Commodore 128 Diagnostic & Harness Kit

• Full Kit: 1x Commodore 128 Diagnostic Cartridge, 1x Keyboard Port testing dongle, 1x Serial Port loopback dongle, 2x Joystick loopback controllers, 1x User Port loopback connector.
• Harness Only: 1x Keyboard Port testing dongle, 1x Serial Port loopback dongle, 2x Joystick loopback controllers, 1x User Port loopback connector (requires a diagnostic cartridge separately to run tests).

Professional-Grade Commodore 128 Diagnostic & Test Suite

Is your Commodore 128 or 128D exhibiting mysterious crashes, showing memory location faults, or having trouble communicating with joysticks, tape drives, or user port accessories? Banish the guesswork with our premier, professional-grade Commodore 128 Diagnostic & Test Harness Set. Handcrafted with modern low-power components, this kit helps restorers, collectors, and engineers easily verify and troubleshoot correct system functionality.

Complete Port-Testing Loopback Harness

During diagnostic routines, the testing software sends specific signals out of each physical port and expects them to loop back input-side. Without the correct loopback connectors (the harness), the diagnostic ROM cannot check the actual internal interface lines, giving you unverified ports. Our loopback harness fully tests:

• Keyboard Connector: Verifies complete scanning matrices and rows.
• Control Ports: Fully exercises pins on Game Ports 1 & 2 via logic loopbacks.
• Serial Port (IEC DIN): Verifies proper serial bus lines and interface controllers.
• User Port: Exercises parallel port input/output lines.

Modular Selection to Fit Your Test Bench

Choose the exact set of equipment you need. We offer two versatile options:

• Full Kit (Diagnostic Cartridge & Harness Set): Includes the standalone C128 Diagnostic Cartridge along with the hardware loopback harness connectors. An all-in-one out-of-the-box solution.
• Harness Only (No Cartridge): Includes the exact test loopback adapters. Ideal if you already have a functional C128 diagnostic cartridge.

Compatibility & Manufacturing Quality

• Perfectly compatible with both PAL and NTSC flat Commodore 128 systems, as well as the metal-cased Commodore 128D and 128DCR models.
• All test connectors feature high-integrity components, thick gold-plated pads, and robust casing molds for absolute reliability.
• Features strain-relieved cabling on loopback endpoints for long durability under repeat testing bench workloads.