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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 have Comcast with Arris SB6183 modem and Apple AirPort Express Wifi router. I keep experiencing perioudic internet drops (every 30 mins or so) and it comes back up. I noticed this in the Arris Event Log

 

Time Priority Description
Fri Apr 10 17:20:10 2020 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:28:23 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:31:12 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:31:12 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:31:19 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:31:19 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:32:22 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:32:22 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 05:32:25 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Tue Apr 14 07:23:22 2020 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:15:41 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:18:22 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:18:22 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:18:42 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:18:42 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:19:21 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:19:21 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:19:51 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:19:51 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;
Tue Apr 14 09:19:54 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received - T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Thu Apr 23 19:25:25 2020 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:9b:70:6c;CMTS-MAC=00:01:5c:63:c0:92;CM-QOS=1.1;CM-VER=3.0;

 

 

Here is Status page information:

 

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Corrected Uncorrectables
1 Locked QAM256 8 447000000 Hz -3.9 dBmV 39.0 dB 2876 0
2 Locked QAM256 9 453000000 Hz -4.0 dBmV 39.0 dB 3217 0
3 Locked QAM256 10 459000000 Hz -3.9 dBmV 39.0 dB 3051 0
4 Locked QAM256 11 465000000 Hz -4.2 dBmV 38.9 dB 3556 0
5 Locked QAM256 12 471000000 Hz -3.8 dBmV 39.0 dB 4120 0
6 Locked QAM256 13 477000000 Hz -3.6 dBmV 38.9 dB 4794 0
7 Locked QAM256 14 483000000 Hz -3.4 dBmV 38.9 dB 4809 0
8 Locked QAM256 15 489000000 Hz -3.3 dBmV 39.0 dB 4898 0
9 Locked QAM256 16 495000000 Hz -2.9 dBmV 39.1 dB 4978 0
10 Locked QAM256 17 507000000 Hz -2.9 dBmV 38.5 dB 4844 0
11 Locked QAM256 18 513000000 Hz -3.1 dBmV 39.1 dB 5098 0
12 Locked QAM256 19 519000000 Hz -3.8 dBmV 38.9 dB 5297 0
13 Locked QAM256 20 525000000 Hz -4.0 dBmV 38.9 dB 4982 0
14 Locked QAM256 21 531000000 Hz -4.5 dBmV 38.7 dB 5868 0
15 Locked QAM256 22 537000000 Hz -4.4 dBmV 38.7 dB 6437 0
16 Locked QAM256 23 543000000 Hz -4.7 dBmV 38.6 dB 7638 0

 

 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 52.8 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 54.0 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 23700000 Hz 54.0 dBmV
4 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 54.0 dBmV

 

Some help would be great as I rely on internet for working from home.

 

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

The upstream power is too high / out of spec. The downstream power is on the weak side as well. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, 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 - Failed to acquire QAM/QPSK symbol timing

My modem's cable is directly connected to the wall. This is a picture of the closet with cables, dont know how things are connected.

 

https://i.imgur.com/1e7gDF9l.jpg 

 

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

Can't see your pic. Since you are a new poster, it needs to be approved by a Forum Admin. That could take some time. In the interim, you could try hosting it at one of those free third-party pic hosting sites like Imgur or Photobucket and post the link to it here.

 

If there is nothing you can do to improve the connection quality, then as stated, you'll need a tech out to investigate / correct the problem.

 

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.

Good luck with it !



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
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Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing