Led TV backlight

[steptoe]

OK, so I've had an led TV in the shed for a few months now, the backlight failed,

So I thought I'd actually dig it out and have a good lok at it,

A load of the LEDs have failed,

Is there any reason I couldn't just put some 'normal' LED strips in,?

Obviously getting the right lumens would be guesswork, 

But, can anyone see any other issue with this,?

BTW, it'll probably just end up as a shed TV for me, so perfect performance isn't the aim, but I still want something watchable. 

 

[Sidewinder]

TBH you'll probably get a replacement backlight for about the same price!

 

[ProDave]

I wondered if LED tv's were going to be reliable or not. I ave only repaired one, and I found it was wired with groups of LED's in series, then several such strings in parallel. All fed from a constant current driver.  One LED fails so that string stops working, same constant current pumped into them, so the other strings are now over running and soon start to go pop.  I was not impressed with the design. I'm not saying they are all wired like that, but they will be running the LED's pretty close to their max rating to get the maximum brightness.

Ebay is a good place for tv parts.

 

[steptoe]

TBH you'll probably get a replacement backlight for about the same price!

I wondered if LED tv's were going to be reliable or not. I ave only repaired one, and I found it was wired with groups of LED's in series, then several such strings in parallel. All fed from a constant current driver.  One LED fails so that string stops working, same constant current pumped into them, so the other strings are now over running and soon start to go pop.  I was not impressed with the design. I'm not saying they are all wired like that, but they will be running the LED's pretty close to their max rating to get the maximum brightness.

Ebay is a good place for tv parts.

Backlight strips are £20 each, there are 12 of them,!

Although its only 6 of them not working, the other 6 shut down after a brief flash, probably some sort of cut out device to save the driver, I video'd it and later it back in slow motion to see just what was happening, 

I can get 20 replacement smds for £10, but I'm not confident,

I've not soldered smds before,

and how would I know just what ones were faulty,?

View attachment TRIM_20170607_181236.mp4

 

[steptoe]

OK, so I 'accidentally' found a way to test which LEDs worked, and which didn't, I've got it down to 2 LEDs on 2different strips, if you look at the picture you can see the gaps, I've temporarily linked them out just to check all worked OK,

So, as I'm unsure about soldering SMDs I'll have a look see if I can simply order those 2 strips, there are 4 different types of strip, differing amounts of LEDs on them. 

Still be a reasonably cheap fix hopefully.

 

[ruston]

OK, so I 'accidentally' found a way to test which LEDs worked, and which didn't, I've got it down to 2 LEDs on 2different strips, if you look at the picture you can see the gaps, I've temporarily linked them out just to check all worked OK,

So, as I'm unsure about soldering SMDs I'll have a look see if I can simply order those 2 strips, there are 4 different types of strip, differing amounts of LEDs on them. 

Still be a reasonably cheap fix hopefully.

View attachment 8104

I am not into TV repairs , but I have a problem you may be able to help me with.

 I did noy know LED TV's were back lit in that way.

 The problem that I have is that whe the tv is switched on it can run for some time , maybe a couple of hours with no problem , then at the bottom of the screen at either side of centre  two dark shadows appear. Now after your post I think this may be two led's going out. When this happens it will run for an undefined period of time , maybe ten minutes or two hours , then the screen goes black.  All other functions still  work.

 Is this repairable , or is it scrap?

 

[steptoe]

@ruston

I don't know, I don't do TV repairs either, this was our house TV, and it conked out over a year ago, I stuck it in the corner of the shed, and just recently decided to dig it out,

I've got 10 replacement LEDs for a fiver from a shop a couple of Miles away, and have literally just replaced them, just getting round to flying the 'diffusers' back on now, I removed a pile of them to get at the LEDs before having a brainwave and scraping a bit of the plastic coating off the holding strip to test that way, 

So, it all seems to work, took me a good 2 hours to strip the TV tho to get at the backlight, and be really careful with the screen, its very flexible, I'm just hoping I haven't done it any damage once put back together, give me another hour or so and I'll let you know.

As for is it worth repairing, I'd say yes, for yourself, in your own time,

as a business, I've probably spent best part of £100 in time on this, ,,,,,, 

I haven't had a clue what I was doing though, so its been a learning curve.

 

[Blue Duck]

Check for dodgy caps before you put it back together.

 

[steptoe]

Check for dodgy caps before you put it back together.

