Commodore 1541: Encyclopedia II - Commodore 1541 - The drive head misalignment issue

Commodore 1541 - The drive head misalignment issue

The drive-head mechanism was notoriously easy to misalign, and had a tendency to make a 'machine-gun' rattle when out of alignment or when formatting a new disk. Some people even wrote code to vibrate the head at different frequencies to play simple tunes such as Amazing Grace. The most common cause of the 1541's drive head knocking and subsequent misalignment, however, was copy prevention schemes on commercial software.

The main cause of the problem was that the disk drive itself did not feature any means of detecting when the read/write head returned to track zero. Accordingly when a disk was formatted or a disk error occurred, the unit would physically drive the head 40 tracks to track zero (although the 1541 only used 35 tracks, the drive itself was a 40 track unit). Once track zero was reached, the head would be physically rammed against a solid stop. This ramming gave the characteristic 'machine gun' noise and would, sooner or later, throw the head out of alignment.

Adapted from the Wikipedia article "The drive head misalignment issue", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki