Amstrad DDI-1 / FD-1 Service Manual

The DDI1 / FD1 Service Manual is Amstrad Consumer Electronics plc's own service manual for the external 3-inch disc system sold for the Amstrad CPC 464 — the DDI-1 (drive plus plug-on interface) and the FD-1 (second drive). 18 pages. No text layer, so values must be read from the page images.

Contents

Amstrad's own contents list:

• Technical specification; safety test
• Cabinet drawing and cabinet parts list
• Software errors
• Diagnostic flow chart
• Power board PCB
• Interface circuit diagram — 10, 11
• Circuit diagram — 12, 13
• Relay PCB — 14
• Interface PCB — 15
• Alignment checks — 16
• Mechanism — 20

What it settles

Each drive has its own integral mains power supply. Amstrad's specification states it plainly, and adds that the first drive (the DDI-1) also supplies power to the disc expansion interface through the interconnecting cable. This is the opposite of the computer itself, which takes all its power from the monitor: the DDI-1 and FD-1 are mains-powered devices with a transformer inside, and should be treated as such.

The drive mechanism is belt-driven, and Amstrad sells the belt. The cabinet parts list names the mechanism as a Compact FDD EME-150A (Amstrad part 190005) and lists, individually, the stepper motor, the head assembly, the capstan motor and a drive belt (part 190015) — along with the mains transformer 0675001E (190003), the interface connector PCB assembly (190004), the slide switch and the edge connector. A perished belt is a documented, replaceable fault on these drives.

Amstrad's own drive specification: a 3-inch system conforming to the Hitachi/Panasonic standard, with the software configured for a 12 ms step rate and 30 ms settling time; the system is designed to control a maximum of two drives; and the interface houses an expansion ROM containing AMSDOS and the machine-dependent parts of CP/M and LOGO.

The "software errors" section is a diagnostic procedure in itself. Before blaming the drive, Amstrad sets out how to distinguish a soft error from a hardware fault: re-read the track ten times or more; if that fails, step the head to the adjacent track in the same direction as it last moved and return it, then re-read; if the data still does not come back, the error is not recoverable. For write errors, repeat the write and write-check up to ten times, then test another track, then another disk — and only if the error follows the drive is the drive at fault. For seek errors the suspects are the step motor, its drive circuit, and carriage torque; recovery is a re-calibration to track 00 followed by a re-seek.

Amstrad also notes that the drive is not ready until two revolutions after the disc is inserted, which is normal behaviour and not a fault.

What this manual does not contain

• No mechanism-level repair. Amstrad states that faulty drive mechanisms are to be returned for replacement and that service agents should not attempt repairs to the mechanism or to its PCB.
• No electrical parts list with component values for the interface or power board — the parts list is the cabinet/assembly list. Values must be read from the circuit diagrams on pages 10–13.
• No text layer, so nothing can be searched.
• Nothing on the built-in drives of the CPC 664, CPC 6128 or the 6128 Plus.

Download here: Amstrad DDI-1 FD-1 Service Manual.pdf

Related pages

• Amstrad CPC 464 · Amstrad CPC 464 Maintenance Guide · Amstrad CPC 464 Troubleshooting Guide
• Floppy Drive Repair