TRS-80 Parts: Schematics and 3-D Printable

Page Index

Model I Motherboard

Model 1-K Motherboard
(updated Model I) Model I-G Motherboard (GO) Model I-G Motherboard (ME) Model I Japan Board Super Model I

Model I Other

Model I ALPS Keyboard XRX-III Mod

Other Items

Model 4 Keyboard EPROM Module Modular Expansion TRS-I/O Diagnostic ROM Talker/80 Floppy Remapper PS/2 & VGA Adapter TRS-NIC WiFi Printable Parts

TRS-80 Related Schematics

Model 1-K

Name:TRS-80 Model 1-K
Description:A remake of the TRS-80 Model I, but updated.
Link:https://github.com/kiwisincebirth/TRS-80-MODEL-1-K
Notes: This is a drop in (mostly) replacement main board for existing TRS-80 Model 1, using larger density (memory) components to reduce component count. Some common features that required a piggyback board's or piggyback IC's were onboarded.

This version is not compatible with 32Kb external RAM expansion (external RAM will need to be disabled) nor is it compatible with Model 1 power supply (it requires a fully regulated 5V DC power supply).

What it does:
  • 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
Download:It is recommended that you visit the github. That said, sites go up and sites go down, so this ZIP file was at least downloaded on October 6, 2025.

Model I Rev G Motherboard

Model I Motherboard
Designer:grandoldian
Link:https://github.com/Board-Folk/TRS80IUS
Description:This reposistory contains the BOM, gerbers and Kicad files for a remake of the final 'G' version (as far as we know), of the TRS-80 Model I original American version motherboard and some related projects and files.

This is intended as a replica, but additional headers have been provided for the common modification of the 8 bit character set - "BIT6" and "D6" - and "L8" for connection of a character ROM substitute like the Gendon3 module. If original operation with 7-bit characters is required, solder jumper UC should be connected. No additional factory bodge capacitors were added either, for example the ones for the horizontal and vertical sync stabalization. You'll still need to add those yourself.

Model I Rev G Motherboard

Model I Motherboard Marcel Erz
Designer:Marcel Erz
Link:https://github.com/RetroStack/TRS-80-Model-I-G-E1
Description:This project is a faithful reimplementation of the mainboard of the iconic TRS-80 Model 1 (Revision G) computer. My own revision, the E1, is designed to replicate the original system's functionality by using a PCB design 1-to-1 to the original, including components, interfaces, and even traces. The entire project is available under the MIT license.

Model I Japanese Motherboard - Erz

Model I Japan Motherboard Marcel Erz
Name:TRS-80 Model 1 (Rev HE11E011550 - Japanese) Replica - E1
Designer:Marcel Erz
Link:https://github.com/RetroStack/TRS-80-Model-I-Jap50-E1
Description: This project is a faithful reimplementation of the mainboard of the iconic TRS-80 Model 1 (Revision HE11E011550) computer, redesigned and produced in Japan later in its existance. My own revision is designed to replicate the original system's functionality by using a PCB design 1-to-1 to the original, including components, interfaces, and even traces. The entire project is available under the MIT license.
WARNING: This project has not been confirmed to work yet. Use at your own risk.

Model I Japanese Motherboard - Board Folk

Name:TRS80IJP
Description:A remake of the TRS-80 Model I Japanese edition motherboard.
Link:https://github.com/Board-Folk/TRS80IJP
Download:It is recommended that you visit the github. That said, sites go up and sites go down, so this ZIP file was at least downloaded on October 6, 2025.

Model I ALPS Keyboard PCB

Model I ALPS Keyboard
Designer:Marcel Erz
Link:https://github.com/RetroStack/TRS-80-Model-I-Keyboard-ALPS
Description:This project is a faithful reimplementation of the ALPS keyboard PCB of the iconic TRS-80 Model 1 computer. My revision, the E1, is designed to replicate the PCB design 1-to-1 of the original down to the traces. The entire project is available under the MIT license.

TRS-80 Model I XRX-III Mod

XRX-III Mod
Designer:Marcel Erz
Link:https://github.com/RetroStack/TRS-80-Model-I-XRX-III
Description:This project faithfully reimplements the small brown mod board often seen attached to the keyboard of an TRS-80 Model 1. It corrects a software bug in earlier versions of the Level II ROMs, a bug later fixed in version 1.3. The design replicates the original mod's functionality using a 1-to-1 PCB design, including components, interfaces, and even traces.

