Old carbon filament bulb. notice the color temperature.
It is quite cool compared to present day filaments.
73
Bill wa4lav
At 05:26 PM 6/17/2012 +0200, oz5tg@post2.tele.dk wrote:
>Leave them on.
>
>http://www.dailymail.co.uk/news/article-2004797/Worlds-oldest-light-bulb-110-years-old-Livermore-California-station.html
>
>
>Best 73 de OZ5TG, Verner
>
>
> > ----- Original Message -----
> > From: "Bill Fuqua" <wlfuqu00@uky.edu>
> > To: <dhallam@knology.net>; "Ian White GM3SEK" <gm3sek@ifwtech.co.uk>
> > Cc: <amps@contesting.com>
> > Sent: Sunday, June 17, 2012 4:41 PM
> > Subject: Re: [Amps] filament instant heating query / simple remedy
> >
> >
> >> You mean a digital light dimmer.
> >> Hey guys, lets not get so carried away.
> >>
> >>
> >> Lets look at other devices that have filaments.
> >> The light bulb is a prime example. It has a tungsten filament that is
> >> turned on and off more often that your amplifiers. It starts at the
>same
> >> start temperature and ends up much hotter than your filaments, thus
> >> surge current relative to final current ratio is less than that of
>your
> >> filament.
> >> And there is little difference between the (on life) of one left on
>and
> >> one
> >> cycled on
> >> and off.
> >> It is important to maintain proper cathode temperature to achieve
> >> emission and
> >> emission.lifetime.
> >> The death of a light bulb filament is due to tungsten evaporation, but
> >> it has
> >> a very thin filament and lower filament temperature. The filaments in
> >> your
> >> tubes
> >> are much thicker. I expect the lifetime for most tubes is due to loss
>of
> >> emission and
> >> not filament life.
> >>
> >> 73
> >> Bill wa4lav
> >>
> >>
> >> At 08:40 AM 6/17/2012 -0400, David C. Hallam wrote:
> >>>Has anyone tried an approach like Carel, PC5M, with a microprocessor
> >>>controlled soft start for the filament. The microprocessor controls an
> >>>optical triac driver The triac is turned on and off over an increasing
> >>>portion of the line AC cycle until full on is reached. His
> >>>microprocessor program does this in 100 sec. It is designed only for
> >>>soft start and does not do any regulation of the filament voltage
>after
> >>>full output is reached.
> >>>
> >>>David
> >>>KW4DH
> >>>
> >>>
> >>>On 6/17/2012 2:35 AM, Ian White GM3SEK wrote:
> >>> > Leigh Turner wrote:
> >>> >> That's right Pete, the SB220 had a well designed filament
>transformer
> >>> >> that self-limited the cold inrush current to a safer value close
>to
> >>> >> what the tube manufacturer Eimac specified. What the NTC
>thermistors
> >>> >> do
> >>> >> in both the SB220 and TL922 is bring the 3-500Z filaments up in a
> >>> >> nice
> >>> >> slow and controlled manner.
> >>> >>
> >>> >>
> >>> >>
> >>> >> Eliminating the inrush current surge completely like this just
>seems
> >>> >> so
> >>> >> intuitively a good thing to do to mitigate thermal stress on the
>cold
> >>> >> filament structure.
> >>> >>
> >>> > But after that initial surge, the truly dedicated obsessive must
>move
> >>> > on
> >>> > to worry about the stability of the filament voltage.
> >>> >
> >>> > So now our filament supply includes a hot, temperature-variable
> >>> > thermistor, connected permanently in circuit... and we are the
>group
> >>> > who
> >>> > can argue for weeks about +/- 0.1 volt.
> >>> >
> >>> > This should be good ;-)
> >>> >
> >>> >
> >>>
> >>>
> >>>_______________________________________________
> >>>Amps mailing list
> >>>Amps@contesting.com
> >>>http://lists.contesting.com/mailman/listinfo/amps
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >>
> >> -----
> >> Ingen virus fundet i denne meddelelse.
> >> Kontrolleret af AVG - www.avg.com
> >> Version: 2012.0.2180 / Virusdatabase: 2433/5075 - Udgivelsesdato:
> >> 17-06-2012
> >>
> >
>
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