Samsung forum: amsung 26in LCD TV Strobing / Flickering on and off, help!

Thanks for quick response!
I have not cleaned vents with canned air. Screen did have dirty patch on it that had turned light brown. visible when pure white backgrpund image was displayed.

Do you think cleaning vents with air is answer?

Is it easy for me to do?

Then the likelihood of some heat issue just went up.
Bob

I dont know where the dust would be? Would it have caused dirty not pure white portion on screen. And liked to current issue?

Screen has vents at top plastic case. I removed case and any dust would only get on top of mother board not behind screen as its sealed. There is no dust on motherboard it just falls to bottom if anywhere.

Not sure where it would be affecting it or how to get to it.

I'm working with the clues you wrote about how it takes a few minutes to mess up. That's a classic heat symptom. Since dust and such can clog up heatsinks and vents and since folk rarely do any maintenance on laptops and TVs your tech is always putting on a dust mask to give the vents a quick blast.

As to green/white specks, as chips can fail in so many ways the results can be any color of the rainbow to nothing on the rainbow as well.

As to other ideas, at this many years your tech may also try replacing heat sink compound.

Lots of good techs out there. Are you getting into the TV repair business?
Bob

Yes seems heat or possibly power. Thats why i thought was capasitors and thet discharge when turn of, thats why works for while when turn on and off set

I have read.that that is what it was online as samsung have problems underating them. Buf they look normail.

Dirty image suggests maybe relateed to dust like u said. I just dont want to take tv apart to much otherside of the board, lcd tube side.
Thks for advice, apreciate it. Will look a little closer see if find anything.
ian

The story about the underrated capacitors is urban lore. If we look at the voltage on a 10 Volt cap, it's usually 1/2 that.

However if you read http://en.wikipedia.org/wiki/Bad_caps you get a better idea of what happened. There are some that want to write the parts were underrated but it's worse than that. The parts were just bad.
Bob

The bad caps symptom is that it works better after it powers up. This set's symptom is the opposite which points us to heat or heat sensitive components.

If this was mine, the heatsinks are cleaned, pulled and new compound applied.
Hope this helps, Bob

thanks for help with this.

I took back of TV and turned it on. Watched some TV until picture started flickering. There is a noise coming from the bottom left of the TV. Which seemed to be coming from two white round things on their sides with wire coils around them. So I blew on them (thinking to cool them down) and the picture stopped blinking!

So I'm thinking that these are the source of the problem (over heating) they can be see in pic 2 of 6 bottom left!

I'm not sure what they are or if they are easy to replace?? but I'm thinking this could be it!

Will now try and find out more about what they are etc...

Really hope I have found problem!

thanks

Ian

I took TV apart again. lol! and looked carefully to see if I could see anything out of the ordinary. But couldn't

I looked at the back of the board and its really not to bad, all solders look silver and looks in good condition.

So decided cleaning would not fix anything.

-----------

Put TV bad together now.

I am now just trying to work out if the problem is most likely on the power board. As I am going to buy a used one on ebay for £22. to save me repair cost which I guess will be a lot? :/

This what I have worked out, My conclusion:

1) When Flickering picture happens, turning off TV and turning straight back on fixes it for about 2 minutes.
2) Getting a piece of paper and waving it over the top air vents (i.e fanning) also stops flickering for about 2 minutes. (discounted previous thing I thought it was)

If anyone knows what it might be before I buy a used power board, I would be very grateful. thks

They swap the suspect board/part and test.

In your case you could have put a fan (I did this to our old cranky RPTV and got 3 more years out of it) in the right place.

It appears you think that tech's know what it is. They really don't. They have a good idea and using symptoms and diagnostics (you did that!) find the board/part and then change that.
Bob

TV is 7 years old!

don't suppose the bulbs would do this?

Thanks again, yes I'm a bit worried now.

think it might be the tubes (bulbs) which I would not be able to fix

see link: Samsung TV LN-T4065F flashing display - Electronics | DSLReports Forums (Page 2)

My TV is old and developed a dirty very slight brownish part on the screen (like dust) visible when displaying pure white background.

I'm just going to need to see how much to repair at shop as I'm not an electrician. Will buy power board and put it in as last resort else I cant fix it shame is brilliant TV

thanks again for all your help
ian

FIXED!! SOLVED!

Just wanted to post this if it helps anyone with same issue:

Put in used power board I brought on Ebay. The problem is now fixed.

thank you for your help! I believe it was indeed dry solder joints causing this issue. I am not an electrician but looking very closely they did have less solder than the ones on replacement board.

there were quite a few small components with not much solder on topside of board way to hard for me to do without mucking up soldering. Main ones seemed to be around the metal heat coolers.

thank you