Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA
Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!genrad!panda!talcott!harvard!seismo!brl-tgr!ron
From: ron@brl-tgr.ARPA (Ron Natalie )
Newsgroups: net.consumers
Subject: Re: Lifetime Lightbulbs
Message-ID: <8054@brl-tgr.ARPA>
Date: Tue, 5-Feb-85 16:33:34 EST
Article-I.D.: brl-tgr.8054
Posted: Tue Feb  5 16:33:34 1985
Date-Received: Sat, 9-Feb-85 09:13:52 EST
References: <1516@hplabs.UUCP> <517@houxu.UUCP>
Organization: Ballistic Research Lab
Lines: 13

> I once had a man who knew light bulbs say that
> there was a failure mode called "tungten migration".
> 
> The material in the filiment "migrates" in the direction of
> the current.  This causes diameter reductions in the light bulb
> filiment.  Which causes higher resistance and heat at that spot.
> And the bulb burns out.
> 
Also, the tungsten actually boils off.  If we fill the bulbs with
a halogen we can get the tungsten deposited back on the filiment.
I used to be able to explain how this works, but I've forgotten.

-Ron