[QUOTE=ctc17;3052349]HAHAHA its not a 70s Zenith, its a silvertone roundie that can hardly produce 24kv when hit by lightning.
I always thought that any color CRT installed in any make or vintage of TV (not just 1970s Zenith sets) could have its neck sheared off from excessive high voltage. Were Zenith TVs the only ones to have this problem under HV runaway conditions?
If there is no regulation of the second anode voltage on the CRT, the voltage will go sky high, of course, until one of two things happens: the flyback burns out or the neck shears off the tube. Another problem when the 2nd anode voltage runs wild is excessive X-ray emission from the front of the tube and elsewhere. This is why all CRT televisions, from about the mid-'70s until the end of the CRT TV era, were equipped by Federal law with HV shutdown systems that would either make the picture unwatchable (by throwing the horizontal oscillator far off frequency, so far that no amount of fiddling with the hold control would bring the picture back into sync) or by blanking the raster entirely.