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Samsung LCD TV LE40B750 flickering when turned on

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khalil

from United Kingdom

Joined: 20 Apr 2010
Posts: 12
Location: United Kingdom

PostPosted: Tue Nov 02, 2010 8:32 am Reply with quote

Hello Everyone

I have a Samsung LCD TV LE40B750. When I turn the TV on the picture is flickering for about 4 to 6 minutes and then it becomes ok.
I have free sat and I have tried watching DVD to see if there is any problem with the set top box, but there was no difference. For the first few minutes the TV flickers regardless of what I am watching.

Can anyone help me to understand the problem?
And any idea how much it may cost to get it fixed somewhere reliable?


Last edited by khalil on Tue Jul 05, 2011 7:35 pm, edited 1 time in total
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cdavid15

from United Kingdom

Joined: 11 Nov 2010
Posts: 1
Location: United Kingdom

PostPosted: Thu Nov 11, 2010 6:01 pm Reply with quote

Hi there,

I stumbled across your post about the tv starting to flicker. Well i have the LE40B551 model and it is about 15 months old and this started flickering last week. No idea what has caused it or how to deal with it.

Have you had any luck finding a solution?
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gman76

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PostPosted: Fri Nov 12, 2010 8:43 pm Reply with quote

My guess would be a drying out electrolytic cap, probably due to a cheap component or located too close to a heatsink.

If so, an easy fix for someone who knows what to look for.
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Mickymoody

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PostPosted: Wed Nov 17, 2010 2:06 am Reply with quote

gman76 wrote:
My guess would be a drying out electrolytic cap, probably due to a cheap component or located too close to a heatsink.

If so, an easy fix for someone who knows what to look for.


I'd tend to agree, but this type of setup needs resetting, to enable a proper picture, so sounds bad, overall.
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bonhamdog

from United Kingdom

Joined: 24 Nov 2010
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Location: Lancashire,
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PostPosted: Wed Nov 24, 2010 11:10 am Reply with quote

Hi,

Just wondered if anyone has found a fix for this problem. I have the same TV and same problem!
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khalil

from United Kingdom

Joined: 20 Apr 2010
Posts: 12
Location: United Kingdom

PostPosted: Wed Nov 24, 2010 10:13 pm Reply with quote

Guys,

Today I realised that when I reduce the backlight from 7 to say 4 or 5 the flickering disappears and the picture becomes fine.
Does anyone know how I can fix this problem? Is it something wrong with the screen or the electric boards?

It is really getting on my nerves as the TV is not that much old.

Any help is much appreciated.

Thanks
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Mickymoody

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PostPosted: Wed Nov 24, 2010 11:29 pm Reply with quote

Reducing the backlight is putting less stress on the invertors/flo tubes, but also on the electrolytics, so could still be power board, or final output stage, but the power board is most likely.

If you can obtain a service manual, there are several pots that can be tweaked to adjust the voltages, but getting the correct balance without diagnostic equipment would be impossible.

Certain models do have common faults, so google the fault specifically, to see if a repair kit is available.

Replacing individual components is possible, but most likely a new power board from ebay is the best bet, probably costing 200 new?

Good luck.
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edbic

from United Kingdom

Joined: 30 Nov 2010
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Location: Bristol,
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PostPosted: Tue Nov 30, 2010 3:05 pm Reply with quote

I too stumbled on this thread looking for a solution. I bought my B750 in July 09 and only recently has this happened, exactly as the OP said. For 5 minutes, the screen is flickering every 5 seconds or so. Same on the Xbox, although the Blu Ray is fine.

I wondered if it was anything to do with the inputs, as the Xbox and SkyHD are both connected to the TV directly via HDMI, whereas the BD is connected via an amplifier.
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SHELDONSTV

from United Kingdom

Joined: 24 Dec 2010
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Location: Newcastle upon Tyne,
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PostPosted: Mon Jan 03, 2011 1:45 pm Reply with quote

the fault is easily repairable and may be down to 2 things-first is smps failure and the second is due to software...there is a service mode available but unless you know exactly what you are doing you can scrap yr set-also depending on model you need compaire to put the set in servicemode and reload software etc
another thing that maybe causing it could be due to ageing backlights.....any chance of a short video uploaded to see the set in the fault condition?
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V2Sam

from United Kingdom

Joined: 14 Feb 2011
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Location: Yorkshire,
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PostPosted: Mon Feb 14, 2011 2:38 pm Reply with quote

I have a LE40R88 with a Flashing Screen, not the clicking problem

Same thing, flashes for anything from 30 seconds to 15 minutes

If you change the source to other AV input most times it doesn't flash, as soon as switch back to the scart AV port that the Sky+ is connected to it carries on flashing. Sometimes this flicking between AV channels stops the flashing, maybe a clue or just a fluke.

