Samsung UN46ES6100F No Backlight

[Truncatedhose]

Hoping someone may have some suggestions for this one. I've found a service manual, but it doesn't seem to offer any help really. It has a troubleshooting section, but doesn't list "no backlight" as a symptom to troubleshoot. I was trying to just find out what the voltages to the LED arrays are supposed to be and I don't think it even shows that? Maybe I'm just not finding it.

Here's the S/M:

What I've tried:

Replaced the PSU and the Main Board and have the same symptom: (I have video which can be seen with a bright light, but the TV's backlight never comes on.)

Any help? I want to confirm that I didn't get a bad board replacement and start over with the troubleshooting; I put the original boards back in.

[mmartell]

Re: Samsung UN46ES6100F No Backlight

The Fast-Tracks for the ES7500 and ES8000 indicate removing the cable between the power supply and main board and plugging the unit in. If that doesn't fire the backlights it says to add a jumper between pins 2-4 and try again.

This may or may not cover the ES6100 but worth a try if you haven't done so already.

[freakaftr8]

Re: Samsung UN46ES6100F No Backlight

Yes thus will cover the ES6100 as well. You may have an led driver bad on the power supply. That's what i found on my 40ES4100

[CapLeaker]

Re: Samsung UN46ES6100F No Backlight

If you changed the main board and the power supply already and no progress, then either the LED backlight wiring is shorted or open circuit, or a burnt out LED in the panel.

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

Thank you everyone for chiming in. I tried the force backlight on procedure both ways and still nothing. Is there a relatively simple way to test the LED arrays without taking the panel apart? Can I verify the voltage going to them from the PSU is correct? It's not listed on the board. Anyone know what voltage it should be? Also, if something is loading down the voltage in the power supply, is there a way to test the arrays using the wires coming into the PSU? I suppose I could test to see if there is a short between them? Also, what about supplying an external voltage to see if they light up?

[CapLeaker]

Re: Samsung UN46ES6100F No Backlight

You certainly can test the wiring for a short against ground. However for a bad LED or LED string, you have to open the panel up.

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

I thought I would take a close-up picture of the plug going to the arrays and also post the voltages I read when the TV is on and has video but no backlight.:

PIN 1 NC: (not connected)
PIN 2 R+: fluctuates between 244.0V DC to 267.0V DC (repeats)
PIN 3 R+: (same as pin 2)
PIN 4 NC: (not connected)
PIN 5 R-: fluctuates between 0.0V DC to 7.0V DC (repeats)
PIN 6 NC: (not connected)
PIN 7 L+: (same as pin 5)
PIN 8 NC: (not connected)
PIN 9 L-: fluctuates between 1.3V DC to 2.5V DC
PIN 10 L-: (same as pin 9)

I'm surprised at the high voltage on pins 2 and 3; it doesn't seem right that it would be so high...? I checked the reading many times and my meter is a Fluke 87.

I haven't checked for shorts between the wires or pins; should I? and where?

[budm]

Re: Samsung UN46ES6100F No Backlight

"I'm surprised at the high voltage on pins 2 and 3; it doesn't seem right that it would be so high...? I checked the reading many times and my meter is a Fluke 87." If there is no load (LED string has open circuit due to failed LED or wiring, the output Voltage will be very high and causes the protection circuit to kick in.

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

"I'm surprised at the high voltage on pins 2 and 3; it doesn't seem right that it would be so high...? I checked the reading many times and my meter is a Fluke 87." If there is no load (LED string has open circuit due to failed LED or wiring, the output Voltage will be very high and causes the protection circuit to kick in.

So I could unplug that plug and test the voltage and if it's back to normal, then that would confirm an LED array is bad?

Wait, that would also mean it would be high if I disconnect it. What should I do to confirm or does this confirm the LED array is bad?

[mmartell]

Re: Samsung UN46ES6100F No Backlight

I just fixed a UN46D7000 that had similar readings - almost 300v on one of those pins!

Opened up the panel and found the connector to the left side led strip was not snapped in all the way. It was working for a while, then intermittent, finally a section had stopped working (you could see the bottom quarter of the screen was not lit like the rest) and the set would reboot itself.

Reseated the connector and all was fine. Be careful opening the panel and you should be ok. And try not to get dust or fingerprints on the layers inside.

[budm]

Re: Samsung UN46ES6100F No Backlight

mmartell is referring to his thread here:
https://www.badcaps.net/forum/showthread.php?t=44541

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

mmartell is referring to his thread here:
https://www.badcaps.net/forum/showthread.php?t=44541

Is there a step by step for opening the panel and putting it back together safely? I thought I saw one somewhere....

[mmartell]

Re: Samsung UN46ES6100F No Backlight

Not sure about that. I can help get you started though. This is what I did..

Put the panel face down on something that won't scratch the screen, obviously.

Remove the back.

You won't have to remove the boards but you will have to remove the speakers and the long metal bar covering the driver board and remove the panel ribbons from the tcon. Now remove the tape keeping the driver board in place to the panel and GENTLY swing down the driver board so it hangs by its ribbons. It won't hurt it but remember if you do any damage to the ribbons the panel is toast.

Now you may or may not have a black tape running around the perimeter of the metal bezel surrounding the panel. If it's there it will need to come off as it will expose the screws that need to be removed. There are something like 30 of them and they are smallish. Make sure to use the right size screwdriver and use plenty of force as you don't want to strip the head on these puppies.

Now you will have to inspect closely the manner in which the backlight assembly is affixed to the panel assembly. On a D6000 I worked on you had to release the plastic tabs by pushing them into the holes they sat in and you could pull up the backlight in that area. The D7000 had five metal tabs that needed to be pried back.

Once you manage the previous step grasp the backlight assembly - it should lift straight up from the panel assembly. Cover the panel assembly with something (I used new garbage bags) as you want to keep the area free from dust and of course your fingerprints.

The reflector panel will probably come up with the backlight as it is glued to it. Try to keep everything as clean as possible.

At this point you should have all the access you need to the leds. Let us know how it goes.

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

Thank you so much, mmartell! When I have time, I will try this and get back to you!

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

Well, I got access to the LED arrays; it was a lot harder than I thought it would be. Thanks for your instructions; they got me started but this one was quite a bit different than what you described. Unfortunately, I can't find anything wrong with the connectors and even if I did, I think getting this back together intact would be a major challenge. I might have another tech friend look at it later, but it may just have to be scrapped.

[freakaftr8]

Re: Samsung UN46ES6100F No Backlight

If you can get it back together you might want to have a look at the IC on the back of the power supply for the led driver IC.

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

If you can get it back together you might want to have a look at the IC on the back of the power supply for the led driver IC.

Actually, I did some more close inspection and found two LEDs on one of the arrays were visibly burnt out. I did some looking for a replacement array, but no luck. Even if I could find one, I don't think this would go back together very well. Then of course it could have further LED failures down the road, so I don't think it's worth it. I went ahead and scrapped it out.

[budm]

Re: Samsung UN46ES6100F No Backlight

Thanks for the follow-up, it is sad isn't it that the LED backlights do not last as long they claimed due to poor design.

[Truncatedhose]

Re: Samsung UN46ES6100F No Backlight

Thanks for the follow-up, it is sad isn't it that the LED backlights do not last as long they claimed due to poor design.

Indeed! Horrible low-quality TVs. It's crazy how so many people don't understand that with the price going down year after year, the quality and longevity goes down, too. People should demand a higher quality and be okay with a higher price. The amount of waste is horrendous!