jsimmons
Premium,MVM
join:2000-04-24
Falls Church, VA
 ·Cox HSI
| reply to thebob6
Re: [VA] Modem Boot Log Issues
said by thebob6  :But Irish have you ever heard of an issue with the Surfboard Sb5120 constantly power cycling itself (once every ~5-10 minutes). The power light stays on but its like someone unplugs the back and plugs in back in real quick. All other lights go off and it goes through the process of reconnecting itself (all lights blinking besides power until they are solid etc). This casues the connection to drop and 2-3 minute 100% packetloss in the process while it tries to reestablish the connection. This is not a power cycling issue, but sounds more like a loss of sync between the modem and CMTS. I've had that problem periodically. Usually in my case it was an upstream signal issue - plenty of downstream signal and SNR, but the Modem was not seeing a clean upstream path. I reported the issue to Cox, and over time, I saw the upstream channel changed (I assumed from the CMTS side) to find a cleaner frequency. Problem was resolved over the course of a few hours. Apparently there was an area-related issue.
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"Everything should be made as simple as possible, but not one bit simpler."- Albert Einstein |
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thebob6
join:2002-09-02
Santa Cruz, CA
edit:
May 6th, @03:32PM
| Yeah this issue has been going on for a week+ now. I may call Cox again and ask if they can do anything on their side. What should I ask for? Them to change my upstream channel? I really wish some Cox reps would hop in this thread and give some advise.
Edit: Called them. They said again the signal looks perfect and the log shows since 12:01 this morning I have had 54 odd resets. He said it is resetting itself consistently 4 times every hour. He said the only thing he can do is send another tech out. Tech is coming tomorrow morning 8-10. I'm not sure what he is going to do :/ |
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thebob6
join:2002-09-02
Santa Cruz, CA | If any Cox cable tech do drop by in this thread I would be very happy if you could give me some advise as to what exactly to tell the tech who is coming tomorrow morning.
Thanks |
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Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
| Tell the tech ....
"They said again the signal looks perfect and the log shows since 12:01 this morning I have had 54 odd resets. He said it is resetting itself consistently 4 times every hour."
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"You can observe a lot by watching". Yogi Berra |
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daveinpoway
join:2006-07-03
Poway, CA | reply to thebob6
Recently, there was something stated in one of the forums that some SB5120's are constantly rebooting themselves as they get older. No idea if this is your problem or not. |
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jsimmons
Premium,MVM
join:2000-04-24
Falls Church, VA
·Cox HSI
| said by daveinpoway :Recently, there was something stated in one of the forums that some SB5120's are constantly rebooting themselves as they get older. No idea if this is your problem or not. Not sure what the definition of "older" is. I've had mine in continuous operation for about 3 years now (I think) with no such issues. I do have it running on a battery UPS with line conditioning (along with my firewall/router, LAN switch and Access Point).
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"Everything should be made as simple as possible, but not one bit simpler."- Albert Einstein |
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thebob6
join:2002-09-02
Santa Cruz, CA
| reply to jsimmons
Hrmph, The tech came out today and replaced the coaxial cable in the house and did verify that the signals seem perfect. Although right before the tech came I was oddly not getting any disconnects. I check the modem info page when the tech left and it seems that my upstream channel has indeed changed and so far I've had not had any disco's. |
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daveinpoway
join:2006-07-03
Poway, CA | reply to jsimmons
I have ben unable to locate the post, but, as I recall, the problem would start when the modem was about 2 years old; only some production dates are affected. |
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jsimmons
Premium,MVM
join:2000-04-24
Falls Church, VA
·Cox HSI
| reply to thebob6
said by thebob6 :I check the modem info page when the tech left and it seems that my upstream channel has indeed changed and so far I've had not had any disco's. I would hope the upstream power level has decreased a bit (meaning the modem is not having to boost transmit power too much to get a signal to the CMTS). I like to see upstream power at 40 dBmV or below - meaning a good low-loss upstream signal path. Good cables, tight connections, low-loss splitters all contribute to good signal path.
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"Everything should be made as simple as possible, but not one bit simpler."- Albert Einstein |
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CoxNVAHSI
Premium
join:2007-07-12
Locust Grove, VA
edit:
May 7th, @04:47PM
| Upstream DOCSIS spec for power is 27 - 54... the sweet spot is 41-48. Anything within 35-52 is fine. The closer you get to the extremes of the DOCSIS spec the more exposure you have in regards to seeing problems. The high end of that range is to ensure that the seasonal drift (temps rise, plant expands resulting in higher transmit)does not put you into a max transmit (55dB on many modems). There are also other design elements that go into it but I would be misrepresenting myself as I am not an RF engineer (I know where they sit though).
So on the upstream your power being low can cause a lot of problems due to being closer to the noise floor. You do not want to be down in the junk. Low Tx is just as bad if not worse (IMHO) than a high Tx. High Tx is a problem but more so when the modem is maxed out (i.e. the CMTS is Kirk and your Cable Modem is Scotty going... "She kinna take any more, Captain. If I give her inny more she'll blow!". Unlike Scotty... your modem knows it's limitations and will not pull a solution out of thin air when asked to tx more than it is designed for.
If you do not get the reference... ask someone that looks older than you to explain. |
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jsimmons
Premium,MVM
join:2000-04-24
Falls Church, VA
·Cox HSI
| Good explanation 
I have always had great service with upstream levels of 38-40. I can say for sure - once it hits 50, problems are not far away.
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"Everything should be made as simple as possible, but not one bit simpler."- Albert Einstein |
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