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Intermittent Drops of Internet - SYNC timing failures

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Regular Visitor

Intermittent Drops of Internet - SYNC timing failures

I had an issue about 3 months ago where my internet would go out for about 30 seconds throughout the day (probably a dozen times).  It would cause me to disconnect from gaming, interupt with work, etc.  I looked at my modem error log and found a lot of sync issues.  I called Comcast and they sent a tech out and there was apparently something wrong with my neighborhood grid.  They openned a case and solved the issue and I haven't had any issues for 3 months.  Recently, the last 3 or 4 days have been showing issues again. Any advice?  I'm using an Arris SB6183.

 

My status log on my modem is:

1 Locked QAM256 20 525000000 Hz 6.8 dBmV 40.0 dB 0 0
2 Locked QAM256 21 531000000 Hz 6.8 dBmV 40.2 dB 0 0
3 Locked QAM256 22 537000000 Hz 6.8 dBmV 40.2 dB 0 0
4 Locked QAM256 23 543000000 Hz 6.9 dBmV 40.1 dB 0 0
5 Locked QAM256 24 549000000 Hz 6.9 dBmV 40.0 dB 0 0
6 Locked QAM256 25 555000000 Hz 6.9 dBmV 40.2 dB 0 0
7 Locked QAM256 26 561000000 Hz 6.8 dBmV 40.2 dB 0 0
8 Locked QAM256 27 567000000 Hz 6.8 dBmV 40.2 dB 0 0
9 Locked QAM256 28 573000000 Hz 6.7 dBmV 40.1 dB 0 0
10 Locked QAM256 29 579000000 Hz 6.7 dBmV 40.1 dB 0 0
11 Locked QAM256 30 585000000 Hz 6.5 dBmV 40.2 dB 0 0
12 Locked QAM256 31 591000000 Hz 6.4 dBmV 40.0 dB 0 0
13 Locked QAM256 32 597000000 Hz 6.1 dBmV 40.0 dB 0 0
14 Locked QAM256 33 603000000 Hz 6.0 dBmV 40.0 dB 0 0
15 Locked QAM256 34 609000000 Hz 5.9 dBmV 40.0 dB 0 0
16 Locked QAM256 35 615000000 Hz 5.7 dBmV 39.9 dB 0 0

 

Upstream:

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 1 5120 Ksym/sec 36100000 Hz 31.0 dBmV
2 Locked ATDMA 2 5120 Ksym/sec 29600000 Hz 30.8 dBmV
3 Locked ATDMA 3 5120 Ksym/sec 23000000 Hz 29.8 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 16500000 Hz 28.8 dBmV

 

I look at my event log and see the following:

 

Thu Apr 09 09:30:54 2020 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:41 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:42 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:45 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:45 2020 Warning (5) MDD message timeout;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:46 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:48 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:54 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:56 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:57 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:45:58 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:46:10 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:46:12 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:46:13 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:46:14 2020 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;
Thu Apr 09 09:46:16 2020 Critical (3)

SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=f8:a0:97:b5:b2:66;CMTS-MAC=00:01:5c:a6:08:5c;CM-QOS=1.1;CM-VER=3.0;

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Expert

Re: Intermittent Drops of Internet - SYNC timing failures

The upstream power is low. The CMTS / system may be having difficulties hearing your modem. An end-user can't fix low upstream power. Consider booking a tech visit to investigate  / correct. Good luck !



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Regular Visitor

Re: Intermittent Drops of Internet - SYNC timing failures

Spoke with an advanced technician over xfinity chat.  Had to explain to him the difference between channel power and internet speed.  He kept trying to tell me that I was capped at 5 mbps upload speed, not 45.  Once I got that explained to him that I meant upstream channel POWER, he said that the speeds were in the recommended power rating.  When I sent him the link to the SB6183 modem specs, showing him 45 to 51 dBmV, he back tracked saying that I need to call their 1800 number in a week to 10 days as they don't have any technicians available at this time.

 

Hopefully this'll be seen by a Comcast employee for some assistance.

 

Thanks for the help so far.

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Regular Visitor

Re: Intermittent Drops of Internet - SYNC timing failures

Would I have any luck placing an attenuator on my modem in order to increase the power of my upstream channels?

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Frequent Visitor

Re: Intermittent Drops of Internet - SYNC timing failures

If u don’t mind me asking where do u get theses numbers from ..I have gig internet...an I’m experiencing drop in speed every now an then like for instance my kids zoom chats for school it some times freezes up an the chrome book will say unstable connection..an it seems to only be hers doing it ..regardless I don’t think all the people she’s taking with have gig speed and theirs seems to be fine ..I’d like to look me into it ..if u can help I’d appreciate it.thanks in advance
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Regular Visitor

Re: Intermittent Drops of Internet - SYNC timing failures

I went to 192.168.100.1 and logged in to my modem.  You can see your modem status on your login page.

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Frequent Visitor

Re: Intermittent Drops of Internet - SYNC timing failures

Oh every time I try that it won’t load
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Frequent Visitor

Re: Intermittent Drops of Internet - SYNC timing failures

The 10.0.0.1 works but not that