Repairing old 1951 sentinel 424

[Patnukem]

Ok I went though it once more and found a loose screw on the flyback also heavily insulated everything under the HV rect with electrical tape and replaced a resistor under there. still no changed so I tried another 1x2b still no change. I am left with thinking it must be a small gap in the doorknob causing arcing inside to get to ground, or one of the other tubes in the HV cage, I will change all the tubes out in the HV and see if it makes a difference. I tried the paper cone trick to try and isolate the sound but it is not easy enough in the HV cage. I did check with the lights out and could not see any arcing.

UPDATE: changed out all the HV tubes I am left with the conclusion it is the HV filter "doorknob" cap. the sound is definitely originating from the top in the HV cage.