Loading...
 
MSPP Home  »  MSPP Wiki  »  Microbee  »  Main boards

Microbee Main boards

Standard Main boards

Overview

  • There are many variations of the Standard Main board. All variants provide standard graphics only.
  • Various add-on boards could be fitted to provide additional functionality, including colour video output. See the Add-on boards page for more details.
  • 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.
Board Number Component Side Image Solder Side Image
  • Notes
1248 REV E
1248 REV E Component Side
1248 REV E Component Side
1248 REV E Solder Side
1248 REV E Solder Side
  • Used for the Microbee Kit.
  • Corresponds with kit Construction Manual "MicroWorld Publication MWP 28/82 (last revision 29/3/81)". Note that the revision year of 81 appears to be an error - should be 82.
  • Uses a single TO3 type voltage regulator that mounts under the board and is attached to the metal base plate of the case for heat sinking.
  • Video circuit resistor R25 is not present.
  • Has a White Space Bar and RESET key labelled as REPT.
1248 REV F
1248 REV F Component Side
1248 REV F Component Side
1248 REV F Solder Side
1248 REV F Solder Side
  • Used for the Microbee Kit.
  • Corresponds with kit Construction Manual "MicroWorld Publication MWP 28/82 (last revision 6/6/82)".
  • Believed to exist in both blue and green coloured variants.
  • Uses dual TO-220 type voltage regulators with pre-attached heat sinks that are installed under the keyboard frame similar to later factory built models.
  • Video circuit resistor R25 is present.
  • Has a Gray Space Bar and RESET key labelled as RESET.
1248 REV H
1248 REV H Component Side
1248 REV H Component Side
1248 REV H Solder Side
1248 REV H Solder Side
  • There are 2 modifications to this board. 1/ Upgrade from 2mHz to 3.375mHz and 2/ Allow it to be used with a DRAM disk coreboard.
1248 REV I
1248 REV I Component Side
1248 REV I Component Side
1248 REV I Solder Side
1248 REV I Solder Side
1248 REV IA
1248 REV IA Component Side
1248 REV IA Component Side
1248 REV IA Solder Side
1248 REV IA Solder Side
  • Unfortunately the unit pictured here has suffered some significant keyboard damage.
1248-3
1248-3 Component Side
1248-3 Component Side
1248-3 Solder Side
1248-3 Solder Side
1248-4
1248-4 Component Side
1248-4 Component Side
1248-4 Solder Side
1248-4 Solder Side
  • Used for the CIAB.
  • The board in these images has been modified to provide a CGA video output in addition to the standard composite video.
1248-6
1248-6 Component Side
1248-6 Component Side
1248-6 Solder Side
1248-6 Solder Side
  • Has holes for extra keys.

 

Premium Main boards

Overview

  • 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 Number Component Side Image Solder Side Image
  • Notes
8501-2
8501-2 Component Side
8501-2 Component Side
8501-2 Solder Side
8501-2 Solder Side
  • This is the first Premium Main board. It contained quite a few faults that required a list of mods to be factory applied. See Hardware Notebook, Section A, Chapter 22 for details.
  • Board errors in the RTC section made it difficult to use so the optional add-on RTC board was recommended for use with this board instead.
  • The board number can be found both on the component side at the rear edge (in silkscreen and copper) and on the solder side front edge in the keyboard section (in copper only).
8501-3
8501-3 Component Side
8501-3 Component Side
8501-3 Solder Side
8501-3 Solder Side
  • This board fixed most of the faults that were found in the earlier 8501-2 board, but still required some factory applied mods for the serial port. See Hardware Notebook, Section B, ECN 5-190586 for details.
  • The board number can be found both on the component side at the rear edge (in silkscreen and copper) and on the solder side front edge in the keyboard section (in copper only).
8501-4
8501-4 Component Side
8501-4 Component Side
8501-4 Solder Side
8501-4 Solder Side
  • This is the final Premium Main board. It included modifications required for the TeleTerm but was also used for later Premium machines as well as for the Premium Plus+.
  • The board number can be found both on the component side in the right rear corner (in silkscreen and copper) and on the solder side front edge in the keyboard section (in copper only).
  • The board in these images includes Premium Plus+ modifications.

 

256TC Main boards

Overview

  • 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.
Board Number Component Side Image Solder Side Image
  • Notes
MB8508-2
MB8508-2 Component Side
MB8508-2 Component Side
MB8508-2 Solder Side
MB8508-2 Solder Side
  • These images are of a repaired board following a battery leak.
  • On the component side, some silkscreen markings are missing on the left side and replacement components have been fitted.
  • The solder side image was taken prior to fitting the replacement components.
MB8508-3
MB8508-3 Component Side
MB8508-3 Component Side
MB8508-3 Solder Side
MB8508-3 Solder Side