Hello, I have Time Warner Cable and an SB5100 Modem I have had forever. Every now and then, when I get home from work, the modem will be offline. Resetting never works. Then I call into TWC support, and they obviously can't get it working either, so they send out a Tech. However, usually before the tech comes, and now 2 times in a row, the service comes back on within an hour or so of my call.
Also, the tech always say there are no service area outages happening at the moment.
Question, are the techs doing anything remotely to get my signal back online? Anything at my switch that I connect back to? I find it very strange that the service works right after I call, multiple times.
Any experiences out there or any help? My modem is old, but I do not think this is the issue, as internet is fine most of the time.
Been there done that. Got it fixed.
Most cable modems have an admin screen. Web browse to 192.168.100.1 (even if you use a different subnet). One screen should show signal strengths for the to-modem (downstream) signal, and from-modem (upstream).
Downstream should be 0dBmV within about + or - 5dBmV. More positive is good.
Upstream should be in the 40's dBmV. More positive is bad.
These levels will foremost depend on your coax splitter arrangement. The best is: Coax enters home, to a 2-way splitter, one leg to your cable modem, the other leg to TVs or an amplifier feeding TVs and cable boxes.
The coax from my home to the "demarcation" point for connecting to the cable Co's system is old and long. The upstream signal strength, on some days, is +53dBmV or more and this is why it then sometimes would lose lock and self-reboot, in a loop. After an hour or two, it would manage to reboot and lock. This is NOT a fault in the modem; it's either too many splitters and/or too much noise in the cable system. The high upstream signal power sent upstream is controlled by the ISP's head-end (CMTS). The power is increased in steps until the head-end gets the desired received signal strength. This is called power-ranging. If the ranging causes upstream levels in the 50's, there's not enough margin left and it will lose lock and try to re-range, repeatedly.
Thus, I got TWC to add an amplifier in my attic, at their cost. It's a bi-directional amplifier- benefiting both up and downstream signals. The cable modem is placed after the amplifier, via the 2-way splitter. The ISPs don't like to use these bi-directional (active return it's called) but in my case it was necessary due to the 150' long and old crummy RG59 coax (not RG8). Also, after huge struggles, I found an illegal 4-way splitter had been put in my coax en route to the demarcation - 15 years ago, by a neighbor. Getting rid of this helped a lot but the active-return amp was still needed.
If you cannot see the cable modem admin screens on your web browser, a "MASTER Tech" from TWC can see it. Most tech's don't know how to assess upstream problems.
Note that the cable set top boxes also send upstream signals - for requesting video on demand from the head end, and for "Switched Digital Video" (SDV). SDV is like video (movies) on demand, but is used for the less popular channels so the cable system frequencies can be re-used based on subscriber demand. Examples include Cooking channel, and so on. In my area most SDV channels are in the 200's and 800's. The upstream signal issues that can affect the cable modem will likewise affect the SDV in the cable box, and thus one wants to minimize the number of splitters before the cable box. It too benefits from the active return amp.
My cable modem was for years the Motorola (GA) Surfmodem - I rent not own, so there's no finger-pointing with TWC. Now it's an Arris combo cable modem and digital phone. Same 192.168.100.1 admin web works with it. Sometimes, the web admin page refuses to display and only a cable modem reboot restores it. This didn't happen with the Surfboard.
The upstream signal will vary a lot hour to hour, day to day, season to season - due to the cable system's noise and lack of maintenance.
