I have a TV which has the above problem.
The picture and sound are fine, prefect however
I get the above noise from the back of the tube (sometimes).

The noise originates from where the big high tension cable
attaches to the tube, on the back near the top (not the
thin neck but the big dome 'bit'.

There is like a big round 'sucker' (plunger shaped thing)
where it atttaches to the tube, this has a lot of (well a fair bit of)
black 'dust' on. I can see some blue 'arcing' on the 'sucker type'
thing which the cable is attached too. this is where the niose comes from.

I only get this in hot weather I think, patricularly humid weather,
opening a window and letting cold air in seems to stop/reduce
the noise.

Any ideas, would brushing away the 'dust' help? (Actually
some of the dust seems to have been 'burnt away by the arcing).

Sorry if the techinical terms are not very technical, and spelling is
bad (in a hurry).

--
half_pint.