To know for certain, you need a reference diskette and an oscilloscope attached to the head amplifier.
You will see the peaks and valleys as it attempts to read track 0. I say reference, because you need to know what the waveform looks like on the oscilloscope with a known good disk, and known good drive. This is your "control".
A mis-aligned drive will have low peaks or even none at all if its completely between tracks.
I haven't done much with Mac drives on alignment issues, but I have done a shitload of laptop and especially PS/2 drives back in the day as a kid just starting out, and I used to have a jig to keep the drive running while I was probing. What I noticed with old PS/2 drives, is the stepper motor locking screw backs out and the motor moves ever so slightly, Thats just enough to knock it out.
But even the initial seek is just enough.
What you do is physically unlock and turn the stepper motor right or left until the peaks begin to top out. You will have high frequencies in the peak as well. If you cant pull in the high frequencies, the head is worn out. If you get nothing no matter how hard you try, well, you have a bad head amp IC. These days its all in 1 IC so I usually have to probe at the head and crank the scope all the way up.
Alignment movement is VERY very touchy, If a stepper motor has a 3.6 degree step, you know your alignment will be within a magnitude of 3.6 degrees, or youll move the head into the next track! and it will be a full track off.
Also I should point out, that rotational speed is another factor. Its much much much more rare, but it CAN happen. if the motor cant get up to speed, you will have what appears to be the exact same problem! and the scope again will figure that out because you will be peaked but the frequencies are stretched.
I would also like to point out that all Mac floppy drives have micro radial electrolytic capacitors on the PCB, and if they are reaching the point of going bad and leaking, well....