Since this mod is no longer required for the latest ROM version, there's no need to create it. If you have an older computer, simply update the ROMs, and this mod becomes unnecessary. This repository serves more as a historical record and recreation of the board rather than for implementation.

Upgrade - Model I - EPROM module

EPROM Module
Designer:Danny Bloemendaal
Link:https://github.com/dannybloe/trs80-m1-eprom-module
Description:Allow for the use of EPROM's in a Model I. This version supports both 27128 and 27256 EPROMs. When using the 256 you kan switch banks by setting a jumper (J1). That way you can put two rom images in your EPROM. It switches A14 to 0 or to 1. When using the 27128 you need to set J1 to 1 (connect to 5V).

Upgrade - Model I - Super Model I Motherboard

Super Model I
Designer:Jeff Sponaugle
Link:https://github.com/jeffsponaugle/supermodel1
Description:A replacement TRS-80 Model 1 motherboard using modern through-hole components available new in 2023

  • Z80 CPU DIP 40, 1-16 MHz software adjustable based on installed oscillator.
  • 512K FLASH, bankable across all 4 16K regions, write protectable as well.
  • 16K of Video memory to support 64x16, 32x16, 80x24 text modes and 512x384 bitmap graphics modes.
  • No interference on video access from the CPU. Video access from both CPU and video is full speed.
  • 256K of FONT RAM with direct CPU access to allow software fonts (8x16)
  • Real-Time-Clock and 192 bytes of NVRAM for setup/boot characteristic.
  • Compatible exeternal inteface port for original Tandy/RadioShack Expansion Interface
  • Cassette interface
  • Work with original keyboard
  • Video output: NTSC Composite B&W or VGA 640x480.
  • Onboard power regulation from DC input 7-36V. Switching regulator, 94% efficient.
  • CPLDS are all ATF1504/1508 family CPLD in PLCC form factor, 5V, 7ns, JTAG flashable.

Upgrade - Model III/4 - Floppy Drive Remapper

Floppy Remapper
Designer:George Hines
Link:https://github.com/mrthreeplates/TRS-80_floppy_remapper
Description:The TRS-80 floppy remapper is a simple board (and microcontroller) which dynamically remaps the floppy disk drives in vintage TRS-80 computers.

The main reason for remapping the floppy drives on these computers is to enable booting from drives other than the fixed internal drive 0. This is particualy useful when paired with a modern external floppy disk emulator such as the USB HxC emulator. This avoids the need to take apart the computer, swap cables or replace your internal vintage floppy drives.

Upgrade Parts

Model 4 Replacement Keyboard

Model 4 Keyboard
Designer:Jay Crutti
Link:https://www.jaycrutti.com/hardware-projects/tandy-trs-80-replacement-keyboards
Description:A replacement keyboard for the Model 4 which is meant to use Cherry/Gateron MX switch footprints and match the Row/Column wiring of the original keyboard matrix as detailed on the maintenance manual schematic. It's designed so that a typical 20 Pin IDC cable connection can connect to the keyboard, and the other end to the motherboard itself. It also adds footprint support for extra keys that are supported in the ROM but were not shown in the schematic keyboard matrix. Extensive support holes are added for use as a generic retro keyboard by enthusiasts. If +5V DC is supplied via Pin 17 and an optional 330 Ohm resistor installed, a Power LED can be installed to coincide with the footprint of the RESET switch for compatible MX key switches.

The keyboard is not compatible with the original keyboard plate, but a new compatible plate has been designed courtesy of user alnwlsn on Discord. If mounted above the original plate, the original bezel will not be compatible. When used with a compatible plate, the original bezel will be compatible if the ribbon cable header is installed on the underside of the PCB using the provided footprint and the extra three keys to the right of the numeric keypad are omitted.

Upgrade - Model I - Modular Expansion System

Modular Expansion System
Designer:Calphool
Link:https://github.com/calphool/TRS80MXS
Description:The TRS80MXS is a modular hardware project that aims to expand and enhance the capabilities of the TRS-80 Model I/III/4/4P computers. It consists of four stackable modules:

  • Base module - Provides 32K memory expansion, power conditioning, and serves as the base for stacking other modules.
  • Floppy drive emulator module - Emulates floppy drives by loading disk images from an SD card.
  • TI video/graphics board module - Adds enhanced graphics capabilities using the TI TMS9918 graphics chip, along with sound capabilities using multiple TI SN76489 sound chips (up to 12 voices).
  • WiFi module (planned) - Intended to provide wireless connectivity, possibly allowing web browsing on the TRS-80.

