View Full Version : Osborne One, faulty B drive

June 15th, 2017, 05:13 PM
Hi everybody,

I have a problem with the B drive on an Osborne One with the Double Density and 80 cols. add-on cards: when I try some commands, like a diskette copy A -> B, the header repeatedly hits the zero track, with a characteristic noise ("trrrrrrrr").

I swapped the floppy PCBs between A: and B: (of course moving the resistor stack who acts as switch for A: and B: ) without luck. It seems the problem is something concerning the mechanic. The disk and the header motors apparently work, the floppy disk spins (I'm not sure if the speed it's ok) and the head moves.

I checked the microswitch and the IR leds and diodes.

Sometimes the B: drive presence affects the A: drive behavior: during the boot phase the B: drive led lites a little bit and the A: drive doesn't work (BOOT ERROR, read error, etc.) but if I remove the flat cable from the B: drive PCB, the A: drive works fine. This is a random issue, usually the A: works fine even with the B: drive connected.

One more strange behavior. If I try a copy from B: to A:, the B: drive doesn't do anything (dead drive). It remains dead even if I switch off the computer, then switch it on again, boot and try an A: to B: copy command.

Any idea? Maybe something related with the DD add-on card?

June 17th, 2017, 11:17 AM
Solved the most tricky issue: when the head moved, its cable felt between the head mechanism and its rail, preventing the head from reaching the zero track position.
Moved the cable in a safer position, and the B: drive magically started to work.
The other problems simply disappeared. I suspect there are some connection issues between the motherboard and the add-on board.


June 17th, 2017, 11:26 AM
Good to know that you've fixed it. Most floppy problems eventually turn out to be mechanical, in my experience.