11 Messages
Experiencing SYNC Timing Synchronization Failure
Recently connected a new Motorola MG 7550 router /modem. We've been experiencing periodic disconnections lasting from less than a minute to several minutes. Logs show the following....
| Time | Priority | Description |
| Time Not Established | Critical (3) | No Ranging Response received - T3 time-out;CM-MAC=xxxxxxx;CM-QOS=1.0;CM-VER=3.0; |
| Sun Jan 07 17:08:41 2024 | Critical (3) | SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=xxxxxxxCM-QOS=1.1;CM-VER=3.0; |
| Sun Jan 07 17:08:45 2024 | Critical (3) | SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxxxxxxxx;CM-QOS=1.1;CM-VER=3.0; |
| Sun Jan 07 17:08:48 2024 | Critical (3) | SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=xxxxxxxxxxCM-QOS=1.1;CM-VER=3.0; |
| Sun Jan 07 17:53:24 2024 | Critical (3) | Resetting the cable modem due to docsDevResetNow |
| Time Not Established | Critical (3) | No Ranging Response received - T3 time-out;CM-MAC=xxxxxxx;CM-QOS=1.0;CM-VER=3.0; |
| Time Not Established | Notice (6) | Honoring MDD; IP provisioning mode = IPv6 |
| Mon Jan 08 03:14:22 2024 | Critical (3) | Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0; |
Accepted Solution
user_vm6n9v
11 Messages
1 year ago
I thought everyone would like to know that this problem has been resolved 100%!
It's tough when there's more than one issue, but we seem to have cured three separate things that were interfering with our connection.
First was poor connections, which the xfinity tech was able to resolve by replacing the connectors in the coax. Helped a little, but stuff still causing disconnects. We then ran WiFi Analyzer which showed we were sharing a channel with a bunch of other routers that weren't broadcasting SSIDs. Changing the channels helped a lot, but still not great. Next, on the advice of a couple of folks(thanks EG) I installed a Forward Path Attenuator which reduced the downstream from around 11 db to around 4.5 dbm. This darn near did the trick but we were still getting random disconnects! Much better, but still not great. Finally, on the advice of a tech from Motorola, we tried going to a Factory Reset and redo everything from scratch. BINGO! That was the final trick. Somehow the reset got rid of the last tiny remnants of the problems. It's now working great and I consider the problems solved!
Thanks to everyone who chimed in and tried to help.
(edited)
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XfinityKatie
Official Employee
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744 Messages
1 year ago
@user_vm6n9v Thank you for taking the time to make this post and letting us know of the interruptions you are seeing with your connection. We definitely want to ensure this is addressed and your service is working as you need! I'd like to ask a few questions to help us narrow down what is going on.
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user_vm6n9v
11 Messages
1 year ago
Thanks for reaching out to us! We've done all the trouble shooting you mentioned and more. Based on researching symptoms in the log files and also the problems with the prior modem, we've scheduled a visit from an xfinity tech for later today. If the problem is resolved, I will be sure to post a follow up here.
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user_vm6n9v
11 Messages
1 year ago
Update: tech checked the setup, and traced coax back to the pole. Replaced all connectors (3) with new. Rechecked and pronounced all as "Excellent". We're now hoping that all is now fixed. We should know by tomorrow if the disconnects are cured.
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EG
Expert
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110.4K Messages
1 year ago
What do the modem's signal stats look like ?
Please copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.
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EG
Expert
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110.4K Messages
1 year ago
@user_vm6n9v
Please post the info that I requested right here in your topic on these public help forums. Thank you.
(edited)
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user_vm6n9v
11 Messages
1 year ago
UPDATE!
It's truly been a long and frustrating grind, but I believe that we have solved the issue! I loaded an app called wifi analizer by olgorDOTcom and was blown away by the sheer number of neighbors who were competing for wifi channels not broadcasting SSIDs. So now I have simply changed from auto to lesser used channels and BINGO problem solved. If you need to try this, make sure to get the version by olgorDOTcom as there's a bunch of them listed on the Play Store.
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EG
Expert
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110.4K Messages
1 year ago
FWIW. WiFi impairments can not cause those modem RF error log entries (SYNC Timing Synchronization failure - Failed to acquire FEC framing;). Those come from an impairment of the connection between the modem and the Comcast plant / system. If the problem returns, the cause of these may still need to be addressed. You should post those requested signal values for the halibut.
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EG
Expert
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110.4K Messages
1 year ago
@user_vm6n9v
The downstream power is high. It may be over-driving the front-end receiver circuit of the modem. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.
Is there a drop amplifier on the coax cable line leading to the modem ? If so, try removing / bypassing it and see. If not, you can try installing a -6 dB forward path-only attenuator pad such as this one on the coax port on the rear of the modem to knock that power level down and see;
https://www.amazon.com/FPA6-54-Forward-Attenuator-DOCSIS-Internet/dp/B08KTRC3XZ
It won't affect the upstream power level which is within spec. Good luck !
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