Hello everybody.

I am trying to repair Samsung TV backlight strip which has apparently all LEDs intact (tested and working) but won't light up as whole.

There are some components between each LED which I am not able to identify and has no markings to help me with that.

If anyone would be so kind and lead me the right way it would be very appreciated

The led strip is from Samsung TV UA40J5200DK and has this identification on it:
Samsung 2015 SVS39.5 FHD FCOM 8LED REV2.2 160925 LM41-00465A

Attaching the picture.

 

Welcome to AAC.

Is the mystery component in the photo?

 

Oh, yes, it's the one right under the LED.

Here's the better picture:
I am new to repairing PCB's amd haven't seen this yet. I can tell rezistors, capacotors, tranzistors etc. but this one is confusing to me.

I am sure you'd guys know right away

 

Is the mystery component in the photo?

Is this the component? It looks like a two legged part like a resistor or inductor.

 

Look at the bonding wire. Diode?

 

Where does this light pipe go?

​

 

That component looks like an LED, is this the back of the PCB with LEDs on the other side?

 

Probably diode. It returns 9.6M ohm one way and infinity the other way. If I measure it on diode settings in one way (correct polarity) the LED lights up the other get 0.783V.

Mystery solved. Now just figure out, what diode rating to put there as a replacement for the bad ones. I guess will just try IN4007. Don't have any SMD laying around.

Thanks for your help!

Ad. 2 : That's not actually light pipe, just the stand to support the dispenser and LCD panel.

 

Or do you think it is possible it is some kind of IR Led?
I found some pictures of SMD IR leds, which look similar. I am not sure what would be the reason to put IR led in backlight of TV, but it might be so.

If I hit it with 3V I don't see any light emitted at all. But also the Info on the strip says 94V which makes a little sense while there are 8 LEDs on it...

And the DC output of the power supply has 101V rating, but I measured about 240V without the strips connected. Because if they are connected it's shorted and cannot measure anything.

There are 3 connections in series which means 240V would be well in the margin.

 

It's giving me a headache. I was hoping to learn something and fix it my self, but start looking like it will end up with some service guy :-/

 

Or do you think it is possible it is some kind of IR Led?
I found some pictures of SMD IR leds, which look similar. I am not sure what would be the reason to put IR led in backlight of TV, but it might be so.

If I hit it with 3V I don't see any light emitted at all. But also the Info on the strip says 94V which makes a little sense while there are 8 LEDs on it...

And the DC output of the power supply has 101V rating, but I measured about 240V without the strips connected. Because if they are connected it's shorted and cannot measure anything.

There are 3 connections in series which means 240V would be well in the margin.

You might try your experiment again but observe it through a phone or other digital camera. Newer phones have much better IR cut filters so they may not be useful. Older phones and cameras a very good for viewing IR emitters.

Ad. 2 : That's not actually light pipe, just the stand to support the dispenser and LCD panel.

Is “dispenser” an autocorrect error? If not, what are you referring to? Also, I wonder why they would use a transparent plastic for that.

 

You might try your experiment again but observe it through a phone or other digital camera. Newer phones have much better IR cut filters so they may not be useful. Older phones and cameras a very good for viewing IR emitters.



Is “dispenser” an autocorrect error? If not, what are you referring to? Also, I wonder why they would use a transparent plastic for that.

I meant those layered sheets below panel to distribute the light evenly. Not sure how it's called.

My guess is the transparent material is used to eliminate to some extent any possible shadow cast or light distortion of the backlight. Most probably.

As for the part, I believe those are diodes. Had hard time removing it and eventually broke it. Which led me to the discovery the LED next to it is actually shorted not the Diode which is weird since I was sure I tested them all separately and all were working. Maybe it was damaged and died along the way or more likely my error.

Decided to order new backlight strips since all 3 of them has issues and it's not worth fixing for the price I could get new ones. Still will keep them. If I will find free time will think of some use for them if I can fix or adjust them.