question about LEDs


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question about LEDs

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dangertomyself
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Jul 5, 2018, 10:43 PM

Post #1 of 14 (1485 views)
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question about LEDs	Can't Post

i have a Samsung UN60J6200AFXZA that i'm trying to diagnose. i'm able to see a picture when i perform the flashlight test, so i know it's an issue with the backlight or the power board. the board is working properly though, i think. when i pulled off the screen and other fixins and got to the LED strips, i tested the output of the board and got 427 volts, but when i turned the tv on and examined the backlights in a pitch black room, the majority of them shone very dimly and some not at all. where should i go from here?

jts1957
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Jul 6, 2018, 3:11 AM

Post #2 of 14 (1481 views)
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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

http://www.shopjimmy.com/...strips-12-strips.htm

Don't forget to match strip numbers / panel numbers & don't forget to lower the BACKLIGHT setting to prevent future failures.

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dangertomyself
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Jul 6, 2018, 11:01 AM

Post #3 of 14 (1475 views)
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Re: [jts1957] question about LEDs [In reply to]	Can't Post

ok, so this is definitely an issue with the backlights? is there a way to test to be sure? i have a voltage generator, but i was having mixed results testing individual strips. had a few strips that shone brightly when i ran 30v through, and then wouldn't light up again, and some that never responded.

(This post was edited by dangertomyself on Jul 6, 2018, 11:05 AM)

jts1957
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Jul 6, 2018, 5:55 PM

Post #4 of 14 (1459 views)
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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

1) Yes. Backlights.
2) Yes. Strip removed. 3V - 3.6V applied in turn to each LED on the strip (with correct polarity observed) should allow each LED to light brightly. Or, apply 3V - 3.6V times the number of LEDs on the strip to the connector at the end of the strip (with the correct polarity observed) should allow all LEDs to light brightly. All tests results should be repeatable. Open, shorted or intermittent LEDs will affect results.

In my opinion, issue with manufacturer shipping out sets with backlight intensity setting at MAX (which shortens LEDs life). Running most things at MAX is not advisably (try doing so with a car engine). I'm reasonably sure their engineers warned against running the LEDs at MAX, over long periods in an enclosed, not well ventilated area (as compared to their test jigs), but the TVs sold so well with the nice bright picture...
Just for grins, see where your sets backlight intensity control is set (using a flashlight).

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dangertomyself
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Jul 6, 2018, 6:07 PM

Post #5 of 14 (1455 views)
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Re: [jts1957] question about LEDs [In reply to]	Can't Post

ok, first off, thank you so much for the help. second, in order to test the individual LEDs, will i need to remove them from the strip somehow?

jts1957
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Jul 6, 2018, 6:52 PM

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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

Just the lenses to access solder tabs of LEDs (or sharp-pointed test probe to puncture through paint covered foils leading to them). All LEDs on each strip should be in series.

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dangertomyself
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Jul 6, 2018, 7:38 PM

Post #7 of 14 (1449 views)
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Re: [jts1957] question about LEDs [In reply to]	Can't Post

alright, once again, thank you. i'll give it a try.

dangertomyself
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Jul 6, 2018, 10:50 PM

Post #8 of 14 (1444 views)
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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

ok, i definitely have some dead LEDs in 2 of the 6 strips. i'm at a loss for how to replace them individually though. the one cap that i tried to remove i ended up having to break off, and then the underlying LED is just like a chip attached to the strip. do i just try to desolder it somehow?

jts1957
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Jul 6, 2018, 11:20 PM

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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

Post #2 contains link to Strips, Rework station, 2-sided tape and a video showing how to disassemble panel and replace strips.

Rework station link has video on how to use to replace single LEDs.

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dangertomyself
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Jul 6, 2018, 11:47 PM

Post #10 of 14 (1440 views)
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Re: [jts1957] question about LEDs [In reply to]	Can't Post

ahh i missed that. thank you.

dangertomyself
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Jul 15, 2018, 2:30 AM

Post #11 of 14 (1389 views)
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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

ok, i got my replacement LEDs and i was able to fix 2 of the 4 strips that were bad. the ones i was able to fix had LEDs that were still good and would come on when i hooked up a voltage generator to the strip; i just replaced the LEDs that were out and now they're g2g. the other two strips appeared to have no good LEDs, so i assumed they were all out. after pulling the LEDs and testing them, it seems all of the LEDs are actually good, they just don't light up when they're connected to the strip... is this the part where i have to buy new strips, or is there something else i can do?

jts1957
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Jul 15, 2018, 1:16 PM

Post #12 of 14 (1377 views)
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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

Many people replace the strips because it is the easiest way to do.

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dangertomyself
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Jul 15, 2018, 10:24 PM

Post #13 of 14 (1373 views)
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Re: [jts1957] question about LEDs [In reply to]	Can't Post

i totally get that, but what could be wrong with the strip if the LEDs are good?

jts1957
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Jul 16, 2018, 12:36 AM

Post #14 of 14 (1369 views)
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Re: [dangertomyself] question about LEDs [In reply to]	Can't Post

The strip connectors, wiring or a break on the strips, usually at a connector/component.

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