On 1/22/2009 5:25 AM Don Klipstein spake thus:

In m, D. Nebenzahl said:
On 1/21/2009 8:06 AM TimR spake thus:

One thing sure, four tubes didn't reach end of life at precisely the
same time.

True; but if it has a newer electronic ballast, it may shut down all 4
bulbs if it senses that one of them is going out. Might be worthwhile
trying new bulbs first.

My experience with electronic ballasts for fluorescents is that they
don't do that. All bulbs going out at the same time is usually (in this
order) a bad connection, ballast failure, lack of grounding, or very
unfavorable conditions (sometimes including bulb-ballast mismatch).

Are you sure about that? I ask because I recently had a problem
installing a new ballast in a fixture; I connected it the way I thought
it should work, but it wouldn't light what I knew were good bulbs. (I
had connected the two leads to each bulb's end together as the old
ballast had been wired.) I called the manufacturer's tech support line,
and they advised me that I had to connect it exactly as shown on the
diagram, because the ballast incorporated a protection feature (I forget
the exact name of it now) that sensed when a bulb was about to fail and
then shut down both bulbs, rather than allowing them to flicker.

This was a 2-bulb ballast; not sure if this would apply to a 4-bulb
fixture, but it certainly seems possible.


--
"I know I will go to hell, because I pardoned Richard Nixon."

- Former President Gerald Ford to his golf partners, as related by
the late Hunter S. Thompson