Crackly fizzy (mechanical ?) noise from TV ?

Our lad inherited out old first-gen LCD HDTV (11 years old). Been fine (lost remote apart) for him for 5 years ...
Now it still works, but when you turn it on, there's a crackling/fizzing sound from the _centre_ of the back. It's definitely not coming from the speakers.
The second I first heard it I thought "capacitor" ?
It's a very light sound - not sharp enough to be arcing. And whatever it is doesn't seem to affect the TV operation. Just be a nuisance.
If I could be bothered to pop round and spend a few minutes investigating, where would the wisdom of uk.d-i-y suggest I look ?
He's already bought a replacement, so this has been relegated to "games console" :)
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Never having taken one apart I can only guess. These used to use small fluorescent tubes behind the screen to provide illumination. Perhaps there's a dodgy contact on one of the tubes; or perhaps a tube is dying and having difficulty striking.
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from KT24 in Surrey, England
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On Wed, 12 Jun 2019 11:24:47 +0100, charles wrote:

Hmm
TV screen lights up fine - if it didn't I wouldn't waste a second on the thing :)
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I think we would need to know the make and model as some people probably know what we used to call stock faults on older sets and whether the problem was serious or merely something rattling. I have an old laptop that whines with the lid in a certain position, its the core of the inverter for the backlight resonating at a sub harmonic of the oscillator frequency. I long remember the old 405 line tvs that really did deafen many with their hf line oscillators in some models. Brian
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On Wednesday, 12 June 2019 11:26:57 UTC+1, charles wrote:

sounds like arcing, which is an immediate fire risk
NT
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On 12/06/2019 20:49, snipped-for-privacy@gmail.com wrote:

Is there any "burned plastic" smell? That would really raise the alarm. Tracking across something non flammable like glass or ceramic is not necessarily so serious. That will still generate an "ozone" smell, if there is enough current
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On Thu, 13 Jun 2019 12:03:45 +0100, newshound wrote:

No smell.
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On 13/06/2019 14:25, Jethro_uk wrote:

Some statistics from 2009
"FLATSCREEN televisions are the cause of an increasing number of house fires, Queensland Fire and Rescue Service figures reveal.
Televisions were found to have ignited almost 70 house fires in the past five years, with more than half of those causing extensive damage.
But other appliances, including heaters and clothes dryers, contributed to a much larger proportion of the 5251 fires started by electrical equipment in the period."
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It happens that Jethro_uk formulated :

Likely the switch mode power supply has begun to age and is whistling and there is some resonance. You could try taking the back off, locating the SMPSU then prodding it gently with something insulated when its running.
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On Wed, 12 Jun 2019 11:31:53 +0100, Harry Bloomfield wrote:

I was kinda thinking something along those lines.
Assuming it's not a Krypton Factor build, I might pop a toolbox in the car next time I pop round.
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On Wed, 12 Jun 2019 11:31:53 +0100, Harry Bloomfield wrote:

Yeah, what could possibly go wrong with a bit of prodding around? Even experienced service persons religiously use an isolation transformer when they absolutely have no choice but to work on a mains supplied SMPS live. It's certainly not the sort of job you should be encouraging an ordinary mortal to attempt.
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On 12/06/2019 14:02, Cursitor Doom wrote:

As long as the OP uses an insulated tool to touch anything I don't see the problem, as long as he has a healthy fear of contact with moderate voltages.
It's not like working on the EHT of an old TV set or on a microwave.
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says...

For the first nine years of my working life I worked on live chassis TVs[1] and radios without the use of an isolating transformer.
We relied on the bench positions being earth free areas and that pasted muster for the one and only inspection from a Factories Inspector I encountered in all that time.
Would you expect a field engineer to lug a hefty isolating transformer around with him from house to house?
[1] The vast majority having unpolarised 2-pin mains connectors on the back.

And you know for certain that the OP is an 'ordinary mortal' with no sense of self preservation and the need to adopt safe working procedures?
--

Terry

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On Wed, 12 Jun 2019 13:02:55 +0000, Cursitor Doom wrote:

I know how insulation works :)
Anyway, my first thought (backed by the replies to this thread, which I thank all for) is to see how easy it is to lift the actual plastic cover, and have a look and listen without any contact at all. Since it's a noise I'm trying to isolate, there's always a plastic rod to the ear. (My Dad used to have a 2' screwdriver he'd use for listening to engines ....)
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On 12/06/2019 10:44, Jethro_uk wrote:

Prolly the HT around the backlight. Or something in te PSU.
Not much else takes enough power to make a noise
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On 12/06/2019 10:44, Jethro_uk wrote:

That still may well be an issue ;-)

Older LCD TVs had fluorescent tube backlights, and typically a SMPSU driving them via a step up transformer to get the ~700V DC they required. The most common failure modes being the caps on the output of the PSU, and the transformer itself.
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John.
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On 12/06/2019 12:17, John Rumm wrote:

It's 11 years old, well past its appointment with the local authority 'recycling' skip, surely ?
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On 12/06/2019 12:46, Andrew wrote:

While it does not owe anyone anything, there is enough of a chance it can be fixed with 15 mins work, and less than £10 worth of components to make it worth at least popping the back of for a quick poke about I would have said.
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On Wed, 12 Jun 2019 15:09:40 +0100, John Rumm wrote:

That's the vague motivation.
If it was making a noise *and* not working, I'd bin it.
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On 12/06/2019 15:09, John Rumm wrote:

And at least it's not like the bad old days when colour TVs first came in. My brother in law (*very* experienced) was a TV repair man at the time, and lost a co-worker to electrocution.
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