Editing Amstrad CPC 664 Maintenance Guide (section)

== Head Alignment ==

The Hitachi 3-inch drive has factory-set head alignment that does not normally drift. Alignment is checked with a calibrated alignment disc (commercially '''Dysan 224/2A''' was the contemporary standard; modern equivalents are rare). For most field service:

* If the drive reads commercial diskettes reliably but fails to read user-formatted diskettes, the user-format diskettes were probably written by a misaligned drive. Reformat fresh diskettes from the suspect drive and test those.
* If the drive cannot read any commercial diskettes, suspect: drive belt (most common), head dirt, stepper lubrication, or in rare cases the head itself failed. Alignment is the last suspect.

If alignment is genuinely off, the procedure requires a service-grade alignment disc, a service-grade oscilloscope and the Hitachi alignment procedure from the drive service manual. This is normally beyond field service and the drive is typically retired in favour of a replacement.