Sourcing replacement backlight SMD LEDs or Strips (LG panel)

[Juanmi]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Hello CMG,

About your test images, I see you have used only two cables on the connector, one for positive and one for negative while the other ones are floating. Can you comment a bit more on the testing procedure that you have used, was it power board pins 6 (VO3) and pin 7 (GND) on the connector the ones you have used?

Thanks a lot for sharing the pics and information, same to everyone else for their input.

[Juanmi]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Hello CMG,

About your test images, I see you have used only two cables on the connector, one for positive and one for negative while the other ones are floating. Can you comment a bit more on the testing procedure that you have used, was it power board pins 6 (VO3) and pin 7 (GND) on the connector the ones you have used?

Thanks a lot for sharing the pics and information, same to everyone else for their input.

[Trevtron]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Happy new year guys!

I found this thread and thought I would share my experience.
Someone handed me a not-very-old LG TV (42LB5610) with sound and no pic. Sure enough there was a trace image visible using the torch (flashlight) trick. I informed the owner he'd be unlikely to see any change out of €100 to fix it. So he asked if he was due me anything for looking at it and off he went to buy a new one.
Now it's nothing fancy but it would still be nice to get it going again, so I had a proper look and to my surprise I discovered that ALL 32 backlight LED's are short-circuit. What also surprised me was that on the PSU there is a label listing the output voltages; the usual 5 & 12V rails and one at 200V. Now when I was at school, 32 (LED's) X roughly 3V would be 96V or thereabouts. So were these 6V LED's?
Well after a quick search on the eBay page mentioned above (thank you @cmg) it would appear so, there are several 6V LED's listed, one specifically mentioning LG 'Innotek'.
So it looks like this set won't be seeing landfill for a while yet. Replacing 32 LED's and then sticking the plastic lenses back on will be a "when I've nothing better to do" job. I've not done much with SMD's having pretty much given up repairing TV's when CRT's were still popular.

[horia]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Did you get the same left hand and right hand side intensity? Ty

[horia]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

I have the same issue on hp z1 g2 27” cheap Samsung. Thank you for the useful forum.

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Updating this due to comments on the other thread.

Pic shows the strip fixed, then tested using a little constant current source PCB (showing 33V). Finally i tested it in situ. This WAS necessary because the connector is very dodgy and once I didn't solder it very well, finding it failed again when I had reassembled the panel.

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

OK.. I fixed it now! This was thanks to the seller mentioned above finding the right LEDs.
Soldering the new ones on was very tricky indeed. The first few i did look pretty awful and eventually the don't look too far off the original ones.

The LEDs were closely spaced so heating the whole strip seemed like a bad idea. The most successful method i had was to tin the pads and the underside of the LED with an iron, then melt the solder on the pads with the hot air set at 315C. Then i'd slowly lower the LED over it, keep heating for a few seconds and remove the hot air. Then go round adding solder paste and either reflowing or using the iron until the A and K were soldered well. I couldnt manage to just sit the LED there with paste and apply hot air. The LEDs got melted and/or flew off the board.

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Thanks for the advice. I'll give it a try on some scrap PCBs while waiting for the new LEDs.

[diif]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Hi. The seller's page is here: http://www.ebay.co.uk/usr/lelos2

He's very helpful and he has lots of LEDs listed. I haven't yet got the LEDs so I can't say if they are definitely right.

Thanks for the videos - that was interesting. The strip i have is small and narrow (see pics). I think I'll continue to try heating from above with the rework gun. I was using the narrowest nozzle (<2mm dia); perhaps I should use a larger one and turn up the flow and/or temp. The specs for such LEDs seem to say the reflow temp should be 260C but this wouldnt budge until the station was set to about 350C.

thanks!

The temperature on your station display is not the temperature at the nozzle.
I have mine set about 380c.
I'd use a larger nozzle as there is less chance of damage to the LED.
I use a dab of flux to remove and another dab to help the reattachment.
I used working LEDs pulled off one strip to repair 4 strips.

[kc8adu]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

too bad its not 3535.lots of choices.
btw most lcd strips i have seen are 7500-8000k
blueish/purplish.

