[Boatanchors] Tube filaments

[Carl]

You were right the first time.

Ive been repairing auto radios for vintage vehicle owners for almost 50 
years and am amazed at how few tubes are bad. Thats objective enough for me 
and most normal people Id guess.

OTOH I cant say the same for AC operated equipment.

As far as remoting the PS National did that with all their early radios and 
the HRO until 1951. The Navy also did that but it may have been more to 
minimize hernias as well as share one PS with 2 radios.  And we all fondly 
remember the pre SP-600 Super Pros.

Carl
KM1H


----- Original Message ----- 
From: "ronw8" <w8ron at sbcglobal.net>
To: "Carl" <km1h at jeremy.mv.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Saturday, December 05, 2009 9:48 AM
Subject: Re: [Boatanchors] Tube filaments


>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
>>
>>
>