Service and troubleshooting
8.12 EST3 Installation and Service Manual
When trying to isolate trouble on a network or audio data circuit,
remember that both shorted and open circuit segments will
interrupt communication between two CPU modules.
Figure 8-4 shows an open or short circuit fault between cabinets
3 and 4.
NETT
2.
DR
Circuit Fault
open or short
1 2 3 4 5
Figure 8-4: Network data circuit fault
Either an open or shorted circuit will interrupt communication
between cabinets 3 and 4. The token ring network will
reconfigure and operate as two independent sub-networks, one
consisting of cabinets 1, 2, and 3; the second consisting of
cabinets 4 and 5.
Due to the isolation between cabinets, during a ground fault
condition, the number of potential circuits to be investigated is
limited to those originating from a single cabinet.
Table 8-5: CPU troubleshooting
Problem Possible cause
RX1 or TX1 off 1. CPU not firmly seated in rail connectors
2. CPU failure
RX2, TX2 or RX3, TX3 off, or
both pairs off
1. (+) and (-) wires reversed.
2. Circuit not properly terminated
3. Network A and Network B circuits crossed
4. Improper wire installed
5 Ground fault
6. 3-RS485 card loose
RS-232 port (J5) inoperative 1. TX and RX wires reversed
2. CPU and peripheral device baud rate mismatched
3. PC improperly configured
Ancillary RS-232 port (TB2-1
to 4 or TB2-5 to 8) inoperative
1. TX and RX wires reversed.
2. CPU and peripheral device baud rate mismatched
3. Peripheral device off-line or improperly configured
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