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CM1150V Upstream Channel Problem with Xfinity
I purchased a CM1150V to replace an Xfinity (Arris) XB6. The XB6 had been in place, running in bridge mode, for 2 months. It showed (4) upstream channels with good power levels, (31+OFDM) downstre...
An Xfinity tech was out today. He found a noise block filter at the pole. No idea when or why it was installed. That was blocking the two lower frequency channels.
A noise block filter had previously been ruled out, because the Xfinity-supplied Arris XB6 was reporting all (4) channels locked. So I now question the veracity of the Arris XB6 status page. All other modems tested (CM1150V, Arris TM722G, Arris SBV3202) were unable to lock the channels with that filter in place. So I don't think the Arris XB6 was actually locking those channels either, even though it said it was.
Once the tech removed the noise block filter at the pole, the CM1150V immediately locked all (4) channels. The constant T3/T4 errors are gone as well. No problems with the CM1150V, the upstream issue was all from a previous Xfinity/Comcast tech installing that noise block filter at the tap.
Thanks to vkdelta for help and supporting information, which helped me explain/prove the problem to Xfinity so they would come fix it!
vkdelta wrote:
1. There might have been an outage on comcast plant. Please reset to confirm if you have 2 or 4 US channels
2. Have you changed anything on your side? such as coax cable? or connector?
Hello vkdelta ,
Thank you for responding.
1a. I have restarted the CM1150V multiple times over a 48hr period. Have also factory reset it. The CM1150V only locks (2) US channels.
1b. Reconnecting the Arris XB6 to same connection, it locks all (4) US channels just as it did before. Reconnecting the CM1150V to same connection, it is only locking (2) US channels.
2a. Drop, cable ends, moca filter, and single splitter have all been checked and swapped out. All quality materials and parts as per Xfinity. Again, the Arris XB6 locks all (4) US Channels on the same cable and connector. The CM1150V is only locking (2) US channels on the same cable and connector.
2b. All downstream signal levels are good, between 0 and -3 dBmV, with SNR between 38 and 39. The two US channels that lock have upstream power between 40 and 42 dBmV. These US and DS levels seem to indicate good cable and connections.
2c. The Arris XB6 locks all (4) channels. Disconnect it, connect CM1150V, and CM1150V only locks (2) channels. Disconnect the CM1150V and reconnect XB6, it again locks (4) channels. Can do this over-and-over, the problem is NOT intermittent. The XB6 always gets (4) US channels, the CM1150V always gets (2). It lists the proper frequency for the other (2), but does not lock. This is on EXACT SAME COAX and CONNECTORS.
2d. Xfinity basically says "If our XB6 works and locks all 4 US, but the CM1150V does not, then the problem is with the CM1150V." I see their logic, but find it difficult to believe that a defect in a brand new CM1150V would only affect locking (2) US and nothing else.
Still having the same problem. I procured a second CM1150V, and it behaves exactly the same way -- it only locks 2 US channels. Yet I can connect the Arris XB6 and it locks 4 US channels. This is in the same location, on same coax and connector. The XB6 locks 4 US, but the CM1150V only locks 2 US.
The CM1150V units (both of them) also have a constant stream of T3/T4 timeouts, roughly every 30 seconds. The Arris XB6 has an occassional T3/T4, perhaps a couple per day. But the CM1150V continuously posts T3/T4 errors about every 30 seconds, they never stop.
What would cause the CM1150V units (both of them) to only lock 2 US channels and get constant T3/T4 errors, while the Arris XB6 is able to lock 4 US and not get T3/T4 errors?
thanks for good explanation.
Can you please PM me few details:
1. your Location
2. your comcast account #
3. CM1150V CM MAC
4. XB6T CM MAC
5. Can you connect both them at same time using splitter ? If you have it. (of course internet will only work on one of them and but it will be useful for comcast folks to monitor it)
5. Are you willing to work with us to debug if this is CM or Comcast issue? (Arris and NTGR are running different DOCSIS Radio chips and I have not seen this issue on other comcast plants so far)
6. Do you have another version of XB6 AKA Technicolor XB6T with you by any chance?
thanks,VKdelta
vkdelta -
I disconnected the CM1150V, connected a splitter in it's place, then connected the CM1150V and XB6 (Arris TG3482G) to the splitter. Both are connected to CMTS. The CM1150V is activated (data and voice), the XB6 is not.
Signal levels are of course degraded a bit for both, because of the additional splitter, but are still within operating range.
I will PM you with additional details as requested. Thanks for the assistance!
An Xfinity tech was out today. He found a noise block filter at the pole. No idea when or why it was installed. That was blocking the two lower frequency channels.
A noise block filter had previously been ruled out, because the Xfinity-supplied Arris XB6 was reporting all (4) channels locked. So I now question the veracity of the Arris XB6 status page. All other modems tested (CM1150V, Arris TM722G, Arris SBV3202) were unable to lock the channels with that filter in place. So I don't think the Arris XB6 was actually locking those channels either, even though it said it was.
Once the tech removed the noise block filter at the pole, the CM1150V immediately locked all (4) channels. The constant T3/T4 errors are gone as well. No problems with the CM1150V, the upstream issue was all from a previous Xfinity/Comcast tech installing that noise block filter at the tap.
Thanks to vkdelta for help and supporting information, which helped me explain/prove the problem to Xfinity so they would come fix it!
