SCELBI: things to be aware of SCELBI

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As I layed out the PCBs and researched things SCELBI, I discovered several things that other SCELBI builders should be aware of. I fully expect that other things will crop up, like they did during my Apple 1 and Apple II builds, but here are a few things that I know about already.

  • Missing connection on +5 volts on DBB board – there is a missing +5V connection on the DBB board – add the wire between the resistors as seen on this image of an original DBB board
    • +5 volt wire on DBB board

    +5 volt wire on DBB board

  • I did find an error on the CPU Schematic. The wires going to IC Z20 pins 12 and 8 are swapped on the schematic
  • There is apparently a problem with the step switch. This is described in the “Improving the Operation of the Step Switch ” document, which can be found on this page. When I first looking at this issue, I thought I found some discrepancies between these instructions and the actual board layout, so perhaps this version of the DBB board already has a fix incorporated – or perhaps the instructions are wrong. I have not seen an actual SCELBI with the fix applied