Check your floppy cable - it should have at least one 34-pin connector
(or edge-card connector) at the controller end, one (or one of each) in
the middle for the B: drive, and one (or one of each) at the A: end.

Wires 10 to 16 are cut free and turned over (counting from the side with
the stripe) at the A: end.  This changes the addressing from B: to A: -
check that you don't have a cable for MFM/RLL hard drive, as they look
the same, except that wires 25 to 29 (or so) are flipped.

With a floppy cable, as above, all drives are addressed as B:, with a
jumper shorting two pins labeled DS1 (of DS0 and DS1) *or* DS2 (of DS1
and DS2) - the second of whichever.  [You could use a straight cable, but
the idea of the flipped portion is to avoid the confusion of having to
address each drive separately.]

The original specification required that the A: drive be terminated
with (approx.) 150 Ohms - either a chip type package of resistors, or
a jumper that switched them into the circuit. The B: drive was not
terminated.  Manufacturers found that by using (approx.) 330 Ohms
terminators on all drives, that it made things simpler, avoided
confusion, and still worked well.

I've heard that if you try hard, you may force a power connector into
the socket upside down, but the "D" shape is supposed to prevent this.
Make sure the ribbon cable is connected properly.  Sometimes the wires
break - usually at the connector.  Sometimes a cable can be cut or even
shorted to ground by the sharp edges of the case - inspect carefully.
You can check them by  clamping the connectors together so that they are
oriented the same way - a big rubber band or a padded vice does nicely.
Probe the connectors with a light or beeper continuity tester and
remember the 10-16 flip.

Older floppies wear, get dirty, and go out of alignment.  It is possible
to clean and even realign them, but unless you want to make a (meager)
living by setting up a repair shop fixing other peoples' grief, don't
go further than blowing out the lint and one of those cleaning kits that
uses (water-free) isopropyl alcohol.  You can check that the floppy in
one system works without removing it by connecting it to another system
that is known to work if the CMOS setting is set for the right type.
Sometimes carelessly "beheading" a component on a floppy drive
as it is installed can cause obvious damage which may be repairable.

I gather you are familiar with avoiding static electricity - at the
least, touch the shiny metal on the power supply case to discharge
yourself BEFORE touching any other components.

Good luck.

Boyd Ramsay

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