The differences are the door, which doesn't really mater, the heads, the
linear positional, and reformat the pack. most regular packs can be
reformatted. There are 2 boards from the A which are interchangeable with
the F (most of the newer drives have them), and they have a few dip
switches that need to be changed.
Another neat option which i don't remember the part #, if the RK05 front
panel with the TU56 type rotary switches to change  the drive ID # on the
fly. I think I kept a few for myself.
On Wed, Dec 31, 2014 at 5:36 PM, Johnny Billquist <bqt at update.uu.se> wrote:
  On 2014-12-31 20:30, tony duell wrote:
  Based on some boxes of stuff I unpacked today...
 How could you quickly distinguish an RK05F spare head from a normal RK05
 spare head?
 
 I wasn't even aware that there were any differences. But I guess there
 are, as you ask.
 It's been close to 30 years since I touched an RK05F...
 But the disk being fixed was the thing I knew. Is the optical thingy that
 tells the head movement a part of the head?
         Johnny
 --
 Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
 email: bqt at softjar.se             ||  Reading murder books
 pdp is alive!                     ||  tryin' to stay hip" - B. Idol