First of all, thank you very much for your useful information Tom.tcat wrote: Straight edged ones are usually Iss#5, the ones on your pictures might be even pre-Iss#5 ones, as they do not have two mods applied, two diodes and one track cut from the rear of the head board assembly.
Indeed they were installed on a iss5 board. Maybe you're talking about the same modifications described in the service manual? So should I apply these mods?
The other units are marked ISS6, but unfortunately these straight-edged ones have no insignatcat wrote: It would interesting to see, what issue insignia you can read on your keyed edged drive?
The strange thing is that these units are working better than the others (in my case). They can read or format cartridges (both original Psion and miscellaneous) otherwise unreadable or unformattable. Also they run tapes that are completely stuck with the other 4 drives.tcat wrote: Higher sector count during format may not possibly be too beneficial, as may result in poorer compatibility with other drives, or with the very same drive in the long run.
Maybe it's only a matter of mechanics: my ISS6 units are electronically better but mechanically worn
Interestingtcat wrote: I have coded `mSpeed', a small tool indicating drive speed, that came underway when programming `mDoubler' mDump1,2 tape cloner/dumper/duplicator.