714 Local Work Station Cable Ohmmeter Test
DANGER
Do
not work with cables during an electrical storm.
Station protectors must
be
removed before using this procedure.
1.
Set the ohmmeter to the times
10
(xlO) scale.
2.
Disconnect the cable to be checked from the system unit.
3.
Measure the resistance between each pin
of
the cable and the ground shield
of
the cable. This
measurement assumes a properly terminated display and printer.
a.
If
the resistance
is
less than
20
ohms (short circuit) or more than 200 ohms (open circuit), repair or
exchange the cable.
b.
Verify
that
the display protectors are present
if
resistance
is
more than 200 ohms (open circuit).
4.
Measure the resistance between the two pins
of
the cable.
If
the resistance
is
less than
80
ohms (short circuit), repair or exchange the cable.
5.
Disconnect the cable being checked from the last work station on the port. The system unit end
of
the
cable should still be disconnected.
6.
Measure the resistance between each pin
of
the cable and the ground shield
of
the cable.
If
the resistance
is
less than 200 ohms (short circuit), repair or exchange the cable. A low resistance can
also
be
caused by a terminating resistor on the plannar board in a display station.
7.
Measure the resistance between the two pins
of
the cable.
If
the resistance
is
less than
200
ohms (short circuit), repair or exchange the cable.
8.
At
the work station end
of
the cable, jumper phase A
of
the connector to the shield.
At
the system unit end
of
the cable, measure the resistance between phase A and the shield.
If
the resistance
is
more than
200
ohms, phase A and phase B are reversed. Remove the jumper and
repair the cable.
Shield
Phase B
Phase A
R36B120·0
Section
7.
Local
Work
Station Procedures 7-15
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