Troubleshooting Resources, Tools, and Equipment
3-14
These procedures address the following problems:
•Hardware problems
• Shorts in data wires and priority wires
• Opens in data wires and priority wires
•Miswiring
•Voltage levels (ACC drivers)
• Cable identification
•Ground checking
Hardware Problems
The cable verification procedures for hardware problems are separated
into two steps.
The first step is performed at the ACC end of the branch and is used to
verify the functional operation of the ACC drivers and the absence of
shorts in the data wires.
The second step is performed at the SDN instrument end of the branch (IC
or monitor/terminal) and identifies opens in the data wires and verifies
proper operation of priority wires. Miswiring of blue and pink data wires
is evident. This procedure is valid whether or not instruments are
connected to the branches. Refer to the following section.
Verify Instrument End
of the Branch Cable
Check for opens between the ACC and instrument
a. Disconnect the local distribution cable (LDC) from the wall box
connector and from the instrument.
Using a digital multimeter, check the LDC for continuity, opens and
shorts.
b. If no problem is found with the LDC, power down the ACC—see page 4-
1.
c. Measure the resistance of the system distribution cable at the
instrument end as follows. Refer to connector pin illustrations shown
in Figure 3-6.
PIN A(+) — — to — — PIN E(–) = 120 Ohms (+11 Ohms; - 5 Ohms)
PIN A(±) — — to — — PIN D (GND) =
∞
PIN E(-) — — to — — PIN D (GND) = ∞
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