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Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

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Frequent Visitor

Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

I'm seeing the following error in my modem's event log regularly (at least once a day, if not more) and it correlates with internet connection being dropped.....  

 

"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=<xx>;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"

 

04/12/2020 00:44 82000200 3 "No Ranging Response received - T3 time-out;CM-MAC=<xx>;CMTS-MAC=<xx>;CM-QOS=1.1;CM-VER=3.1;"
04/12/2020 00:44 84000100 3 "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=<xx>;CMTS-MAC=<xx>;CM-QOS=1.1;CM-VER=3.1;"
04/12/2020 00:44 84000100 3 "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=<xx>;CMTS-MAC=<xx>;CM-QOS=1.1;CM-VER=3.1;"
04/12/2020 00:39 82000200 3 "No Ranging Response received - T3 time-out;CM-MAC=<xx>;CMTS-MAC=<xx>;CM-QOS=1.1;CM-VER=3.1;"

 

 

Any Ideas as to what might be causing this and/or how to resolve it?

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Expert

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

You need to also post the signal stats.


Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.




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Frequent Visitor

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

Arris Surfboard SB8200 (upto 10Gbps)

Standard Specification Compliant Docsis 3.1
Hardware Version 6
Software Version AB01.01.009.32.01_122319_183.0A.NSH

 

DOWNSTREAM:
Modulation Power SNR/MER
QAM256 -1.5 dBmV 42.0 dB
QAM256 0.5 dBmV 43.4 dB
QAM256 0.4 dBmV 43.5 dB
QAM256 0.4 dBmV 43.4 dB
QAM256 0.3 dBmV 43.2 dB
QAM256 0.0 dBmV 43.1 dB
QAM256 0.1 dBmV 43.3 dB
QAM256 -0.1 dBmV 43.1 dB
QAM256 0.0 dBmV 43.0 dB
QAM256 -0.2 dBmV 42.8 dB
QAM256 0.0 dBmV 43.1 dB
QAM256 -0.3 dBmV 42.8 dB
QAM256 -0.4 dBmV 42.6 dB
QAM256 -1.0 dBmV 42.3 dB
QAM256 -0.9 dBmV 42.3 dB
QAM256 -1.0 dBmV 42.4 dB
QAM256 -1.1 dBmV 42.3 dB
QAM256 -1.2 dBmV 42.2 dB
QAM256 -1.4 dBmV 42.0 dB
QAM256 -1.4 dBmV 41.8 dB
QAM256 -1.7 dBmV 41.9 dB
QAM256 -1.5 dBmV 42.1 dB
QAM256 -1.7 dBmV 41.9 dB
QAM256 -1.7 dBmV 41.9 dB
QAM256 -2.1 dBmV 41.5 dB
QAM256 -2.0 dBmV 41.7 dB
QAM256 -2.1 dBmV 41.6 dB
QAM256 -1.8 dBmV 41.8 dB
QAM256 -1.6 dBmV 42.0 dB
QAM256 -1.4 dBmV 41.9 dB
QAM256 -1.8 dBmV 39.5 dB
QAM256 -1.9 dBmV 41.4 dB
Other -1.2 dBmV 39.8 dB

 

UPSTREAM:
US Channel Type Power
SC-QAM Upstream 38.0 dBmV
SC-QAM Upstream 36.0 dBmV
SC-QAM Upstream 37.0 dBmV
SC-QAM Upstream 37.0 dBmV
SC-QAM Upstream 37.0 dBmV

 

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Expert

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

The stats are o/k. Are there more errors than just those being shown ? If so, please post them all.



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Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

@EG Between the "No Ranging Response received - T3 time-out" error and the "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing", that is all the errors I see .. 

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Expert

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

The signal stats are o/k but the error log entries may indicate that something is going on. Perhaps there is noise ingress into the line(s) somewhere.

 

There are other signal stat figures that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

 

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They will be able to poll the CMTS to see whether or not everything is in the green zone, see your node / cable plant and modem health, and also see a history plot for the modem. You should get a reply here in your topic. Good luck !



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Official Employee

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

Hi @jlg777

Thank you for posting to the Xfinity Forums. Sorry for the issues you're having with your internet. I agree with @EG. Your signals look ok, but there could be noise on the line or an issue at the node. I'll be able to confirm once I can take a deeper look into your account. 

Please send me a private message with your full name, the name of the account holder, and the house number of your address, so I can assist you."

To send a private message, click on "ComcastChe" and then click send a message.  

 


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Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

Thank you for your help, @EG 

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Expert

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

Quite welcome !  😊



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Official Employee

Re: Arris Surfboard SB8200 DOCSIS 3.1 Modem - SYNC timing synchronization failures

Hi @jlg777, I was able to locate an issue at your node and have replied to your private message with my findings. Please let me know if it is ok that we monitor this over the next 24-hours based on the maintenance that is scheduled in your area. Thank you for allowing me to investigate. Chat with you soon! 


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