Basic Internet Connectivity And Modem Help

[itisdesign]

(see bottom of post for temporary fix)

1) This intermittent connectivity drop issue exists with both SB6120 and SB6121. It began sometime in July (after mid-July I believe) and occurs well over a dozen times per day.
2) This issue occurs even when no Ethernet cable is connected to the cable modem (thus, not a router issue).
3) Restoring the modem to factory defaults doesn't resolve the issue.
4) After the modem auto-reboots, sometimes the modem's Status page says it is 'Offline' and most, if not all, of the other tasks have a status of 'Not Started'. In this scenario, the Signal page says the Ranging Status for upstream channel 11 is 'T4 Timeout'.
5) After the modem auto-reboots, sometimes the modem's Status page says it is 'Operational' and all the other tasks have a status of 'Done'. In this scenario, the Signal page says the Ranging Status for all upstream channels is 'Success'.
6) Recently I connected a coax to a TV that hadn't been connected in a while. After I did this, then Internet stayed connected for just under 24 hours before the issue resumed again.
7) I've also disconnected the coax from various TVs and left them disconnected, but none of this resolved the issue.
8) I have over a dozen pages of logs saved to PDF, and I've seen about every error message that others have already posted on this page: http://forums.comcast.com/t5/Connectivity-and-Modem-Help/Having-issues-with-your-Motorola-SB6121-Ple....
9) Comcast rates the SB6121 as 3 stars on their DOCSIS info page here: http://mydeviceinfo.comcast.net

Regarding Motorola Broadband Technical Support (1-877-466-8646):
-----------
I have an open ticket w/ them. As they've suggested, I've tried 2 purchased SB6121 modems, in addition to the SB6120 I'm renting from Comcast. Since the same issue existed with all those modems, they said it is a Comcast issue. They also said the Logs page merely displays messages that the modem receives from the service provider and must be interpreted by the service provider, even tho the sentence at the top of that page says: "This page displays detailed information intended for use by an authorized Motorola Corporation Cable Modem technician.". They also said all Motorola Broadband Technical Support representives are "authorized Motorola Corporation Cable Modem technicians". (sounds like Motorola needs to change the wording of that sentence at top of Logs page, if they're unable to do what that message says they're able to do)

Regarding Comcast Customer Service reps:
-----------
They are unable to decipher the meaning of those error messages on the modem's Logs page, even tho Motorola says the messages came from Comcast. However, they did say that on a scale of green/yellow/red:
- My transmit Power Level of 51dBmV is rated as yellow
- My upstream Receive Power Levels of +6.4dBmV to +555dBmV are rated as red (they said: -0.9 to +0.9 is green; +1 to +3 is yellow; above 3 is red, even tho the following page says +3 is good: http://forums.comcast.com/t5/Connectivity-and-Modem-Help/Connection-Troubleshooting-Tips/td-p/125357...)

Regarding Comcast Service Technicians:
-----------
A Comcast technician was already here a few days ago and connected modem's coax cable to a line tester and said all signal levels were good and then left. He did not even look at the modem's error logs (I even printed a few pages of the PDF'd logs, but he didn't care).

Regarding the cable/splitter setup:
-----------
Comcast previously ran a new coax from the pole to the house. They installed a 2-way splitter at the house, and ran a coax from one output port of that splitter to a wall jack, and ran a coax from that wall jack to the back of the modem. The second output port on that splitter feeds all the TVs.

-----------
Rented Modem:
-----------
Model Name: SB6120
Vendor Name: Motorola
Firmware Name: SB_KOMODO-1.0.6.6-SCM00-NOSH
Boot Version: PSPU-Boot 1.0.0.4m1
Hardware Version: 3.0
Firmware Build Time: Apr 17 2012 15:09:37

Downstream Channel ID: 1, 3, 6, 7
Frequency: 549000000 Hz, 531000000 Hz, 555000000 Hz, 525000000 Hz
Signal to Noise Ratio: 37 dB, 36 dB, 37 dB, 34 dB
Downstream Modulation: QAM256, QAM256, QAM256, QAM256
Power Level: -3 dBmV, -4 dBmV, -4 dBmV, -5 dBmV

