Calibration of 8" floppy drive?

[Jon Elson]

On 02/05/2016 08:02 PM, Dan K wrote:
> Another great tip. This plagued me for a long time, until 
> I realized that I had only one drive connected, and it had 
> the resistor network IC unpopulated. I borrowed it from 
> the other drive (they were on the same wire, so I suppose 
> that only one resistor network is necessary) and that's 
> what led to my initial success. 
Yes, the terminating resistor pack should only be in the 
last drive on the cable.
> It seems to do the job, but I still don't have a 
> replacement pad. That seems to be okay however, because on 
> one drive the head load solenoid doesn't appear to come 
> down far enough to push the disk very much. I don't think 
> I've ever seen the pad on either drive come down enough to 
> physically touch the disk--maybe just brushing it, barely. 
> What might cause this?
Probably wear, or maybe warpage of the parts over time.  The 
pressure pad should be fairly soft, usually a felt-like 
material. It needs to push the media into contact with the 
read-write head. Without it, you will occasionally get good 
enough contact to read a sector header or even a whole 
sector, but it won't be consistent. The data will come and 
go as the disk rotates.

Jon