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Louie, Technician
Category: TV
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Experience:  25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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LG 42" flat screen TV keeps shutting off

Customer Question

My LG 42" flat screen TV keeps shutting off then turns right back on but the hd cable box doesn't turn off any idea why?
Submitted: 5 years ago.
Category: TV
Expert:  TV Tech1 replied 5 years ago.

It depends on WHEN the TV shuts itself off.

If you turn it on, does it on/off/on/off/on/off the moment you press the power button?

Does it turn on....and then the TV screen go from Pitch Black to a gently lit screen and it turns off?


Does it light up, then you see the LG logo appear on the screen, then it shuts off, and cycles back to the point you see the LG appear again over and over??

The first one is the power supply or main board.

The second one is a bad lamp

The third one is the main board's software.

We repair it differently according to what the TV does.

Customer: replied 5 years ago.

We turn the TV on and after it has been on awhile it just turns off no warning the red light on the TV flashes then the TV turns back on I see the HDMI! then the picture & sound when it turns off it's as if I pressed the power button on the remote and it turns on as if I pressed the power button on the remote

Expert:  TV Tech1 replied 5 years ago.

Ok, so the TV turns on....stays on for a while. Eventually it just turns off.

But you can SEE the HDMI 1 appear with no problems whatsoever, correct?

How about the TV's MENU or Volume bar? Can you make it show up using the remote or the Keys on the TV?

That would at least tell us --

The Screen can display on command, and the Micro does respond to the buttons.

If it can, tell me. The good news is if you CAN SEE HDMI showing on the TV screen, then it's going to be LESS costly, and you can repair it yourself.

But let's run a test BEFORE we delve into your TV set.

First, you may simply have scrambled computers....either in your TV or possibly the Cable or Satellite box you are using.

That'll give you a TV showing HDMI on it, but with no picture.

UNPLUG the power cord on your TV set, Cable/Sat box, and any OTHER boxes (DVD or games) for a FULL 5 MINUTES to reset the computers.

Also UNPLUG any HDMI cables, because they can get scrambled too.

Wait that 5 minutes, then plug in the power cords, and turn EVERYTHING back on.

WAIT ONE MORE MINUTE, then reconnect the HDMI cables.

That process resets all computers, and all HDMI connections.

See if you get a picture and sound now.

If not....activate the TV menu or volume bar and see if those show up on the TV screen.

Because of storms, we see a lot of locked up TVs and cable boxes making the TV look like it's bad, when it's not.

Customer: replied 5 years ago.
It's almost as if the TV gets hot & turns off . When it turns off everything turns off then turns right back on & everything works. It works perfectly before it turns off & works just the same as soon as it turns back on. I will try what you said & then let you know
Expert:  TV Tech1 replied 5 years ago.


On the Front of your TV are some lights. If they are ON when it's running normally, SEE if they SHUT OFF when it goes bad for that second or two.

That tells us the Power supply could be losing POWER. Then the moment power is restored, it will light up, then the picture appears afterwards. Notice the lamp lights FIRST.

Now if those lights stay ON all the would point to the TV just losing the picture signal.

Heat related issues are generally the power or Video overheating.

Customer: replied 5 years ago.
OK we tried what you suggested about shutting everything off etc. There is a light on the front right corner of the TV. The TV just turns off the red light blinks a few times then the TV turns back on after 2-3 secs the light blinks blue we see HDMI1 .....connecting then we get picture & sound at the same place where it was when the TV turned off like I said it's as if we press the power button & turn everything off then press the power button & turn it back on except it stays where it was when the TV turned off
Customer: replied 5 years ago.
BTW when the TV goes off it comes back on after 4 secs & the LG remote does not power it back on it just comes back on by itself
Expert:  TV Tech1 replied 5 years ago.

Interesting...the PICTURE does not advance at all, nor does the sound. Yet you get no breakup of either one when it restarts?

The video and audio buffers have still got to be Storing information if it behaves that way, and then the micro has got to running to do that too. Yet the picture and sound disappear on the screen, the micro ACTS like it's turned off the TV and turned it back on. The power supply can't be turning off. The video processor has got to be stopping the data transfer like someone put it in pause.

Double check your TV for a product code or product service number on the model sticker. See information in the picture --