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My tv keeps blinking on and off. How to fix? It's not the power supply

My Lg47lb5900 tv keeps blinking on and off. It's not the power supply. Any other suggestions? It's only 2 yrs okd

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Hi,

Presumably as you state that it is not the power supply, you have tested all the power supply rails or have tried a known working replacement power board?

There may be a problem with the LED backlight strips. As best as I can determine though the LED backlight power comes from the power board not a separate inverter board. It's probably too hard to tell if the display is still there when the backlighting turns off. Just a thought.

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@rburke26 what "keeps blinking on and off"? The power LED? The display itself? What did you check? How did you check?

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The display keeps flashing on and off. I ordered a new power supply and replaced it. Still flashing though.

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Jayeff the display is still there when it's flashing. It's very hard to see but I did catch it.

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... kind of sounds like you need a service manual. Before the days of replaceable circuit boards, that was the first step for repairing a television. Is there a burned smell? (you might have to get close to smell a burned component. Be sure power is not off, but disconnected) OR With unit on, you can always use a plastic probe to poke around on the printed circuit board. That could possibly reveal a cold solder joint. That has worked for me many times. If you do find a bad solder connection, and if it is not on a multi-layer board, it should be an easy fix. However multi-layer boards are common and can rarely (if ever) be repaired. New boards can be found online, but be sure it is [not close, but] an exact match. If something has gone wrong with a driver circuit allowing LEDs to get too much voltage, a new TV might be the only solution.

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@rburke26 if your screen does something in spite of the new power board which includes the backlight circuitry like this there will be an error with the LED backlight strips themselves. These are replaceable but it is not easy since you will have to dismantle the panel. Post your panel number, not the TV's model number so we can try to find the right strips for you. The numbers are usually on a label fixed to the panel.

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I have to remove the power cord from the wall and connect it again and no problems. Doesn't always happen, generally after not being used for a few days. Will need to update the advanced video settings for backlight.

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So an update. I toggled several settings on the TV and the issue is resolved. Unfortunately I don't know exactly which change corrected the issue, but no issues after.

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You said it is not the power supply. Does that mean you have taken the back off? Is the power supply built in or is it external, like a tablet 19 volt transformer? If you have opened the TV unit, can you identify a relay that clicks as it powers on? If so, as it powers on, hold a small rare earth magnet near the relay. BE CAREFUL not to touch anything, let the magnet stick to anything, hold it near any integrated circuit chips, etc. Sometimes the coil inside the relay gets weak. Holding a magnet NEAR the relay, (but not touching anything) can boost the magnetic field which operates the relay, allowing the contactor inside the relay to close (make connection) and the unit will remain on even after the magnet is taken away. If that works, the relay is bad.

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I ordered a new power supply board. It is basically a plug and play. Didn't fix it though. I have heard of the back light suggestion but have no idea if it's worth repairing.

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I just laid dwn to go to sleep. I turned my tv off and it started flickering white or maybe gray every 2 to 3 min can someone tell me what that could be? Tyia

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I was able to finally fix ours by just switching to a different HDMI port on the side!

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Yep, this worked for me too, thank you!

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Had the same issue, blacking in and out with no real pattern. One thing I did notice is that it only happens with the service from Comcast/Xfinity where I have a box attached to it. With Netfllix and Amazon through my Wifi, no issues at all. Changed the HDMI cable and all seems to be well for now. My opinion is that it has all to do with the HDMI connection. Change the cable and cross your fingers!

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Electronic circuits the tend to draw the most current, will run hotter, and heat degrades electronics, so when shooting trouble, It makes the most sense to start with those item. In LED flat screens, its the LED back light panel.

Best way I have found to diagnose a back light problem is to place the Tv in a very dark room, and turn it on in the set up menu, and using a bright flash light pointed at the screen, and see if one can observe the setup screen.

It will be very dim, but you will be able to make out the text, or something. This is the Flash Light test. This means that that the information IS being sent to the display. The LED back light which is not working, allows the signal to the display to be viewed, in normal operation.

As mentioned elsewhere, the LED back lights are LEDs mounted in a strip. which each strip draws a good amount of DC Current,which is why a flat screen feels warm to the touch when operating.

Changing the LED back light strips involves disassembling the many layers of the flat screen, not an operation for the faint of heart ! In that one has to be careful that the display isn’t damaged in the disassembly process, and needs to be preformed in a very Clean environment as any dust/ stuff that gets trapped between the layers will be visible all the time the display is on, assuming your successful getting it to light up again.

With the sell price of new flat screens tv coming down, ( 32 in 720 P Insignia Brand At Walmart on line this morning is $89.00.{12_29_2018}. The repair shop has no way to a descent hourly way to pay him self, which is why I left the field in 1978.!!

If the dead flat screen is not your main go to Tv, & have a place where one can leave a flat screen disassembled for the long periods of time for the container ship to come from China to Long Beach Ca., and you work for free, then !&&* yeah give your best shot. You Tube videos are your BEST friend.

In my experience with no display / black screen, its the LED driver electronics.

Just my 3¢. g²

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Ah....,i m so mad ...I have a samsung old school chinese LCD with an extefnal power supply and i m sure that it works great but as soom i press the power button on LCD its small leds of blue colour turns ON showing that it is being powered then after some time screen blinks grey and turns off and it is OFF..

I have to press power button again and again to see that grey blink again ...Pls help!

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Power supply board for sure

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Hey HiDrOid its the power supply board for sure replace that and your golden

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@HiDrOid replace the power supply board before I had same problem with a tv I got for free replaced the board n worked great

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It isn't the power supply board if it has an EXTERNAL power supply, as HiDrOid stated. But it could be a faulty External power supply. I know it's kinda late now. This is more for anyone reading this searching for solutions in the future. That's how I got the 42" monitor I am using right now. One day the TV didn't turn on so my customer just bought a new one and told me to just take the [not] old one. It needed a new 18 volt ext power supply. It's not hard to imagine a television being hard on the equivalent of a tablet charging transformer. (A constant demand for near or over the maximum current rating

+ no air circulation so if there are any heat sinks, they're ineffective)

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Com on people power supply is rarely an issue in LCD or LED unit!! I guarantee it it Main board

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I just had this problem on and off continuously I took the batterys out both of my remote that are tuned into the TV and it solved the problem

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