The Commodore PET 4032 video system was generated by a 6545 (6845 equivalent) cathode ray tube controller, which generated the video buffer addresses and the HS and VS sync pulses. This was memory mapped and if one was not careful with POKE commands, you could effectively stop the CRT raster scan, leaving the beam parked at the center of the screen. This could burn the phosphors off that spot in a matter of minutes. Not exactly HCF, but a similar vibe.

(The PET had its own monitor that, unlike common composite monitors of the era, apparently would not continue to scan when the sync went away)