My understanding is that any organic material on the high temp
envelope of a halogen/short arc tube will carbonise and heat up
locally in the intense radiation causing local thermal stress to a
quartz tube already running close to it's temp limit. So that
applies to any greasy/proteinaceous stuff found in fingerprints. Of
course no problem with vacuum tubes which you could run under oil if needed.
When I have seen halogen failure it is due to overheating and
melting of the quartz with bubbling and deformity.
Peter
www.tesladownunder.com
----- Original Message ----- From: "Jim Lux" <jimlux@xxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, February 11, 2008 2:54 AM
Subject: Re: [TCML] unknown tube...
The
actuall arc is normally in contact with the "glass" envelope (
normally made from quartz glass, halogen having the tungsten
element within millimeters of the glass) and knowing that an arc
can create excessive temperatures ( whe are talking plasma temps),
the oils left behind from handling can in many cases compromise
the general integrity of the envelope ( causes tiny hairline
fractures in the glass surface which leads to an explosive
failure). As far as contaminating the envelope of a vacuum tube
device, you must ask the question of does it lend itself to the
same heat levels as an arc lamp? Is an arc being formed and is it
in close proximity to the envelope? With what I do know of vaccum
tube devices, I would have to say that touching the outer envelope
would not be detrimental to its life as it would be for say a
laser style discharge lamp... Im old enough to remember the TV
repair man coming to the house to replace tubes in the TV and he
never cleaned the tubes he handled when he replaced them.... and
they would glow red when the TV was on... damn Im old....someone
would actually come to the house to fix the TV!!!
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