Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!ncar!gatech!mcnc!thorin!oscar!tell
From: tell@oscar.cs.unc.edu (Stephen Tell)
Newsgroups: sci.electronics
Subject: Re: Do Halogen lamps need ballasts?
Message-ID: <17899@thorin.cs.unc.edu>
Date: 3 Dec 90 14:02:16 GMT
References: <714@skipper.dfrf.nasa.gov> <1147@inews.intel.com> <1197@inews.intel.com> <153447.28605@timbuk.cray.com>
Sender: news@thorin.cs.unc.edu
Reply-To: tell@oscar.cs.unc.edu (Stephen Tell)
Distribution: sci.electronics
Organization: University Of North Carolina, Chapel Hill
Lines: 40

In article <153447.28605@timbuk.cray.com> kilian@cray.com (Alan Kilian) writes:
>In article <1197@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P. Houghton) writes:
>> In article <1990Dec1.032426@envy.bellcore.com> karn@thumper.bellcore.com writes:
>> >In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P.
>> >Houghton) writes:
>> [...deformation ==> rupture...]
>> >|> The oil doesn't "weaken the structure."  You can
>> >|> wipe it off.

You can certainly clean the oil off before turning the lamp on and get
near-normal bulb life.  Instructions packed with lamps I've seen say to
clean them with alcohol if you accidently touch them during installation.
I've done this with no problems.

>> >I think the problem is that the heat will decompose the oil, producing
>> >elemental carbon which will then absorb the light hitting it from the
>> >filament.  This causes a hot spot on the surface of the envelope which
>> >could well cause it to soften and fail.

>> I don't think you can "soften" quartz without _extreme_
>> temperatures (thousands and thousands of K).

I have personaly replaced a 750 Watt (or maybe it was 1KW) quartz/halogen lamp
that had a big blackened "tumor" of glass on the side where the envelope had
deformed.  I was told that this happened because someone got a fingerprint on
the bulb when installing it.  If this is not correct, what caused this?  BTW,
this lamp was not the long thin kind found in $10 backyard lights, but one
with a two-pin base and the filament coiled into about a 1" x 1/4" dia spiral.
(Type FEL for 1K or the equivilent in 750).

Sometimes the envelope has broken; we attributed this to rough handling fo
the stage fixture, but it could be the
"different thermal expansion --> breakage" mechanism.

>I guess I'll have to buy some bulbs and try this at home because I don't
>buy any of these theorys. (Except the carbon one maybe)
I've noticed some computer-surplus places advertising 1KW quarts lamps for
very reasonable prices...

>[Alan Kilian  Cray Research, Inc.      kilian@cray.com]


Brought to you by Super Global Mega Corp .com