Regular Visitor
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4 Messages
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; |
EG
Expert
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111.4K Messages
5 years ago
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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rwickham
Regular Visitor
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4 Messages
5 years ago
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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Nixon27
Contributor
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12 Messages
5 years ago
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rwickham
Regular Visitor
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4 Messages
5 years ago
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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Nixon27
Contributor
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12 Messages
5 years ago
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Nixon27
Contributor
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12 Messages
5 years ago
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rwickham
Regular Visitor
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4 Messages
5 years ago
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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