Drive misalignment is something that doesn't usually happen all at once. It's normally a gradual process that begins with occasional disk errors (bad disk or intentional errors from copy protection) while loading (red LED flashing), failure to work with some programs, or excessive head chatter (the drive getting "lost" and having to go back to track zero to "find" it's place again.) Drives are forced out of alignment mostly while hot from extended use. Heavily copy protected programs or disk errors can cause the head to chatter against the track zero stop repeatedly. If the alignment is far enough off, you will get "FILE NOT FOUND" errors and red LED flashing with all disks, and the drive may try several times before "giving up". Note that misalignment will cause read errors with known good disks but such a drive will probably still be able to format a disk and read it back again. A disk formatted on a misaligned drive will not read properly on a correctly aligned drive.
To properly realign a drive, you need special software. I use "1541/1571 Drive Alignment" by Free Spirit Software. The flipside of the program disk is the alignment disk, and as such, should not be copied. A copy is only as good as the drive that made it. The program provides a menu screen that indicates what track you're on, drive speed, etc. You make adjustments to the drive while watching the screen. The instructions even tell you how to load the program when nothing else will load. You can -check- the alignment of the drive without taking it apart, but of course realignment requires disassembly. I always final-check my drives with several different program disks to verify alignment... any commercial program disk can be used to do that.
Drive speed can drift over time, but it's rather rare to find it off far enough to cause problems. Spindle speed (Note: some drives have no adjustment) is reset with a small screwdriver adjustable control on a small PC board near the spindle motor. On older belt-driven spindle motors, the belt may be slipping. On all drives, the spindle collar (clamper) can get sticky and a tiny bit of lube helps. Don't overdo lubrication. Excess oil will be thrown off and could get on the disks.
-- Ray Carlsen --
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