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Apple 5.25" Drives
The Disk II (and many other Shugart-based drives) uses a little ball bearing that rides in a groove. Dirty rails can add enough resistance that the ball pops out of the groove and can no longer track. And then when the head is zeroed, it spins the groove in the other direction and catches the ball bearing again.
Cleaning the rails with isopropyl alcohol and then lubricating them with a very light coating of silicone lubricant can usually fix the problem.
Another common problem is that the disk used for the test is not completely formatted. Frequently this happens because the same disk is used for the Profile Drive operation, which erases some tracks when trying to find the maximum reachable track. Try using the Disk Writer function to format the disk.
Typical spindle motor power consumption is about 160 mA. If your drive is reading high, it probably means that the spindle is sticking, causing the motor to work too hard. The best treatment is a bit of silicone lubricant applied to both ends of the spindle. If you have spray lubricant, spraying it directly into the drive can be very messy, so apply it to a microfiber cloth or other applicator before dabbing it on the spindle ends. You may have to wait for it to work its way inside, so do one end, wait, then flip the drive to do the other end.
⚠️ WD-40 is not recommended. WD-40 is a combination of Stoddard solvent and light mineral oil that just attracts dirt and gums up over time.