IBM 1PA, Operational, Installation, And Maintenance Manual

Page: 63 / 108

8. All the devices are terminated. The resistance between the Phase A and
Phase B connectors must measure 110 ohms
±
5%. The resistance between
Phase A and the Shield and between Phase B and the Shield must measure
55 ohms
±
5%. For an illustration, see Figure 4-1. If either of these
measurements is out of specification, the device is not terminated correctly and
will not work reliably.
Figure 4-1. End View of Female Connector
Debugging the 7299
To debug the 7299, check the first item in the list first, and then continue through
the list until you resolve the problem. For each list item, the potential causes of
failure are given.
Models 2EN, 2EX, and 2FX
1. Check whether the power LED on the front of the 7299 is on:
Ÿ
If the LED is not on, continue with step 2.
Ÿ
If the LED is on, continue with step 3.
2. Check the LED on the AC power adapter. If the LED is on, check the
connection between the AC power adapter and the hub:
Ÿ
If the connection is faulty, reconnect the AC power adapter to the hub. For
an illustration, see Figure 3-1 on page 3-3.
Ÿ
If the connection is
not faulty, try using the hub with a different AC power
adapter. To obtain service or a replacement AC power adapter, contact
your IBM service representative.
3. Check the host port LED. If the host port LED is not on:
a. Check that the cable in the host jack is active.
b. Check whether the host is active.
c. Check the cabling from the host for the problems that are described in
“Potential Problem Areas” on page 4-12.
d. Perform the steps in “Debugging the 7299 Cabling” on page 4-9.
e. Replace the faulty 7299.
4. If the problem is still not resolved, call Technical Support. For more
information, see Appendix A, “Technical Support” on page A-1.
Chapter 4. Troubleshooting
4-7