This board features printing in ENIG.

The project is an upgraded / evolved TRS-80 Model I main board replacement. It was designed to provide a reliable, compact, and modern replacement, removing some limitations of the original 1970's product, while still remaining faithful to the original technology (i.e. no emulation)

Features at a Glance

• CPU double speed (3.56 Mhz), configurable by jumper or external switch.
• System ROM's have been replaced with standard 32 pin EPROM (27xxx) or EEPROM (28xxx).
• Larger ROM's allow multiple paged ROM images selectable by Jumper.
• ROM can be configured to occupy the empty memory region (12-14kb) above the main ROM.
• A full 48Kb of RAM is provided by a single modern SRAM chip.
• Video character generation is provided by standard 32 pin 27xxx EPROM's or 28xxx EEPROM's
• Video character generator provides full 6x12 pixel matrix (Gendon3 compatible) descenders.
• Multiple character sets can be defined, the character set chosen is by dip switches.
• The Video sync has been upgraded with improved stability, and 50Hz PAL support.
• Video Output is via traditional DIN, or optional RCA socket.
• An internal 40 pin header is provided for plug in expansion cards
• A FreHD board has been developed primarily for internal expansion.
• Power and Reset switches can be either traditional or modern components.
• The cassette input has minor improvements in the A/D design.
• All internal power regulation circuitry has been removed, now externally provided.
• Overall modernisation, including full GND planes, decoupling capacitors, silkscreen.
• A prototyping area is provided on the board, for user provided enhancements.

Schematics, BOM and build instructions are provided.

(This was developed by Mark Pruden (kiwisincebirth on Github) and produced by an an external PCB manufacturer with his approval)