Commodore 64 Diagnostic Kit

• Full Kit: 1x switchable 2-in-1 Diagnostic / Dead Test Cartridge & 1x Keyboard Port testing dongle, 1x Serial Port loopback dongle, 2x Joystick loopback controllers, 1x User Port loopback connector, 1x Cassette Port tester.
• Harness Only: 1x Keyboard Port testing dongle, 1x Serial Port loopback dongle, 2x Joystick loopback controllers, 1x User Port loopback connector, 1x Cassette Port tester.
• Cartridge Only: 1x Switchable 2-in-1 C64 Diagnostic / Dead Test Cartridge.

Professional-Grade Commodore 64 Diagnostic Suite

Is your Commodore 64 having boot issues, displaying memory bank errors, or failing to interact with serial devices and joysticks? Our comprehensive Diagnostic and Dead Test suite represents the absolute pinnacle of repair utilities for hardware enthusiasts, hobbyists, and professional restorers. Available in multiple highly functional options—ranging from cartridge or loopback harness components up to a complete all-in-one bundle kit.

2-in-1 Switchable Diagnostic & Dead Test Cartridge

Our custom hardware features a convenient external toggle switch allowing you to seamlessly swap between the highly critical C64 Dead Test ROM and the classic C64 Diagnostic ROM (rev. 586220).

• Dead Test Mode: Essential for completely dead systems that show only a blank black screen. This utility bypasses standard system ROMs and executes directly inside low RAM space to issue visual flashes mapping out exactly which SRAM/DRAM chip of the 8 RAM locations is dead.
• Diagnostic Mode: Runs full systematic operations including CPU instructions, SID chip waveforms, CIA timing limits, color RAM spaces, and port integrity checks.

Full Port-Testing Loopback Harness

To run complete assessments, the original diagnostic software must receive loops back through its input-output ports. Our precision-engineered, hand-crafted port testing harness feeds the output lines directly back into the system's inputs to check full read-write pipelines. This custom-made harness allows you to completely test:

• Keyboard Connection: Tests the functional row-column scanning.
• Serial Port (IEC DIN): Verifies disk drive lines and operational channels.
• Control Ports (Joystick 1 & 2): Pinpoints short circuits or faulty control chips.
• Cassette (Tape Port) & User Port: Fully loops read lines, motor signals, and general logic operations.

Every piece is manufactured with professional circuit boards, strain-relieved cables, and is meticulously tested before shipment for immediate plug-and-play operation.

Broad Compatibility

• Compatible with all Commodore 64 (C64) models, revisions, and power specs (including PAL and NTSC versions).
• Compatible with the Commodore SX-64 portable computer (harness requires standard connector accessibility/clearances).
• Works directly alongside original standard hardware and custom modernized replacements (such as our standard cooler or gold-pin PLA replacements).