SCSI CARD

In Win98 2nd. I am trying to connect a CanoScan 300 flatbed scanner to my computer. The instant I connect the scanner cable to the computer SCSI the scanner shuts off as if a circuit breaker had tripped. I’ve tried two different SCSI’s and get thesame results. I removed the SCSI card from the computer and with the scanner swtich on connected the cable to the SCSI and it shuts the scanner off. If make all the connections the I am not able to turn the scanner on at all; before or after the computer boots. Why