Quote:
Originally Posted by Old1625
Some later model TVs had a "spot killer" circuit added. Perhaps a relay in the focus circuit, or cathode circuit of the CRT could provide such feature in an older set...  |
Some sets had the G1 grid bypassed with a cap to B+, and when the set gets turned off, the B+ quickly goes to zero, and the voltage charge on the cap gets pulled to a negative voltage, thus cutting off the electron beam that would otherwise go to the screen. The bypass cap would take longer to discharge than the collapse of B+, and this time constant was selected to last longer than the residual heat on the cathode. Thus no spot.