At long last, a Chromacolor II!

[marty59]

You could be hearing some corona discharge but I wouldn't go sniffing for it!! Make sure the HV lead is clean/not sticky along with the anode connection on the tube. As mentioned elsewhere, if the sticky goo around the anode has run down towards the yoke, slide it back/off if necessary and clean it all up. The HV block could be gooey too..or leaky.

And while you're at it, make sure all the CRT ground straps are secure too! You can troubleshoot this with a lack of equipment. Just be sure to be safe about discharging the anode and during your cleaning process continue to keep it discharged. Oftentimes some residual voltage will exist. The anode wire should be ok but check it out good too. There may be a screw that fastens the clip to the cup that also serves as the wire connection too. Easy to check.