I have 4 Disk II drives, but only one of them is working. I am convinced that one of the 4 is a clone, as it has a different analog board with no Apple part number on it and has asian characters on a label on the bottom. I am attempting to get at least one other working drive as I intend to sell one of my Apple II systems and want it to come with at least one good drive.
I am focusing on one of the drives at the moment, and have done some various testing with my osciliscope and the Apple Disk Alignment Aid floppy. I am a noob when it comes to using a scope, but luckily the Disk II service manual has settings for the scope in it to make it easier. So far the only issue I have for sure identified is that the amplitude is slightly under the 150 mA the manual says is the minimum. It's so close though it could be that my scope is probably somewhere around 30 years old and hasn't been calibrated in who knows how long. I cannot get the Azimuth tests to show up correctly on my scope, but I think that is an issue with my trigger control being out of whack. Also, the drive speed test on the floppy never shows the drive's speed. I don't know if this is because it is not reading the disk or not. So, I used a strobe app on my phone to adjust the speed using the wheel on the bottom. Still no dice on reading disks.
Anyways, I had the genius idea of swapping the analog board from the working drive into the faulty drive. This gives me the same issue of the drive not reading disks. So then I took the unkown condition analog board and installed it in the working drive, and wouldn't ya know, it works.
So, what test or procedure should I be looking at next to see what the issue is with the mechanism on the non-working drive? Is it possible I just have a bad read/write head? I have cleaned it multiple times already.
Thanks for any comments or expertise you send my way!