The cap being changed is the boost A.K.A. 200V filter cap. One of the
most common problems on any brand. Can cause many symptoms inc.
looking like a bad CRT. The 200V runs the 3 video outs R, G & B.
Buzz I dont know BUT many NAP sets got noisy yokes in the vert winding.
Cure was to spray it with something from the hardware store but I forgot what.
Keep in mind these sets have 3 grounds. Hot, cold & HV. To discharge
short between HV & outer CRT coating ( dag).
Blob usually purity. Degauss ( DGS ) may not be working. Neck components moved. Broken DGS thermistor, cold joint.....
Last is pull chassis & go over the PCB real good for cold joints especially
around the HOZ & flyback. Almost guarrantied to have some.
Good luck
Zeno
LFOD !