[petehall347]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

hope you can get them hot enough without damaging the led.s . they are normally done with a heat pad .
i would use leaded solder because it melts at lower temp. . not sure if you can get leaded paste for these days though ..we used to use leaded for tinning the steel for body soldering on vehicles before they invented polyester body filler ..

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

did you add flux ?

No. I've got flux and lead free solder paste in the mail. Actually I didn't realize flux will help with desoldering. I'm new to hot air soldering. I'm planning to solder the new LEDs on with solder paste and hot air. It is not possible to solder these with an iron as the pad is right underneath. When i get the paste and flux i'll practice with some scrap PCBs. Hopefully small SMD power transistors / voltage regs will seem similar to solder.

[petehall347]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

did you add flux ?

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Hi. The seller's page is here: http://www.ebay.co.uk/usr/lelos2

He's very helpful and he has lots of LEDs listed. I haven't yet got the LEDs so I can't say if they are definitely right.

Thanks for the videos - that was interesting. The strip i have is small and narrow (see pics). I think I'll continue to try heating from above with the rework gun. I was using the narrowest nozzle (<2mm dia); perhaps I should use a larger one and turn up the flow and/or temp. The specs for such LEDs seem to say the reflow temp should be 260C but this wouldnt budge until the station was set to about 350C.

thanks!

[vinceroger69]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

have you got a link to the seller your using thanks
this is a good video showing the heat pad method but you can also use a hot air gun on the underside of the strip
https://www.youtube.com/watch?v=EZVQKEp6jxk

and from 12 minutes in on this video
https://www.youtube.com/watch?v=Bf5T2wwtydY

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

only way i know of doing it properly is using a heat pad so the heat comes from the back of the strip
.. i have not tried replacing single led.s yet .
fingers crossed the light is the same as originals when you do yours .
i have only replaced whole strips from same id number panel .
in the manuals i have read it says replace all strips . as you will know this is too expensive even if used ones are used .never mind a set of new ones .

Thanks Pete.

Well, Google hasn't shown me any hits at all that point to being able to find a replacement strip so that is not an option anyway. It is definitely special for this panel as the PCB has the panel model # on it.

When i was trying to remove it i was focusing on the side with the A, K pins and didn't think of the huge heat pad underneath the other side. Maybe better next time as there are a handful i need to replace. I cracked the lenses off when removing the strip. I think the original fault was a dry joint on the connector (which is really weedy and fell off the PCB whist removing). All but one of the LEDs worked and the strip that was causing the PSU to shutdown was not the one with the shorted LED in.

[petehall347]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

only way i know of doing it properly is using a heat pad so the heat comes from the back of the strip
.. i have not tried replacing single led.s yet .
fingers crossed the light is the same as originals when you do yours .
i have only replaced whole strips from same id number panel .
in the manuals i have read it says replace all strips . as you will know this is too expensive even if used ones are used .never mind a set of new ones .

[cmg]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

Hi. Thanks for the help. I think i've got the right parts on order now thanks to Mr 'lelos2' on eBay.

I had seen the Osram ones looked similar but they were not the same. The parts he found were Lumileds LXML-PWD9N, 3W 3V 3030. They certainly are the same voltage, have the same type of lens and have the same solder pad pattern. I'm awaiting the order, so will be able to try in a couple of weeks.

My advice is that it is really hard to find the exact correct LED, and that I found someone who was able to help locate the right part in the end!

I realised that the other 3V 3mmx3mm ones i found simply would not fit due to the different solder pad patterns. I just looked at the data sheet for the Osram ones on RS which you posted (thanks PeteHall). These have 3 parallel strips as pads. See attached for the pads on these LEDs which seem pretty unique.

I'm hoping these turn out to be exactly the same as the originals, and hoping i can solder them on with the hot air station OK. Both things harder than anticipated

[stj]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

or here:
https://www.rapidonline.com/surface-mount-power-leds

[petehall347]

Re: Sourcing replacement backlight SMD LEDs or Strips (LG panel)

see if any of these match up ...https://uk.rs-online.com/web/c/displ...333020534D4426