Upstream Channel ID: 12, 10, 11
Frequency: 34800000 Hz, 22600000 Hz, 27900000 Hz
Ranging Service ID: 6999, 6999, 6999
Symbol Rate: 5.120 Msym/sec, 2.560 Msym/sec, 5.120 Msym/sec
Power Level: 51 dBmV, 52 dBmV, 51 dBmV
Upstream Modulation: [3] QPSK [3] 64QAM, [3] QPSK, [2] 16QAM, [3] QPSK [3] 64QAM
Ranging Status: Success, Success, Success
Upstream Signal to Noise Ratio: 36 dB
Upstream Receive Power: 555dBmV

hahahahah, yes, that's five-hundred fifty-five!!  The CSR said that reading is "off the charts" 

-----------
Purchased Modem:
-----------
Model Name: SB6121
Vendor Name: Motorola
Firmware Name: SB_KOMODO-1.0.6.6-SCM00-NOSH
Boot Version: PSPU-Boot(25CLK) 1.0.12.
Hardware Version: 5.0
Firmware Build Time: Apr 17 2012 15:09:37

Downstream Channel ID: 1, 3, 4, 7
Frequency: 549000000 Hz, 537000000 Hz, 531000000 Hz, 525000000 Hz
Signal to Noise Ratio: 36 dB, 35 dB, 35 dB, 34 dB
Downstream Modulation: QAM256, QAM256, QAM256, QAM256
Power Level: -5 dBmV, -6 dBmV, -6 dBmV, -6 dBmV

Upstream Channel ID: 12, 10, 11
Frequency: 34800000 Hz, 22600000 Hz, 27900000 Hz
Ranging Service ID: 6775, 6775, 6775
Symbol Rate: 5.120 Msym/sec, 2.560 Msym/sec, 5.120 Msym/sec
Power Level: 51 dBmV, 52 dBmV, 51 dBmV
Upstream Modulation: [3] QPSK [3] 64QAM, [3] QPSK, [2] 16QAM, [3] QPSK [3] 64QAM
Ranging Status: Success, Success, Success
Upstream Signal to Noise Ratio: 36 dB
Upstream Receive Power: 6.4dBmV

===========
===========
TEMPORARY FIX: Unscrew any coax cable in the house, and touch the copper wire to threaded portion on the device that the cable was connected to. Or touch the wire with finger. Repeat until Internet is restored. =P
===========
===========

I have a service technician coming out here tomorrow.  I'll follow-up here.

[rabbit555]

Upstream signals seem high.

Do you have an amp on the drop for cable modem?

or a splitter with an unterminated coax cable?

[itisdesign]

---

rabbit555 wrote:

Upstream signals seem high.

Do you have an amp on the drop for cable modem?

or a splitter with an unterminated coax cable?

---

Hi rabbit555,

I agree the upstream signals are high.  There is no amp anywhere at all.  The only unterminated coax cable was the one that I'd connected to a TV which then caused my Internet to remain connected for just under 24 hours.  After which point the connection drop issue resumed it's frequent/irregular pattern.

During one phone convo w/ Comcast, they saw my Upstream Receive Power was 555dBmV.

A tech will be here w/in the next 90 mins, so I'll follow-up here w/ more info.

Thanks!

[itisdesign · Accepted solution]

Comcast tech replaced corroded coax cable ends w/in the junction box.  (note: all the cabling, as well as the junction box itself, was installed new 2 yrs ago by Comcast)  Finally, my Internet speeds have been restored and I've had no disconnects since he left (22 hrs ago).

I'll give this a few more days, and follow-up on Friday.

[itisdesign]

---

itisdesign wrote:

Comcast tech replaced corroded coax cable ends w/in the junction box.  (note: all the cabling, as well as the junction box itself, was installed new 2 yrs ago by Comcast)  Finally, my Internet speeds have been restored and I've had no disconnects since he left (22 hrs ago).

I'll give this a few more days, and follow-up on Friday.

---

It's been 2 weeks and I've had 0 intermittent connectivity issues w/ SB6120 and SB6121.

Resolved.