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Low Upstream Power T25

datatox
Regular Visitor

Low Upstream Power T25

Hi all, I've had a number of events where my T25 has stopped responding and has had to be manually rebooted, or where I've had a spontaneous reboot. The downstream power levels seem to fine (at least according to to the Touchstone support page) but I do seem to be getting quite a few Correcteds/Uncorrectables although not sure if the volume is high enough to worry about. Dowstream QAM power levels don't seem to be in spec and Touchstone suggest +45 to +51 ? 

 

Could the low up power be the cause of my drop outs and any suggestions for correcting. Thanks in advance for any help.

 

Upstream and downstream QAM as follows:

Upstream QAM

 UCIDFreqPowerChannel TypeSymbol RateModulation
Upstream 1623.70 MHz41.00 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 2836.50 MHz41.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 3730.10 MHz41.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 4517.30 MHz41.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM

 

Downstream QAM

 DCIDFreqPowerSNRModulationOctetsCorrectedsUncorrectables
Downstream 16459.00 MHz-8.10 dBmV37.64 dB256QAM7505330200
Downstream 27465.00 MHz-7.90 dBmV38.61 dB256QAM1402072800
Downstream 38471.00 MHz-7.90 dBmV38.61 dB256QAM1346792400
Downstream 49477.00 MHz-7.60 dBmV38.61 dB256QAM7094069600
Downstream 510483.00 MHz-7.60 dBmV38.61 dB256QAM7073432800
Downstream 611489.00 MHz-7.40 dBmV38.61 dB256QAM1076248600
Downstream 712495.00 MHz-7.20 dBmV38.61 dB256QAM1158852600
Downstream 813519.00 MHz-7.80 dBmV37.36 dB256QAM779143640
Downstream 914525.00 MHz-9.40 dBmV37.36 dB256QAM981092600
Downstream 1015531.00 MHz-10.20 dBmV37.36 dB256QAM790455400
Downstream 1116537.00 MHz-10.10 dBmV37.36 dB256QAM751027300
Downstream 1217543.00 MHz-9.90 dBmV37.36 dB256QAM1052708020
Downstream 1318549.00 MHz-10.00 dBmV37.64 dB256QAM1024351020
Downstream 1419555.00 MHz-9.50 dBmV37.64 dB256QAM1028832600
Downstream 1520561.00 MHz-9.00 dBmV37.36 dB256QAM1019656200
Downstream 1621567.00 MHz-8.80 dBmV37.64 dB256QAM852923000
Downstream 1722573.00 MHz-8.50 dBmV38.61 dB256QAM6781362100
Downstream 1823579.00 MHz-8.50 dBmV37.64 dB256QAM1026634520
Downstream 1924585.00 MHz-8.70 dBmV37.64 dB256QAM947270800
Downstream 2025591.00 MHz-8.70 dBmV38.61 dB256QAM978286500
Downstream 2126597.00 MHz-8.50 dBmV38.61 dB256QAM1024601000
Downstream 2227603.00 MHz-8.20 dBmV38.61 dB256QAM1091906000
Downstream 2328609.00 MHz-7.90 dBmV38.98 dB256QAM1147199000
Downstream 2429615.00 MHz-7.70 dBmV38.61 dB256QAM7533908490
Downstream 2530621.00 MHz-7.70 dBmV38.98 dB256QAM790205430
Downstream 2631627.00 MHz-7.90 dBmV38.61 dB256QAM7975279680
Downstream 2732633.00 MHz-7.80 dBmV38.98 dB256QAM14697364260
Downstream 2834639.00 MHz-7.90 dBmV38.61 dB256QAM165423263951
Downstream 2935645.00 MHz-7.60 dBmV38.98 dB256QAM1578440720
Downstream 3036651.00 MHz-7.80 dBmV38.61 dB256QAM1512688200
Downstream 3137657.00 MHz-7.90 dBmV38.61 dB256QAM151676152

0

CCAndrew
Diamond Problem Solver

Re: Low Upstream Power T25

It’s your downstream that’s low, upstream is good

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EG
Expert

Re: Low Upstream Power T25

Couldn't agree more with @ComcastAndrew !! FWIW, Arris is wrong ! They have been passing the buck and have been conning people with that statement lately !! Only the Comcast plant / engineering specs matter;

 

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



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
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EG
Expert

Re: Low Upstream Power T25

Stuff that you can try;

 

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 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart 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.



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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datatox
Regular Visitor

Re: Low Upstream Power T25

Thank you both. As suggested I've ordered a two way splitter and I'll also try swaping out the cable from the splitter to the modem. Hopefully his means I won't have to work with the service guys.

CCAndrew
Diamond Problem Solver

Re: Low Upstream Power T25

Take the levels again at your point of entry so you have something to compare with. To give you an idea of outside vs inside

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jimfenton
Frequent Visitor

Re: Low Upstream Power T25

Similar problem here with T25. Occasional disconnects, generally in the middle of the night, that require a reboot of the modem. Comcast came out a few weeks ago and we replaced the coax splitter in my home and verified the signal levels, but the problem still occurs. Spoke with Arris and they said that my upstream signal levels (35.25-38.25 dBmV) are out of spec. But it's interesting that their web page that shows the signal level requirements says the upstream level should be +45 to +51 dBmV, but has an example showing 36.25-38.75 dBmV. I don't think they know what the correct signal levels are.

 

Regardless, the signal level is high enough for the modem to work well except for the occasional lockup, so I think this is a different problem than signal level: it's just not recovering from a line glitch of some sort (apparently there was a brief outage in the neighborhood around the time of my last problem). So I have ordered a Motorola MT7711 that I will run in bridge mode and need to figure out what to do about the T25. Apparently there's a class action lawsuit. Any other ideas?

 

Comcast REALLY needs to get this modem off their certified products list.

 

 

datatox
Regular Visitor

Re: Low Upstream Power T25

I actually got a response from Arris today. Apparently there is a firmware update being deployed by Comcast by the end of the year addressing the issue.
jimfenton
Frequent Visitor

Re: Low Upstream Power T25

So, 2 1/2 months from now? That's an awfully long time. But I suppose Comcast has to move carefully to make sure it doesn't break something else.

vadeltachi
Contributor

Re: Low Upstream Power T25

@datatox   Have you heard anything more about whether there has been or still may be a firmware update created or pushed out?

 

I yanked my T25 and went back to the MB8600 and have had no errors since, but I don't want to trash the T25 if there's hope for a fix...

jimfenton
Frequent Visitor

Re: Low Upstream Power T25

About 11 pm yesterday evening, they pushed a software/firmware update to my T25. I didn't capture the old version numbers, but the new one is:

SW_REV: 11.02.057.12.PC20

Firmware Name:TS11.02.057.12_092820_711.PC20.03

 

You'll know you got it if when you connect to the modem (normally https://192.168.100.1 )it prompts you to set a password (with ridiculous password rules, but that's another story...).

 

Fingers crossed that this version will correct the reliability problems!

emaurice
Frequent Visitor

Re: Low Upstream Power T25

I purchased a T25 earlier this year.  I have had intermittent connection issues as reported in multiple posts in this forum.

 

FYI - Comcast has not yet pushed the firmware update on mine.

 

The original firmware on mine is:

Firmware Name:TS11.01.142_061719_701.PC20.03
Firmware Build Time:Mon Jun 17 15:46:15 EDT 2019