Black Screen/LG 47LN5400/tested voltages/need guidance


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Black Screen/LG 47LN5400/tested voltages/need guidance

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fseipel
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Sep 6, 2015, 6:26 PM

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Black Screen/LG 47LN5400/tested voltages/need guidance	Can't Post

I have an LG 47LN5400 TV. It stopped working. Screen is black. I have no audio. When power is turned on, the standby light throbs twice (i.e. lights, goes out, lights again, stays out). Pressing POWER does NOT cause standby light to come on NOR does remote control. Screen is black. No sound. I have checked visually for bad caps, and none blown. All voltages are good on power board (3.5 V, 12V, 24VDC). I am not very familiar troubleshooting these. Do I need a mainboard or other component? I am not qualified to desolder capacitors to check them, but as I say, visually they are not bulged or blown on power board. I also have 3.5VDC going over to the board with the pushbuttons on it. If there is a basic guide to troubleshooting, please point me towards it. I'm thinking I need to replace the mainboard but I'm not sure... This is the first TV I've worked on.

jts1957
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Sep 6, 2015, 11:53 PM

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Re: [fseipel] Black Screen/LG 47LN5400/tested voltages/need guidance [In reply to]	Can't Post

Unplug power to main board cable to see if panel lights.

"All voltages are good?" At the correct time(s)? http://imgur.com/EekJi8G
All voltages at all times or do PWR_ON and/or DRV_ON affect certain one(s)?

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(This post was edited by jts1957 on Sep 7, 2015, 1:33 AM)

fseipel
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Sep 8, 2015, 1:39 AM

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Re: [jts1957] Black Screen/LG 47LN5400/tested voltages/need guidance [In reply to]	Can't Post

Panel does not light when I unplug power to main board cable. I've read about PWR_ON and DRV_ON but not sure where to activate them. It seems most likely my main board is bad but I couldn't find a P/N match on eBay. I will try following the flow chart you send, thanks!

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