform coverage.

In comparison to my LED video lights which are 5500K and 6500K they are edging towards the blue end of the colour balance, at a guess 7000K but I haven't got anything of that temperature to check against.

I'll try to characterise them when I've got a window of time this week, current draw curve over voltage if at all possible. Should at least give me a starting point of where to find near-identical chips to replace them with. I think most of the magic is in those lenses which seem to do a fantastic job of removing any hot spots from the light pattern.

A thought that came to mind was using LEDs on small round aluminium backed PCBs and use thermal adhesive to mount them to the rear panel, using pieces of wire to connect each LED "Island" into the correct configuration. This would prove a fairly modular solution for any size TV if the PCB and appropriate lens could be created.

[JeffJ]

Re: LG 47LN578V - Brief Backlight flash on power up.

The lenses literally just pop off give them a twist or a little pry with a smaller flat head.

[budm]

Re: LG 47LN578V - Brief Backlight flash on power up.

54 LED/2 = 27 LEDs *3.3V (typical) =89.10V, you measured about 96V on the working string so that sounds about right.
Thanks for the info.

[JeffJ]

Re: LG 47LN578V - Brief Backlight flash on power up.

These strips are actually labeled 94V

[budm]

Re: LG 47LN578V - Brief Backlight flash on power up.

The 94V is referring to the flammability of the PCB UL compliance rating.
http://www.ulttc.com/en/solutions/te...y-ul-94-v.html

[JeffJ]

Re: LG 47LN578V - Brief Backlight flash on power up.

Thanks for the info Budm

[rossoreed]

Re: LG 47LN578V - Brief Backlight flash on power up.

My LG TV is now suffering the same problem. How did you get on?
Did you manage to source replacement LED's?

Paul

[RobbieC]

Re: LG 47LN578V - Brief Backlight flash on power up.

Great reading this thread and the other LG related ones which all seem to be near identical guts. I acquired this set as a project suspecting the led issue. Stripped down and low and behold identified a blown led on the top row. I was going to source a 2nd hand L2 from ebay but at £25 in the uk it was bit dear. PoC was to short the discoloured led and test. End result was a functioning backlight. What i wasnt expecting was 9 out of the 54 total leds having failed (the other 8 had failed shorted).
At present, the only source of these strips / leds are 2nd hand units on ebay. I could replace the dead ones but the fact the set was driven at 100 backlight tells me the others arent far behind. Better solution would be to replace the lot which follows on from this and a few other threads here.
Annoyingly i reassembled the unit but initially like to confirm if these are 3535 or 3030 leds. A bit of googling found this http://led.lginnotek.com/ which lists 3030 and various specs. Also from that site http://led.lginnotek.com/common/file...ileId=MzA2Mw==
If these are correct specs of 6500k and flux of 100-130lm 120 deg angle
^ that cant be accurate as 100+ lumen are all 6v rated which isnt the case. 3.3v and 6500k seem definite, lumen rating is likely to be 40-60 in this case

[budm]

Re: LG 47LN578V - Brief Backlight flash on power up.

If it is rated at 6.2V because it has TWO LEDs in one body as you can see the schematic symbol.
I believe the one in your panel are single LED (I never seen Dual LED used on those kind of LED strips), you can easily verify by measuring the Vf.
The 5152 series are single LED.

[RobbieC]

Re: LG 47LN578V - Brief Backlight flash on power up.

Damn thing died again this morning (maybe more led's failed or my pikey fix).
From the physical size I dont think they are 5mm wide so 3 or 3.5mm would make sense.
On basis its being dismantled again I will do some a bit more detailed analysis.
Will certainly confirm vf and hopefully current draw although wont be able to confirm what the backlight number was without some messing (think i reduced it to 20 or 30).
Endgame would be to find a sensible replacment and swap the whole lot out. Light output becomes irrelevant then as its knocked down to whatever is suited and would be linear accross the both strings

[flocko]

Re: LG 47LN578V - Brief Backlight flash on power up.

Check out eBay UK item number:252260850432 the easy way to repair LED strips
.

[RobbieC]

Re: LG 47LN578V - Brief Backlight flash on power up.

haha thanks - i'm guessing that's your auction seeing as they are based in Dover as you are, although I was led to believe some of the vestel strips were different sized led.
For me - using a 2nd hand led / strip from an already failed or damaged set isnt a full term fix, neither is it really cost effective.
For example, I picked up a cheap damaged set which had 9 failed led on over several strips. The strips were around 25 - 30 GBP each which had either 4 or 5 led on each one.
This has failed again so I am maybe at 10. The set was ran @ 100 for backlight so all of the led have had a hard life and are likely to be not far from failing.
This may also be true for any 2nd hand replacement(s) which I buy.

Personally I am more than happy to identify the best match for replacement new led's. 54 new led's which i can happily replace with smd equipment will take longer but cost far less and be a substantially better long term goal - plus I fully intend to share which led's i use on here if and when i get them.

[flocko]

Re: LG 47LN578V - Brief Backlight flash on power up.

Yes hands up it me, if you want to replace all the LEDs then these will do the job? been there done that ? xenon bright white 3528 PLCC-2 you can get on ebay item number:252260850432, they do not like to much heat the same goes for the pads on the strips .use a good SMD solder paste as soon as you see it run stop the heat. i have used these on a 26" set replacing all LEDs and its still in use, they are a little brighter than the ones they replaced but as all were done this was not a problem just wind back the back lights when done, this will help give a longer life as well. hope this helps and good luck