SB6121: Troubleshooting Information

1. Checking the physical connection
2. Verifying the LEDs
3. Verifying the cable signal
4. Power Reset
5. Factory Reset

Checking the physical connection

1. Verify that the SB6121 power cord is connected from the power port of the SB6121 to the power outlet.
2. Verify that the coaxial cable is connected from the cable port of the SB6121 to the cable outlet.
3. Verify that the Ethernet cable is connected from the Ethernet port on the SB6121 to the Ethernet port on the computer.
   
    

Verifying the LEDs

With the proper setup, the Online LED should be solid green, and the Link LED should either be amber or blue. If this is not the behavior that the SB6121 is displaying, please refer to this table for more information regarding LED behavior.

Verifying the cable signal

1. Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter http://192.168.100.1 into the address box.  The Cable Modem Status page will appear.
    
2. Click the Signal link on top menu.  The Signal page will appear
    
3. In the Downstream section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel. 
   
   
    
4. In the Downstream section, identify the Modulation and Power to find verify SNR levels are within the acceptable range for each downstream channel. 
   
   Acceptable SNR Levels (dB): 
   If QAM64, SNR should be 23.5 dBmV or greater. 
   If QAM256 and DPL( -6 dBmV to +15 dBmV) SNR should be 30 dBmV or greater. 
   If QAM256 and DPL(-15 dBmV to -6 dBmV) SNR should be 33 dBmV or greater.   
   
   
    
5. In the Upstream section, identify the Symbolic Rate to find verify Upstream Power levels are within the acceptable range. 
   
   Acceptable Upstream Power Levels (dBmV):
   
   
    

   Upstream Transmit Power Level
   Channel	US Channel Type	Symbol Rate	Acceptable US Power Level
   Single	TDMA	1280 Ksym/sec	+61 dBmV to 45 dBmV
   	ATDMA	2560 Ksym/sec	+58 dBmV to 45 dBmV
   		5120 Ksym/sec	+57 dBmV to 45 dBmV
   Two	TDMA	1280 Ksym/sec	+58 dBmV to 45 dBmV
   	ATDMA	2560 Ksym/sec	+55 dBmV to 45 dBmV
   		5120 Ksym/sec	+54 dBmV to 45 dBmV
   Three or more	TDMA	1280 Ksym/sec	+55 dBmV to 45 dBmV
   	ATDMA	2560 Ksym/sec	+52 dBmV to 45 dBmV
   		5120 Ksym/sec	+51 dBmV to 45 dBmV

6. Refresh the page at least twice to identify variations in SNR, Downstream Power, and Upstream Power.   
   
   NOTE: If the either of the signal levels are outside of the acceptable range, power cycle or factory reset the modem. 
    
7. Contact the cable provider to adjust the signal level to the acceptable level range.

Acceptable Signal Levels (per channel) 

Power Reset

1. Shutdown the computer.
2. Unplug the cable modem from the AC wall outlet and wait one minute.
3. Plug the cable modem into the wall outlet.
4. Wait until the Power, Receive, Send, and Online LEDs are solid.
5. Restart the computer.

Factory Reset

1. Disconnect the coaxial cable.
   
   NOTE: If the SB6121 is connected to a router, it is recommended to disconnect the router and connect the SB6121 directly to a computer with an Ethernet cable.
    
2. Power cycle the unit by disconnecting the power cord for 10 seconds, then reconnect the power cord.
   
   
    
3. Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter http://192.168.100.1 into the address box. The Status page will appear.
   
   
    
4. Click the Configuration link on top. The Configuraton page will appear.
    
5. Click the Reset All Defaults button (as shown below).
   
   
   
    
6. When asked, Do you want to proceed?, click the OK button.  The modem will reset to it's factory state, and will go through the initialization process.
    
7. Connect the coaxial cable to the modem.
   
   NOTE: The initialization process may take 5 to 30 minutes​.