Electronics → Samsung TV LN-T4065F flashing display

I am posting this since a search for "Samsung flashing display" showed no results found.

Recently, my Samsung LN-T4065F TV keeps flashing on and off like a strobe light when it is turned on. A few times before, I also noticed a number of dots on the display (think starry night) though that went away.

Anyone else have this problem? Is it a case of the bad capacitors on the power board that people have talked about? Or something else?

Any help will be deeply appreciated.

Thanks!
Sam

Well, without further investigation, my snap judgment would be to point at the Caps, or tubes going bad. (The CCFL lamps that probably illuminate your TV)

Flashing, and weird (usually reddish / orange) colors from the dislpay is usually CCFL envelope compromise, and the resultant increase in breakdown voltage overwhelms the inverter card, and you get flashing.. But this is my (admittedly dated, and limited) experience.

I think further investigation would be warranted.

Edit: I see the Samsung LN-T4065F is a 40" LCD, so yeah.. it will probably have CCFL lamps in it.

Thanks, Jason for your prompt and useful suggestions.

Given the TV is 3 years old and out of warranty and not clear Samsung is repairing the power board caps for free:

a) How expensive would it be to have a tech come and repair it? Meaning is it worth it given that prices have fallen so much on new LCD TVs?
b) Is it something I could do myself? I know lots of folks are in these forums changing the caps themselves. But I haven't anyone talk of changing the CCFL lamps. How much do those run (approximately of course )? Can I do that myself?

Thanks so much!
Sam

Without knowing that particular TVs setup, I'll go out on a limb and say, yeah.. with a bit of patience, and a couple tools (and the parts) you could probably do the change-outs yourself.

The bulbs shouldn't be more than $40 or $50, but I dont know the size, or qty of them, so that could be way off.

The caps are probably available online for $12-$20 for a kit specific to your TV

As far as calling out a tech, Id be willing to bet you'd be in over $100 just to get a tech to diagnose it (let alone fix it)

With 40" Flat panels coming in under the $400 mark in some cases, the call on weather to repair, or replace is your call.

Years ago, i did a little tutorial on replacing CCFLs in a Dell Laptop screen, and posted it here on DSLR.. It will have little to do with your situation, but it *could* offer insight as to what you may be in for, if you choose to repair a Flat panel LCD.

»Inpiron 8100 Tube replacement tutorial...

-Jason

Jason, Thanks again!

Is it possible that the problem of flashing is because of a faulty Backlight inverter board? I know they sell for around $60.

And is that easy to replace on these TVs?

Sam

its been my experience that inverter boards rarely fail.

Power supply caps (High amperage, High freq makes Caps unhappy, and they tend to swell, and fail) and tubes (It is just a glorified light bulb, after all) both are *way* more common failures than an inverter card.

Personally, I'd look at the caps, and perhaps the bulb.. If it were My project, I'd take the case apart, and if I saw swollen caps, then Thats what I'd replace first.

If that didnt fix it, I'd replace the CCFL tubes.

If still no love, than I'd probably toss the set and buy a new one..

I've personally built over 300 LCD fronted Human-machine-Interfaces (Glorified industrial computers) and never once saw an inverter failure.

I'd say it's either the power supply, the inverter board, or maybe the CCFL light is getting old.

How much use is on the TV? What kind of test equipment do you have for troubleshooting?

The TV was bought in September 2007 but is not used that much so I don't think CCFL has had enough hours on it.

I have no special test equipment. I was only thinking of doing this sequentially along the lines of Jason's suggestions.

Sam

I don't necessarily mean specialized or expensive stuff.
Do you have a multimeter?

Probably higher quality displays than a lot of the consumer junk that gets produced these days.

I've found that when monitors or TVs go bad, most of the time it's either the power supply (capacitors) or the inverter.

It's mostly due to the push to reduce costs. Manufacturers select components that just barely meet spec, which greatly reduces reliability.

I have access to a multimeter. Are there specific tests you would recommend I do?

Thanks!

Sam

Thanks so much for the advice.

I have some additional data from last evening that may shed more light.

When I had chatted online with a Samsung support person, he had recommended unplugging the set from a power strip and plugging it directly. I had tried that once before and it didn't seem to help. Since I saw someone else recommend this on a bulletin board as a potential solution for an LCD computer display doing the same thing, I unplugged it from my power strip and connected it directly to an outlet. And guess what, it stopped flashing (the capacitors I could tell discharged from the sparking when I connected to the outlet). But after viewing a while, when I changed the source/input to a DVD instead of FIOS, it started flashing again. Then I unplugged the set and when I plugged it back on the power strip, it stopped flashing.

