[Coco] FD-501 Service Manual

[Kevin Becker]

Here is a link to the service manual for the older full-height floppy drive.  I don’t know how much it will help, but the adjustment process might be similar.  It looks like it used a special diagnostic disk

http://www.colorcomputerarchive.com/coco/Documents/Manuals/Hardware/Mini%20Disk%20Service%20Manual%20(Tandy).pdf <http://www.colorcomputerarchive.com/coco/Documents/Manuals/Hardware/Mini%20Disk%20Service%20Manual%20(Tandy).pdf>



> On Feb 5, 2019, at 9:31 AM, Frank Thompson <frank.thompson.iv at gmail.com> wrote:
> 
> I'm looking for a copy (digital or physical) of a service manual for the
> CoCo floppy drives.  I recently picked up a really nice FD-501 drive and
> controller.  I have an older generation coco floppy drive (the generation
> just prior to the FD-501) that includes two drives (the original as drive
> 0, and an IBM labeled drive as drive 1).
> 
> My problem is that disks made using the upper drive (the IBM drive) of my
> old unit won't always work on the lower drive (which reads disks made on my
> new FD-501 drive just fine).  The disks read fine on my new FD-501 drive.
> I've tried the process of elimination with formatting and creating a backup
> disk with each of the drives, but I don't get a result that indicates to me
> which drive is definitely the culprit.  (The IBM drive reads disks made on
> either of the other drives)
> 
> I set/confirmed the drive speed using flourescent lamp illumination of the
> checker pattern on the bottom of the motor (60 Hz scale).  Assuming that
> this is accurate (given the tolerance of the line frequency of my household
> AC) I'd like to check the tracking adjustment.
> 
> I've not been able to really find information on the official process for
> adjusting the head tracking.  Thinking about it, it seems like I would
> adjust the tracking to achieve the highest amplitude of an analog signal at
> some point in the signal path on the drive PCB.  I really don't know, but I
> have an oscilloscope and the desire to learn (and drives that don't all
> play well together).
> 
> Thanks in advance for any info the group can provide.
> 
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