User`s guide

158 Hard Disk ToolKit• Personal Edition Reference Guide
Hard Disk ToolKit• PE does
not recognize a device on
the SCSI bus after bus
rescan.
Is the device getting power? Check the power indicators on the device. For example, for an
internal hard disk, you should see the LED turn on (if it is
externally visible) and hear the drive spinning up. If you have
an external hard disk, you should also hear the fan inside the
device spinning.
You might be having problems with
cabling on the SCSI bus.
• Are the cables connected properly?
• Are the cables still working properly?
• Are there any burn marks on the
connectors?
• Do all of the cables have the same
impedance?
• Make sure the cables and connectors are seated properly
and that there are no bent or broken pins on the
connectors. These pins are especially delicate on 68-pin
Fast & Wide SCSI-2 connectors.
• Bad cables aren’t always visible. To check for bad cables,
try swapping cables with ones that you know work
properly.
• Burn marks indicate arcing, which can happen if the
connectors are not seated properly.
• Be sure to use SCSI cables with the same impedance.
Some devices won’t boot up unless all
devices on the SCSI bus are turned on.
• Were the devices on the SCSI bus
powered on before the computer?
• Are all devices on the SCSI bus
powered on?
Make sure all of the devices on the SCSI bus are turned on,
then restart your computer with the Restart command in the
Finder’s Special menu.
To prevent this in the future, power on all SCSI devices first,
wait a few seconds, then power on your computer.
You might have problems with the SCSI
bus configuration.
• Are the SCSI IDs set properly?
• Was the SCSI bus terminated
correctly?
• Is the device the last device in a long
SCSI chain?
• Make sure each device on the SCSI bus has a unique ID.
• Make sure that only the first (internal) and last
(external) devices on the SCSI bus have a terminator
attached to them.
• Try attaching just the device in question to the SCSI bus. If
the system then recognizes the device on the SCSI bus,
your SCSI chain might have been too long (6 meters, or
20 ft., maximum), there might be a bad cable, or there
might be some other communications problem.
Sometimes SCSI chips on computers fail
and cause failures.
Test the device on another computer.
If you’re running System 7.5 or later, SCSI
Manager 4.3 can cause SCSI problems for
some users.
If you continue to run System 7.5, disable the SCSI Manager
4.3 extension. You can use SCSI Manager v. 4.3.1 on the
Quadra 840
AV
or newer. Upgrading to System 7.5.3 can also
help with this problem.
Table 1. Troubleshooting
Problem/Question Potential Cause Solution
7. HDT2 Troubleshooting Page 158 Friday, June 6, 1997 3:12 PM