Check the installation

1. Confirm that A and B are connected consistently across the RS485 bus.
2. Confirm that baud rate, parity, stop bits, and Modbus address match the connected equipment.
3. Disconnect other devices temporarily to rule out a bus wiring, addressing, or termination problem.

Run the built-in RS485 self-test

The self-test runs inside the affected SB1000 and cannot be started from the public WordPress site.

1. Open the affected SB1000 web interface and go to Help → Serial Broker – Troubleshooting.
2. Disconnect both RS485 ports from the field bus.
3. Connect Port 1 A to Port 2 A.
4. Connect Port 1 B to Port 2 B.
5. Start the RS485 self-test shown in the device Help page and follow its result.

If the device web interface is unavailable, resolve the power or network connection first. If the self-test fails with only the loopback wiring connected, record the result and contact Varibits support.