Suggest use a metered variac,
No diode test fix needed, easy to just use banana plug jumper cables and Alligator clips to put any diode or 1 k resistance as load.
Bring line to 30v, observe mains current, raise to 60, 90, 120, observe normal mains current
Should have a trace or dot on the CRT, be careful with the intensity
Jon
Jean-Paul