In devices with a moving coil there are no pre-fixed positions. Instead, they use a special guidance system (positioning), which accurately brings the heads to the desired track.
The system of precise guidance of the heads on the tracks is called a servo drive, and for its operation a feedback signal is required that carries information about the real relative position of the tracks and heads.
Temperature fluctuations do not affect the accuracy of the drive. When compressing and expanding disks (rotation, temperature), all changes in their sizes are monitored by a servo drive and the positions of the heads are adjusted. To search for a specific track, auxiliary information (servo code) pre-recorded on the disc is used. Since the servo code is read continuously, changing the disk size under the influence of temperature causes the head to track changes in track positions and data loss.
As a rule, servo codes are recorded on the media by the manufacturer and are not changed during the entire period of its operation. It is also known that recording servo codes requires very accurate, expensive equipment that uses a laser sight to accurately set the heads, and the distance between the positions where servo codes are recorded is determined by the interference method, accurate to a fraction of the laser wavelength.
Unfortunately, there is no information, and Iomega does not publish it – about the structure of servo codes and their locations on tracks. We know that service information is stored on special, closed to the user tracks of the cartridge disk, known as Z-tracks. There are 4 of them, on each side two, and one of them is duplicate. When all of these four Z-tracks are damaged, there is no way to read any data from the disk and information is lost forever.
Moreover, there are no known means of restoring or changing dead Z-tracks of the cartridge. They probably can only be revived by the manufacturer. It is precisely with the Z-tracks that the problem is called the “click of death”.
Clicks – an audible sign that the device has problems accessing data stored on a floppy disk. In the event of such problems, the Zip drive will recalibrate the heads, i.e. returns the carriage with magnetic heads to its original state, and then again brings the heads to a position above the diskette to ensure stable reading of servo tags and writing information to disk. In this case, not only is a repeated attempt to reliably close the feedback on more stable reading of information on a diskette, but also the “wiping” of the heads takes place to remove magnetic particles from them and eliminate the electrostatic charge accumulated on them.