Adding a floppy disc drive to the IM-403

The IM-403 contains a bay for adding a floppy disc drive.  Unfortuanetly, the drive required is this REALLY tiny drive made especially by Epson for the IM-403.  If you can track down the correct model, the SMD-1140, go for it.

I decided to add a stock PC 3.5" floppy disc drive.  Due to size constraints, I needed to mount my disc drive in a bracket bolted to the top of the IM-403 chassis.  Since the IM-403 floppy disc interface uses a non-standard data and power connector, I had to add a floppy drive data cable between my disc drive and an I/O card that I plugged into the IM-403's ISA slot.  Check this page for details on adding an I/O card.

Since the drive sits on the outside of the case, I had to use a Dremel tool and cutting disc to cut a slot in the lower left edge of the chassis top, to allow room for the data cable to come out of the chassis.

Whenever you use a Dremel tool, BE SURE TO WEAR EYE PROTECTION!  I've had cutting discs shatter on me before, and you can be blinded if you aren't wearing goggles when that happens!

I also needed to connect the floppy disc drive to a source of +5 and +12 VDC.  These voltages, plus ground, appear on the following pins of the ISA slot:

Ground  --  B1
+5 VDC  --  B3
+12 VDC  --  B9

If you use the SIIG SI-1132+ I/O card, as I did, pin B1 is labeled on the silk-screen along the card edge near the I/O bracket.  If you use a different card and the silk-screen doesn't tell you where B1 is located, hold the I/O card with the edge connectors pointing down and the I/O bracket towards your left.  In this orientation, B1 is the edge finger closest to the I/O bracket; the remaining edge fingers (plated or not) on that connector are labeled B2, B3... in order.

I built a one-foot long three-wire cable to carry power to the floppy disc drive.  I soldered one end of each wire to one of the above pins, using as little solder as possible and keeping the connections as close to the solder mask as possible.  DO NOT get any solder on the lower portions of any edge finger, as this will contaminate the connection when you later seat the card in its slot.

I then added a four-wire floppy disc power connector to the other end of the cable.  Observe the correct locations for +5 and +12 VDC when you wire this connector.

I plugged the data cable and the power cable into my floppy disc drive and bolted the drive into its bracket on the top of the IM-403 chassis.  I also jumpered the SI-1132+ card so its floppy drive controller was enabled.  Then I powerd up the IM-403 and used its System Configuration Utility to disable the IM-403's floppy drive (under Preferences). Done!

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