On Mon, 16 Nov 2009 16:13:17 +0000 (UTC), (Don
Klipstein) wrote:

In article , dgk wrote:

On Sun, 15 Nov 2009 05:40:26 +0000 (UTC), (Don
Klipstein) wrote:


The house wires are so old that I can't tell which is white and which
is black. So I went by the wires that went into the old ballast. The
wire that went to the white ballast wires was assumed to be the white
one.

I wired it in, turned it on, and it worked fine. Then I tried again
and only one bulb goes on. Odd. I jiggled the bulbs a bit, still only
one goes on. If the wires were reversed would that make a difference?

I switched the bulbs and the one that works still works and the other
doesn't. So it seems like something is wrong with one of the bulbs.
Not that I care since even the one bulb is too much light for that
little room.

Looks like a reasonably successful fixture transplant. Thanks to
everyone for their help.

Congratulations on getting this fixed.

And it looks like maybe the second time in my life so far that my first
guess for a fluorescent fixture problem turned out to be wrong. If I saw
how it was blinking or seen a video, I would probably have recognized what
was going on.

Meanwhile, as for why after first use only one bulb lights? You did say
you like it that way, but this did catch my attention.

You did say that switching bulbs around indicates that one of the bulbs
themselves is now refusing to work. Since the bulb is supposedly new, my
first guess is that the bulb got broken somehow or was defective.

My second guess is that the bulbs have some differences between them in
electrical characteristics and you have a cheaped-out-design 2-bulb
electronic ballast that cannot handle above-average difference between the
two bulbs (production tolerances, etc.).

(Are the bulbs new, or did you put old bulbs in the new fixture? Are
the bulbs even ones that the fixture is rated to accept? There are a few
different 4-footers that have the same pins.)

My third guess is that reversing the power wires will make a difference,
by affecting electric field distribution within bulbs that are trying to
start (or that the fixture is not grounded, which also unfavorably affects
electric field distribution within a bulb that is trying to start).

My 4th guess is that the cranky bulb has a coating of dirt or grime
that, if humidity gets high enough, gets conductive enough to screw up
electric field distribution within a bulb that is trying to start. Since
the bulb is supposed to be new, and humidity in November in a house in
.com-land is not that likely to be high, I consider this to be very
unlikely. This problem is more of one in coastal areas where salt gets
into the air.

- Don Klipstein )

Odd that you mention grounding as a possibility. There is a screw on
the frame that is supposed to go to a ground wire, but there is no
ground wire in the electrical box so I figured that the screws that
now hold the fixture to the box would be sufficient ground. Maybe not?

They're new bulbs - and a much narrower diameter than the old ones.

One more odd thing, though not so odd in my house. The wall switch
that operates the light works backwards. On is down. And I can't
recall whether that worked that way before. It very well might have
and there are two other switches in the house that work that way. I
never bothered fixing them. I use this light so infrequently that I
just don't recall.

I wondered if that indicates that the wiring in the fixture is
backwards, but that doesn't make any sense to me. I mean, the switch
is just open/close right? Even if the wires were reversed it doesn't
seem that it would make the switch work the inverse way.