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SYNC timing synchronization failure

New Poster

SYNC timing synchronization failure

Hi,
I have been seeing these in the Motorola MB8600 Cable modem Event Log. What does this event mean?

I have been having intermittent connection issues also and a reboot of the cable modem usually fixes it. Just trying to understand whether this could be related.

18:56:54
Sun Apr 14 2019 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(Re:da:ct:ed);CMTS-MAC=(Re:da:ct:Ed);CM-QOS=1.1;CM-VER=3.1;
Expert

Re: SYNC timing synchronization failure

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




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New Poster

Re: SYNC timing synchronization failure

Connection
Startup Sequence
Startup Step Status Comment


Acquire Downstream Channel 681000000 Hz Locked

Upstream Connection OK Operational

Boot State OK Operational


Configuration File OK

Security Enabled BPI+



Connection Status
System Up Time 0 days 00h:14m:06s

Network Access Allowed



Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (d Corrected Uncorrected
1 Locked QAM256 32 681.0 5.8 33.6 8069 0
2 Locked QAM256 2 507.0 3.7 36.0 0 0
3 Locked QAM256 3 513.0 3.7 36.1 273 1020
4 Locked QAM256 4 519.0 3.9 35.7 308 1027
5 Locked QAM256 5 525.0 3.8 35.6 350 993
6 Locked QAM256 6 531.0 3.8 35.7 402 1012
7 Locked QAM256 7 537.0 3.9 35.4 441 1007
8 Locked QAM256 8 543.0 4.0 35.5 629 976
9 Locked QAM256 9 549.0 3.8 35.5 669 1000
10 Locked QAM256 10 555.0 3.5 35.5 895 999
11 Locked QAM256 11 561.0 3.8 35.1 1029 1013
12 Locked QAM256 12 567.0 4.3 35.3 1361 985
13 Locked QAM256 13 573.0 4.2 35.1 1538 979
14 Locked QAM256 14 579.0 3.9 34.9 2164 992
15 Locked QAM256 15 585.0 4.0 34.9 2487 1000
16 Locked QAM256 16 591.0 4.6 34.7 3100 1008
17 Locked QAM256 17 597.0 4.9 34.6 3579 1008
18 Locked QAM256 18 603.0 4.7 34.5 4605 1014
19 Locked QAM256 19 609.0 4.7 34.3 5883 963
20 Locked QAM256 20 615.0 4.8 34.8 6603 965
21 Locked QAM256 21 621.0 5.1 34.9 8613 973
22 Locked QAM256 22 627.0 5.4 34.6 10427 955
23 Locked QAM256 23 633.0 5.4 34.3 12353 940
24 Locked QAM256 24 639.0 5.3 35.0 14624 948
25 Locked OFDM PLC 25 693.0 6.2 12.6 23699 0
26 Locked QAM256 26 645.0 5.6 34.5 17062 955
27 Locked QAM256 27 651.0 6.1 34.1 21270 947
28 Locked QAM256 28 657.0 6.0 34.2 25086 941
29 Locked QAM256 29 663.0 5.8 34.0 29400 954
30 Locked QAM256 30 669.0 5.3 34.3 35648 964
31 Locked QAM256 31 675.0 5.5 34.0 42534 960
32 Locked QAM256 33 687.0 6.0 34.2 57214 957


Upstream Bonded Channels

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
1 Locked SC-QAM 13 5120 36.5 50.8
2 Locked SC-QAM 14 5120 30.1 51.3
3 Locked SC-QAM 15 5120 23.7 51.3


Downstream Frequency Setting
Downstream Frequency Select



LAG Enable/Disable
LAG(Link Aggregation Group, or Ethernet Port Bonding)



Expert

Re: SYNC timing synchronization failure

The SNR values on the downstream channels are fairly low. Perhaps there is some noise leaking into the line somewhere. The upstream power is a bit on the high side and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, and speed and latency problems.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.



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New Poster

Re: SYNC timing synchronization failure

I literally got the connection last week and ever since then the modem and the Internet have been failing intermittently. I spoke with comcast customer rep and they said everything is good from their end. I mentioned the errors in the log file on the cable modem but they didn’t seem to think there was an issue. I am likely done at this point with Comcast.
Expert

Re: SYNC timing synchronization failure

Get a tech out to investigate ? Show them this thread. Best of luck with your future choices ! Smiley Happy



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