My garage has several shoplights with the older type of fluorescent dual
light fixtures, 4 feet long, 40 Watt, thicker than the modern ones.

Both lamps went dead. I replaced only one of the lamps because it is
difficult for me to reach above my head. However, the new single lamp in the
fixture does not burn steady. It flickers mightily and also turns on and off
intermittently.

Does this mean the ballast is bad and that I should replace the fixture with
a more modern one?.

Thanks

Walter