TV Buzzing....any ideas?

Last year i bought a Philips reconditioned TV off Ebay. (please, dont groan so loud ;-), it seemed a good idea at the time!)
The snag was that in transit it had been dropped, cracking a bit of casing off at the side. When plugged in, it did work fine, all channels perfect and crystal clear sound. Great, so i phoned the supplier, got him to refund me 60 off the price, got some super glue out and had both a fully working and very good value TV. For about 6 months. Recently, more and more often, it starts gving out a high pitched noise. THis can be cured by hitting it or turning it off and on again a few times. I am pretty sure it is not signal related as i have both analogue, digital and dvd and the telly will hum for all of them!
I have a worrying theory that things that can be temporally fixed by being hit or turned on and off generally dont get better by themselves, they get worse. I have to say this noise is not unknown to me, i think that i have heard different tvs that do the same thing, so now i am wandering if anyone else knows what it is that has 'gone' or is 'going' in my telly and if it can be replaced/ bashed or soldered in to submission.
I look forward to any advice. I am however aware of my ebay related faults and wont do it again.
Thanks
Colin.
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Your missus has dropped her favourite handbag toy down the back??

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To be honest, difficult to say without hearing it. I'm guessing the noise comes from the set itself, and not from the speaker?, in which case its probably caused by vibration between the coils / formers of some wound component (inductor, transformer, deflection coils?), and probably something that you can do little to fix. It's not likely to be because you bought it reconditioned off EBay, or anything (my TV also has an intermittent annoying hum, same thing).
Possible solutions if you can localise the component (can be difficult as they are temperamental buggers, and never buzz when you're listening for them) is replacement like-with-like, or possibly apply a SMALL quantity of epoxy resin (obviously, non conductive variety) and see if that cures (pun!) the problem.
Usual caveats above messing inside the back of a telly apply.
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casing
me
it
or
signal
being
get
have
it
faults
something
annoying
(pun!)
"Sorry if this is a repeat reply, and apologies for possible top posting in the other reply. Still a bit of a newbie to newsgroups."
Thankyou for the reply. Im sure the sound is not from speakers.....mute, tells me that. It does sound like an electrical type noise....sort of like high pitched version of a transformer hum.
I think i shall wait untill it gets worse before having a go at any surgery, i just thought i would post in case there was a obviouse 'thingumy' that can be replaced.
Thanks again for the reply.
Colin
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<snip>
surgery,
can
Why do people say / do this when they are 99 percent certain that there is a problem, all that will happen is the cost of repairs go up and an increased chance of the problem causing damage to other components...
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my phillips idtv has been making a noise, probably the same noise as yours, for over 2 years now. it seems to only happen when first switched on and once it has warmed up is ok. I am not worried about it as I will be replacing it either when it does decide to breakdown completely or within the next 6 months anyway.
Dave
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dave wrote:

degaussing coil playing up?
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Don't touch it unless competent...... but...
From my time in the RN on RADAR buzzing/whistling/screaming used to occur when the display HT lead (rubber capped thing on the tube) was dirty and the air was humid. Usually, only a clean with a dry cloth, from transformer to tube, was all it took to silence it.
WARNING: After getting 25Kv up my arm just the once (lesson learned) I would suggest that before touching the HT _EVERYTHING_ is switched off and unplugged and all contacts are earthed. The HT remains charged for some considerable time after switch off.
Yours with no responsibility attached
AndyM
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I have a problem that whenever my son puts one of his CDs in the stereo, a horrible noise comes out of the speakers
--
geoff

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yours,
That's normally caused by old age. Yours. ;-) LOL !!!
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I don't know what you mean !
--
geoff

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Colin wrote:

What frequency is the note? are we talking mains hum (50/100Hz), Line scan (16KHz ish)? or something else.
The coil/core/xformer suggestion seems most likely. If so it does not necessarily indicate an actual problem, sometimes coils can just be noisy.
--
Cheers,

John.

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wrote:

I have experienced this problem with a few TV's. They all had Panasonic tubes. As yours is a Philips it could have such a tube. Unfortunately I have never solved the problem. I just make sure I always buy a TV with a tube that is not made by Panasonic. I've had too many duff ones to take the risk nowadays.
Mark
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Mark wrote:

The two most probable causes have already been cited
(i) EHT 'tracking' - solution is to remove all dust from around the EHT led etc.
(ii) loose windings or laminations in various coils. Thin warm epoxy dripped into the offending part is basically what the manufacturers do anyway. Used to be wax. Or replace the EHT transformer, if is a whistle at line frequency.
Could also be PSU - but (not sure) think this is usually the same transformer anyway..
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wrote:

In my case these TVs were brand new so I wasn't about to mess about with their innards. Although repairs were attempted they were unsucessful and I (eventually) got refunds on the TVs.
Mark
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Mark wrote:

Oh., Never mess with new equipment under warranty. Its always somebody else's problem.
Unless you bought it at Dixons, in whch case its your problem :-)

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wrote:

Currys, Some Internet retailer (Value Direct maybe) and Apollo 2000. Believe it or not Currys had the best after-sales service of the three!
Mark
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wrote:

Main frequency PSU you wouldn't hear, too low, and switchmode would be too high to hear.
Mostly likely line, 15kHz. If the linearity is still corrected with a core they can whistle. Of course, it bears pointing out that the voltages inside a TV are VERY DANGEROUS. The EHT can still bite when the TV is switched off and unplugged. All metalwork should be consider live too. The switch on the front may not isolate the TV so it should always be unplugged.
--

Malcolm

Malcolm Reeves BSc CEng MIEE MIRSE, Full Circuit Ltd, Chippenham, UK
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