The TV is 18 months old and out of warranty, I rang Samsung and they said it could be a screen/backlight problem and not covered as part of the clicking problem.

I then paid 100 to have an authorised Samsung repairer look at it, they "fixed" it and all was good for 2 months.

The flashing is back again. I removed the power board and the repair company had replaced the usual 1000uf caps but with 25v items, not the suggested 16v ones.

They looked ok and not burst/bulging but I still went ahead and replaced them with the 16v versions, I replaced all 5No and not just the usual 3No

Still no different, still flashes.

This weekend its got worse, flashing faster and for longer periods. If I turn the backlight down from level 10 to 1 it stops flashing, if I change it back to 10 it starts flashing again, if I leave at 5 it's ok.

Somebody has mentioned the invertor ? Can this be bought/replaced by somebody who is handy with a soldering iron but no understanding of TV electronics icon_smile.gif

Here's a video

YouTube - Samsung LE40R88 Flashing Screen, not the clicking problem icon_sad.gif
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radioredcat

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PostPosted: Mon Feb 14, 2011 4:25 pm Reply with quote

I was given a samsung analogue tv/pcmonitor with the same symptoms and i found all 5 470UF caps in the power supply were bulging so replacements solved the problem.

This cap problem affects all samsung sets because they used crap caps and samsung are repairing some sets out of guarantee FOC because of this problem.


Andy
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V2Sam

from United Kingdom

Joined: 14 Feb 2011
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Location: Yorkshire,
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PostPosted: Mon Feb 14, 2011 4:29 pm Reply with quote

I checked those Andy before even taking it to the repair centre and they were perfect, they've now been replaced twice and no effect, I guess the samsung repair place changed the Eprom or did a system reset which helped it carry on for another 2 months before starting again.

As far as I can find from various forums the bulging capacitors is indeed a common problem but only associated the with black screen and clicking relay, not this flashing screen problem ?
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radioredcat

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PostPosted: Mon Feb 14, 2011 9:23 pm Reply with quote

There are caps on the inverter board worth replacing with low ESR types,also the CFL's could be worn.

I have a acer monitor which showed a picture for a couple of secs and then go blank this was fixed by replacing badcaps on the inverter board.

Buying an inverter board would be prohibitive price wise unless you have a look on ebay but that will be a gamble if i were you i would ask on the excellent badcaps site below.

http://www.badcaps.net/forum/index.php


Andy
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Mickymoody

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PostPosted: Tue Feb 15, 2011 1:11 am Reply with quote

radioredcat wrote:
There are caps on the inverter board worth replacing with low ESR types,also the CFL's could be worn.

I have a acer monitor which showed a picture for a couple of secs and then go blank this was fixed by replacing badcaps on the inverter board.

Buying an inverter board would be prohibitive price wise unless you have a look on ebay but that will be a gamble if i were you i would ask on the excellent badcaps site below.

http://www.badcaps.net/forum/index.php


Andy


Upgrading capacitors to a higher voltage is always good, and low ESR.

Think of the TV set as a flourescent light, the inverter, is the starter, and the screen works, as the light. So if the starter fails, you get a flo tube that flicks on and off...if the flo tube is faulty, it flickers, but doesn't start? In a TV, at a higher frequency..So the picture gets better eventually, so maybe the invertor is faulty? I wouldn't call it an invertor board? As all the invertors in TV/computer screens I've repaired, it was a self contained item, not a board? And in itself no openable, a self contained item..

But could be the PSU, not supplying the correct voltage to the invertors..hard call.
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radioredcat

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PostPosted: Tue Feb 15, 2011 8:47 pm Reply with quote

I agree mickmoody.

I have found a service manual for the set see below but it only opens with adobe reader x.

http://elektrotanya.com/

Andy
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