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twztid13's avatar
twztid13
Aspirant
Mar 29, 2025

CM600 Modem all of a sudden stopped working...

I have had a CM600 cable modem with a tp link ac1200 router for over 4 years, working great. I used to have Suddenlink, but Optimum bought them out, so that's who the service is through. About 1.5 years ago, my apartment complex started charging a discount rate included in the rent, so it's through bulk services, but it's worked great until a few nights ago. All of a sudden, it had a red light only, which seems to mean the modem overheated. I tried lots of suggestions, but nothing worked. Of course, i power cycled both devices, i know to always turn the modem on first, then the router 2 minutes later. The red light continued to stay on.

The next day, i tried it again, but it worked this time. I was assuming it cooled off, so i now kept a fan blowing on the modem just in case. I even ordered a new modem, same model, but got scammed (was sent body wash, so now i have to get that sorted, or order another new one). I was leaving on Friday for a few hours, so I turned them both off. When i came back 5 hours later, only the red light would come on again, no matter what i tried.

Today I started both devices up again, but this time, the Ethernet port wasn't recognized. I don't have access to a PC, all i have are mobile devices and game consoles. I tried replacing all of the Ethernet cable and coax cable with new cables, but same result. I have a new router that i have never used so i was going to try it (Linksys mx4300 i got on sale), but first i tried to connect the modem to my PlayStation 4. It didn't recognize a wired connection, even with my original and new Ethernet cables (cat 5e and cat6, respectively). So, i tried to hold the reset button on the modem for 15 seconds, as the manual describes. That actually worked & now it's recognizing the Ethernet port (for now).

I don't have the ability to buy a docsis 3.1 modem, as the cheapest non puma chipset are close to $200. I also can't afford the ISP technicians to come out until i make sure it's not something on my end, because it will be $75 or more if it's my fault. I'm unemployed right now, so on a very limited income. I was hoping someone could help me figure out what the issue is, and whether a new modem would help? I have kept the modem in a place where it gets plenty of air, and isn't next to anything hot. I've lived here 20 years, and the only modern i have ever needed to replace was to upgrade speed, or they were no longer supported by the ISP. I know how to treat my electronics, and i have only ever bought new equipment, not used, so it's hard for me to believe that it's something i did that caused this. Now I have to decide if i need to order another new modem (since i was already seemingly scammed, and have to hassle to get my money back or the modem i ordered and that will take a few days, at best). I don't have mobile data on my TracFone plan, so i will need to buy data if i need anything online when the Internet goes out again (this gets expensive for someone without much money). Any help resolving this, so i can
have stable Internet access once again, would be greatly appreciated.

I forgot to screenshot the event log from the 1st time after i got the Modem working again (i only have the status page), but i have the most recent instance, so i will attach that. Thanks in advance.


https://imgur.com/a/LBVCyIN

2 Replies

  • FURRYe38's avatar
    FURRYe38
    Guru - Experienced User

    Power levels and correct and un-correctables are good.

    However lots of criticals in the event logs. Any Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.

     

    Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
    Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
    Be sure your using good quality RG6 coax cable up to the modem. 
    Start with removing any amplifiers, signal attenuators, or splitters from the coax.
    From there check the line for kinks, damage, moisture in the line.
    Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
    Be sure to power OFF the modem for 1 minute then back ON.
    https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853
    https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router
    https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html
    https://highspeed.tips/docsis-events/

     

    I just bought a used NG CM1200 cable modem off shopgoodwill for $40.

    • twztid13's avatar
      twztid13
      Aspirant
      Ok thanks. The coax cable is the one installed by the ISP originally (both were made by them) & seem perfect (no bends,,rust, or anything other than looking exactly like they have for the last several years,, when they've worked properly). There are no splitters & the cable is less than 2 feet long,, coming directly from the wall in my apartment going into the modem. There are none of the things you mentioned to check for.. It's the exact same cables, connectors,,etc that have been working fine for over 4 years without any changes, so it's odd that it would be any of the associated cables or accessories (nothing touches them, as i live alone, & they're out in the open on a stand,,not in a cabinet or anything that blocks airflow. I'm very careful when i occasionally dust around them & wipe them off. No kinks, moisture, rust, anything other than new looking, clean cables & connectors). The other cable i tried was new, though, just out of the package.

      I have already tried everything that everyone has posted on these forums or others that had problems with Netgear cm600 modems not connecting, overheating, etc (everything i could find except slow or bad connection), including the troubleshooting steps from the links you posted from Netgear, in addition to the same from optimum website, before i posted here.

      I will have to contact the ISP & ask them to check the signal & line quality up to the modem, but i will probably get a new modem first, in case they try to blame it on the modem (they will charge a fee if they claim it's my fault, which is what I'm trying to avoid). Thanks for the response.

      Edit: i have heard too many horror stories about used electronics, so with my luck it's not worth the chance to me. I see everything listed on the site you listed is "sold as is" with no ability to return. The only guarantee is that it powers on. The fine print says some may be returned if listed in the description, but you have to pay the shipping and handling for return & you lose the shipping and handling charges you already paid for the device. I can't afford to take risks like that,, personally. Thanks for the suggestion, & that's amazing you were able to find such a great deal on a used modem.