Heater and cathode sharing

[timmy]

Ok so if you have a crt that has the cathode tied to the heater and try to use it in a set that has a separate cathode by tieing that cathode to one side of the heater in that tube why is it that there seems to be what looks like ac ripple in the pic. Is there a way to get rid of that, besides using a separate heater transformer. I did this once befor and it had that ac ripple in the pic.