02/21/2024

I recently received an Osborne-01 for the collection. But it was broken, of course. It would turn on, but immediately and invariably showed the message “boot error.” Not bad, but not ideal. Thankfully I already had a perfectly working unit in my hoard. Being able to swap hardware and software from a known-good system can be a pretty expeditious troubleshooting method.

The easiest thing to start was to check the CP/M system disk. Put the known-good disk in the suspect system, and the suspect disk in the known-good system. In this case, the problem stayed with the suspect system. Both disks functioned in the working system, and no disk worked in the failing system. So definitely something in the hardware.

I cracked open both units, and was initially dismayed to find evidence of previous damage/rework of the floppy drive cable (replacing that in 2024 would be a challenge). But I moved ahead with another simple swap test, just swapping the known-good Drive A between both systems. This time, the problem followed the suspect drive, so no issues with the previously repaired cable. Another swap between the suspect Drive A and Drive B proved that ONLY the one drive from the system was failing.

The Osborne-01 comes with two floppy disk drives, Drive A and Drive B, but by default will only look to boot from Drive A, as assigned by a terminating resistor block on the physical drive. Just swapping the two drives, and that terminator pack, meant this second Osborne-01 could boot and run again. A qualified success until I can further fix or replace the bad drive, but that is a project for another day.