Subject: Re: Wanted: vacuum tube logic circuits

Roy J. Tellason rtellason at
Sat Aug 30 12:31:25 CDT 2008

On Saturday 30 August 2008 13:05, Chuck Guzis wrote:
> On 30 Aug 2008 at 7:42, William Blair wrote:
> > Thank you!  That's the perfect tube multivibrator lead which allowed
> > me to find these references using "code oscillator" and "6SN7" as
> > search terms:
> It all was very long ago.  I can tell you what I see in my mind's eye
> (however accurate that is).  A small chassis with a filament
> transformer on one side, an interstage audio transformer on the other
> and an octal tube socket in the middle.  A pot on the front to vary
> the pitch and a phone jack.  The tube was definitely a dual triode;
> it might have been a 6SL7 or 6SN7 (perhaps in the application, it
> didn't matter).  Construction was from either the ARRL RAH or perhaps
> "The Radio Handbook" from about the same time.
> I'm almost 100% certain that this was no multivibrator application;
> indeed, half of the triode may have been used as a rectifier.

Would that interstage transformer perhaps be making it a blocking oscillator?  
I remember those (indeed using 6SN7s) being fairly common in very early TVs, 
say 1950s or earlier.

> All of this is subject to the bit-rot that increasingly pervades my
> wetware nowadays.

I hate it when that happens!

Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

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