Diagnostic Cartridge 1541 (World of Jani) – Test and Repair of Commodore Disk Drives

A Complete Service Toolset in One Cartridge

The diagnostic cartridge for the Commodore 1541 disk drive is an indispensable tool for anyone repairing, maintaining, or simply checking the condition of their drive. The software, authored by Jani Tahvanainen (World of Jani), is designed to run directly from the C64/C128 expansion port – with no need to load anything from a floppy disk. This is a key advantage: the tested drive doesn’t need to be operational at all to initiate diagnostics.

What’s in the cartridge menu?

• Alignment Check – Quick assessment of the read/write head alignment
• Speed Check / Performance Test – Measurement and control of motor rotational speed (correct value: 300 RPM)
• Head Exerciser – Forced head movement across all tracks, helpful for dried-up mechanism grease
• Error Scan – Scanning the disk for read and write errors
• Validate Disk – Validation of disk structure and integrity
• View BAM, Sector View, Directory – Low-level media content viewing, bypassing standard DOS
• Fast Format – Quick test formatting of disks
• Disk Command, Send IO, Reverse Knock – Advanced tools for direct communication with the drive's control electronics

Who is it for?

Ideal for both professionals repairing retro hardware daily and hobbyists who want to diagnose drive issues themselves – from suspected head misalignment to unstable rotational speeds or disk read errors.

Compatibility

Works with Commodore 64, C64C, C128, C128D, and C128DCR.

Technical Specifications

• Format: 8K ROM cartridge (optimized to avoid overwriting the BASIC interpreter)

Project:
http://blog.worldofjani.com/?p=2180