Help with calibration of stepper motor of Disk II

Submitted by Gabriel Montoya on September 14, 2026 - 6:45pm

Hello everyone, I am new to the group. I joined as I became a proud owner of an Apple Ii+ which I have been restoring and making it work again. 

I am currenly using a Yellowstone disk card an a flopp emu as my main software devices as the Disk II I have is not working. I have used Claude and other AI, searched every online resource available to fix issues with microchips, cleaning, lubricating, calibrating speed etc. I seem to be close, as the drive is almost in working condition. I run some of the utility programs and the drive passes all or most tests , but when it comes to actually read a disk (or write) on the drive, i get an I/O error. The culprit seems to be the stepper motor is misaligned, (not finding sector 17) so i ran some hand coded programs to manually try to calibrate the motor by slightly rotating it etc. but I have not been able to find the "sweet spot". I was researching in the forus and it seems at some point someone had published a few pages of instructions and images of how to calibrate the drive, but they are not accesible anymore (they are from 2012). I am happy with the EMu as is very convenient, but I miss the actual feel of inserting a physical disk! If anyone here has experience with this issue and can provide some guidance I would greatly appreciate it.

Thanks,

Gabriel

 

 

Tags: 
Disk II
Apple Ii+
Stepper motor
Content Type: 
Hardware Guides

Comments

Submitted by robespierre on September 15, 2026 - 12:23pm.

The alignment of the stepper motor is what determines if a drive will be compatible with disks made with other drives.

Two consequences follow immediately from this:

  1. To calibrate a drive, you need a reference disk made with a correctly-calibrated drive. There were very expensive Alignment Disks used by technicians to align drives using an oscilloscope, but any factory-created disk can be used in a rough way.
  2. You don't need a calibrated drive to format and use disks on the same drive. 

Submitted by Gabriel Montoya on September 15, 2026 - 2:49pm.

Thanks for the suggestions. I have been using an original DOS 3.3 diskette whcih should be ok for a Apple II Disk from 1979. As I mentioned, all tests with software  come out correct, but when I try to INIT a disk in the Disk II it gives me an I/O error. All the research I have done points to miscalibration of stepper motor and failing to read track 17, but it could be something else. The Aligment disk/oscilloscope may be out of my skill set.

 

Submitted by robespierre on September 25, 2026 - 4:38am.

Every interaction I have ever had with "AI" has included wrong answers that it only changes after they are pointed out. Conclusion: you cannot depend on the tool to steer a conversation, the user must be more knowledgeable on the subject, or the answer will simply be the wrong one.

Your disk interface and drive is unable to read or write, is that what you are saying? So it doesn't work at all. Why do you say things like "passes most tests"? What testing are you talking about? What chain of reasoning, exactly, leads you to the stepper drive motor, which until its mounting was loosened by you, was most likely aligned by the factory?