LG 47LN578V - Brief Backlight flash on power up.

[flocko]

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

If you care to read it again these are new LEDs. if you can collect repair and return for £30.00 and take the risk of damaging the panel you deserve a medal. In the trade we call that suicide. or a fast one way trip to the dole office?

[RobbieC]

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

For starters, this is my tv I have sourced and wish to repair for me. I quite like having it as my main tv so if that can be done for sensible money then I will. The background I have is that these are middle of the road tv's produced with corners cur, one being the led's which seem a very common fault. This is not helped by default backlight being set to max which reduces the life significantly.
Now to replacment led's, I had also assumed the ones @flocko was selling were used ones as per all the others on ebay (the link above to the new set for best art of £100 were the only new ones I had seen - or noticed).
Now I work in the electronics service industy - albeit not tv - and I have done and will do in the future supply 2nd hand parts to a customer as part of the fix.. This is 100% a gamble and comes with mixed results. Sometimes they last years, sometime you are fixing the issue again under warranty in the near future. As this is a project and potentially my maint tv i want a long term fix, plus I am prepared to throw time and effort at the issue to get it right.
If any of the ebay sellers were to offer a waranty / lifetime on the strips I would take them up - but they dont.

I have no history or knowledge of fixing tv's and what 1) people are prepared to pay or 2) experience in how long a fixed tv lasts, both of which reflect on what you can charge to a customer and their expectations of what they will get.

I have spent many hours fixing something which I have done on the cheap and regretted it. I now live by the motto a few people I know use which is
fix it once, fix it right - this usually involves more expensive, pukka parts as a general rule. There will always be exceptions however!!

Without testing to death one of these led's we wont know the correct lifetimime. However, we can extend it.
Virtually all the led's i have worked with are pwm controlled to adjust for brightness. I am not sure doing this at Vf of ~ 100v is viable but I dont have my scope to confirm.
There is obviously a V and I tolerance in the supply before cutoff / extended failure of the reamining led's. I have no information to suggest this was the cause of the individual led's other than 9 in total originally failed, 8 in short circuit. I shoted the 9th which was open and continued use @ 20 backlight down from 100. Within 3 weeks another led which was failed in short also died in open circuit. These 2 were a right sod to remove with hot air / iron as had passed some long term current and had joined to the pads.
This was a different string to the 1st so would not have been effected by differentia voltage drop / current draw accross the string.

[michael dranfield]

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

If you care to read it again these are new LEDs. if you can collect repair and return for £30.00 and take the risk of damaging the panel you deserve a medal. In the trade we call that suicide. or a fast one way trip to the dole office?

Odd that I have been in business for over 30 years and still going then when all around me have closed down, £30 labour charge for 30 minutes work is about all you can get these days , charge excessive prices and people just go out and buy a new set, and having no customers is a much faster way to the dole office.

[michael dranfield]

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

For starters, this is my tv I have sourced and wish to repair for me. I quite like having it as my main tv so if that can be done for sensible money then I will. The background I have is that these are middle of the road tv's produced with corners cur, one being the led's which seem a very common fault. This is not helped by default backlight being set to max which reduces the life significantly.
Now to replacment led's, I had also assumed the ones @flocko was selling were used ones as per all the others on ebay (the link above to the new set for best art of £100 were the only new ones I had seen - or noticed).
Now I work in the electronics service industy - albeit not tv - and I have done and will do in the future supply 2nd hand parts to a customer as part of the fix.. This is 100% a gamble and comes with mixed results. Sometimes they last years, sometime you are fixing the issue again under warranty in the near future. As this is a project and potentially my maint tv i want a long term fix, plus I am prepared to throw time and effort at the issue to get it right.
If any of the ebay sellers were to offer a waranty / lifetime on the strips I would take them up - but they dont.

I have no history or knowledge of fixing tv's and what 1) people are prepared to pay or 2) experience in how long a fixed tv lasts, both of which reflect on what you can charge to a customer and their expectations of what they will get.

