'Tis true the GE Prog Line and similar 2-way mobile gear from that era used
indirectly heated cathodes, mostly receiving tubes with the exception of the
PA section, which still used indirectly heated tubes like 6883's, 6146's,
etc, depending on the model.
I think it was very common for those tubes to be operating at below their
normal heater voltage rating, as well...since most of the rigs were
trunk-mounted at the far end of 15-20' of cable, away from the battery, and
IR drop was pretty high with the rather huge load currents being drawn.
WB2WIK/6
"Each success only buys an admission ticket to a more difficult problem." --
Henry Kissinger
> -----Original Message-----
> From: 2 [SMTP:2@vc.net]
> Sent: Wednesday, October 31, 2001 7:51 AM
> To: Lamb; Peter Chadwick; 1AMPS; 'Randall DuCharme'
> Subject: Re: [AMPS] Henry 1KD5 Rectifier question
>
>
> >
> >I have also heard that dc on the filaments causes migration.
>
> / True with filament type [directly heated] cathodes, but not true with
> heater type.
>
> > It makes
> >sense. However, practicall experience leads me to question whether the
> >conclusion may not be relevant.
> >
> >My old GE Progress Line 2 meter rig was all tubes and it ran on dc.
>
> / My guess is that the tubes used heater type cathodes and not filament
> type cathodes.
>
> >It was
> >in my car for years without replacing any tubes and without reversing
> >polarity of the battery. Finally replaced the Prog Line by little
> devices
> >that do not have filaments.
> >
> >I have run the tube vfo's in many of my rigs on dc filaments. Left the
> tube
> >on for years with no failure of the filament.
> >
> >I have never had a failure of a power tube filament - except for one I
> >dropped off the table and one that failed while in the hands of United
> >Parcel Service. So, even if the dc causes premature failure of the
> >filament, it may still outlast the operator or other failure.
> >
> >After all this, would I occassionally change polarity if dc was applied
> to a
> >filament of an expensive power tube - probably.
> >
> cheers, Colin
>
> - R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
> end
>
>
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