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Samsung UN40EH5000FXZA - sound, but no picture    
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Bnystrom



Joined: 11 Mar 2017
Posts: 2
Location: New Hampshire

PostPosted: Sat Mar 11, 2017 2:13 pm    Post subject: Samsung UN40EH5000FXZA - sound, but no picture Reply with quote

The panel appears to be fine (flashlight test), but the backlight is not working. The power supply board shows no evidence of component failure. I get 216V at pins 1&8 and 2&7 with the TV powered on, zero when powered off. I've got 5V between JP813 and JP812 (or ground).

Testing the LEDs individually revealed a single dead LED in the center of the top strip. All of the others are working. Is that enough to shut down the entire array?

Any suggestions would be greatly appreciated.

Thanks

Brian
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JTS1957



Joined: 21 Jan 2009
Posts: 2343
Location: Far, Far Away

PostPosted: Sat Mar 11, 2017 4:07 pm    Post subject: Reply with quote

Yes, a single LED can stop all.
I'd suggest applying enough voltage to the driven end to light the whole strip.

If/When done repairing, be sure to decrease backlight intensity to extend replacement's lives.
Bnystrom



Joined: 11 Mar 2017
Posts: 2
Location: New Hampshire

PostPosted: Sun Mar 12, 2017 7:37 am    Post subject: Reply with quote

JTS1957 wrote:
Yes, a single LED can stop all.

Excellent, now I know what I need to fix it. Thank you!

One thing I'm curious about is the voltage to the LED array. There are a total of 38 LED at 3V each, so I would expect the voltage to be around 114V. However, I'm getting 216V+ at the connector. Is there additional resistance that must be overcome or something?
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