I have spent many hours fixing something which I have done on the cheap and regretted it. I now live by the motto a few people I know use which is
fix it once, fix it right - this usually involves more expensive, pukka parts as a general rule. There will always be exceptions however!!

Without testing to death one of these led's we wont know the correct lifetimime. However, we can extend it.
Virtually all the led's i have worked with are pwm controlled to adjust for brightness. I am not sure doing this at Vf of ~ 100v is viable but I dont have my scope to confirm.
There is obviously a V and I tolerance in the supply before cutoff / extended failure of the reamining led's. I have no information to suggest this was the cause of the individual led's other than 9 in total originally failed, 8 in short circuit. I shoted the 9th which was open and continued use @ 20 backlight down from 100. Within 3 weeks another led which was failed in short also died in open circuit. These 2 were a right sod to remove with hot air / iron as had passed some long term current and had joined to the pads.
This was a different string to the 1st so would not have been effected by differentia voltage drop / current draw accross the string.

Fix it once and fix it right is of course the right attitude to adopt especially if you do this for a living like me , and as you have already seen replace one led and 3 weeks later another one goes does not make commercial sense unless you are just doing this as a hobby,using second hand parts can save money granted but you have to consider the time taken to fit , and in the case of an LCD screen the risk of damage by removing it over and over again , if someone on e bay was selling a used part with a guarantee and it failed within there guarantee period would they reimburse your labour cost ? Somehow I think not.

[flocko]

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

As i have said you deserve a medal or two. to be able to collect, strip and replace all the sets LED strips, reassemble,test and return to customer all in 30 mins and for£30.00.but it could be that after over 50 years in the trade retail and repair i am getting old and slow. I cannot see Charles Hyde trade account holders being dealt with much sympathy with guarantee claims for LED strips, I am saying this as a long standing trader with an account ?

[michael dranfield]

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

As I give free estimates I dont collect and delivery because I cant get free petrol , customer has to bring job into workshop there selves ,as far as CHS is concerned I know they are very expensive but there is no one else left to buy spares from

[flocko]

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

So as I see it, you are putting yourself out of work, free estimates? no collection ? so you tell the customer whats wrong, they say thank you very much take the set away, then go on ebay and buy the parts you have told them are it fault,just remind me how long you have been going, as for others that do parts ,Andy at Ohms, sparedparts to name just two.

[RobbieC]

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

The joys of tinkering!! My viewpoint being I am messing with my set as a project and not as a business and working on someone else's tv!
I refitted all the 'dodgy' lens (some were very poorly aligned) using my heat gun from below to soften the plastic. I was pretty pleased with the end result at they were all central to to led with only the height varying (true height is around 1mm) but not by much! I also noted all the 'dead' led which I had replaced with new ones but wrong colour, removed them and shorted the pads.
End result, halo effect was still there and more working led's had failed. Also the newly failed led's were running very hot. My concern was that the psu spec would tolerate a 'few' dead led's but not loads of them.
Am currently looking at sourcing a full set of all the backlights.

For anyone reading this thread in the future looking at a similar fix please bear the following in mind before starting!:
If you start removing lens from above the led's I do not believe you will refit them correctly and will leave a effect on the diffuser which will be visable once the screen is in place. (if you know otherwise then you a better person than me and well done - feel free to share)
You could fit new led's but this is unlikely to work as the colour / spec is unknown and you would have to fit all the lens accurately and you are likely to have lost the will to live before that is complete!
If you are faced with a dead string then at least one led has failed to destruction. In this instance I am unaware of there being only 1 failed led as usually there are others too which do not light, these are prime candidates to kill the string again in the near future (mine lasted 3-4 days having originally fixed). This is usually caused by the screen being ran @ a backlight of 100 - this will mean the remaining led's have had a hard life.

