HP 3000 Series Installation And Service Manual page 55

I
Maintenance
5-15. Off-board Loopback Testing
When support-user diagnostic testing is required beyond the
physical limits of the INP PCA boards, certain portions of the
data communications network can be synthesized. A test hood and/
or a test connector are needed for testing with certain cable
options (see table 1-2 for test equipment compatibility
information). These test attachments are used with the off-board
loopback tests described in the HP 30010A / 30020A Intelligent
Network Processor Diagnostic Procedures Manual. The test hood
and test connector are illustrated in figure 1-1 and listed
by
part number in table 1-2. The test attachments are used as
follows:
a. With the data communications cable (direct-connect or modem
cable) disconnected from the edge connector of the INP PCA
board, attach the appropriate test hood in its place. Run
Test Group 6 of DSM.
b. If Test Group 6 passes step a, this indicates that the
problem is originating farther "downstream" on the communi-
cations line. Remove the test hood, and reconnect the data
communications cable to the !NP PCA board. Disconnect the
other end of the cable, and attach the appropriate test
connector to the data communications cable. Repeat Test
Group 6 of DSM. A failing test indicates the fault is
located in the cable.
c. If your data communications system uses the modem cable anJ
if the modems include analog and digital loopback options,
testing in Test Group 6 can continue. Connect the modem
cable to the modem. Configure the computer and modem for:-
normal operation, but select the analog loopback option on
the modem. Run Test Group 6 in DSM. A failing test indi-
cates that the problem lies in the local modem.
d. Disable the loopback option on the local modem, and select
the digital loopback option on the remote modem. Run T~st
Group 6 again. A failure of this test indicates that the
problem lies with the telephone line or the remote modem.
Repeating steps a, b, c, and d on the remote computer system
will isolate the problem source.
5-12
JUN 1980