[Boatanchors] Tube filaments

[ronw8]

I meant subjective.

(Remember: Always proof read your emails before hitting send )

ronw8 wrote:
> "Seem to happen" is an objective statement.
>
> I ran all sorts of life tests.
> It happens to all filaments .... even lamp filaments with no external 
> current.
> "Early" is a relative term.  AC run filaments just have a longer life 
> due to the migration physics.
> ---
> Ron
>
>
>
> Carl wrote:
>   
>> That doesnt seem to happen with indirectly heated filaments that have 
>> a long and reliable history in mobile enviroments.
>>
>> In fact a tube such as the 6V6 which is known to be prone to heater 
>> cathode leakage resulting in hum in AC sets merrily chugs away on DC.
>>
>> Carl
>> KM1H
>>
>>
>>
>>
>> ----- Original Message ----- From: "ronw8" <w8ron at sbcglobal.net>
>> To: "Singley, Rodger" <rbsingl at ilstu.edu>
>> Cc: <boatanchors at mailman.qth.net>; "Ed Berbari" <eberbari at indy.rr.com>
>> Sent: Saturday, December 05, 2009 7:31 AM
>> Subject: Re: [Boatanchors] Tube filaments
>>
>>
>>     
>>> Running DC on filaments would cause the filament material to migrate to
>>> one side with early failure.  No issue with AC.
>>> ---
>>> Ron
>>>
>>>
>>> Singley, Rodger wrote:
>>>       
>>>> Tektronix used DC for the filaments in their vertical plug-ins on 
>>>> the 500 series "lab" scopes.  In this case the filaments are in 
>>>> series and few from one of the regulated B+ supplies.
>>>>
>>>> Given the desired performance of these scopes and the selling price 
>>>> (many of the plug-ins sold for as much as a typical ham 
>>>> receiver/transmitter setup) it was possible to justify the cost of 
>>>> this circuitry.  But that wouldn't be the case for typical consumer 
>>>> gear.
>>>>
>>>> I seem to recall reading somewhere that filaments (tubes or light 
>>>> bulbs) are more prone to developing localized "hot spots" on DC as 
>>>> compared to AC.  Anyone else recall this potential problem?
>>>>
>>>> Rodger WQ9E
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: boatanchors-bounces at mailman.qth.net on behalf of Ed Berbari
>>>> Sent: Fri 12/4/2009 7:46 PM
>>>> Cc: boatanchors at mailman.qth.net
>>>> Subject: Re: [Boatanchors] Tube filaments
>>>>
>>>> I would like slightly change the direction of this discussion on tube
>>>> filaments.  My background is in medical electronics and when I first 
>>>> got
>>>> started in this field tube amplifiers for biophyscial measurements 
>>>> (ECG,
>>>> EEG, etc) were still common.  A leading company was Electronics for 
>>>> Medicine
>>>> (E for M, now defunct) and they used DC voltages for filament 
>>>> supplies. It
>>>> was their way to limit 60 Hz hum from interfering with these low level
>>>> signals.  I always wondered why this practice was not used with 
>>>> receivers
>>>> and other low level signal circuits.  Instead we are burdened with 
>>>> numerous
>>>> bypass capacitors and other means to limit 60 Hz interference.  Any 
>>>> wisdom
>>>> or thoughts out there on this approach?
>>>>
>>>> Ed, W9EJB
>>>> ______________________________________________________________
>>>> Boatanchors mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:Boatanchors at mailman.qth.net
>>>>
>>>> List Administrator: Duane Fischer, W8DBF
>>>> ** For Assistance: dfischer at usol.com **
>>>>
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>
>>>>
>>>>         
>>> ______________________________________________________________
>>> Boatanchors mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Boatanchors at mailman.qth.net
>>>
>>> List Administrator: Duane Fischer, W8DBF
>>> ** For Assistance: dfischer at usol.com **
>>>
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html 
>>>       
>>     
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com ** 
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>