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wah001

join:2009-01-02
united state

[Connectivity] Upstream bonding drops and high power level

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Before issues
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After
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Log file
I have been having problem with my upstream for a couple of weeks. I even went as far as purchasing a new SB6141 modem which appeared to have corrected the issue for a while.

My upstream bonding drops from 3 channels to just one and the power level goes through the roof. (From 51dBmV to 57dBmV)

This is usually accompanied by T4 timeouts and a modem reboot
(Screen shots attached)

Any suggestions?


NetFixer
Snarl For The Camera Please
Premium
join:2004-06-24
The Boro
Reviews:
·Cingular Wireless
·Comcast Business..
·Vonage

said by wah001:

I have been having problem with my upstream for a couple of weeks. I even went as far as purchasing a new SB6141 modem which appeared to have corrected the issue for a while.

My upstream bonding drops from 3 channels to just one and the power level goes through the roof. (From 51dBmV to 57dBmV)

This is usually accompanied by T4 timeouts and a modem reboot
(Screen shots attached)

Any suggestions?

Check all of the coax connections for tightness and corrosion, and replace any older crimp style connectors with compression connectors. Also connect your modem directly to your demarc (the first connection in your home before any splitters); that will eliminate inside wiring and splitters as the source of the problem. If that doesn't help, then you will need to ask Comcast support for help.
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wah001

join:2009-01-02
united state

The modem is on a dedicated RG6U Quad line.
Im on with support and she is grasping at straws now

Apparently "that the signal shows red and yellow still." according to their end


ExoticFish

join:2008-08-31
Stuarts Draft, VA

Your upstream is way too high. You need a tech visit.
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»www.VAJeeps.com
»www.BronzedBod.com



flwpwr

@comcast.net
reply to wah001

The upstream limit for multiple upstream channels is 54, after that it will drop to one channel which has a limit of 57. Something is wrong somewhere, you need a tech visit. For now try tightening or reseating fittings along the path and using a wrench to snug them up [do not try to break them they are in reality thin pieces of metal and not that durable]. Visually inspect the interior wires for sharp bends, kinks, or crushing and replace as needed as well.



EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

1 edit

said by flwpwr :

The upstream limit for multiple upstream channels is 54, after that it will drop to one channel which has a limit of 57.

It's not an exact science. Don't forget about accuracy issues.. These figures can be inaccurate by 3-4 dB in either direction than they really are. FWIW, for many years now I have seen connectivity problems with modems that are transmitting at 50-51 dB even with a single 16 QAM carrier.

ExoticFish

join:2008-08-31
Stuarts Draft, VA

I agree. When I began to see upstream around 50 I had issues.
--
»www.VAJeeps.com
»www.BronzedBod.com


Oedipus

join:2005-05-09
kudos:1
reply to wah001

I've never seen an upstream power level higher than 57, which may mean that 57 is the highest number the modem will report.

So yeah, get a tech visit.


wah001

join:2009-01-02
united state
reply to wah001

Click for full size
Splitters and cables
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Cable box
I decided to take a look in my cable box and found 4 splitters and a rats nest of cable.
I connected my dedicated modem line straight to the comcast cable.
Rebooted the modem and my up upstream bonding came back with 3 channels. One of them had a T4 timeout even after a power off.
I did some digging and found a thread saying to reset the modem defaults.
Once it came back up the full bonding was restored with no errors.
Upstream power level is back to 51/52 dBmV.

I have a tech booked for Thursday so i'll keep an eye on things and have him put in a single 4 way splitter.

ExoticFish

join:2008-08-31
Stuarts Draft, VA

51-52 is still too high for MY liking. Had issues with my upstream @ around 50.
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»www.VAJeeps.com
»www.BronzedBod.com


Oedipus

join:2005-05-09
kudos:1
reply to wah001

51-52 can be good enough, but it will get worse when the weather warms.



flwpwr

@comcast.net
reply to EG

said by EG:

said by flwpwr :

The upstream limit for multiple upstream channels is 54, after that it will drop to one channel which has a limit of 57.

It's not an exact science. Don't forget about accuracy issues.. These figures can be inaccurate by 3-4 dB in either direction than they really are. FWIW, for many years now I have seen connectivity problems with modems that are transmitting at 50-51 dB even with a single 16 QAM carrier.

I have no idea what talking about. You appear to be under the impression there is some real level versus what the modem reports. As a tech, with a meter, that is the case for troubleshooting to and within the plant only, but NOT for DOCSIS negotiating. If the modem says its at 54, it's at 54. Even if the supposed perfect meter says you are at 56. As far as the cmts is concerned you're at 54 and it does not change anything until the modem claims it is at 55 [basically the cmts is not within it's receive specs, for us its -1 to +1, others may be different, if it is not there the cmts will say lower or raise the transmit at this time if it goes out of the appropriate range, things must change.]. If you are having issues at 51 staying with multiple channels this is most likley a config issue with the cmts or a noise issue, and has nothing to do with the modem being off on its transmit value.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

said by flwpwr :

I have no idea what talking about.

That would seem to be *your* problem...