Dynex TV - screen goes black


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Dynex TV - screen goes black

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nhdon333
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Nov 29, 2017, 3:25 AM

Post #1 of 8 (6351 views)
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Dynex TV - screen goes black	Can't Post

Hi,
Looking for some assistance. I've got a Dynex DX-46L262A12. When you turn the tv on, "please wait" appears on the screen, then the picture appears and is visible for 5 to 15 seconds, it varies each time, then the screen goes black, but you can still hear sound.
Has anyone experienced this and knows what the fix is?

Thanks

jts1957
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Nov 29, 2017, 6:55 AM

Post #2 of 8 (6341 views)
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Re: [nhdon333] Dynex TV - screen goes black [In reply to]	Can't Post

Are the back lights lit when the screen goes black?
Results of 'Flash light Test?'

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nhdon333
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Nov 30, 2017, 12:40 AM

Post #3 of 8 (6333 views)
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Re: [jts1957] Dynex TV - screen goes black [In reply to]	Can't Post

Thanks for the reply.
With the tv on, if I shine a flashlight, I can images, words, people, etc on the screen.
Audio works fine and for the first 20 seconds or so, every time I turn the tv on, the image is fine, then it goes black.

jts1957
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Nov 30, 2017, 1:45 AM

Post #4 of 8 (6330 views)
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Re: [nhdon333] Dynex TV - screen goes black [In reply to]	Can't Post

So I take that for a NO.

1) Inspect Inverter board for bad solder.
2) 24V?
3) BON / BLON / Backlight enable?

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Location: Far, Far Away

nhdon333
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Nov 30, 2017, 2:51 AM

Post #5 of 8 (6326 views)
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Re: [jts1957] Dynex TV - screen goes black [In reply to]	Can't Post

My understanding of the flashlight test, was that if you shine a flashlight on the screen and you can see images, then the backlight is not functional...so yes, that would be a no.
What confuses me, is that the image works fine for upto 30 seconds when you turn it on, so it seems odd that it's the backlight...unless it's just not completely gone yet.

I haven't opened it up yet, but will shortly, so I don't know if there is any bad solder.
I'm assuming you are asking if the inverter is 24v.. again, having not opened it up yet, I don't know. If that's not what you are asking, please clarify.
As for BON / BLON / Backlight enable... I don't know what you're asking.

Thanks again.

jts1957
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Nov 30, 2017, 3:24 AM

Post #6 of 8 (6323 views)
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Re: [nhdon333] Dynex TV - screen goes black [In reply to]	Can't Post

Open set up. The back of the LCD Panel should have many holes or other cutouts that back light lighting can be observed.
CCFL back light bulbs (think similar to fluorescent bulbs, approximately the diameter of the graphite lead of a child's first pencil) are each part of a balanced circuit that has the ability to determine, if say, a bulb is broken, arcing, etc. Inverter transformers and drivers can also trigger. Bad solder joints / broken wires.

The labels on the Internet's Inverter board pictures show IDs for each pin of connectors.

So, short version: You request the TV to turn on; The Main board tells the Power board to give the Inverter board 24VDC; and an enable signal From either the Main or possibly the Power board tells the Inverter to light the bulbs.

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nhdon333
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Dec 1, 2017, 7:20 AM

Post #7 of 8 (6314 views)
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Re: [jts1957] Dynex TV - screen goes black [In reply to]	Can't Post

Opened it up.... The backlight starts out on and after about 40 seconds, it goes off.
I see no broken wires, no bad solder.
If the backlight is going off, do you think the most likely cause the inverter?

jts1957
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Dec 1, 2017, 8:22 AM

Post #8 of 8 (6313 views)
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Re: [nhdon333] Dynex TV - screen goes black [In reply to]	Can't Post

YOU will need to make the measurements requested to narrow down the possibilities.
Current possibilities (in no particular order): Bulb inside panel - Inverter Board - Main Board - Power Supply Board.

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