On old CRT's its common to find cold solder joints in the socket
( CRT end ), especially the filaments. Check that first.
BTW when working on any old set with that type base carefully & slowly
work at it with a thin screwdriver. Go in a circle while keeping the CRT end from moving. If you just grab & pull you can rip the socket right off &
maybe break off a wire right at the glass.
73 Zeno
LFOD !