BBC Mirco Dual Disk Drive 40/80 track selection issue
Hello Everyone,
I have what I feel is a very specific issue with a dual drive unit that I have connected to my BBC Model B micro.
The two drive unit uses Mitsubishi M4853-342M drives as in this article I’ve been reading.
https://forum.winworldpc.com/discussion/13282/bbc-floppy-drive-config-for-ibm-pc-compatible
The drives I have are stacked and the number of tracks for each drive is controlled by a switch on the rear.
The issue I have is that the top drive (drive labelled B and 1/3) will not switch to 40 tracks. The bottom drive (A), when the switch is moved to the top position will switch to 40 tracks.
I believe the switch is wired correctly. You can see that the two green wires from the switch (drive A) and the two orange wires (drive
are both at 80 tracks in the switch bottom position, then in the middle Drive B should be 40 (as the connection on the orange wires is broken) and then in the top position both wires are broken and both drives should be at 40 tracks.
I have tested both drives with disks that work in 40 track and others that work in 80 track setting which is how I know the top drive (B) is not playing ball.
What I have noticed is that if I disconnect the wires from the switch, the green wires are an open circuit and the orange wires are closed (so my continuity test makes a beep for the orange wires), so I have made the assumption that this is why that drive B is remaining at 80 tracks no matter what the switch position is.
Other than that the drives will read and write, but I sometimes need the ability to have both drives at 40 tracks and this currently isn’t possible.
I have included a set of photos and hope that someone can help me please.
https://photos.app.goo.gl/vDAWyeFe2LWqFoRY6
Thanks
Chris
I have what I feel is a very specific issue with a dual drive unit that I have connected to my BBC Model B micro.
The two drive unit uses Mitsubishi M4853-342M drives as in this article I’ve been reading.
https://forum.winworldpc.com/discussion/13282/bbc-floppy-drive-config-for-ibm-pc-compatible
The drives I have are stacked and the number of tracks for each drive is controlled by a switch on the rear.
The issue I have is that the top drive (drive labelled B and 1/3) will not switch to 40 tracks. The bottom drive (A), when the switch is moved to the top position will switch to 40 tracks.
I believe the switch is wired correctly. You can see that the two green wires from the switch (drive A) and the two orange wires (drive
are both at 80 tracks in the switch bottom position, then in the middle Drive B should be 40 (as the connection on the orange wires is broken) and then in the top position both wires are broken and both drives should be at 40 tracks.I have tested both drives with disks that work in 40 track and others that work in 80 track setting which is how I know the top drive (B) is not playing ball.
What I have noticed is that if I disconnect the wires from the switch, the green wires are an open circuit and the orange wires are closed (so my continuity test makes a beep for the orange wires), so I have made the assumption that this is why that drive B is remaining at 80 tracks no matter what the switch position is.
Other than that the drives will read and write, but I sometimes need the ability to have both drives at 40 tracks and this currently isn’t possible.
I have included a set of photos and hope that someone can help me please.
https://photos.app.goo.gl/vDAWyeFe2LWqFoRY6
Thanks
Chris