31 Aug
2006
31 Aug
'06
4:25 a.m.
Subject: Re: Vacuuum tube digital circuits (50 year rule)
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Date: Thu, 31 Aug 2006 17:55:47 +1200
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
On 8/31/06, woodelf <bfranchuk at jetnet.ab.ca> wrote:
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 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. 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