Just wanted to pass along something I learned the other day (amazing!
actually have enough functioning brain cells for new information!).

A client had an under-counter fluorescent fixture go bad. Weird
fixtu uses two T-5 lamps of different sizes (12" & 6"). I looked at
it and decided to just replace the ballast, assuming it would be
cheaper. To make a long story short, it was a pain in the ass just
getting the ballast: took many, many phone calls to the electric supply
place, which is actually a pretty good supply house, to locate the
correct replacement, order it (including having to fax a credit-card
authorization form that they emailed me!) and pick it up.

Anyhow, I finally got the ballast, which was just barely small enough to
fit into the fixture. Got it all hooked up the way I *thought* it should
go, following the little wiring diagram on the label: that is,
connecting the existing wires from the fixture to one of the terminals
on the ballast. Connected it to power; no go. I disconnected the wires
and connected them to my voltmeter, then applied power: no voltage on
the output side at all. That's strange.

Called the electric supply house back, who then gave me the number of
the manufacturer, Advance Electric. I called their toll-free customer
service number and quickly got through to a technician. After telling
him what ballast I had and what the problem I was having. I told him I
had only connected to one each of the connectors for each color; there
were two reds, two blues and two yellows. I've connected ballasts this
way before and they worked (like the ballast I was replacing, which tied
the two pins at each end of the socket together).

After looking something up for a minute, he came back and said, well,
that unit has lamp failure detection, which is why it doesn't work for
you. Apparently, that little ballast is pretty smart: it's got a circuit
that detects an imbalance in lamp current across the two pin pairs,
which tells it that the lamp is about to fail, in which case it shuts
down completely rather than going dim, flickering, etc. (If the bulb
goes out, you know it's time to replace it.) The ballast only works
correctly when all connections are used, exactly as indicated on the
label, with one connection going to each pin of the lamp.

I hooked it up as indicated, and it worked. So I just wanted to pass on
this bit of information. I had no never heard of "lamp failure
detection". (Plus I have to give this company credit for having pretty
damn good tech support.)


--
"Wikipedia ... it reminds me ... of dogs barking idiotically through
endless nights. It is so bad that a sort of grandeur creeps into it.
It drags itself out of the dark abyss of pish, and crawls insanely up
the topmost pinnacle of posh. It is rumble and bumble. It is flap and
doodle. It is balder and dash."

- With apologies to H. L. Mencken