LG LCD no backlight


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LG LCD no backlight

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85XJS
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May 30, 2016, 8:57 PM

Post #1 of 8 (3070 views)
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LG LCD no backlight	Can't Post

LG 47LN5790 Power on and the tv backlight flashes then goes dark. Flash light test shows video image present also setting screen can be brought up. Also audio not present. Power supply shows only millivolts on the output test points. Put in another power supply and same thing. Where should I look for problem? Perhaps main board? On t-con board?

jts1957
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May 30, 2016, 9:09 PM

Post #2 of 8 (3069 views)
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Re: [85XJS] LG LCD no backlight [In reply to]	Can't Post

The Panel.

Which input are you using that sound is NOT present?

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85XJS
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May 30, 2016, 9:32 PM

Post #3 of 8 (3066 views)
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Re: [jts1957] LG LCD no backlight [In reply to]	Can't Post

Just using the coax from dvr

jts1957
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May 30, 2016, 10:38 PM

Post #4 of 8 (3062 views)
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Re: [85XJS] LG LCD no backlight [In reply to]	Can't Post

Try a couple of other inputs. Sets with dead LEDs that have video and Menus/OSD will usually have audio present too.

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85XJS
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May 30, 2016, 11:46 PM

Post #5 of 8 (3057 views)
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Re: [jts1957] LG LCD no backlight [In reply to]	Can't Post

Does the main board control the power supply and that is why I am not getting any voltage out to the LEDs

jts1957
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May 31, 2016, 12:38 AM

Post #6 of 8 (3056 views)
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Re: [85XJS] LG LCD no backlight [In reply to]	Can't Post

More like the manufacturer shipped the TV with the LED intensity at 100% and nobody thought to turn it down, significantly shortening the life of one (or more) LED back light bulbs inside the panel.

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85XJS
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May 31, 2016, 1:13 AM

Post #7 of 8 (3053 views)
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Re: [jts1957] LG LCD no backlight [In reply to]	Can't Post

I will check the LEDs next. But I am still wondering why there is no voltage at the power supply test points with the LED plug disconnected.

jts1957
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May 31, 2016, 9:09 AM

Post #8 of 8 (3051 views)
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Re: [85XJS] LG LCD no backlight [In reply to]	Can't Post

From Shop Jimmy site:
PLEASE NOTE: Models that use this power supply are also HIGHLY susceptible to LED failure. What may seem like a power supply failure may be caused by the failure of one or more LEDs inside the panel (screen).

Is there voltage with the LED plug connected (during brief 'flash')?

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