Newbrain repair (COP420 replacement)

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  • 31 March 2026 at 9:13 pm #3684
    Olipix
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      Hi

      I’m actually trying to repair my Newbrain, but apparently it’s the COP420 that has gone wrong.
      Keyboard not responding and 1-line display going wrong.
      Is there is a way to replace the COP420 ?
      I can find a new controller online but I believe it has to be mask programmed ?!
      Thanks for your time

      Olivier

      youtube.com/@olipix
      youtube.com/@olipixretrotech

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      • 1 April 2026 at 10:29 am #3685
        CDesp
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          You are right COP420 is masked programmed so you can’t just take a replacement chip and burn it with the rom. You need a COP402 that takes an extrernal eprom or eeprom or flash ram but that is a 40 pin chip and you need a custom pcb to put the eprom and make it pin compatible to cop420 which is a 28pin chip.

          Another possibility is to take a tang nano 1K fpga and use this VHDL Code (https://github.com/devsaurus/t400) along with the Newbrain Cop420 rom burned to internal flash ram. Of course you will also need a custom pcb along with some voltage converters (3.3v to 5v).

          These sollutions probably will  not fit on the newbrain case so the last option is to use the FPGA chip of the tang nano 1k which is quite small and build a custom pcb using the necessary voltage converters and support components to fit it on the same space as the 28pin cop420.

          Maybe it would be easier to 3d design the newbrain bottom plastic case to be a bit taller and fit the tang nano.

           

        • 2 April 2026 at 11:03 am #3699
          Olipix
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            Hi CDesp

            Thanks a lot for your detailed reply.
            Your solutions are pure theory or you know that it has been done before ?

            Thanks

          • 2 April 2026 at 12:06 pm #3704
            CDesp
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              If you mean if i have done it then no i haven’t.

              But in my opinion this is the only way to do it.

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