---
title: HEATHKIT / ZENITH ET-3400
categories:
- Computers
types:
- Home Computer
origins:
- U.S.A.
years:
- '1976'
cpus:
- Motorola 6800 then 6808
params:
  name: ET-3400
  image: /media/museum/photos/heathkit_et3400_system_s1.jpg
  company: /companies/heathkit-zenith
  company_name: HEATHKIT / ZENITH
  specs:
  - label: NAME
    value: ET-3400
  - label: MANUFACTURER
    value: Heathkit / Zenith
  - label: TYPE
    value: Home Computer
  - label: ORIGIN
    value: U.S.A.
  - label: YEAR
    value: '1976'
  - label: BUILT IN LANGUAGE
    value: Monitor in ROM
  - label: KEYBOARD
    value: 17 keys Hexadecimal keypad
  - label: CPU
    value: Motorola 6800 then 6808 (1981) and 6802 (1987)
  - label: SPEED
    value: 1 MHz
  - label: RAM
    value: 256 bytes expandable to 1 KB
  - label: ROM
    value: 1 KB
  - label: TEXT MODES
    value: 6 x 7-segment LEDs
  - label: SIZE / WEIGHT
    value: 30.5 (W) x 30.5 (D) x 10.15 (H) cm. / 2 Kgs
  - label: POWER SUPPLY
    value: External AC adapter
  - label: PERIPHERALS
    value: Prototype area
  - label: PRICE
    value: $199.95 Kit, $279.00 assembled, $99.95 for the ET-3401 course
  tabs:
  - photos
  - emulators
  - links
  forum_thread: 766
  photos:
  - title: 'LARGE VIEW #1'
    subtitle: ''
    text: At power on or after a Reset, 'CPU UP' is displayed.
    image: /media/museum/photos/heathkit_et3400_system_s2.jpg
  - title: 'LARGE VIEW #2'
    subtitle: ''
    text: ''
    image: /media/museum/photos/heathkit_et3400_system_s3.jpg
  - title: REAR SIDE
    subtitle: ''
    text: No connectors and no ability to save typed programs to a tape recorder.
    image: /media/museum/photos/heathkit_et3400_rearside_s1.jpg
  - title: MAIN BOARD
    subtitle: ''
    text: The upper part of the main board is covered by the case.
    image: /media/museum/photos/heathkit_et3400_mainboard_s1.jpg
  - title: MAIN BOARD CLOSE-UP
    subtitle: ''
    text: Each area of the circuitry is clearly marked.
    image: /media/museum/photos/heathkit_et3400_cloeup_s1.jpg
  - title: PROCESSOR CLOSE-UP
    subtitle: ''
    text: Here a 6802 version
    image: /media/museum/photos/heathkit_et3400_proccloseup_1.jpg
  - title: OPENED
    subtitle: ''
    text: A crude power supply unit is fixed to the hidden side of the main board.
    image: /media/museum/photos/heathkit_et3400_opened_s1.jpg
  - title: MANUALS
    subtitle: ''
    text: |-
      The ET-3400 was delivered with a full set of manuals and tests:\
      \- Microprocessors flipchart,\
      \- Two Assembly Language Programming Workbooks,\
      \- An hardware assembly manual,\
      \- A ten chapter reference book,\
      \- Two audio cassettes,\
      \- Two final exam kits(assembly language test and microprocessor test),\
      \- A poster sized schematic of the computer,\
      \- A parts pictorial illustration booklet.
    image: /media/museum/photos/heathkit_et3400_manuals_1.jpg
  emulators:
  - title: ET-3400 simulator
    url: http://www.pilgrimworks.com/trainer.htm
    platform: Windows
    text: ''
  links:
  - title: Heathkit ET-3400 Resources (Yahoo Groups)
    url: http://tech.groups.yahoo.com/group/ET-3400/
    text: Modifications, schematics, manuals and other resources for the Heathkit ET-3400 Microcomputer Learning System.
  oc_id: 785
  source:
    url: https://web.archive.org/web/20230510155752/http://www.old-computers.com/museum/computer.asp?c=785
    date: '2023-05-10'
---

The Heathkit/Zenith MicroComputer Learning System model ET-3400 was a very popular item designed to teach principles of computers and programming at Universities in the 1970s., and to educate the students of internal computer hardware and software components by self-assembly and programming the machine in pure Hexadecimal language.

It was delivered in assembled or Kit form. It also featured a prototype area and could be used as a design aid for developing special interface circuitry with common 6820 parallel interface or 6850 asynchronous chips.

Several software in ROM were also available. Among them an Assembler and a Tiny BASIC.

---

**Mendel Cooper's** memories:\
I built one of these from a kit back in about 1984, I guess. Price was approx. $200 in kit form.\
Heathkit used to sell three educational courses based on the ET-3400:\
1\) Microprocessor Course, EE-3401\
2\) Microprocessor Interfacing Course, EE-3402\
3\) Microprocessor Applications Course, EE-3405\
Using the specs in the manual, it was pretty easy to build homebrew memory expansion. For a couple of dollars worth of parts, I built a 2K module, using a 6116 (2K x 8) static RAM chip.

<table> <tr> <td></td> <td>We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.</td> <td></td> </tr> </table>