The Heathkit ET-3400 is a Motorola 6800 logic trainer, designed to help people understand how the CPU works while allowing them to test designs and theories.

The trainer has 2x 2112 Static RAM chips. These are 256 Bits of 4-Bit RAM, paired to give 256 Bytes of 8-Bit RAM (256 x8). This is upgradable to 512 Bytes of RAM by installing two extra IC’s. If this still isn’t enough, it is theoretically possible to expand it up to 48k with additional circuitry. The trainer provides a 6-character 7-segment display output for hex, and a somewhat strange 17-key keypad for user input. Address and Control buffers are made available with easy wire-in connectors. 1k ROM monitor with Tiny BASIC is supplied.

The trainer was supplied in a kit form, with detailed instructions on how to build it. The kit was available from 1977 onwards.

This unit has a label on the back stating it was from Maricopa County Community College (Arizona, US). It is unknown how it has found its self in the UK.

Make & ModelHeathkit ET-3400
GenerationLogic Trainer
CPUMotorola 6800
RAM & ROM256 Bytes RAM, 1k ROM
Exhibit No.1351

1 thought on “Heathkit ET-3400

  1. Curtis Dillahay Reply

    The FAA used these back in the 80s to teach their correspondence courses on microprocessors. I ordered the course, and borrowed the unit (signed it out), until I finished. You had a pack of about 150 4″ to 8″ insulated copper wires, which you inserted into the holes on the risers to complete circuits. There was also a small speaker. Built a timer, a clock, a calculator, and a synthesizer, among other things, using the course manual.

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