The modules are designed to interconnect and work together, allowing users to build a capable system by stacking the desired functionality. Features include: higher resolution graphics, multi-channel audio, and convenient storage/loading of software via disk images are some of the enhancements offered by the TRS80MXS project.

Upgrade - Model I/III/4 - Talker/80

Talker/80
Designer:lambdamikel
Link:https://github.com/lambdamikel/Talker-80
Description:Modern Voice Synthesizer for the TRS-80 Model 1, Model 3, and Model 4.

Offers:
  • DECtalk-Based Text-to-Speech (TTS) Synthesis.
  • TRS Voice Synthesizer Emulation - MODEL 1 VERSION ONLY.
  • VS-100 Voice Synthesizer from Alpha Products Emulation.
  • Cassette Sound Input Port and Audio Mixer.
  • Optional Amplifier and Loudspeaker.
  • Expansion Port Pass Through Connector.
  • DIP Switch for Initial Mode Selection.
  • RESET button: for reinitializing / "rebooting" Talker/80.
  • Three LEDs: These LEDs are used for mode indiciation, to signal data being received, to indicate when Talker/80 is speaking, and when a single phoneme is being uttered.

Upgrade - Model III/4 - PS/2 Keyboard and VGA Adapter

PS/2 and VGA Adapter
Designer:Matt Boytim
Link:https://github.com/maboytim/TRS-80_Model3-4_Keyboard-Display-Adapter
Description:The adapter can be used to replace the keyboard of a TRS-80 Model 3 or 4 computer with a PS2 keyboard and/or the CRT with a VGA or HDMI monitor. The adapter uses a low cost Nano-9k FPGA module to simulate the keyboard matrix and to capture and reformat the video signal.

Upgrade - Model 1/3/4 - Diagnostic ROM

Diagnostic ROM
Designer:ki3v
Link:https://github.com/misterblack1/trs80-diagnosticrom
Description:The main goal of this ROM is to test the functionality of the video RAM (VRAM) and the dynamic RAM (DRAM, system memory.) It does not test any other component unrelated to those two subsystems. If a TRS-80 has good VRAM and DRAM, it should boot into basic where you can then run further tests.

Upgrade - Model III/4 - TRS-NIC WiFi/TCPIP

TRS-NIC
Designer:Pete Cetinski
Link:https://github.com/pski/trsnic
Description:Trsnic is a general purpose WiFi TCP/IP network interface for the TRS-80 line of microcomputers. It is a fork of Arno Puder's amazing TRS-IO. The product will initially support the TRS-80 Model III and 4 as this is the current support level of the TRS-IO source repository. The long term goal is to support all TRS-80s, including the Models I/II/III/4/12/16/16B/6000.

trsnic provides the foundational protocols required to implement existing network interactions on the TRS-80 microcomputer. The first such protocol provided is TCP/IP via an implementation of the Berekely Sockets API. TCP/IP is the dominant low level network protocol in use today. Many of today's higher level network protocols like HTTP and FTP are implemented on top of TCP/IP. This means many modern networking systems can be built upon the base TCP/IP support provided by trsnic.

Upgrade - Model I/III - TRS-I/O

TRS-I/O
Designer:Arno Puder
Link:https://github.com/apuder/TRS-IO
Description:TRS-IO gives a TRS-80 Model 1/III online capabilities and provides access to a variety of services. TRS-IO currently features the following capabilities:

  • Access to the RetroStore
  • FreHD emulation
  • Access to files mounted on a SMB share or located on a micro-SD card
  • Access to remote servers via TCP
  • Virtual printer support

TRS-80 Related Printable Parts

Treatstock will 3-D print STL images. To order, visit https://www.treatstock.com/c/astra-3d-printing

TRS-80 Model I - Level II ROM Upgrade PCB Mount

Level II ROM Mount
Creator:Barrakuda
Last Update:December 01, 2018
Source URL:https://www.thingiverse.com/thing:3252566
Description: Mounting bracket for Level II ROM Upgrade PCB, on a Radio Shack TRS-80 Model I computer.

