I am curious on how many self-oscillating mains switching power supply topologies (no ICs!) there are. They appear to be countless! 
In many live chassis TV sets, most are dependent on pulses (usually from the Heater winding) from the EHT flyback transformer, and most power supplies shut down when these pulses stop (such as an overload or X-ray detection), requiring a manual restart.
When the self-oscillating power supply is synchornized to horizontal pulses from the EHT flyback transformer, TV picture interference is minimized.
In many live chassis TV sets, most are dependent on pulses (usually from the Heater winding) from the EHT flyback transformer, and most power supplies shut down when these pulses stop (such as an overload or X-ray detection), requiring a manual restart.
When the self-oscillating power supply is synchornized to horizontal pulses from the EHT flyback transformer, TV picture interference is minimized.