What is the function of Q442 ???
Does this set use a separate circuit for the high-voltage and
the horizontal sweep ????

On many sets, an FET transistor is used to regulate the voltage
going to the Horizontal output transistor (HOT) and the sweep
driver transistors. If these short, it will usually blow the transitor
it is supplying. Also check the electrolytic capacitor and the diodes
that are part of these regulator circuits.
Hope these help...
John