blowing fuses

Hi all,

I installed a NEMA 23 stepper on my drill press and put on a timing
belt. I am using a 60 tooth large gear and a 16 tooth drive gear.
3.75: 1 drive ratio.

The VEXTA stepper is 5.4 volts, 1.5 amps. Unipolar.

Tried to take 100 steps as a test.

No movement, then pop, blew the 4 amp fuse on the power supply.

After the second fuse blew, I figured I better refer to a higher
authority.

I know I did something wrong, but I'm not sure what.

I was using a Chapps, serial port stepper controller as the stepper
controller.

Any ideas ?
Need more information ?

Dave