question about using the disk controller on the backplane with 2 physical drives.

[John Galt]

I just got my second disk drive operational.

I have found that there must be enough of a difference between both disk drives which are the same model but different years of manufacture to cause:

A disk I made in one drive will not work in the other.

Is there a way to calibrate a Teac FD-55GFR drive?

basically i have them setup as C: and D: drives.

I can format either drive and copy files between them.

but if i flip the disks from C: into D: or vice versa then i get a CPM error.

obviously both drives are reading and writing disks slightly different.

is this something that can be adjusted easy?

obviously its annoying to make disks and have to make sure to label them as working only in one drive and not the other.

these drives were tested in a IBM PC for a while and did not have issues with reading disks from 3 different drives. 

thanks for reading.

[John Galt]

just some information so far

Command: m1
Turning motor ON.
Measuring rotation period for drive 0... 166.672ms

Command: m1
Turning motor ON.
Measuring rotation period for drive 1... 166.651ms



Command: d0
Selecting drive 0


Command: I

Current Drive     : 0
Type              : 5.25" HD emulating Altair 88-DCDD (8" disk system)
Sync after step   : no
Number of Tracks  : 77
Number of Sectors : 32
Rotation speed    : 360 RPM
Sector length     : 5208us (soft-sectored)
Sector offset     : 2604us
Sector tail       : 424us
Read clear        : 200us
Write protected   : no
Current Track     : unknown


Command: d1
Selecting drive 1


Command: I

Current Drive     : 1
Type              : 5.25" HD emulating Altair 88-DCDD (8" disk system)
Sync after step   : no
Number of Tracks  : 77
Number of Sectors : 32
Rotation speed    : 360 RPM
Sector length     : 5207us (soft-sectored)
Sector offset     : 2603us
Sector tail       : 423us
Read clear        : 200us
Write protected   : no
Current Track     : 0

[John Galt]

would turning on "force sync after step" do anything helpful?

[John Galt]

it tried

Command: F1,1
Drive 0 flags    : 0
Drive 1 flags    : 1
Controller flags : 0
Drive 0 is type 2: 5.25" HD emulating Altair 88-DCDD (8" disk system)
Drive 1 is type 2: 5.25" HD emulating Altair 88-DCDD (8" disk system) (forced sync after step)


Command: F0,1
Drive 0 flags    : 1
Drive 1 flags    : 1
Controller flags : 0
Drive 0 is type 2: 5.25" HD emulating Altair 88-DCDD (8" disk system) (forced sync after step)
Drive 1 is type 2: 5.25" HD emulating Altair 88-DCDD (8" disk system) (forced sync after step)


Command: x

It didn't change anything between C and D disk swapping issues.

[da...@hansels.net]

The timing numbers look good to me, I don't think that's your problem.

I suspect that one (or both) of the read/write heads is out of alignment.

I had the same problem here and was able to slightly adjust the position
of the head. I used a disk written on the other drive and slightly moved
the head until it was able to read the disk. I don't know exactly which screws
I had to loosen to move the head and there are multiple versions of
that drive so unfortunately I can't help with that part.

[John Galt]

having c64 1541 flashbacks.

[John Galt]

I had a pickle of a time.

found one drive that was just too different from the others.

found 2 drives that almost worked together. half working with errors.

spent a few hours trying to adjust the alignment to make both drives work.

finally got something workable between 2 drives.

for the Teac FD-55GFR drive the newer ones, on the lower side the rear PCB has 2 screws to loosen, the entire pcb can then be moved back or forward limited by a pin cast into the case of the drive.

by moving this PCB is has the head sensor on it, moving the board then changes the track location. 

be really careful as some drives appear to be really sensitive to the location of the sensor and you can send the alignment off into LALA land, and might not be able to get it back.

be careful if you are going to build a system with 2 or more floppy drives as you might be in a situation where you can only get 2 of the drives to align to each other.

you might have good luck and find a bunch of these drives and mix and match to get a set of 4 that read close to each other to not have a problem

or you get 3 drives off ebay and all of them don't match.

with a single drive you won't know anything is wrong until you share a floppy with another person then you may not be able to trade floppy disks and will have to send the Disk image to each other instead.

really annoying.