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  • Author Author: baldengineer
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Are you still using 7400-Series Logic, if so, where?

baldengineer

Over the past several months, I have been learning about and repairing 8-bit computer and video game systems. So far, I have worked on the VIC-20, C64, ZX-81, Apple II, and have been learning about the TI 99/A.

 

It always amazes how much of these early computer systems were built almost entirely with standard 7400-series (LS and HC) chips.

 

Occasionally, I need to replace a 7400-series chip. (I always hope it is one of those and not one of the ASICs!) While looking for modern replacements, I have noticed the trend that they are becoming more scarce. The LS-series is almost entirely gone--and with good reason. While HC and HCT continue to be somewhat available, they are usually only available in surface-mount packages.

 

That leads me to the question: Who is still using the venerable 7400-series logic chips today?

 

To me, there are three groups that might be using them:

  1. Learning. Students and hobbyist learning about digital logic
  2. New Design. Hardware that needs glue-logic. Are these using multi-gate chips or the single-gate variants?
  3. Repair. Older electronics in need of replacements. Here is where I mostly sit.

 

Do you fit into one of those categories? If not, where do you land?

 

And THEN, which chips are the must-have on-hand?

Obviously, the answer depends on how you might be using them. But, I'm curious to know how you use 7400-series chips and which ones would you keep in stock?

Parents

  • The high spot of my 74xxx design works was about 1987 when I designed this beastie.

    Subsequent designs used FPGAs or micro-controllers.

    I was lucky enough to find one on Ebay recently, not quite working but easily fixed.

    It's based on a Motorola 6809 8 bit micro with memory shared two ways between the video system and

    the digital arbitrary and test pattern wave form generator.

    It could generate digital trios which were modulated at different frequencies to stimulate filters in remote

    booster amplifiers so that the gain of the nth booster down the line could be checked.

    I did the digital and analogue hardware design and the code in 6809 assembler.

    I think it was one of the last board sets we did with tape (before CAD)

     

    These things are never a one person effort and needless to say I didn't do this on my own.

    I can't remember all the good people who worked on the project with me but I'll mention the following:

     

    Alan Bodiam - who did the mechanical design

    Peter Churchill - who was in charge of the machine shop which made all the metal bits

    Peter French and Tim Summers who worked in the lab with me (I think they were both involved on this one)

    Bob Odell - production manager

    Alan Babs - who inspected every one we made (100s)

     

    image

     

    image

    Analogue and PSU, CRT on left and just visible at bottom right huge high Q filter inductor in metal pot.

    image

    Processor and video

    image

    Pattern generator

    image

    Camera having trouble with scan speed of CRT !

     

     

    You could get all this into a decent micro-controller and and a (smallish) FPGA now, not sure if image or image

     

    MK

Comment

  • The high spot of my 74xxx design works was about 1987 when I designed this beastie.

    Subsequent designs used FPGAs or micro-controllers.

    I was lucky enough to find one on Ebay recently, not quite working but easily fixed.

    It's based on a Motorola 6809 8 bit micro with memory shared two ways between the video system and

    the digital arbitrary and test pattern wave form generator.

    It could generate digital trios which were modulated at different frequencies to stimulate filters in remote

    booster amplifiers so that the gain of the nth booster down the line could be checked.

    I did the digital and analogue hardware design and the code in 6809 assembler.

    I think it was one of the last board sets we did with tape (before CAD)

     

    These things are never a one person effort and needless to say I didn't do this on my own.

    I can't remember all the good people who worked on the project with me but I'll mention the following:

     

    Alan Bodiam - who did the mechanical design

    Peter Churchill - who was in charge of the machine shop which made all the metal bits

    Peter French and Tim Summers who worked in the lab with me (I think they were both involved on this one)

    Bob Odell - production manager

    Alan Babs - who inspected every one we made (100s)

     

    image

     

    image

    Analogue and PSU, CRT on left and just visible at bottom right huge high Q filter inductor in metal pot.

    image

    Processor and video

    image

    Pattern generator

    image

    Camera having trouble with scan speed of CRT !

     

     

    You could get all this into a decent micro-controller and and a (smallish) FPGA now, not sure if image or image

     

    MK

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