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SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

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SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

I've seen this posted a few times, but can't seem to find a clear answer (and many do not include their signal levels).  Thoughts welcome.

 

Plenum-protected drop installed a year+ ago from backyard box to 1:2 splitter.  2-side splitter only has single modem drop via new Comcast installed cabling.  Motorola SBG6580

 

Wed Jan 03 13:39:08 2018 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=64:55:b1:3e:95:f9;CMTS-MAC=00:01:5c:83:92:72;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 03 13:39:05 2018 Warning (5) MDD message timeout;CM-MAC=64:55:b1:3e:95:f9;CMTS-MAC=00:01:5c:83:92:72;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 03 13:39:05 2018 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=64:55:b1:3e:95:f9;CMTS-MAC=00:01:5c:83:92:72;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 03 13:36:51 2018 Warning (5) MDD message timeout;CM-MAC=64:55:b1:3e:95:f9;CMTS-MAC=00:01:5c:83:92:72;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 03 13:36:49 2018 Critical (3) SYNC Timing Synchronization failure - Failed to receive MAC SYNC frame within time-out period;CM-MAC=64:55:b1:3e:95:f9;CMTS-MAC=00:01:5c:83:92:72;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 03 13:36:37 2018 Warning (5) MDD message timeout;CM-MAC=64:55:b1:3e:95:f9;CMTS-MAC=00:01:5c:83:92:72;CM-QOS=1.1;CM-VER=3.0;

 

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Corrected Uncorrectables
1 Locked QAM256 12 555000000 Hz 5.4 dBmV 40.5 dB 505 2081
2 Locked QAM256 13 561000000 Hz 5.3 dBmV 40.4 dB 424 1435
3 Locked QAM256 14 567000000 Hz 5.7 dBmV 40.3 dB 743 2735
4 Locked QAM256 15 573000000 Hz 5.3 dBmV 40.3 dB 768 2552
5 Locked QAM256 16 579000000 Hz 5.1 dBmV 39.4 dB 695 2158
6 Locked QAM256 19 597000000 Hz 5.5 dBmV 39.4 dB 669 2400
7 Locked QAM256 20 603000000 Hz 4.6 dBmV 39.9 dB 656 2438
8 Locked QAM256 21 609000000 Hz 4.8 dBmV 39.9 dB 721 2334

 

 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 8 5120 Ksym/sec 17300000 Hz 42.5 dBmV
2 Locked ATDMA 5 5120 Ksym/sec 36500000 Hz 42.7 dBmV
3 Locked ATDMA 6 5120 Ksym/sec 30100000 Hz 43.0 dBmV
4 Locked ATDMA 7 5120 Ksym/sec 23700000 Hz 42.0 dBmV



Diamond Problem Solver

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

The stats as read at the modem level at that moment in time were o/k but there are three additional signal stats that can cause those errors which can't be read by the modem. They can only be read from their end by them polling the CMTS (Cable Modem Termination System) at the local headend facility.

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.

You can call in and ask what these figures are. The Upstream Receive Power Level should fall within the range of -2dB to +2dB with 0dB being in the middle and perfect.

The Upstream SNR should be least 31dB, and the higher it is the better.

The ICFR should be no higher than 2 dB.

You could have an intermittent noise ingress issue in only the upstream channel(s) / return path only somewhere.

They will be able to see whether or not everything is in the green zone and also see a history plot for the modem.


New Poster

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

EG,

 

Thank you for the detailed info and recommended readings.  I'll give them a call tomorrow and see if they're showing a history of it.  It's happening multiple times/day, so even if their logs aren't exhaustive, they should hopefully contain some symptoms.

 

Thanks again,

 

Tom

New Poster

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

was this solved?