Tv turns on and there is sound, but no picture... - AVS Forum
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post #1 of 11 Old 05-27-2011, 11:27 PM - Thread Starter
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Hello,

My buddy was given a 40-in Dynex lcd tv. The tv powers on and there is sound but the is no picture. We read about this and found some limited solutions. We read that it might be the inverter for the display. Does that sound about right? I believe the brand of the tv is Dynex DX-L40-10A. Does anybody have the service manual?

Thank you
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post #2 of 11 Old 05-27-2011, 11:56 PM
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well at least you wont suffer from banding, flashlighting, black crush and other picture problems.....

kidding try checking the wires make sure they are all in the correct spot
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post #3 of 11 Old 05-28-2011, 07:06 AM
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Is the backlighting for the TV working? If it is you will see it at night when there is no other light in the room.
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post #4 of 11 Old 05-28-2011, 07:34 AM
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You might be able to check if it's just a backlight problem by shining a flashlight close and into to the panel. You may be able to faintly see a picture.
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post #5 of 11 Old 05-28-2011, 11:49 PM - Thread Starter
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Let me get back to you on that, I will have to ask my buddy to check this out.
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post #6 of 11 Old 05-29-2011, 05:28 AM
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Check the owners manual and the rear of the panel for any inset reset buttons. In particular if its a Sharp rebadge - I own two older Sharps that have a power setup systems that requires a reset so that during power outage issues this can occur (but sound always remains with no picture) and I have to insert a thin device into that inset button and leave it off for about five minutes and then reboot fresh and they are back to normal.

However, I don't know that this is an issue on newer Sharps built today since I don't ever recall ever seeing anyone post about this PITA event on current models.

Just a possible thought that may be on yours since half of Sharp's production globally gets rebadged by others - check the owners manual or back of the set for any power protection resets. Good Luck!

I've also had a similar event as yours on a particular cheaper LCD monitor lines on my network and my Tech Assistant and I decided to disassemble a few of the failures layer by layer since they were beyond warranty after viewing the EngineerGuy video of how the Monitors are assembled and work and we found on this cheap line that the thin backlit tubes at the top/bottom the connector ends top or bottom would literally burn out - very cheap power components/connectors - I won't be buying that line again anytime soon for my network -Brand was AOC .

For an interesting EngineerGuy demo view here: (The Forum should have a sticky area and post Demo's like this - extremely interesting)

http://www.engineerguy.com/videos/video-lcd.htm

Samsung 65F8000, 60D8000, 40HU6350, Panasonic 50E60 LCD's
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post #7 of 11 Old 05-29-2011, 03:38 PM
 
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Someone gave me a free Insignia NS-32LCD today (Dynex 1st cousin), that powered on OK, but there was no picture.

Found the problem in a couple of hours. The power supply board has 3 fuses and the fuse feeding the 24 volt output connector was blown.

It was a miniature 'pica' type fuse that is soldered directly onto the board.

Although I did not have to trouble shoot any further, I understand that the inverter board is fused as well.

While you're at it, check for and replace any faulty (e.g. leaking, bulging tops) electrolytic capacitors as well.

However, in this case, the only problem I found was the bad fuse (which is a $ .50 part).
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post #8 of 11 Old 05-31-2011, 05:38 PM - Thread Starter
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My friend hooked up a dvd player and with a flashlight up to it he could see the movie. Looks like backlight. Is this easy to fix and identify when you get the tv apart and attempt to fix?
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post #9 of 11 Old 06-01-2011, 04:16 AM
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The question you should be asking is: is it easy to start tracing the "Inverter - backlight chain" to find the problem? If you did some faultfinding before and you are good with electronics and you know what's inside the TV - in particular what inverter is, then yes -> it is easy. The good starting point would be to know how to recognise the inverter board. If you know this already -> good, you may have a chance... just get the same new board & make sure that the voltage needed for the inverter to function properly is there – it comes from the SMPS module and it is usually around 24V DC… and can go up to 60V DC or higher on some models. Usually it is a single rail, but some inverters may use “symmetrical” voltage rails; +24 and -24V DC for example.


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post #10 of 11 Old 06-01-2011, 04:32 AM
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Quote:
Originally Posted by 2002Z28 View Post

Is this easy to fix and identify when you get the tv apart and attempt to fix?

Here's a picture of the inverter:
http://www.usefulparts.com/index.php...oducts_id=1153
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post #11 of 11 Old 06-01-2011, 05:44 PM - Thread Starter
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Thank you for all of the replies. I have little experience taking tvs apart, although i recently took apart my Elite plasma and fixed the easy problem it had. My friend and I will take the tv apart, make sure we can id the board in that one pic, assess what needs to be done and move on from there.

Thank you again
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