On Sat, Feb 15, 2020, 14:38 Chuck Guzis <ccl...@sydex.com> wrote: > On 2/15/20 10:47 AM, Patrick Finnegan wrote: > > > I'm not sure why the index sensors on both are broken, but not the write > > protect notch sensors. Hopefully once the replacements arrive, replacing > > that will fix the drives. The drives look pristine on the inside. > > The biggest (and most misleading) issue with optical index sensors tends > to be dirt. The phototransistor or LED gets obscured by crud and ceases > to operate, even though electrically, it's fine. >
In this case, the sensor seems to be stuck "on" as if it were receiving light all the time, so I don't think it's an alignment issue. I verified by pulling the disk out, checking the LED was working, and playing with the alignment of the sensor. I got no change in the output according to my scope. Moving the disk in and out to block/unblock the light from the write protect notch let me verify that that sensor was working correctly. > The same phenomenon accounts for many so-called "alignment" issues with > floppy drives--the track zero sensor gets crud and the position at which > the sensor is interrupted changes. It's a mistake to attempt to > re-align a drive before cleaning the sensor. In reality, most floppy > drives do not exhibit drifting alignment. > The track zero sensor works fine (I could manually move the head and get it to track back, and the drive doesn't have a spec of dust in it. As usual my stuff is the atypical case. :) Pat >
