Weak CRT or not?

[Xdevo1973]

Hi Everyone,

I've written on here about the Magnavox CT-220A that I have up and running. I've changed all of the capacitors, some resistors here and there, and the video detector diode. I'm pretty impressed. The set is stable and plays fairly well. The picture tube, I think is weak. I don't have a CRT tester but I really can't turn up the brightness that much. The contrast has to be full on, and when I turn up the brightness, the focus disappears, the picture blooms while the image enlarges and the high voltage drops. I've changed the horizontal output and high voltage rectifier with the same results. Should I just assume the tube has low emission?