Teac FD-54

[Patrick Finnegan]

On Sat, Feb 15, 2020, 14:38 Chuck Guzis <cclist at 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

>