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Old 17 November 2012, 05:14   #1
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Any TV engineers in da house?

We've got a problem with one of our LCD tellys. Before I make a decision on whether to chuck it, just keep it till it dies completely or pay somebody to look at it (assuming I can find anybody round here) I wondered if anybody on here worked in that line of business and maybe had an idea whether it was a common/repairable fault?

Basically it's temperature related, when you switch it on the picture is overwritten with flickery digital noise with just a band of picture at the top, its worse if the room is cold. After a period (from about 5 min to about 15 min depending on temperature) it works fine and continues to work fine no matter how long you leave it on for. Switch it off e.g. overnight and it's back to being wonky again, let it warm up for a few minutes and it's fine again.

Typical problem is illustrated in the photo below, though it can splurge across almost the whole screen and it gradually gets better over a period of minutes till the picture is perfect. Any thoughts please?

Ta
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Old 17 November 2012, 06:09   #2
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Not very scientific but does the problem change if you grab the frame and try and try to 'twist' it a little .. just in case its a dodgy ribbon cable in a socket .. or some other dry joint perhaps
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Old 17 November 2012, 08:49   #3
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Had a similar problem with a Series 5 LCD Samsung. In the end I chucked it after putting it in for a TV repair. Their diagnosis was a fault in the ribbon where it connects to the tube. It was manufacturing fault, was out of warranty and unrepairable, and that was on a 3 year old tv!

Prior to that I had tried an inverter off Ebay, as that can give a similar fault as shown. If it's a few years old (bear in mind everything is going LED), then it might be worth opening it up yourself and checking connections. If you have to remove the tube, then be very careful when placing it back in the aluminium or pressed steel surround. If you nip a corner - it's goosed so-to-speak!

Replaced it with an LG with a 5-year warranty.

Good luck.
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Old 17 November 2012, 09:08   #4
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Quote:
Originally Posted by spartacus
(bear in mind everything is going LED)
Technically the majority are not actually true LED, they are just LED back lights. It looks to me like a component failure such as a capacitor or resistor whose value changes with temperature or maybe a dry joint which closes up through expansion once warm. Doubt it's DIY repairable. Saves you peering out the window for the aurora australis!
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Old 17 November 2012, 09:19   #5
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I still have CRT TV's in my house. Nothing wrong with them apart from being old hat. I was wanting to replace the 33" one in our living room with a 42" LED Smart TV this Christmas. After reading reviews and doing a little homework it would seem that buying any LCD/LED TV is a risky business in terms of reliability and sound/picture quality. What do you guys think? Is it worth the risk?
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Old 17 November 2012, 09:33   #6
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What do you guys think? Is it worth the risk?
Got two Panasonic LCD/LED jobbies. Both excellent. TBH can't think of a single neighbour or relative or friend that has ever had a flat screen of any flavour fail. Most I know of that have been replaced is coz folks want bigger.
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Old 17 November 2012, 09:33   #7
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It looks to me like a component failure such as a capacitor or resistor
Possible .. but most componentry is fairly reliable IMHO. Its not uncommon for a connector to be at fault or a dry joint, especially on something that has a wide operating temperature band, and something that gets moved a lot. (clearly, not usual for telly's)

I had a 21" LCD Viewsonic monitor that started playing up with me last month which I stripped and rebuilt .. which cured its fault.

Its when you get a failure in the larger semiconductor chips that its almost impossible to repair .. plus .. in modern kit, so much of it is surface mount and tiny, that its no easy task to fault find .. but .. a poke about with a plastic tool can sometimes reveal the problem. Mind how you go though
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Old 17 November 2012, 16:21   #8
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Quote:
Originally Posted by Erin View Post
It looks to me like a component failure such as a capacitor or resistor whose value changes with temperature or maybe a dry joint which closes up through expansion once warm.
The capacitor failures I've seen wouldn't manifest themselves like that. Father-in-law had a Polaroid TV (yes they made TVs too) which was a bleed'n nightmare. Turns out the capacitors that were used were purchased dirt cheap from the far east, and they failed prematurely in their thousands. Check out US forums. If it's failed, then the tops will bulge. Extreme examples blow, although I've never seen one. Easy DIY - if you can source replacements from Ebay or Maplin. You'll need a half-decent soldering iron, flux, and solder wire.
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Old 17 November 2012, 17:04   #9
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That'll be the flux capacitor. Try Libyan Nationals for a replacement.
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Old 17 November 2012, 17:36   #10
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The suggestions of a dry solder joint seem pretty sensible.

Not being funny, but have you tried giving it a bit of a whack at various places around the case? Not too hard, obviously - don't want to wreck it. If it is a dry joint, it's possible that a bit of movement from a sharp knock might temporarily make the connection.

Even if it is a dry solder joint, finding it isn't at all easy. There'll probably be several PCBs inside and it could be any component on any of them I'd say it's unlikely to be the main processing circuit - assuming that's a digital picture you're showing, if there was a problem with the MPEG decoding, you'd get a more dramatic effect on the picture than that.

There are ways to try and trace it by putting some pressure on the pcb (e.g. slight bending), but I wouldn't recommend that if you don't know what you're doing, e.g. electrical safety issues!
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