U

Visitor

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5 Messages

Thu, Jul 21, 2022 7:58 PM

MB8611 connection regularly drops

At least once a day, my modem seems to lose connection. We installed this modem in the last few weeks and it's pretty much been happening the whole time.

Below are the downstream and upstream bonded channels taken from a snapshot when the connection was working fine.

In the modem event log, I see a critical error from sometime in past, but I can't remember if that was associated with one of the times it dropped.

Started Unicast Maintenance Ranging - No Response received - T3 time-out;

Any ideas of what I should look into to fix this?

Accepted Solution

EG

Expert

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96.9K Messages

5 months ago

Both the Downstream power and the upstream power levels are out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an 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.

Also check the coax cable for any damage such as cuts, nicks, kinks, sharp bends, etc.

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 with it !

Visitor

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5 Messages

5 months ago

Thanks! I measured the power levels coming into the house and those seemed ok(-1dBmV). I ended up disconnecting the splitter that feeds the different rooms in favor of direct wiring the room with the modem since we aren't using the other rooms anyway. That ended up with about -5 to -7 dBmV per downstream channel.

EG

Expert

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96.9K Messages

5 months ago

That's still on the low / weak side... What do the upstream power levels look like now ?

Visitor

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5 Messages

@EG​ They're about 47-48 dBmV. What levels should I be aiming for for downstream and upstream? Is the power level coming into the house normal?

EG

Expert

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96.9K Messages

4 months ago

So the upstream is a tad on the high side but both should be o/k as long as they remain stable. The bottom line now is to live with it for a while and see if the problem returns.

Here are the desired signal values from the pinned Troubleshooting Tips topic at the top of this board;

 

Specification      Min             Max
Downstream Power Level    
Cable Modems -10dBmV +10dBmV
Gateways and EMTAs -7dBmV +7dBmV
Downstream Signal to Noise Ratio 35dB -
Upstream Power Level +35dBmV +50dBmV
Upstream Signal to Noise Ratio 31dB -
Upstream Receive Power -2dBmV +2dBmV

 

Good luck with it !

Visitor

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5 Messages

4 months ago

Unfortunately the problem has been persistent again. Usually at least once every other day, sometimes multiple times per day. I tried a couple different modems and it's happening on them all. Sounds like I should try to get a technician to come out? Is there a quick way I can schedule this?

Visitor

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5 Messages

4 months ago

Just for reference, I did find that my signals are going outside the values you referenced occasionally. I wrote a script to monitor the values throughout the day for the last few days and created some charts. The vertical lines are times associated with a critical error log.

Downstream

Upstream

(edited)

Official Employee

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202 Messages

@user_b40d1a

 

Thanks for the screenshots. I hate to hear you continue to experience issues. May I ask the make and model of your equipment, is it a Comcast leased modem? 

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