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Intermittent outages — S34 upstream at 54.5 dBmV, repeated T3 / Loss of Sync / TCS failures
I'm experiencing intermittent internet outages and have isolated a DOCSIS upstream/return-path problem at my ARRIS S34.
Current signal levels:
- Four bonded SC-QAM upstream channels: 54.5 dBmV each
- OFDMA upstream: 48.5 dBmV
- Downstream power approximately -3.5 to +0.1 dBmV
- Downstream SNR approximately 40.4–45 dB
The modem event log is repeatedly recording:
- No Ranging Response received — T3 time-out
- SYNC Timing Synchronization failure — Loss of Sync
- TCS Fail on all Upstream Channels
- RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW
The modem and router are both on UPS power, and the modem-to-router Ethernet link is stable at 2.5 Gbps.
There is approximately a 10-foot coax extension inside the residence that I have not yet had time to bypass-test, so I cannot completely exclude an in-home coax contribution. However, the DOCSIS logs clearly show repeated upstream ranging/synchronization failures.
I would like the upstream return path, drop, connectors, and levels from the modem back to the tap/plant checked, rather than only a modem reboot or provisioning reset.
The problem is intermittent, so the modem may appear online when checked remotely.
EG
Expert
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122.5K Messages
25 days ago
Yep. The upstream power is out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.
In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/reconfigured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.
Also, check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, or animal chews.
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.
Good luck with it !
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