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Blog Are you still using 7400-Series Logic, if so, where?
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Engagement
  • Author Author: baldengineer
  • Date Created: 9 Dec 2020 7:50 PM Date Created
  • Views 3322 views
  • Likes 11 likes
  • Comments 37 comments
  • 7400 logic chips
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Recommended

Are you still using 7400-Series Logic, if so, where?

baldengineer
baldengineer
9 Dec 2020

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?

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Top Comments

  • michaelkellett
    michaelkellett over 2 years ago +13
    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…
  • shabaz
    shabaz over 2 years ago +8
    Here an electronics chain called Maplin was selling 74-series TTL right until 2018, when it closed for good! I guess people were still buying them, perhaps to repair old equipment. I think this is the…
  • ralphjy
    ralphjy over 2 years ago +7
    I just used a couple of 4000 series logic chips in the Pong game that I rebuilt. And I have an assortment of 74 and 74LS (even some 54 mil grade parts) from the late 70s and early 80s when I did a lot…
Parents
  • michaelkellett
    michaelkellett over 2 years ago

    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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  • michaelkellett
    michaelkellett over 2 years ago

    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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Children
  • dougw
    dougw over 2 years ago in reply to michaelkellett

    Very nice tape job.

    I still have some red and blue tape somewhere, but my light table seems to have disappeared.

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  • michaelkellett
    michaelkellett over 2 years ago in reply to dougw

    I got rid of mine and all the little pad stickers and stuff a good while ago, I didn't think I'd ever use it again and the sticky stuff was going nasty.

     

    I never had a light table, we used a drawing board for big boards and almost always worked at x2 size.

     

    It took ages - PCB CAD on a PC was why we bought our first IBM compatible.

     

    MK

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  • phoenixcomm
    phoenixcomm over 2 years ago in reply to dougw

    dougw  michaelkellett , Dito I had a slab of plexiglass with the stainless reference bar.  My brother was a PCB layout guy and did more than A few Double Sided PCB, once even  4 layers; top signal, ground, power, and a bottom signal side. We had the boards done locally with gold fingers, and feed-through holes.

    ~~Cris

    BTW No pics as they are still packed.

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  • Jan Cumps
    Jan Cumps over 2 years ago in reply to michaelkellett

    michaelkellett  wrote:

     

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

    I'm going for image.

     

    Mind blown also. What a beautiful and well-designed kit.

    It's not easy to make an appealing and functionally understandable front panel.

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