Backlight turns on with TV then off.

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Sylvia Parsons @sylp

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Postato: 1 nov 2018

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Backlight turns on with TV then off.

Hi, I got a Magnavox 40in LCD TV (40MF401B/F7) with a display problem.

When I press the power button, the tv turns on and lights up and the words “DIGITAL TELEVISION” are displayed, then the screen goes dark.

Picture is visible when a light is shined into the screen and sound plays fine. Problem persists on HDMI and Component inputs with different devices.

Vertical black lines also sometimes appear within the picture and did so before the screen stopped working. Checked tv settings and all appears normal but haven’t yet found how to do a factory reset.

Any suggestions for some diagnostic or repair steps would be greatly appreciated.

Thank you!

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oldturkey03 @oldturkey03 Rep: 781,5k 1,1k 893 2,3k · Answer 1 · 2018-11-01T20:31:59-07:00

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oldturkey03 @oldturkey03

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Postato: 1 nov 2018

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@sylp “Picture is visible when a light is shined into the screen “ means your main board is displaying the video but you have no backlight. Check the power board for any obvious damaged components. Measure the voltage output to the LED backlight from the power board to the LED’s let us know what voltage you get (connector CN1914 Pin 1-5 should give you 24V). It is possible that this is a power board issue or a failed backlight array. Post some pictures of all of your boards with your question so that we can see what you see. Use this guide Aggiungere immagini ad una domanda for that. It will allow us to see what you see.

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Hi, just in case it wasn't clear, the backlight does light up when the tv is first turned on but then it turns back off which I thought might be unusual enough to have an immediately clear cause.

My multimeter is broken but I will open it up and take a look and take pictures and pick up a new meter if I don't see anything.

Thanks!

2 nov 2018 da Sylvia Parsons

Yes you made the backlight situation clear in your original question. Remember that it is the main board that turns it on by signalling the power board to supply the voltage. Since it turns out, your main board sends the signal. Then it turns off could be caused by a bad power board or the backlight array itself. My first suspect is the power board.....

This "Vertical black lines also sometimes appear within the picture and did so before the screen stopped working." could be a T-con board issue or a mainboard issue (less likely).

3 nov 2018 da oldturkey03

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