Diagnostic Cartridge PCB for Atari ST

Diagnostic Cartridge PCB for Atari ST

This is a professional diagnostic tool originally designed for the technical services of authorized ATARI distributors. It enables comprehensive testing of hardware across the entire ATARI ST series (excluding the FALCON model) – from the classic 520/1040 ST, through STE, to TT and MEGA STE.

The operating principle is simple and elegant: the device connects directly to the computer's cartridge port. The board features two 27C256 EPROM chips (2×256KB) containing a proprietary test program, which, once launched, takes control of the machine while bypassing the internal TOS. This ensures the test operates independently of the state of the operating system installed on the computer, which is crucial for diagnosing potentially damaged hardware.

The range of tests performed includes RAM and ROM, keyboard and mouse, Glue and MMU chips, FPU coprocessor (in models that have it), Blitter, as well as the audio section and video output. The manufacturer also mentions available tests for the printer and DMA interface, but these require an additional, separate expansion module.

In terms of construction, it is a double-sided PCB, requiring the following components for assembly: 2× programmed 27C256 EPROMs, 2× 100nF capacitors, 2× 32-pin edge connectors, and wire connections between layers (the board does not have plated-through holes, so vias must be manually created using thin copper wire). The project is, therefore, a typical "hobbyist" DIY requiring precise soldering with a fine tip.

The author strongly emphasizes one safety precaution: the device must never be connected or disconnected while the computer is powered on – this risks damaging the cartridge port or the tester itself.

The project includes ROM images ready for programming for various TOS versions (ST v4.4, STE v1.9, TT v1.4, MEGA STE v1.5), as well as a schematic and PCB layout in PDF format – making this a complete, reproducible open-source project that can be built from scratch.

Project:

https://www.gossuin.be/index.php/archives/27-test-kit-atari-st