[time-nuts] Digital Clock kit - no Integrated circuits!

[Bruce Griffiths]

At high temperatures the circuits with the additional diodes in series 
with the base will have problems with transistor leakage currents when 
all inputs are low.
The person who created that page doesnt know how to design reliable 
circuits.
A base to emitter shunt resistor is one way of avoiding this problem.

Bruce

Stanley Reynolds wrote:
> Knowledge of history doesn't = having lived it :-)
>
> http://www.play-hookey.com/digital/electronics/dtl_gates.html
>
> 3 to 1 is not all that odd if you have 5 to 1 and 2 to 1 ratios as the page above indicates.
>
> Stanley
>
>
>
> ----- Original Message ----
> From: Bob Camp<lists at cq.nu>
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Sent: Fri, January 8, 2010 8:10:34 PM
> Subject: Re: [time-nuts] Digital Clock kit - no Integrated circuits!
>
> Hi
>
> It seems like the diode to resistor ratio is a bit off in that design.
>
> In order to go into further detail, I would have to admit to starting out in the pre-integrated circuit logic era ....
>
> Bob
>
>
> On Jan 8, 2010, at 8:07 PM, Tom Clifton wrote:
>
>    
>> http://transistorclock.com/  has a very interesting (though a bit expensive) kit for sale.  A 10" x 11" circuit board sporting nearly 200 transistors and 600 diodes to drive six seven-segment displays.  Suitable for framing...  As delivered runs on 60hz but there is a note about conversion to 50hz mains.  You can buy a  bare board, just the components or a full kit.
>>
>> You must see it to believe it!
>>
>> Tom
>>
>>
>>
>>
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