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From: news@pasteur.Berkeley.EDU (Six o'clock News)
Newsgroups: sci.electronics
Subject: Re: Fluorescent lamp failure mode(s)
Message-ID: <9829@pasteur.Berkeley.EDU>
Date: 17 Dec 90 06:50:42 GMT
References: <1990Dec14.044303.9610@murdoch.acc.Virginia.EDU>
Reply-To: charless@cory.Berkeley.EDU
Organization: University of California, Berkeley
Lines: 21
Summary:failure mode: Filament emmision material shot

>I've often wondered what the failure mode is for fluorescent light
>bulbs. 
From: e221a-bx@crux.Berkeley.EDU (Charlie Sullivan)
Path: crux.Berkeley.EDU!e221a-bx

The usual failure mode is for the emission material on the cathodes to get
'used up.'  It gets bombarded by ions during normal operation and especially
during startup, and gets chemically degraded and/or evaporated.  The tungsten
filament often stays intact, but tungsten doesn't emit electrons near as well as
the
special goop they use.

>[...]    It had been running fine for a couple of hours when it
>flickered and made a ticking sound and started flickering dimly.

Ticking sound could be the starter.  A bad starter might do this itself,
or a good starter could do it when the lamp (lighting jargon for light bulb--
they call the whole fixture a 'luminaire') dies.  I can only recommend
swapping out the bulb, and if that doesn't do it, try the starter.

Charlie Sullivan                          charless@cory.Berkeley.EDU