Internet dropping repeatedly. Arris SB6141 Logs shows multiple Cable Modem Reboots but physical power to box is ok. Is this a modem fault?

The upstream power is too high / 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 there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, 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, kinks, sharp bends, etc.

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.

BTW. That modem is no longer supported by them. You should consider upgrading it soon;

https://www.xfinity.com/support/articles/end-of-life-devices 

@user_0f3abf 

My pleasure ! Best of luck with it ! Please post back with how things turn out.

Sorry to hear that.....

You need to keep pressuring those premises-facing techs to escalate it to their line / network / maintenance dept. techs. The problem may indeed lie beyond your home in the local neighborhood infrastructure somewhere.  And if the problem is found to be on their side of the demarcation point, there will not be any charge.

Good luck !

Since I last posted 4 tech visits out the house (not counting the one that went to the wrong house). Cable from the pole was replaced 2 times. Inside one splitter removed and all others replaced and I swapped in a new Netgear CM1000v2 modem. The signal strength did not budge from the low-to-mid 50 dBmV area on the Upstream channels. The new modem seemed to tolerte these conditions better than the old SB as it stopped rebooting every 45 mins or so. I manged to get a very good tech who made a lot of the changes ad took ownership of the problem. He installed an amplifier on the inside and we saw better numbers. He came from a different team servicing a nearby town and said that or town's numbers all look fairly similar. He had surmised that ongoing Comcast upgrades in the area cabling infrastructure may be having a negative impact effecting different areas.

I will say that Comcast's support is absolutely horrible. Not the techs or call center agents, as they seem to be all good people, but the way in which it is being executed and constricting rules they must work by. To have to go through this "Sending a Signal to your Modem" exercise every time you call in, even on a known problem with an existing ticket, is outrageously inefficient from my point of view.. All totaled it took 9 hours of my time just waiting to talk to a human and a similar amount of tech's time, if not more.

If it were not for the help from you, EG, and this forum and the excellent local tech's dedication to fix these issues (If they are fixed yet) I don't know what I would do. I have ben Comcast customer for over 30 years and it has never seemed this bad trying to get support. I will be looking for other options as this cannot be the solution for my connectivity. We work from home and remotely support our elderly family members communicate using Alexa and similar internet based virtual assistants. We cannot have the network failing like this.

Thanks for your help

Latest numbers:

Here are the new numbers from our modem using the amplifier

Channel 1    49.0 dBmV

Channel 2   49.0 dBmV

Channel 3   48.8 dBmv

Channel 4   50.0 dBmV

Channel 5.  50.3 dBmV

The tech says the amp is giving us 3 dBmV

It is still marginal. It will likely go a few dB higher in the peak heat of the Summer season. Hope things hold up for you. Best of luck !