The noise is altering with beam current.
Harsh, rasping low buzz?
Most likely the scan coils are loose. They are fixed with sealant during manufacture but the sealant can become brittle and crack with age.
If the set is under warranty, get onto it straight away as the scan coils are integral to the cathode ray tube, very expensive.
If it's under warranty do not accept sealant, demand a new cathode ray tube.
If out of warranty, an engineer can attempt to re-seal or tighten the scan coil yoke but will not have anywhere near the access to apply it as they did at the tube factory. Although, they may be able to reduce the noise.
Other coils/transformers in the TV can suffer similarly and vibrate with the current passing through them but scan coils are renowned for it and are the largest coil in the TV.
Cobweb, January 2005