TRS-80 Model I - Screw Standoffs Plate

Screw Standoffs Plate
Creator:Barrakuda
Last Update:July 18, 2018
Source URL:https://www.thingiverse.com/thing:3010034
Description: TRS-80 model I computers have screw standoffs that can break or get stripped over time. This screw standoffs plate can be used to replace all screw standoffs completely.

The standoffs plate needs to be printed in two separate pieces due to the length. Unit of measure is millimeters (mm).

To install, remove all original screw standoffs with a rotary tool like a Dremel. Then, use a strong epoxy plastic adhesive to glue the plate down to the surface plane where the original standoffs used to be. Make sure the plate is positioned so that the new screw standoffs align with where the original standoffs used to be.

NOTE: Before permanently gluing this to the case, do a test fit with a hot glue gun.

TRS-80 Model I - Screw Post

Screw Post
Creator:Barrakuda
Last Update:November 07, 2018
Source URL:https://www.thingiverse.com/thing:3202410
Description: Replacement screw post for Radio Shack TRS-80 Model I computer.

TRS-80 Model I - Keyboard Screw Post / Spacers

Keyboard Spacers
Creator:Mr Lurch
Last Update:November 07, 2018
Source URL:https://www.thingiverse.com/thing:3764548
Description: Quick and easy design for the spacers that go in between the keyboard and the mainboard

TRS-80 Model I - Expansion Interface Port Cover

Port Cover
Creator:barrakuda
Last Update:January 02, 2019
Source URL:https://www.thingiverse.com/thing:3330282
Description: This is a replacement cover for the Expansion Interface port on the Radio Shack TRS-80 Model 1 computer. It's been modeled by taking precise measurements of an original cover. It fits really well, but you might have to shave off a little bit from one of the sides if it does not fit correctly because the opening on the TRS-80 seems to be a bit angled. Just use a razor blade or even fine sand paper.

TRS-80 Model I - Expansion Interface Expansion Port Covers (Various)

Port Covers Various
Creator:jwiggins1234
Last Update:October 19, 2019
Source URL:https://www.thingiverse.com/thing:3925677
Description: TRS-80 Model I expansion interface Expansion port covers.

TRS-80 Model I - Power Supply Case

Power Supply Case
Creator:anewcomb2
Last Update:October 19, 2023
Source URL:https://www.thingiverse.com/thing:6273822
Description: Replacement for TRS-80 power supply case that came with the model 1. There are several variants of the top part of the case depending on how you want to treat the text on top. There is also a version with vents and text.

TRS-80 Model I - Expansion Interface Power Supply Cover

Power Supply Cover
Creator:BYTESHiFT
Last Update:July 10, 2023
Source URL:https://www.thingiverse.com/thing:6117675
Description: This is a replacement for the power supply cover for a TRS-80 Model I expansion interface. My unit was missing this cover, so I designed one. I made some revisions to this model after printing mine, so, if you give this a try, please let me know how it worked.

This supports one half of the monitor, so heavy infill is recommended. I would suggest a minimum of 35% -- more wouldn't hurt.

TRS-80 Model I - Expansion Interface PCB Case

PCB Case
Creator:NightfallVT
Last Update:July 10, 2023
Source URL:https://www.thingiverse.com/thing:5742225
Description: A simple case for the TRS-80 Expansion Interface PCB. Uses four 8-10mm M3 bolts for similar.

TRS-80 Model I - Keyboard Button Placeholder

Button Placeholder
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Keyboard_Button_Placeholder
Description: The placeholder is used to guide the Enter key straight down as the ALPS key is located on the other side of the 2x size key. Without it, the key will create too much strain on the Enter-key stem and break it.

TRS-80 Model I - Keyboard Clip

Keyboard Clip
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Keyboard_Clip
Description: The clip is attached to the keyboard shield and holds the spacebar rod fixed to the keyboard shield. This is the counter part to the Keyboard Spacebar clips.

TRS-80 Model I - Keyboard LED Standoff

LED Standoff
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Keyboard_LED_Standoff
Description: The LED Stand-off gives rigidity to the LED on the keyboard PCB. It also makes sure that the LED easily fits into the casing hole at the keyboard.

