So I"ve been having an ongoing issue with my Comcast provided internet. The US light has been blinking with intermediate connections, modem reboots & slow speeds. Comcast techs cannot fix my issue since March of this year. All my power levels seem fine, but the event log tells a different story. Even their automated phone system recognizes errors with the modem. This all started after they did some maintance in my area. Modem/router is a c7000. Firmware v1.01.33. Any help would be greatly appreciated.

Have the ISP check the signal and line quality UP to the modem. If they did maintenance in the area and problems started after this, then the ISP needs to review this and look into this. Be sure there are not 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.

All lines to the home are all new per ISP. Event log shows SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;at the begining of every boot & ends with Unicast DSID PSN startup errorwith multiple T3/T4 timeouts in between. This also happened with their provided modem. ISP cannot figure it out for 8 months now. They wont even make any more troubleshooting call to my home.

"This also happened with their provided modem. ISP cannot figure it out for 8 months now"If this is happening with there modems, then the ISP needs to fix this. This is there responsibility. Any chance of using a different ISP?

Nope. I read on this forum that some users of the CM1000 were having similar issues & it possibly being related to a CMTS needing to be updated or patched. Was hoping to get some insight on that with hopes of providing my ISP with something they can use to resolve my connection issue.

Maybe a forum moderator can comment. Again if this was happening with other modems, this seems to be an ISP issue as well.vkdelta

c7000 T3/T4 timeouts & US Light blinking

12 Replies

FURRYe38
Guru - Experienced User
Dec 02, 2019
Have the ISP check the signal and line quality UP to the modem. If they did maintenance in the area and problems started after this, then the ISP needs to review this and look into this.
Be sure there are not 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.
- JayQue2
  Aspirant
  Dec 02, 2019
  All lines to the home are all new per ISP. Event log shows
  SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
  at the begining of every boot & ends with
  Unicast DSID PSN startup error
  with multiple T3/T4 timeouts in between. This also happened with their provided modem. ISP cannot figure it out for 8 months now. They wont even make any more troubleshooting call to my home.
  - FURRYe38
    Guru - Experienced User
    Dec 02, 2019
    "This also happened with their provided modem. ISP cannot figure it out for 8 months now"
    If this is happening with there modems, then the ISP needs to fix this. This is there responsibility.
    
    Any chance of using a different ISP?

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c7000 T3/T4 timeouts & US Light blinking