That was the first thing I done, 10 mins to get the back off, another 10 fkn hours to get at the backlight,!!!!  X(

Appears its a reasonably common problem on these model type, 

Did I ever tell you about LG customer service,? I think its taught in the same class as bnq service. 

baddayexplode

 

[steptoe]

Just need to get the screen back on now and get it all screwed back together,

 

[steptoe]

Be real careful how you handle the screen,

I have no idea if this was present beforehand (I don't watch much TV in the house,), and the wife can't remember, 

But there is now a 5-10mm line down the middle, (still good enough for the shed,) 

Did I crack it,? Did I break a cable,? I dunno,,,,   ,,,,,, 

Have checked everything is pushed fully home,

Other than that, a five quid fix, and its all good,

 

[Doc Hudson]

View attachment 8104

I just hope you are getting enough product placement royalties off CPC & Electricfix to cover the unauthorised forum advertising fee's that will be charged, if any of the four horsemen spot what you have sneaked in at the top of this photo.

Doc H.

 

[OnOff]

Feckit! Only just binned a dead LG I said I'd take and get rid of for someone. Tbh it had sat in the shed for a year and I got sick of it being in the way. Can't even really remember if it had sound but no picture when I turned it on to try. (I think it might have).

 

[ProDave]

That line down the middle is one of the tab connections has failed. Those very fine pitch ribbon cables that are glued to the screen. Almost impossible to repair properly.

I have stripped LCD screens down to change ccfl tubes, not a fun job. It really annoys me that they are not designed to make changing the lamps easy.

Tip: never, no NEVER take a complete tv to the tip.  first open it up, take out all the pcb's, photograph them and put them on ebay. You will often sell them for more than the tv was worth if it was working.

 

[steptoe]

I just hope you are getting enough product placement royalties off CPC & Electricfix to cover the unauthorised forum advertising fee's that will be charged, if any of the four horsemen spot what you have sneaked in at the top of this photo.

Doc H.

:slap

The corner shop gets mentioned regularly, so I think its OK,

I use the electricfix flyers to mop up spills,

Feckit! Only just binned a dead LG I said I'd take and get rid of for someone. Tbh it had sat in the shed for a year and I got sick of it being in the way. Can't even really remember if it had sound but no picture when I turned it on to try. (I think it might have).

:shakehead

Ye, I've prob had this in the shed for a year, got fed up moving it around to get at other stuff, 

That line down the middle is one of the tab connections has failed. Those very fine pitch ribbon cables that are glued to the screen. Almost impossible to repair properly.

I have stripped LCD screens down to change ccfl tubes, not a fun job. It really annoys me that they are not designed to make changing the lamps easy.

Tip: never, no NEVER take a complete tv to the tip.  first open it up, take out all the pcb's, photograph them and put them on ebay. You will often sell them for more than the tv was worth if it was working.

Yep, I noticed one if them has a little crease in it

Still, I don't mind , its liveable in the shed.

 

[binky]

bit late now, but the trick to soldering SMDs is two fold:-

1/ pre-heat components ie gently warm first

2/ use silver solder paste as it has a very low melt point.

by doing the above you avoid thermally shocking the components. They tend to delaminate if heated too much which alters their values, and that can be in the order 0.5seconds for such small components

 

[steptoe]

bit late now, but the trick to soldering SMDs is two fold:-

1/ pre-heat components ie gently warm first

2/ use silver solder paste as it has a very low melt point.

by doing the above you avoid thermally shocking the components. They tend to delaminate if heated too much which alters their values, and that can be in the order 0.5seconds for such small components

Ah,

I got another good trick,

Told to me by the guy I got the LEDs off actually,

use 2 soldering irons, and use lead solder, shock horror,!!!!!

I've got a gas one as well so used that, and seemed to do the trick for me,

I've still got a line in my screen though,

 

[Blue Duck]

I've still got a line in my screen though,

Jus Chuck it out and buy a new one! :slap

Are the screens all that expensive?

 

[binky]

not the point, @steptoe is fullfilling proper eco-warrior principles by fixing things instead of just throwing them away :Applaud

 

[steptoe]

not the point, @steptoe is fullfilling proper eco-warrior principles by fixing things instead of just throwing them away :Applaud

 I throw NOTHING away,

Hence the name, the wife swears I'm his long lost love child,    ,,,,,

I really do need to have a big clear out tho, I can barely get into my lockup, I can't get into the little shed, and I have to continually move stuff in my workshop/shed/mancave to get to other stuff.