TRS-80 Model I - Keyboard Shield

Keyboard Shield
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Keyboard_Shield
Description: The stem transfers the force from a finger press on the keycap to the spring and simultaneously presses the metal flap inside the button, creating the contact needed for the button press to be recognized. These components easily break and often require replacement.

TRS-80 Model I - Keyboard Spacebar Clip

Spacebar Clip
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Keyboard_Spacebar_Clip
Description: The spacebar clip holds the small metal bar in place to ensure consistent pressure on the button across the spacebar keycap. It also helps to reduce pivoting, thereby decreasing the overall stress on the keycap pin.

TRS-80 Model I - Keyboard Stem ALPS

ALPS Stem
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Keyboard_Stem_ALPS
Description: The stem transfers the force from a finger press on the keycap to the spring and simultaneously presses the metal flap inside the button, creating the contact needed for the button press to be recognized. These components easily break and often require replacement.

TRS-80 Model I - Main Enclosure Panel

Enclosure Panel
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Main_Enclosure_Panel
Description: The Main Enclosure Panel is used to cover an opening at the back of the computer, protecting the main PCB. It also provides access holes and labels for power, video, and tape interfaces, as well as a hole for the power button.

TRS-80 Model I - PCB Standoff

PCB Standoff
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/PCB_Standoff
Description: The PCB standoff is being used to separate the keyboard from the mainboard to avoid electronic connectivity. Additionally, since it is made of gummy like material, it buffers each keystroke on the keyboard a bit, reducing the stress on the mainboard.

TRS-80 Model I - Expansion Interface Cover

Interface Cover
Creator:Marcel Erz
Source URL:https://github.com/RetroStack/TRS-80-Model-I-Parts/tree/main/Extension_Interface_Cover
Description: There are three types of covers used: small, medium, and large. I only have the medium, and therefore, only that was digitized.

TRS-80 Model I/III - Mise and Mise3 Enclosure

Mise Enclosure
Creator:bkw
Last Update:April 23, 2016
Source URL:https://www.thingiverse.com/thing:1511122
Description: Enclosure for a MISE and MISE3 Add-On Board.

TRS-80 Model III/4 - Key Switch Stem

Key Switch Stem
Creator:Asshen
Last Update:December 28, 2020
Source URL:https://www.thingiverse.com/thing:4700907
Description: 3D-printable replacement for broken key stems. You can desolder the key switch in your system, open them (be careful not to break the clamps which are VERY fragile), and apply conductive paint to the domes.

TRS-80 Model III/4 - Keyboard Support

Keyboard Support
Creator:kpw
Last Update:November 19, 2019
Source URL:https://www.thingiverse.com/thing:3988058
Description: A USB Keyboard support post to be used with a TRS-80 Model 3 or 4.

TRS-80 Model III/4 - Keyboard Cover

Creator:jwiggins1234
Last Update:December 04, 2020
Source URL:https://www.thingiverse.com/thing:4674901
Description: TRS-80 keyboard cover. You need a big build plate for this.

TRS-80 Model III/4 - FreHD Bezel

FreHD Bezel
Creator:jwiggins1234
Last Update:June 02, 2020
Source URL:https://www.thingiverse.com/thing:4419334
Description: Design modified by Jay Newirth of newSOFT fame. Jay created a period-perfect FreHD bezel for TRS-80 Model IIIs and 4s. Using this design, with a couple of extra finishing touches, including the most perfect FreHD badge you'll ever see, you'll keep your M3/4 with one foot firmly planted in 1983, and the other in the gigabytes of the 2020s.

TRS-80 Model III/4 - FreHD Bezel - 3.5" Bay or External

FreHD Bezel 3.5
Creator:Rick_S
Last Update:February 21, 2019
Source URL:https://www.thingiverse.com/thing:3444384
Description: This will allow for mounting a FreHD TRS-80 hard drive emulator in a 3 1/2" drive bay. There are versions for two FreHD board layouts (Rev 3.01 and 3.03) and an LED back plate. For more information see the TRS-80 Model 1-4/4P group on Facebook.

The photos show it mounted in a 3 1/2" to 5 1/4" bay adapter.

2 adapters are for 3.01 and 3.03 Rev FreHD have only bottom mounting holes and the other 2 have both bottom and side mounting holes. The ones with the side mounting holes have the _1 suffix.

Newly Added, cover.stl. A snap on cover for the bay adapter to make a full external enclosure.