How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask TV Tech1 Your Own Question
TV Tech1
TV Tech1, Technician
Category: TV
Satisfied Customers: 5316
Experience:  30 Years experience. Authorized Warranty servicer.
Type Your TV Question Here...
TV Tech1 is online now
A new question is answered every 9 seconds

Samsung flatscreen keeps turning on and off

This answer was rated:

Our Samsung flatscreen repeatedly turns on and off in secords. It is so fast the picture does not even come on, it just is clicking on and off over and over. I had to unplug the TV to get it to stop and when I plugged it back it in started all over.
Is this something that can be fixed or is the TV shot? The TV is not that old.
Hi There,

Chances are there is a problem with the power supply board in the TV.

The only thing I would suggest is to leave it unplugged for 24hrs then try turning it on again. This has the effect of discharging all of the capacitors within the unit, and effectively soft rebooting the unit.

What to do next depends entirely on whether you want to try and fix it at home, and have a good multimeter and are comfortable with soldering. If you are then let me know and I'll tell you what to look for. Otherwise you'd be best off taking it to a local electronics repair shop.

Typically the some of the capacitors on the board can go faulty, this is a known problem with some of the Samsung sets, I've heard that quite a lot of people have had the power board replaced for free outside of the warranty period, so you might want to try contacting Samsung directly before taking the set apart.

Alternatively, if you have had it for less than a year, take it back to the place you bought it from and have them deal with it.

Hope this helps

Customer: replied 6 years ago.

HI James,

I opened the back panel and am looking at the tv. The on/off switch is not the issue. The power cord is working. What am I looking for?


Hi There,

The best thing to do in that case is to take the case of the back of the TV, and find the PSU board, it will be the board where the power cable from the wall connects to.

Have a look at the board and check all of the capacitors, they should have a completely flat top and should not be leaking any liquid. I've attached a picture below of a bulging capacitor which would need to be swapped out.


If you do find some then let me know, as it means my diagnosis was correct, you can then either buy a complete replacement board, or swap the capacitors out yourself. Make sure the replacements are of the same capacitance, if you can fit them in there, use a slightly higher voltage as they will last a little longer.

Hope this helps

Customer: replied 6 years ago.

Hi James,

All the capacitors are in perfect condition.

Hi There,

Could you provide me with the model number of the unit please ? It should be on the rear of the unit near the power cable inlet.

It's still very possible that some of the caps on the powerboard have silently failed, the only true way to check them is with an ESR meter.

Customer: replied 6 years ago.

Whats an ESR meter?

The model number is *****

The model code is LN40A500T1FXZA


Hi, you may find your question closed due to a time out which is nothing more than no response within a time period.

James was on the right track about your TV set, the fact that it clicks on and off repeatedly usually points to bulged capacitors on the power supply board. Since you state the top of the caps are "flat as a pancake" it may very well be the clicking on and off could still be bad caps.

However...nobody informed you that questionable caps should eventually improve to the point the TV starts working again, given enough time.

So, what I'm going to suggest is this. Plug in and turn on the TV set and ignore it for 45 minutes to an hour. If it starts up all by itself, and stays functioning, then the power supply caps are at fault.

If it still clicks after an hour, I have seen some main board failures that can cause that problem too.

So try that -- plug it in, let it run for an hour, and let it click. See what happens to your TV set 30 minutes, then 45, the an hour later.

Forget the ESR meter, they are great for testing caps, but we have to work with what we've got available to us.

An hour of your time doesn't cost you anything, and worst case scenario is we buy a $30 Sears voltmeter to check the 5 volt power supply and test the Power On command line to see if it stays high or not.

Time will tell....

Let me know what happens.

Customer: replied 6 years ago.

Good evening. Just got home and plugged the tv in. I will send another email in about an hour.


Customer: replied 6 years ago.

So after turning on and off on its own for about 10 minutes, the TV turned on and stayed on. I pressed the power button and the tv turned on. When I tried to turn it on, it started struggling again for about 5 minutes.

Then the cycle started all over again.\

Please advise.


Bad got bad caps, no matter HOW FLAT and Perfect they look.

Yes, they will bulge and crown as time passes by...

James knew, but the caps haven't visually died yet, and you don't have an ESR meter, and I wouldn't expect you to buy one unless you were a TECH...

Bench Tech that is....not a field Tech.

They're kinda salty....

Ok, let's COMPARE the cost of buying a power supply ---VERSUS--- the cost of the caps, solder, solder wick, SOLDERING IRON , and your time .....

Personally, I 'd just get the board and not worry about testing and finding them -- that's for guys with Lab Coats like this character --


Yeah, I'm thinking of changing my Avatar -- This one character epitomizes how the rest of the world sees most techs...made me laugh the moment I saw this 20 years ago.

I'm just going to do the research now....

Model number -- LN40A500T1FXZA

Hmm, no service bulletins about the bad caps on your model...there is one about the TV shutting down, but that's not your symptom.

Your's won't start...

But the LVDS cable should be unplugged on both ends to "buff" the contacts, it can cause a startup problem, AND if you disconnect ONE END and it starts reliably, then I'd replace it.

LVDS part number -- BN96-07161C

Don't buy one, just disconnect it and see if the TV turns on and off reliably.


This place has pictures of a lot of the boards, no picture of the LVDS cable, but it's a GOOD REFERENCE so you can use it to verify what board we are talking about.

Now the power board's part number is *****BN44-00199A

And that's only $50 for the board, cheaper than the cost of a soldering iron, solder, caps, wick etc...and easier for you to install.

Here is where you can order it --

ShopJimmy has the better price than any other.

Run that LVDS cable test, and if it starts when cold, plug it back in and see if it fails -- that helps to VERIFY the problem as the LVDS cable, or the power supply board !

If you have any questions, just ask

Thank you.

TV Tech1, Technician
Category: TV
Satisfied Customers: 5316
Experience: 30 Years experience. Authorized Warranty servicer.
TV Tech1 and other TV Specialists are ready to help you
Customer: replied 6 years ago.

Good Morning,

I ran the tests and the tv did not stay on an any of the tests. I think I will order the power board. The model number that you gave me was a little off: should have been an A at the end of the model number, not a B. Nevertheless, its $51.99 at Jimmys. However, the order process is a nightmare: would not let me register due to error on their webpage, then when I registered, it said that my information was not "properly registered" with their \company for me to place an order.

I will look around as the other links you gave me were fine except they are too expensive. Thanks for all of your help! If you come accross a cheaper one, please let me know.

Customer: replied 6 years ago.

There was an error on the site and I think that the question was re-submitted. It also did not allow me to finish my feedback. I did accept your answer, by the way :)

Just wanted to let you know.

Thanks, ***** ***** did show up.