dgk wrote:
A fixture in my basement has a single 48" florescent tube which
recently started flickering and now fails to start - it just flickers.
I replaced it and have the same behavior. The fixture is at least 15
years old and might be much older.

I don't see anything that looks like a starter. I've searched around
and see that the ballast may be the problem, but I don't see what
looks like a ballast. It may very well be under a metal cover that
runs most of the way under the bulb. Well, above the bulb actually.

According to this site, the problem might be trying to use a
rapid-start lamp in a pre-heat fixtu

http://nemesis.lonestar.org/referenc...t/trouble.html

Because the fixture is in an infrequently used small storage room
(formerly a sewing room) I bought the cheapest tube they had - but I
don't see anything on it about rapid-start.

I guess I can try a more expensive bulb, and if that doesn't work,
unscrew the metal cover and see if I can find a ballast. It could also
be the wallswitch, but that seems the least likely culpret to me.

Any advice appreciated.

It could be cold in your basement; cold temperatures cause unstable
performance in fluorescent fixtures.

It could be corrosion on the wires; they are often just connected with "push
in" holders, and corrosion can cause problems.

If it is an electronic "ballast", usually it is the capacitors that go bad.

If it is an iron ballast, the starter (on modern units) is integral to the
ballast.

Jon