Apple Hard Disk 20 Service Source

The Hard Disk 20 volume of Apple's Service Source is a 19-page take-apart document for the Apple Hard Disk 20, the 20 MB drive that connects to the Macintosh external floppy port over Apple's Directly Connected Disk protocol; it is not a SCSI device. The PDF was created on 5 December 1995.

Contents

• Take Apart (PDF pp. 2-17): Cover, Controller Board, Bottom Shield, Fan, Power Supply, Hard Drive. Each procedure lists the parts to remove first, so they run in that order.
• Exploded View (PDF pp. 18-19).

The cover procedure uses a Torx screwdriver, a jeweller's screwdriver to release the tabs and the Macintosh pull-apart tool, with the caution "Do not use a screwdriver to separate the case." The hard drive procedure warns that the drive cable is not a standard ribbon cable and that an incorrect cable will seriously damage the drive or the controller board.

What this manual does not contain

There is no Basics, Specifications, Troubleshooting or Adjustments chapter: no capacity or transfer figures, no supply voltages, no symptom chart, no parts list, no schematic and no component values. It does not describe the DCD interface; the Apple Directly Connected Disks Specification gives the DB-19 pinout, the 489.58 kbit/s line rate and the fact that the drive is self-powered.

Apple's earlier Hard Disk 20 Technical Procedures (1985-86), also hosted here as File:Apple Hard Disk 20 Technical Procedures.pdf, has what this volume lacks: setup and switch-off procedure, diagnostics, a troubleshooting flowchart, startup and daisy-chaining problems and a parts list with Apple part numbers. The two differ on the fan: this volume gives two fan screws and the rotation arrow pointing down, the Technical Procedures four screws and the arrow pointing up. Both put the air-flow arrow to the rear of the case.

Pages that cite this document

• Apple Hard Disk 20 Maintenance: the disassembly order and Apple's cautions.
• Apple Directly Connected Disks Specification

Download: Hard disk 20.pdf