A few notes
First either your set is a 1964 or 5 or the diodes have been changed before
they have a date code of 1964 38th week.
Keep in mind for the future these come 3 ways. Common anode,
common cathode, & series. Common cathode is almost
always what is used.
If that dont do it a tube is next. If not a tube probably a cap is
drifting, watch out for the clear silver jobs. The tube should be cheap
compaired to a hoz out.
73 Zeno