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S33: Troubleshooting Internet Connection

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How do I troubleshoot Internet connection issues with my S33 cable modem?
If all the client devices in the home network have lost Internet connectivity, troubleshooting may resolve or provide insight on the cause of the issue.  This document provides helpful troubleshooting steps for Internet connectivity issues with the S33.  

Troubleshooting on the S33 is not needed if the following scenarios are applicable.  
  • Compatible Cable Providers
    S33 is compatible with major U.S. cable service provider including Cox, Charter/Spectrum, and Xfinity.  Please check the compatible modem list on the cable provider's website for compatibility.

  • First Time Setup
    For first time installation of the S33, refer to article # 18549 - S33: First Time Installation and follow the installation steps.

The following troubleshooting steps are to be followed in sequence.
  1. Check the Power Supply
  2. Check the Modem's LED Light Status
  3. Power Cycle the Modem
  4. Check the Cable Signal Levels

Check the Power Supply
Use the power supply included with the S33.  Overall functionality and performance cannot be guaranteed if the incorrect power supply is used when installing the S33.  If using an incorrect power supply, the S33 may get online and function, but firmware upgrades will not complete successfully.  

Check the Modem's LED Light Status
The first step in troubleshooting is to check the LED light located on the front of the S33.  Reference the table below to identify the possible issue of the LED status and the steps to perform listed under Possible Solutions.  The detailed troubleshooting steps for power cycle and check cable signal levels are available below the LED Light Status table.
LED StatusPossible IssuesPossible Solutions
Off - No power on the modem
  • Bad power adapter
  • Power adapter disconnected
  • No power to the electrical outlet
  • Modem power on failure
  1. Check for damages on the power adapter.
  2. Connect the power adapter from the modem and to an electrical outlet.
  3. Check that the electrical outlet is working; if controlled by a wall switch, confirm the wall switch is on.
  4. Try a different known good electrical outlet.
Blinking - The modem receives low quality or no cable signal or scanning for Internet connection
  • Loose or disconnected coax cable 
  • Cable signal outside acceptable range
  • Modem activation is needed
  1. Securely tighten the connectors on each end of the coaxial cable by hand. 
  2. If applicable, check the television service to ensure cable service is operating properly.
  3. Power cycle the modem by disconnecting power adapter for one minute and connecting it back to the outlet.
  4. Check the cable signal levels in the Web Manager of the S33.
  5. Contact the cable provider to activate/reactivate the modem.

Power Cycle the Modem
Power cycling the modem is one of the easiest troubleshooting methods that may resolve connectivity issues.  It allows the S33 to establish connection while retaining its current configuration settings.  Follow the steps below to power cycle the S33.

  1. Disconnect the power adapter from the AC wall outlet and wait one minute.
  2. Connect the power adapter into the wall outlet.
  3. Wait until the LED light is solid green (DOCSIS 3.0 mode) or solid blue (DOCSIS 3.1 mode).

    NOTE: It may take up to 15 minutes for the S33 complete the boot-up sequence and connect to the Internet.

  4. Restart the computer.

Check the Cable Signal Levels
All DOCSIS cable modems require that the cable signals fall within a very specific range to be at an acceptable level for the modem to connect to the Internet.  The Downstream PowerDownstream SNR (Signal to Noise Ratio), and Upstream Power levels must be within the acceptable range for the S33 modem to operate properly.

NOTE: If the S33 is connected to a router, it is recommended to disconnect the router and connect the S33 directly to a computer with an Ethernet cable.
  1. Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter into the address box, and press the Enter key.  The Login page will appear.

    NOTE: A security or private risk alert may appear on the web browser advising users to proceed with caution when accessing the Web Manager.  There is no risk in proceeding to the Web Manager.  For instructions to by-pass the alert screen, refer to article # 18181 - Alert Message for Web Manager Access.
  2. On the Login page, enter admin in the Username field.

  3. Enter a customized password or the default admin password in the Password field.

    NOTE: If this is the first time login to the Web Manager, the default password could be password or the last 8-digit of the serial number.  It is required to set a unique password to proceed to the Web Manager. 
     For assistance with Web Manager Access, refer to article # 18552 – S33: Web Manager Access.
  4. Click the Apply button.  The Product Registration will appear.

    User-added image

  5. The Product Registration window includes information about enhanced product support, product warranty registration, and promotional offers from ARRIS.
    • Click the Register button to take a few minutes to register the product.  For assistance with product registration refer to article # 18558 - S33: Product Registration.  When the product is registered the product registration window will not appear during the next login. 
    • Click the Ask me later button to by pass the product registration window.  The product registration window will appear during the next login.
    • Click the Stop asking button to stop the product registration window from appearing the next login.
      User-added image
  6. In the Downstream Bonded Channels section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel. 

    User-added image
  7. In the Downstream Bonded Channels section, identify the Modulation and Power to verify SNR levels are within the acceptable range for each downstream channel. 

    Acceptable SNR Levels (dB)
    If QAM64SNR should be 23.5 dB or greater. 
    If QAM256 and DPL( -6 dBmV to +15 dBmV) SNR should be 30 dB or greater. 
    If QAM256 and DPL(-15 dBmV to -6 dBmV) SNR should be 33 dB or greater.    

    User-added image
  8. In the Upstream Bonded Channels section, identify the number of Channels and Type to verify Upstream Power levels are within the acceptable range for each upstream channel.  
    Upstream Transmit Power Level
    ChannelUS Channel TypeAcceptable Upstream Power Levels
    SingleSC-QAM 45 dBmV to 61 dBmV
    TwoSC-QAM45 dBmV to 54 dBmV 
    Three or moreSC-QAM45 dBmV to 51 dBmV
    Right click on the image to save it to your computer.
  9. Refresh the page at least twice to identify variations in SNR, Downstream Power Level, and Upstream Power Level.   

    NOTE: If either of the signal levels are outside of the acceptable range, power cycle or factory reset the modem.  
    Performing a Factory reset will erase any configuration changes and revert the custom admin password back to the default password (password).  For assistance with the Web Manager, refer to article # 18522 - S33 Web Manager Access.

  10. Contact the cable provider to adjust the signal levels to the acceptable level range.



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