|Looking for CoCo help? If you are trying to do something with your old Color Computer, read this quick reference. Want to contribute to this wiki? Be sure to read this first. This CoCo wiki project was started on October 29, 2004. --OS-9 Al|
This page was last updated on 12/23/2013. Total Pages: 716. Total Files: 985.
the 26-3022 Mini-Disk System was the first production release of a disk controller/drive for use with the original Color Computer.
The controller is based on the Western Digital WD1793. It features an analog data seperator circuit, infamous for its inherent unreliability and has multiple potentiometers which are used to calibrate various delay and timing features of the disk-side interface. It requires a +12 volt DC supply to operate, and is thus not compatible with a CoCo 2 or 3 unless a Multi-Pak Interface (or other source of +12V) is used or the CoCo or controller are "hacked", also contains the Disk BASIC ROM chip, and the necessary interface logic.
The 26-3022 controller was though to be the only one capable of being modified (though with considerable difficulty) to allow use with high-density 3.5" floppy drives. Early 26-3029 controllers had a Fujitsu MB8877A (5-volt only equivalent of the WD1793) and are also capable of HD drive operation. Mike Pepe has a page showing how he upgraded a 26-3029 controller: 
All subsequent controllers use the WD1773 controller chip, do not use the unreliable analog data separator, do not require +12V (so they will work with any CoCo model), and are capable of double-density operation only.
The disk drive is a TEC (Tokyo Electric Corp.) (or Texas Peripherals?) drive mechanism unit encased in a gray-silver-colored enclosure, matching the exterior of the original CoCo (and other early TRS-80 machines and peripherals). The drive unit stands vertically, making it taller than it is wide, with a simple linear power supply and a 5.25" full-height, single-sided (in most cases), double-density, half-height (in most cases) floppy drive. The drive is capable of accessing about 37 tracks, so a 35 track limit was imposed in Disk BASIC. This resulted in a capacity of approximately 160 kilobytes per disk.
The drive unit has an AC power, power switch, fuse and power cord and in the front an activity LED.
A captive (in most cases) ribbon cable exits the drive unit, terminated in a 34-pin card-edge connector which attaches to the controller pak.
Even though the drives and controllers were sold as packages, they can be interchanged almost universally.
These drives are not the most robust, and many that are out there are probably in need of work. (if they work at all)