Regular Visitor
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4 Messages
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
| UCID | Freq | Power | Channel Type | Symbol Rate | Modulation | |
| Upstream 1 | 6 | 23.70 MHz | 41.00 dBmV | DOCSIS2.0 (ATDMA) | 5120 kSym/s | 64QAM |
| Upstream 2 | 8 | 36.50 MHz | 41.25 dBmV | DOCSIS2.0 (ATDMA) | 5120 kSym/s | 64QAM |
| Upstream 3 | 7 | 30.10 MHz | 41.25 dBmV | DOCSIS2.0 (ATDMA) | 5120 kSym/s | 64QAM |
| Upstream 4 | 5 | 17.30 MHz | 41.25 dBmV | DOCSIS2.0 (ATDMA) | 5120 kSym/s | 64QAM |
Downstream QAM
| DCID | Freq | Power | SNR | Modulation | Octets | Correcteds | Uncorrectables | |
| Downstream 1 | 6 | 459.00 MHz | -8.10 dBmV | 37.64 dB | 256QAM | 75053302 | 0 | 0 |
| Downstream 2 | 7 | 465.00 MHz | -7.90 dBmV | 38.61 dB | 256QAM | 14020728 | 0 | 0 |
| Downstream 3 | 8 | 471.00 MHz | -7.90 dBmV | 38.61 dB | 256QAM | 13467924 | 0 | 0 |
| Downstream 4 | 9 | 477.00 MHz | -7.60 dBmV | 38.61 dB | 256QAM | 70940696 | 0 | 0 |
| Downstream 5 | 10 | 483.00 MHz | -7.60 dBmV | 38.61 dB | 256QAM | 70734328 | 0 | 0 |
| Downstream 6 | 11 | 489.00 MHz | -7.40 dBmV | 38.61 dB | 256QAM | 10762486 | 0 | 0 |
| Downstream 7 | 12 | 495.00 MHz | -7.20 dBmV | 38.61 dB | 256QAM | 11588526 | 0 | 0 |
| Downstream 8 | 13 | 519.00 MHz | -7.80 dBmV | 37.36 dB | 256QAM | 7791436 | 4 | 0 |
| Downstream 9 | 14 | 525.00 MHz | -9.40 dBmV | 37.36 dB | 256QAM | 9810926 | 0 | 0 |
| Downstream 10 | 15 | 531.00 MHz | -10.20 dBmV | 37.36 dB | 256QAM | 7904554 | 0 | 0 |
| Downstream 11 | 16 | 537.00 MHz | -10.10 dBmV | 37.36 dB | 256QAM | 7510273 | 0 | 0 |
| Downstream 12 | 17 | 543.00 MHz | -9.90 dBmV | 37.36 dB | 256QAM | 10527080 | 2 | 0 |
| Downstream 13 | 18 | 549.00 MHz | -10.00 dBmV | 37.64 dB | 256QAM | 10243510 | 2 | 0 |
| Downstream 14 | 19 | 555.00 MHz | -9.50 dBmV | 37.64 dB | 256QAM | 10288326 | 0 | 0 |
| Downstream 15 | 20 | 561.00 MHz | -9.00 dBmV | 37.36 dB | 256QAM | 10196562 | 0 | 0 |
| Downstream 16 | 21 | 567.00 MHz | -8.80 dBmV | 37.64 dB | 256QAM | 8529230 | 0 | 0 |
| Downstream 17 | 22 | 573.00 MHz | -8.50 dBmV | 38.61 dB | 256QAM | 67813621 | 0 | 0 |
| Downstream 18 | 23 | 579.00 MHz | -8.50 dBmV | 37.64 dB | 256QAM | 10266345 | 2 | 0 |
| Downstream 19 | 24 | 585.00 MHz | -8.70 dBmV | 37.64 dB | 256QAM | 9472708 | 0 | 0 |
| Downstream 20 | 25 | 591.00 MHz | -8.70 dBmV | 38.61 dB | 256QAM | 9782865 | 0 | 0 |
| Downstream 21 | 26 | 597.00 MHz | -8.50 dBmV | 38.61 dB | 256QAM | 10246010 | 0 | 0 |
| Downstream 22 | 27 | 603.00 MHz | -8.20 dBmV | 38.61 dB | 256QAM | 10919060 | 0 | 0 |
| Downstream 23 | 28 | 609.00 MHz | -7.90 dBmV | 38.98 dB | 256QAM | 11471990 | 0 | 0 |
| Downstream 24 | 29 | 615.00 MHz | -7.70 dBmV | 38.61 dB | 256QAM | 7533908 | 49 | 0 |
| Downstream 25 | 30 | 621.00 MHz | -7.70 dBmV | 38.98 dB | 256QAM | 7902054 | 3 | 0 |
| Downstream 26 | 31 | 627.00 MHz | -7.90 dBmV | 38.61 dB | 256QAM | 7975279 | 68 | 0 |
| Downstream 27 | 32 | 633.00 MHz | -7.80 dBmV | 38.98 dB | 256QAM | 14697364 | 26 | 0 |
| Downstream 28 | 34 | 639.00 MHz | -7.90 dBmV | 38.61 dB | 256QAM | 16542326 | 39 | 51 |
| Downstream 29 | 35 | 645.00 MHz | -7.60 dBmV | 38.98 dB | 256QAM | 15784407 | 2 | 0 |
| Downstream 30 | 36 | 651.00 MHz | -7.80 dBmV | 38.61 dB | 256QAM | 15126882 | 0 | 0 |
| Downstream 31 | 37 | 657.00 MHz | -7.90 dBmV | 38.61 dB | 256QAM | 15167615 | 2 | 0 |
EG
Expert
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107.6K Messages
4 years ago
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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CCAndrew
Gold Problem Solver
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25.9K Messages
4 years ago
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EG
Expert
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107.6K Messages
4 years ago
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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datatox
Regular Visitor
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4 Messages
4 years ago
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.
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CCAndrew
Gold Problem Solver
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25.9K Messages
4 years ago
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jimfenton
Contributor
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13 Messages
4 years ago
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.
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datatox
Regular Visitor
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4 Messages
4 years ago
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jimfenton
Contributor
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13 Messages
4 years ago
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.
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vadeltachi
Contributor
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60 Messages
4 years ago
@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...
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jimfenton
Contributor
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13 Messages
4 years ago
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
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!
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emaurice
Frequent Visitor
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20 Messages
4 years ago
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:
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