AMRAD reservation for Winterfest, 22 FEB 2009

Michael O'Dell mo at
Thu Dec 25 18:49:49 CST 2008

a "tube" design has much better alternatives than
reproducing a TTL/DTL design in 12AX7s

there are "bi-quinary" counter tubes which work
by "glow transfer", running a blowing neon blob
around a ring of electrodes sticking through a
plate. some counters used the counter tubes poking
through the panel so you saw the glow directly.
(You've probably seen these in S/F movies - they
look like spinning wheels, or very old depth sounders!)
that isn't the only way they can be used, though.
one can use them to do the switching/dividing duties
and then drive Nixie tubes with them if you don't like
the spinning dots.

and on this subject, the all-transistor design
struck me as a bit of overkill. for a clock,
RTL would do a fine job, as Don Lancaster demonstrated
so many times in Popular Electronics.
and i'm certain i've seen a transistor ring-counter
design that would use a lot fewer transistors than
the corresponding binary stages and decoders done
with DTL.

I remember having a "product guide" from Motorola
which went over all the logic families they produced
in the late 60s: RTL was popular with hobbyists because
it was cheapest for a long time until TTL got enough
volume. But MOT made RTL, TTL, DTL, ECL, and i *think*
they made some CTL parts as well (capacitor-transistor
logig). with caps being hard to make on ICs, made CTL
unattractive for ICs. I believe Burroughs was the big
user of DTL for the longest time, and the US Postal
Service kept an old Sylvania line making DTL parts
long, long after everyone else quit because the big
mail sorting machines that did the address recoginition
were built by - you guessed it! - Burroughs! my
ex-father-in-law was one of the most senior backup
repair techs for USPS and they could keep the sorting
machines running, but they couldn't add new features.
he and his buddy came up with a Z80-based adjunct
processor - the ZMT (Zip Mail Translator) which
connected up somehow to the system and was the vehicle
which allowed deployment of full zip-code routing
on all 5 digits instead of the first 3 (last two
were done by the station hand sort) and eventually
ZIP+4.  I would *hope* that stuff has been phased-out
by now, but if i were a betting man......


Joseph Bento wrote:
> On Dec 23, 2008, at 5:24 PM, Richard wrote:
>> Hi All,
>> I wonder if the clock could be made with tubes.  Imagine what it might 
>> look like.
>> Best Wishes
>> 73s
>> Richard
> Hi Richard and all,
> Happy Christmas to all.  All tubes?  It's been done.  Imagine the heat! 
>  Richard, remember the KWR-37 in the military?  I hope this clock has 
> better reliability!  :-)
> see
> Regards,
> Joe
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