Samsung UN46EH5000, No Backlight

[ame123]

Hi Everyone. This will be my second post on this forum so go easy on me. I have a Samsung UN46EH5000 with no picture displayed. I have never repaired a TV but have repaired a couple of tablets and replaced some parts and digitizers and stuff. I have a cheap multi-meter but I have never really used one. I am willing to learn and do what's needed to get this baby up and running. Here are all the facts.

1) The TV does power ON
2) There is Sound
3) With the flashlight test in a dark room there is a picture and the menu options are visible.
4) There isn't any kind of backlight or light bleeding visible in a dark room when turning the TV on or while its running.
5)Disconnecting the CMN803 does not turn the backlight on.
6)I've looked at the orange board over pretty closely and can't see any budging capacitors, don't see any burn marks or smell anything burnt.

My educated guess is that either one of the LED strips failed.
If I need to remove the stand to reach the T-con board I will. Please let me know if you need anymore pictures or info. Thank you

[budm]

Re: Samsung UN46EH5000, No Backlight

leave the cable between the main board and the power supply/LED driver board disconnected then measure the DCV between the two legs of the main filter cap (the large 450V cap), it should have close to 400VDC.
How many wires (I see blue & black) are thee on the LED connector?

[ame123]

Re: Samsung UN46EH5000, No Backlight

Do I set my multi meter to 20, 200, or ,1000 DCV? Do I power the TV on or Just have it plugged in? Also Here is a picture of the LED connector wiring. Thanks

[budm]

Re: Samsung UN46EH5000, No Backlight

We are looking for 400VDC or so think what your meter should be set to.
Plug the AC plug into the outlet, no need to hit power switch. You must be real careful not to let the probes slip on you and do not touch any any thing with your hands or body because you are working in the HOT DEADLY side of the circuit.

[ame123]

Re: Samsung UN46EH5000, No Backlight

It measured 163 plugged in. sorry forgot to unplug it. 400 when unplugged

[budm]

Re: Samsung UN46EH5000, No Backlight

It measured 163 plugged in. sorry forgot to unplug it. 400 when unplugged

Good, the PFC Voltage booster is working. Now I have to trace out the LED connector to see how the LED strings are driven, and test the Voltages.
So far it looks like the two strings are connected in series to form one big string.

[ame123]

Re: Samsung UN46EH5000, No Backlight

Thanks, I'll wait for your response.

[budm]

Re: Samsung UN46EH5000, No Backlight

OK, check the DCV between pin 1 (D1+) of the connector CNL802 and the chassis with the LED connector in place and without the connector in place. You must leave the meter in place so when you plug the AC plug into the outlet we can see what Voltage you get and the Voltage reading after 3 seconds.

[ame123]

Re: Samsung UN46EH5000, No Backlight

Do you want the logic board connected as well? Do you also want the TV turned on or not? Will an exposed screw work as the chassis ground?

[ame123]

Re: Samsung UN46EH5000, No Backlight

So with the LED cable plugged in its around 296-312, after 3 seconds of turning on the AC power. It measures the same unplugged.

[budm]

Re: Samsung UN46EH5000, No Backlight

You have open LED or open connection in the LED strings.
http://www.ebay.com/itm/Samsung-UN46...3D281842546686

Typical failure on these LEDs:
https://www.badcaps.net/forum/showthread.php?t=46403

[ame123]

Re: Samsung UN46EH5000, No Backlight

Will this work https://www.shopjimmy.com/samsungltj...face-board.htm

Should I replace all of the LED strings and the board that this comes with. The price seems pretty good.

[budm]

Re: Samsung UN46EH5000, No Backlight

You should check the panel sticker: Is it Panel Sticker Number: LTJ460HN05-V
Good price for 12 strips. Contact SJ.
You may want to take the panel apart to see if it may have loose connection first.

[ame123]

Re: Samsung UN46EH5000, No Backlight

is this the panel sticker?

[budm]

Re: Samsung UN46EH5000, No Backlight

Your panel is 'DE460BGM-C1'

[ame123]

Re: Samsung UN46EH5000, No Backlight

Will the LED bar have a part number on it when I take it apart?? I am curious if the same LED bar is used in other TVs.

[budm]

Re: Samsung UN46EH5000, No Backlight

Some interesting info:


http://www.displaybank.com/_eng/share/index.html

[ame123]

Re: Samsung UN46EH5000, No Backlight

Hi, is this a valid way of testing the LED strip? You've been a great help, By the way do you know of any other websites where I can possibly locate this type of LED strip. I'll take the TV apart completely tomorrow and see what the part number for the LED strips is.

Thank You very much.

https://www.youtube.com/watch?v=eEJoPCa7Kt0

[budm]

Re: Samsung UN46EH5000, No Backlight

I would use 3 AA to get about 4.5V and a 100 Ohms (1/4W) in series with the LED to limit the current to test the White LED.
http://led.linear1.org/why-do-i-need...r-with-an-led/

[ame123]

Re: Samsung UN46EH5000, No Backlight

I am kind of in a pickle here. How would I remove the LED strip from the interface board, it looks like its glued together with some kind of black tape maybe. Here are some more pics.