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.
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!)
Usual caveats above messing inside the back of a telly apply.
"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
Thanks again for the reply.
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...
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.
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
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.
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.
The two most probable causes have already been cited
(i) EHT 'tracking' - solution is to remove all dust from around the EHT
(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
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 Reeves BSc CEng MIEE MIRSE, Full Circuit Ltd, Chippenham, UK
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