[Amps] filament instant heating query / simple remedy

[Verner Topsøe]

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 at uky.edu>
To: <dhallam at knology.net>; "Ian White GM3SEK" <gm3sek at ifwtech.co.uk>
Cc: <amps at 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 ;-)
>> >
>> >
>>
>>
>>_______________________________________________
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>>Amps at contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>
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