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SYNC Timing Synchronization failure

Frequent Visitor

SYNC Timing Synchronization failure

Hello, I live in Florida and i had been using an older model of a modem that Comcast had given us about 2 years ago. Everything worked perfectly fine and it would never drop except for when there was an outage, understandably so. However about two weeks ago, it had been expired and we had to replace it with a new (albeit refurbished) modem provided to us by the local xfinity store.... Which we've had to replace three times now because each one fails to connect or randomly drop the connection.

The "new" modem's model name is TC8305C. And when i look at log errors it shows:
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=e0:88:5d:3e:20:5a;CMTS-MAC=58:97:bd:2e:c0:f0;CM-QOS=1.0;CM-VER=3.0;
And:
Unicast Ranging Received Abort Response - Re-initializing

I don't know what to do, it keeps dropping every 3-10 minutes randomly, please help.
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Diamond Problem Solver

Re: SYNC Timing Synchronization failure

Start with the modem's signal stats. Perhaps they already are, or they are close to being out of spec and intermittently they go completely of spec. Try getting them here http://192.168.100.1 or here http://10.0.0.1

Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.


Frequent Visitor

Re: SYNC Timing Synchronization failure

Is this it?woop.jpg

Diamond Problem Solver

Re: SYNC Timing Synchronization failure

Yes. The upstream power is a bit on the high side and *may* be intermittently fluctuating even higher out of spec. That can cause random disconnects and spontaneous re-booting of the modem. In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, etc. Splitters should be swapped with known to be good / new ones to test.

 

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Good luck !

 

Frequent Visitor

Re: SYNC Timing Synchronization failure

Alright, I followed your advice and I let a few days pass to see what other problems might show up or how best to optimize my setup. I had one splitter from where it was connected from the electricity pole meets around the power meter of my house. Then I had a cable from there directly to the modem. I still have a router connected to it too. For the most part it has stopped constantly reseting, however I will loose the connection momentarily and get a lag spike randomly. I notice this everytime that I am playing a game and it happens about 15-45 minutes at random.  When it does, I look at the modem and router but all the lights seem to indicate that everything is fine. However, all the computers in the house are unable to get an internet connection. Sometimes the issue solves itself after a few seconds, but sometimes it stays like that for several minutes and I have to reset the modem. Last time I reconnected ethernet cable from the router and the modem (unplugged and plugged them gain). This also fixed the problem but I don't know if the modem had righted itself or not in that time. Anyways, should I disconnect the router and just use the modem's wi-fi or is the problem part of something else entirely?

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Diamond Problem Solver

Re: SYNC Timing Synchronization failure

The upstream power is now WORSE / out of spec. This has nothing to do with having a separate / side-car router. I will mention that if are using a separate router with that gateway device, the gateway should be put in to bridge mode. Again, this has nothing to do with your RF signal / connection quality problem from the street. As mentioned before, get a tech visit if you can't get the signals to be any better.

 

Bear in mind that if the premises facing techs can't find / fix an issue at your home, it is they who are responsible to escalate it to the line / maintenance dept. The problem may indeed lie beyond your premises in the neighborhood infrastructure somewhere.

Frequent Visitor

Re: SYNC Timing Synchronization failure

Alright, I see. Thank you very much for all your help and patience. I appreciate your timely and knowledagble responses. I'll be calling in the tech and see what they can do.

Diamond Problem Solver

Re: SYNC Timing Synchronization failure

Good luck with it ! Smiley Happy

Frequent Visitor

Re: SYNC Timing Synchronization failure

Hi. What ended up happening when discussing this with Comcast? 

Diamond Problem Solver

Re: SYNC Timing Synchronization failure

Year and a half old dead thread now being closed.