Here is another for reggieman to laugh at . I have spent 45 years fixing tellys ! I am retired of course now , I don`t want to know what model and make your tv is because I don`t need to look up the fault in a database of TV faults . Instead I rely on gut instinct and my inbuilt database of faults acquired from a life time of repairing TVs. I feel that your fault is due to an arc taking place somewhere around the eht section eg anywhere from the eht connector to the CRT to the eht transformer itself , Quite often arcing will take place under humid conditions and gradually stops as the interior of the set heats up . Cure for that is clean all eht leads and parts and dry them , alcohol or metho can be used on a cloth , The fault could also be a dry joint ( yes we really do call them dry joints in my part of the planet ) in the horizontal stages which connects when hot !!!!. Well that covers the symptoms ! High pitched noise ( arcing ) lines of interference from the arcing and fault clearing when set heats up . Better not give reggieman too much to laugh at though , we don't want him to damage anything . Cheers Pete !
Interal arc does`nt usualy get better as set heats up Kc, it was a thought though Thanks.
45 years fixing tellys