In Case Of Failure - HP 27140A Hardware Reference Manual

In Case of Failure
Troubleshooting
4-2 Troubleshooting
If the I/O channel fails, and does not allow the results to be read from the
host, an LED mounted on the board may be used to interpret the test
results. If the optional test hood is in place, a second LED mounted on
the hood itself also shows whether the tests were successful. Using the
test hood does not change the length of time that the self test takes to run.
The LED mounted on the board (and the one on the hood)
will
light up
for approximately 2 seconds, go out and blink again if the test was ex-
ecuted due to a RESET (or power on) condition. This sequence
will
repeat up to five times while the computer verifies backplane operations.
A second method for initiating self test is through the DEVICE CLEAR!
DEVICE ENABLE sequence, which will light the LED(s) for 13 to 15
seconds. In either case, if the LED fails to go out, self test has failed.
In the event the board fails the EPROM-controlled self test, repeat the
operation (RESET or DEVICE CLEAR/DEVICE ENABLE) using the
on board LED(s) to verify the failure. You should call your HP Customer
Engineer and give him the results of the self test. This
will
enable him to
resolve any problem more quickly.
Since the MUX is the hub of a network of devices, including the host com-
puter, it may appear to malfunction when another device has actually
failed. When you are faced with such a failure, the troubleshooting tree in
FIgUre 4-1
will
help isolate the problem.
When checking the device protocol settings, you should also check the sys-
tem control panel for error status messages.
When we ask you to test the terminal, remember that all Hewlett-Packard
terminals have a self-test function built in. For terminals built by other
manufacturers, you will have to refer to their literature to determine how
to test the terminal.
When checking the RS-232-C physical connection, you should check the
cable connector on the card and at the RS-232-C Junction Panel, and each
peripheral cable as it leaves the junction panel. You should also check the
connection at the peripheral connector. Check the continuity of the
cables; rats and mice like to chew on them.
When you try another cable, you should use a known good cable in place
of the one being tested. This might mean "borrowing" one from a device
that is working. Likewise, the card-to-junction panel cable can be ex-
changed for one from another working MUX card.