In a poorly constructed CRT you can definitely damage the drive circuits by an excessively high line rate. That's basically the reason why CRTs tend to include

In a poorly constructed CRT you can definitely damage the drive circuits by an excessively high line rate. That's basically the reason why CRTs tend to include "out of range" warnings and shutdowns. You could, I think at least theoretically, also cause damage by incorrect blanking, because line rate + blanking determines the drive waveform for the LOPT.