[ARC5] Filament Question

[Bill Cromwell]

Hi

I only read *most* of the replies before I replied to this thread. So I 
said pretty much the same thing about the battery tubes. I doubt the 
tube life would be shortened by leaving the filaments on all the time 
but the battery life or battery charge definitely will be shortened.

I will be learning just how much drift in the oscillators is introduced 
by cycling the oscillator tube filaments on and off with the rest of the 
radio for "standby/operate". I may have to leave those on but I won't if 
I don't have to.

If the B+ has no path to ground (consider the screen supply) then B+ 
current will also stop when the filaments are turned off so that a B+ 
switch will not be needed. That can also simplify the T-R switching.

73,

Bill  KU8H


On 10/03/2015 12:20 PM, Kenneth G. Gordon wrote:
> On 3 Oct 2015 at 14:53, Leslie Smith wrote:
>
>>    Hello Wayne,
>>    Lacking any specific knowledge about your question, my guess would be
>>    a definite "yes".
> I disagree for reasons I have previously stated.
>
>>    I guess that thermal cycling would reduce the life of the filaments
>>    and therefore the tubes.
> I reply: that would depend on the tube in question. In this case, a "blanket"
> statement does no apply.
>
>>    I suspect (from your question) you think the same as I do.
>>
>>    In an editorial in "Ham Radio", the editor Jim Fisk, wrote about a
>>    surplus receiver he had operated from the mid-40s.
>>    I may be wrong in detail here, but as I recall his editorial, his set
>>    was wired so the filaments were always on.
>>    He switched the B+ line when the set wasn't in use.  He believed (as I
>>    recall) that the thermal cycling of metal to glass (in the tube base)
>>    was the main source of failure of tubes.  He pointed to the 30 year
>>    life of his set, with the filaments constantly on, as evidence of his
>>    hypothesis.
> And I operated an RAL-7 receiver for over 12 years, only turning it off once
> to test the tubes. Finding nothing wrong with them, I turned it back on and
> left it on until I was able to aquire a more modern receiver...but in this case,
> the tubes, 6D6s and 41s, were 6.3 VAC filamented tubes which draw
> significant current when compared with battery tubes.
>
> Wayne is talking about battery tubes with 1.5 V and 3.0 V filaments. The
> tubes are DESIGNED for "instant-on", are designed to "ramp up" internally,
> and IMHO, leaving them on would result in REDUCED life.
>
>>    I don't know if he's right, or not, but his theory seems to have
>>    reason on-side.
> Well, yes, but not if he is dealing with battery tubes...which, btw, are, to me,
> a favorite category of tube.
>
> Ken W7EKB
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