>
>Subject: Re: Vacuuum tube digital circuits (50 year
rule)
> From: "Ethan Dicks" <ethan.dicks gmail.com>
> Date: Thu, 31 Aug 2006 17:55:47 +1200
> To: "General Discussion: On-Topic and
Off-Topic Posts" <cctalkclassiccmp.org>
>
>On 8/31/06, woodelf <bfranchukjetnet.ab.ca> wrote:
>> The ads list a 12au7 for about 65 cents in 1955. In
2006 a generic 12au7
>> is about $8.00. I suspect a better deal now than 50
years ago.
>
>Hmm... if I leave off seconds and just go with
minutes/hours, I think
>I have enough. Even with modern wages, a bag full of
tubes costs
>enough to make me want to simplify the design.
Hunt a bit I've found Vacuum tubes NOS (New Old Stock) to
be widely available.
The prices vary widely.
To do time.. 12:59 should give you a hint. You need 3
counters only one
is decade. the tens of minutes is 0..5 (/6) and hours is
either /12 or /24.
>The real trick, now, I guess, is how to take 60Hz mains
and clock it
>down to 1/60Hz with 1955 technology.
You need a decade counter and a /6 counter for that, same
general circuit
just no disply. For simpler you can use several
retriggerable monostable
with time out being just longer than say 10 cycles and a
second with
time out of >6 cycles. At most three tubes to do that
(12au7/12ax7/12at7).
Back when Grumman plant-33 closed (LM project) I picked up a
Beckman EPUT
(events per unit time) and it was basically 5 digits of that
style counter
(counted to 5mhz, 8 on a good day) a time base and input
circuits (Schmidt
trigger). All tubes!
Allison
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