What are the odds?

August 5, 2011

This week our son located a large pile of used, good quality fluorescent lights taken from a drugstore undergoing renovations.  Desiring an ample supply of lighting for his new garage, he bought the contents of the large pallet which turned out to contain seventy lights of the eight-foot size, each with four thin, energy efficient bulbs, and three shorter units.

To our astonishment the poor Tacoma could barely carry the load.  The reflectors stacked together densely and Charlie and I discovered we could lift only small piles of them.  And there were a lot.  Similarly, there were a great many bulbs to load onto the top of the pile in my sagging pickup.  Everything rode well on the road home after the vendor added air to my tires, though.

In anticipation of the weekend rush I picked a few lights out of the back of the truck, cleaned and assembled them.  The first two lit up like champions.  Out of the first bundle of bulbs I had two rejects:  one was burned, I guess (no way to tell), and one had a prong bent at one end, so I disposed of it.

Bet and I hung the two completed prototypes from the ceiling of my new workshop, “as an experiment.”  Yeah, right.  I like the even light.

Flushed with success, I assembled another for Charlie to put up in his garage.  All went well until I added power.  Nothing.  Now what?

I dutifully took the thing apart and checked each connection.  No dice.  Ballast?  I pulled one out of another light from the pile and spent twenty minutes wiring it in.  Still nothing.

Time for the burnt fingers method.  In I went with the multi-meter with the current on.  Power to one end was fine.  Voltage was a little variable at the other end.  Re-jigged things until the flow was steady.  Still no lights.

What does a ballast do, anyway?  On my way to the house to ask Google, I thought, “What are the odds of having two bad ballasts from a collection of working lights?  About four times the odds of having four bad bulbs from a similar collection.  Come on, now.  Four bad bulbs in a row?  No way.”

I pulled an unwashed bulb from the centre of a bundle and put it in.  It lit up.  Three more, same story.

Do you apologize to a ballast you have wronged?

So what are the odds of hitting four bad bulbs in a row out of 286 which were working when they took them apart?

Could their failure have anything to do with my amusing discovery that they make a high- pitched hamonic sound when polished with a wet towel?  It didn’t hurt the others, though.

An experiment the following morning with damp cloth produced the expected (and hilarious) high-pitched screech on the first one I cleaned.  Then the cloth grew drier or gummier from the dust and didn’t sing any more as I worked through the four new (dusty) bulbs.  It looks as though I had just hit a phenomenal run of bad bulbs last evening, and the harmonic effect doesn’t destroy fluorescent bulbs.

You know what?  There’s a huge gap in the world of knowledge here.  Google doesn’t know about this phenomenon!  I typed in “Why does a fluorescent bulb squeal when rubbed with a damp cloth?” and Google served up stern lectures by talking heads about the dangers of compact fluorescent bulbs.  YouTube offered a how-to lecture on repairing Apple mouse balls and some dude with a wash cloth on his bald head.

Clearly this is an area for further research, or at least an amusing YouTube clip.  Tip:  not the whole tube sings.  On 48″ bulbs, the harmonic point is about 7″ in from the ends.  I used a dirty blue terrycloth towel, fairly wet.  As the towel dried, the tube performed less energetically.  Enjoy.  Get back to us on this one with your results.

For American readers I’ll add the expected caveat:  Rubbing glass rods with towels is a dangerous activity and may produce broken glass, spilled toxic chemicals, or annoyed family members.  Do not do this at home!  The owner of this website, the Review-Mirror and Google accept no responsibility whatever for injury or property damage which results from foolish experiments in this area.

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