[Diah]

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

The joys of tinkering!! My viewpoint being I am messing ......this will mean the remaining led's have had a hard life.

well i got under my hand LG47LA6208, and it was suffering from short LED and 2 open one. ( Open LED mean it doesn't make Light, but the Opposite Ziner Diode keep in touch and forward current to the next LED

I purchased from China LOT 100 pieces for less 10 USD and replace only the defect one and it had almost working perfect at background light 80%

the SMD LED are with 400 mA and it had round 100lum voltage 3.5 -3.65 Volt

the back light at TV are consider of 2 group, each had 3 right and 3 left, total are 54, mean each line had 27 LED. as well the TV had energy save mode, this mean it will used low current, if 1 LED had 3 Volts mean 27x3=61 Volts this is minimum save and can go by dimming lower than 2.9 Volts

the max 3.65 x 27= 98.55 and you cab find this value on the strip as labeled max 98 Volts.

the LED had cool white color mean from 6000 to 6500 K
more info on this to you

3528 2835 SMD LED 1W LG Cool White
Model Number: LATWT470RELZK
Brand Name: LG
Forward Current:400mA
Size:3.5*2.8*0.6mm
lumens: 100LM
Forward Voltage:3.05-3.65V

Notice most IPS Panel use this Backlight.

lens easy to put pack with no bad reflection. if the the 3 points all of them in correct high. while you remove the bad SMD LED by heat GUN, remove the black bed from the3 wholes, and rset the lens with heat white silicon glue.

[RobbieC]

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

Good find! So do have / plan to replace all 54 then - I think this is good practice IF you can refit the lens correctly as if the light colour is not the same as the original it is not noticed.
My observations though:
Colour temp of originals i thought was more in range 6500-7000k as I compared a few i replaced (rated 6500) against the originals and the originals were a touch whiter.
I very much suspect they will be a fixed voltage & current rail with varying duty cycle for dimming. Obviosuly this may alter slightly if one / many led's fail.
If doing again, i would do each led individually to make sure the lens is replaced from where it was originally. Would love to see some pics of the lens you have refitted and a final pic of diffuser - very well done if it looks half decent!

[Diah]

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

Colour temp of originals i thought was more in range 6500-7000k as I compared a few i replaced (rated 6500) against the originals and the originals were a touch whiter

well 7000K it would be in range of high power LED, which in this case of energy save A+ wouldn't be good idea.

if the lens set in correct way all 3 legs go down in the hols you will not experiences any different.

the Idea of change all of the 54 LEDs are to keep all new and at same new life. just add replace new 2--3 LED to old strip. will cause soon or later dead open LED. and this wouldn't be happy story to risk again by toking the panel out.

[rossoreed]

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

I've taken the plunge and purchased a set of LED's from Charles Hyde Ltd. It's cost me over £100 but although replacing the LED's individually (from Radiospares) proved fairly successful, I couldn't get the LED colour correct and re-seating the lens resulted in unacceptable shading, no matter how many times I tried.
The TV was only just out of guarantee so it was a bitter pill to swallow, but all good now!
I'm left with the original LED strips, which I'm considering cutting into individual LED/Lens to enable them to be used to repair faulty strips - similar to this ebay seller. Is there any interest?

Paul

[michael dranfield]

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

just try it and see , you have nothing to lose , the ones you provided the link to are very expensive though when you can buy a whole brand new strip for just over £11 each .

[TheDoctors]

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

Hi peeps I brought a set on ebay only few weeks ago and got this problem with Back Light coming on quickly then going out so I have opened up the panel made up a test rig and found one dead led and one strip and one whole strip not lighting so I replaced single led on the one strip and found another dead led that had shorted on the other and replaced with some led's I had lying around tested all strips and they now work fine on my test rig but plug TV psu back in and i still get the exact same problem.

Please any help would be amazing.

Kind Regards

The Doc

[RobbieC]

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

The shorted ones are fine (to a point) the open circuit ones will cause the whole string (or both) to fail to light as the psu self check knows there is an issue and switches off.
Find the open circuit led and bridge it to get partially working string which works enough to view.
Failing that you have to buy a whole new set.

[zomi]

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

Also check the connectors sometimes you need to bridge these with wire.

thanks