The CRT is a glorified lightbulb, so it can't be the cause of what you're seeing. Instead, your Mac is suffering from the common Type 2 (or possibly Type 1) framistat/grodulator failure. You might find some troubleshooting and repair tips in http://68kmla.org/files/classicmac2.pdf.

Try resoldering the deflection yoke and flyback connections as described in the doc. That will likely restore much framistatic grodulation. If not, replacing C1 may also be needed (read the doc for this and other tips).