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Upstream light blinking on my modem


I had this issue with my upstream light blinking on my modem for a couple months and Teksavvy couldn’t solve the problem. It was a major factor in my deciding to shop around for other ISP’s at the time and really was serendipity in hindsight. My Thomson DCM-475 one day just started blinking. I hadn’t seen a modem blink like that before but I chalked it up to an anomaly of being a Teksavvy customer (never do that) and I was too busy with audio to stop and figure it out. Hell, the internet was still working. One day when I should have been doing something more fun, I was poking through the diagnostics of the modem to see what was amiss. I had seen a few error messages so I decided to try and get an RMA going in case the modem was kaput. I described the signal strength in the GUI to Tek’s support staff. They said the signal levels were a bit low but should be fine. They told me to reset the router as per the script they read to everyone and that was that. is the address to enter into your browser when you need to check out the diagnostics of your Thomson or Technicolor Modem

Only, that wasn’t simply it.

The US light kept flashing. I let it go for a while, and eventually it began bothering me again, so I called tech support and they said they would send out a technician. It was directly after an ice storm, so it would be a free service call.
I had to wait a week or so but finally, one snowy afternoon I saw a white unmarked van parked a few houses down. I knew the day of reckoning had come. The tech did a great job cleaning up the last tech’s mess. He fastened the exterior connection to the house, which was loose, re-terminated all the coaxial cables and brought in his own modem to confirm the issue was with my modem.  Or so it seemed.
I called support again and told them the line is fine and my signal should be clear but something was wrong with the modem. They told me it was just out of warranty a few weeks ago. I was pretty miffed, naturally. . I went through all the troubleshooting steps and multiple calls and now I am just left screwed without a proper modem. I was going to get this damn upstream light blinking on my modem to go solid, period, end of sentence. I wasn’t going to buy a new one, however.

I took to which is a great site for researching ISP’s. Someone on the forum pegged the error (much earlier) to an unbound connection. Previously, I had been unable to identify the post message, which is a sequence of flashing lights that you need to match up to a table to interpret the blinking lights. The US light wasn’t blinking like the manual described.
Unbound connection? Sounds like a provider issue to me, I was a bit irked. I then found someone else who had mentioned power levels for binding and it struck me. What if my PSU had failed and my voltages were drooping on the control channel? I know, you were probably thinking that all along…

I went and got another wall wart, ya know the black thing you stick into your already jammed up power bar. This is the kind you get lucky with and they’re offset so you can actually plug things in above and below it. Well, that’s a DC power supply. It steps down the current of the AC in your walls. It was just a matter of matching the same amperage, voltage and polarity to get a new one for a few bucks at Active Surplus and bam, the issue was solved. Polarity is marked with a little picture like this.


It saved me shilling out $100 for a modem that wasn’t broken so hopefully this helps someone out there put their mind at ease too.





Man, it’s because of people like you that I still have hope for the internet. I kept looking at that US light blinking and trying not to notice it for weeks, since like for you the internet was working. Anyway, your solution is worth it’s weight in gold for me.

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