The backlight seems quite bright and not fading.

Wouldn't the above experiment suggest that it is probably the power board or the caps that are the problem?

The set was manufactured in Aug 2007 and I bought it in September 2007. I saw the dots and streaks appear only a few times and they don't show up all the time. I haven't had the clicking or power cycling that others have reported. So I am not sure Samsung will cover it.

I have located the same part numbers for the power supply and inverter boards. A site called avsjimmy seems to have these available.

I am now thinking of opening the back and checking the caps to see if they are bulging before calling Samsung to see if they will do the replacement of the power board.

Sam

i sent you an email.

Just an update on my LN-T4065 LCD TV:

I diagnosed my problems as coming from bad caps. Elite Data thought so too!

Samsung's policy as stated by the ECR is that they will do a one-time repair of the caps up to 36 months from purchase or 39 months from Manufacturing date.

While I was beyond the 36/39 month period, the ECR at Samsung was willing to accomodate me. I had called a few weeks earlier but that request got cancelled since no authorized repair shop could come by and fix it at my home. However, when I called the second time to say that I had not got any authorized repair center to come by, they told me I was not eligible since I had crossed that deadline. But when I was forwarded to an ECR, he was exceedingly helpful since he acknowledged that since Samsung had agreed earlier to fix this under coverage (they claim mistakenly), Samsung would honor their commitment.

I then got an authorized service person to come home (the absolutely wonderful John McAndrews from Audio Video Service in Billerica) to come and replace the power board. And he told me the new boards have higher rated caps - not just better caps at the same rating.

And giess what - all my problems are gone! No more flashing, no spots and stars, no streaks of multi-colored lines, and no clicking (I had this happen a few times but I used to unplug the set completely!). In fact that is what convinced me it was the caps thar were the problem, because I assumed unplugging helped discharge the caps!

I thought I would say Samsung did come through! And I will again consider very seriously to buy a Samsung LCD TV again!

Sam

I have the same problem with the same model Samsung. Capacitors on the power supply board were changed by Samsung a year ago. Visual inspection of all capacitors indicates none are blown. I have read a couple of posts that indicate that it may be either the power supply, or the inverter. I am tempted to change both of these boards out and hope for the best. This appears to be about $150 for both boards.

Can anyone tell me if this is a good gamble, a bad idea, or might I try something else.

Thanks for any help.

alram

what is the tv doing?

The display flashes off and on like a strobe. If I turn the set off and let the heat dissipate (for an hour or so), it will work for a couple hours before flashing again.

more than likely the inverter, but this part may not be available directly from samsung or parts retails that deal directly with samsung however, you may find it from shopjimmy.com though the CCFL tubes are probably worn and replacing the inverter pcb may not produce expected results.
inverters on older 2007/2008 sets generally dont go bad, the CCFL tubes do though, the main reason is the drive level the tubes are being driven at, generally driven high to satisfy contrast expectations from customers.

Thanks much for the reply. Have searched hi and lo for p/n for tubes as well as a video on replacing the tubes for this TV. No luck on either. Can you point me in the right direction. Also, is this a difficult install. I have no problem trying it as I cannot use the tv as is and cannot afford a repair. Thanks for any help. Al

replacing the CCFL tubes on the panel is very tedious and complicated.
generally, when i am changing them out, im using a comparable sized panel from the same manufacturer in the same date range.
there is the lcd panel itself which is less than 1/4 inch thick, below that is several layers of white plastic "diffusers" and below that is more clear plastic "diffusers" that also assist in supporting the lcd panel.
under all of that are the CCFL tubes, they generally pop-out but have a very small diameter and can break very easily.
they work just like fluorescent tube lights, they get black ends when they are worn out and can sometimes "pop" at the corners and break. [both these symptoms cause flashing, split second display then goes out or no display at all (backlight)]
it could be a good learning experience to take the panel apart piece by piece (if you dont care about the loss of the set), but i recommend wearing gloves that will resist the sharp edges of the glass lcd panel as well as other sharp objects, also eyewear protection is recommended.
only caution here is the power supply that may retain a slight charge, enough to give you a shock.
leave the set unplugged for about 3 days and you should be okay.
the panel taken apart would look very similar to this
»www.thomas.com.au/media/ ··· atm2.jpg

Joe - Thanks very much for your help. Unfortunately, this job clearly exceeds my capability. Guess I'll go back to reading!!! Good luck - Al

youre welcome.
you could still always take it apart piece by piece if you have interest in seeing the innards of the set.
after all, thats how i became highly intrigued in what i do, i started when i was a very young child taking electronic things apart to learn their innards (and learning lots of "shocking" experiences along the way LOL)