1770 Floppy Upgrade (BBC Micro)
If your floppy interface on the BBC Micro is using the 8271 you can only load 40 track disks.
There is an official upgrade guide here.
There are modern upgrade kits from places like RetroClinic, with official install guides.
In short:
Remove the yellow bridge wire if it is there (or cut it).
Replace IC79/80 with 78F38 versions (ideally, not always required).
Remove the old 8271, socket in the new 1770 upgrade.
Remove IC86 (74393), and add a bridge wire between pins 1 and 4.
If IC87 (near the rear) is missing, bridge pins 9 and 12. If it is present, leave it in and do nothing with it.
Finally, replace your old DFS ROM (usually 0.9)...
With DFS 2.26 or Watford1.54.
Now you should be able to use and read/write/format 80 track disks.
If you have issues with reading/writing/formatting you can also try changing the DIP switches on the keyboard PCB. Pins 3 and 4 can both be set high or low, to change the speed of the drive. Find which works for you.
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