I have seen various threads with TTL requests regarding how to and build a TTL clock or counter with discrete components.
As I have build around 7 of these clocks in the early 1990's and these TTL, LED clocks are still going strong I decided to have a look in my archives and post the basic diagramme for it.
I have learned building them also by trial and error and from various sources like
TTL Cookbook (Don Lancaster) and
Digitale klokschakelingen (Herbert Bernstein) written in Dutch origin Germany.
As i like the old TTL technology and with carefull and accurate ratsnest wiring a very accurate clock can be build at very low cost but labour intensive but that doesn't matter for a hobby.
Important is the decoupling of every 74xx IC with a 100 nF disc capacitor.
I omitted these in my earlier clocks and later addition of these was painful but not impossible.
The numbers 6 and 9, can be made with tails by adding an extra 7408 AND gate to drive a BC 547 to sink the A and D segment when these have to light up.
A 74247 IC has those functions built in but i have never seen one of those.
IC's.
Attached is the basic schema which works well and i'm more than happy to give more info to potential TTL clock builders. Also i'm happy to post more photo's if required.
**broken link removed**
hm: :mu:
hm: