Microbee Main boards
Standard Main boards
- There are many variations of the Standard Main board.
- All variants provide standard graphics only.
- The board could be modified to use the optional add-on colour board. Viatel video and de-glitching boards were also other optional add on boards.
- The board number is marked on the solder side in the keyboard section.
- Some versions have 'MICROBEE Z80 S.B.C' marked on the component side as part of the silkscreen.
Premium Main boards
- The Premium and Teleterm models use the Alpha+ graphics enhancement.
- An optional SN76489AN sound chip location was provided but not used on production models.
- The Teleterm model had an add on keyboard interface circuit so that it could be used with the more modern TC keyboard. This was connected into the optional sound chip (SN76489AN) position using an IC header plug.
- Later Premium models had the option to fit a battery backed RTC to the main board.
- Variations exist in how the inverse/flashing attribute works between different version of the main board along with the RTC and other areas of the design.
- Board numbers are etched on the solder side at the bottom edge of the keyboard section and are also screen printed on the component side near the DIN connector. Different numbers may exist on each side.
256TC Main boards
- The 256TC model uses the Alpha+ graphics enhancement and adds a new type of keyboard.
- Unlike the Standard and Premium Main boards, there is no additional plug-in Core board for the 256TC. All components are installed on the Main board with the keyboard being a separate unit.