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user_jn7ahv
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Tuesday, December 19th, 2023 2:17 AM

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Internet going in/out due to "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing"

Hello, seeking help with an internet issue. I work for a call center remotely, and throughout the day I have dropped calls. At the time of the dropped call I will get modem errors such as these, and when doing a ping test I get packet loss for very short period of time. I have read else where this might be a signal strength issue. My modem/router is Motorola - MG8702. Any help on this would be greatly appreciated, and let me know if you need more info.

Event Log
   Log  
  
    Time    Priority    Description 
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;;CM-QOS=1.1;CM-VER=3.1;
    02:34:13
Tue Oct 31 2023		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;
    09:09:03
Thu Nov 16 2023		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;;CM-QOS=1.1;CM-VER=3.1;
    09:09:08
Thu Nov 16 2023		   Critical (3)   No Ranging Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Notice (6)   Honoring MDD; IP provisioning mode = IPv6
    20:47:07
Fri Dec 8 2023		   Notice (6)   DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;;CM-QOS=1.1;CM-VER=3.1;
    23:45:52
Sun Dec 17 2023		   Notice (6)   CM-STATUS message sent. Event Type Code: 23; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;;CM-QOS=1.1;CM-VER=3.1;
    23:45:52
Sun Dec 17 2023		   Notice (6)   CM-STATUS message sent. Event Type Code: 20; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;;CM-QOS=1.1;CM-VER=3.1;
    23:45:54
Sun Dec 17 2023		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;;CM-QOS=1.1;CM-VER=3.1;
    23:46:17
Sun Dec 17 2023		   Notice (6)   CM-STATUS message sent. Event Type Code: 22; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;;CM-QOS=1.1;CM-VER=3.1;
    23:46:25
Sun Dec 17 2023		   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-QOS=1.1;CM-VER=3.1;

   Downstream Bonded Channels  
  
   Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 20 555.0 8.7 40.9 0 0
   2 Locked QAM256 17 537.0 7.9 40.7 0 0
   3 Locked QAM256 18 543.0 9.0 40.8 0 0
   4 Locked QAM256 19 549.0 7.8 40.6 0 0
   5 Locked QAM256 21 561.0 7.4 40.5 0 0
   6 Locked QAM256 22 567.0 8.4 40.7 0 0
   7 Locked QAM256 23 573.0 8.1 40.5 0 0
   8 Locked QAM256 24 579.0 8.6 40.6 0 0
   9 Locked QAM256 25 585.0 8.5 40.7 0 0
   10 Locked QAM256 26 591.0 8.4 40.7 0 0
   11 Locked QAM256 27 597.0 8.6 40.6 0 0
   12 Locked QAM256 28 603.0 7.8 40.5 0 0
   13 Locked QAM256 29 609.0 7.7 40.5 0 0
   14 Locked QAM256 30 615.0 7.4 40.3 0 0
   15 Locked QAM256 31 621.0 7.7 40.4 0 0
   16 Locked QAM256 32 627.0 6.9 40.2 0 0
   17 Locked QAM256 33 633.0 7.4 40.4 0 0
   18 Locked QAM256 34 639.0 7.0 40.2 0 0
   19 Locked QAM256 35 645.0 8.9 40.9 0 0
   20 Locked QAM256 36 651.0 8.0 40.4 0 0
   21 Locked QAM256 37 657.0 8.9 40.5 0 0
   22 Locked QAM256 38 663.0 8.5 40.5 0 0
   23 Locked QAM256 39 669.0 8.8 40.2 0 0
   24 Locked QAM256 40 675.0 9.0 39.3 109 2
   25 Locked QAM256 41 681.0 8.4 40.1 257 19
   26 Locked QAM256 42 687.0 9.1 40.0 187 37
   27 Locked QAM256 43 693.0 8.0 39.8 0 0
   28 Locked QAM256 44 699.0 8.8 39.9 0 0
   29 Locked QAM256 45 705.0 7.7 39.6 0 0
   30 Locked QAM256 46 711.0 8.6 39.8 0 0
   31 Locked QAM256 47 717.0 8.9 40.0 0 0
   32 Locked OFDM PLC 48 805.0 10.3 39.6 -441603775 68

Question

 • 

Updated 

1 year ago

164

3

0

EG

Expert

 • 

110.1K Messages

1 year ago

This may or may not be the root cause of the problem (YMMV) but the downstream power is a bit on the high / strong side.

Please also copy all of the text in its entirety of the *Upstream Power Level* numbers and paste them into your next post.

1

0

user_jn7ahv

4 Messages

Hello, thank you for taking a look. Here is the upstream:

   Upstream Bonded Channels  
  
   Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 1 5120 16.4 43.0
   2 Locked SC-QAM 2 5120 22.8 43.0
   3 Locked SC-QAM 3 5120 29.2 43.5
   4 Locked SC-QAM 4 5120 35.6 43.5

1 year ago

0

EG

Expert

 • 

110.1K Messages

1 year ago

Those are in spec. As stated, the higher downstream power may not be the root cause of the problem but here is some stuff that you can try and see;

Is there a drop amplifier on the coax cable line leading to the modem ? If so, try removing / bypassing it and see. If not, you can try installing a -6 dB forward path-only attenuator pad such as this one on the coax port on the rear of the modem to knock that power level down and see;


https://www.amazon.com/FPA6-54-Forward-Attenuator-DOCSIS-Internet/dp/B08KTRC3XZ 

It won't affect the upstream power level which is within spec.

Please post back with how it goes. If you still have the problem I will escalate this to the Comcast Corporate Employees here. 



(edited)

1

0

user_jn7ahv

4 Messages

Would this one work? https://www.amazon.com/6db-Attenuator-Pad-1-each/dp/B0013L48XA/ref=sr_1_3?keywords=-6+dB+forward+path-only+attenuator+pad&sr=8-3

1 year ago

0

EG

Expert

 • 

110.1K Messages

1 year ago

No. That's an overall attenuator pad. It going to raise the upstream power close to being out of spec which is something that we don't want to do. Try the one that I linked to.

2

0

user_jn7ahv

4 Messages

Gotcha, the one you linked to isn't available any more. Do you have any other recommendations? Specifically one that would arrive quicker?

1 year ago

0

XfinityBenny

Official Employee

 • 

790 Messages

@user_jn7ahv Looks like there is one available with the exact same name and specs in the top left corner in the Amazon link that EG posted. The page says it can arrive within 6 days with shipping. If that doesn't work or you don't find one, let us know. We can troubleshoot and get a tech out asap if it isn't resolved remotely!

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1 year ago

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