Troubleshooting - Siemens SIMATIC NET PROFIBUS Owner's Manual

Troubleshooting

Table 6-1
LED Display
L+ 24V LED not lit
L+ 24V LED flashing
CH1 LED not lit
CH1 LED lit
But PROFIBUS nodes signa-
ling bus problems
CH2, CH3 LED not lit
CH2, CH3 LED lit
But PROFIBUS nodes signa-
ling bus problems
If none of the LEDs indicates a problem and you still encounter communication
problems (for example no confirmation, unexpected frames), check the monitoring
times set on the PROFIBUS nodes (such as the Slot Time).
For more detailed information on these parameter settings, refer to the description
of your PROFIBUS DTEs and the configuration software.
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-02
Possible Cause of Problem
- Power outage
- OBT defective
- The transmission rate could not be set
- Break on one or more wires of the RS-485 LAN cable
- Wires A and B of the RS-485 LAN able connected to wrong terminals
- Attached PROFIBUS node is defective or not sending
- PROFIBUS node not attached or attached node is not turned on
- Wires A and B of the RS-485 LAN able connected to wrong terminals
- Short-circuit on the RS-485 LAN cable
- Break on one of the wires of the RS-485 LAN cable and wires A and B con-
nected to wrong terminals
- No or wrong termination
- Send and receive FO cords swapped over
- Break on FO cord receiving receiving from partner module
- No partner module connected or partner module is not turned on
- Attached partner module is defective (not sending)
- FO connector is loose
- FO cable distance to next module too long
- Receive FO cord interrupted and disturbance caused by extraneous light
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