Dear Allison,
   
   You wrote:
> I know the write current jumper well as using two of the drives in an
> amprolb (z80 system) for 96tpi/782k operation (known in the early '80s
> as DSQD) would read disks all day but could not write a reliable one
> because the write current jumper was set wrong.
   
   Oh, you mean the density select jumper! I have never heard anyone call
it the write current jumper, so I've got confused. (But it does control the
write current...) The density (the write magnetic field intensity H) is
selected by pin 2 on the interface cable. In both IBM PC AT and KA410 low
level selects H=300 Oe (for "double density" disks with iron oxide coating)
and high level selects H=600 Oe (for "high density" disks with cobalt-
containing coating). Presumably on some machines it's the opposite, so TEAC
has made this jumperable. For both IBM PC AT and KA410 set the jumper
labeled "HG".
   
> Sorry, some of the FD55GFV-55Us and one 57-U I have removed from VAXMATEs
                                                                   ^^^^^^^^
> do have that jumper.
   
   I have always wondered what is a VAXmate. Would you please enlighten me?
   
> I happen to have 6 of these and only two of them
> are identical.  There were no less than 4 different versions of the FD55G
> series and I have samples of all including an engineering sample provided
> to DEC for initial testing.  Of the four different version there are
> three distinctly different locic board varying greatly in the number of
> jumpers and position of them.  Also the lock/eject lever mech varies from
> a basic lock to a full spring loaded eject on unlock.
   
   Hmm, I have pulled 3 RX33s out of VS2000s, and all of them look
identical. The jumpers perfectly match the description from TEAC. You were
probably more lucky. :-)
   
   Sincerely,
   Michael Sokolov
   Phone: 440-449-0299
   ARPA Internet SMTP mail: sokolov@alpha.ces.cwru.edu