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brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
im not at home now, but this morning after the splitter was taken out in the office, upstream was 57 dbmv and downstream was -2 dbmv.
Im guessing the 57 was what cause the reboot?
Interesting though, this is as much fluxuation as i have seen, and in my area these last two days have been unseasonably cold (45-50 degrees)
 

Weaselboy

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Jan 23, 2005
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California
im not at home now, but this morning after the splitter was taken out in the office, upstream was 57 dbmv and downstream was -2 dbmv.
Im guessing the 57 was what cause the reboot?
Interesting though, this is as much fluxuation as i have seen, and in my area these last two days have been unseasonably cold (45-50 degrees)

-2dB downstream is pretty good, but with that downstream level there is no way upstream should be at 57. It sounds like the cable modem is boosting upstream to overcome a bad connection or line noise. You are going to need to have the cable dude come back out. :(

Hopefully you will get a better tech this time that will check signal levels.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
signal to noise ration was 37 db
are there other measures to show good/bad connection issues?
could it be a defective modem?
i have sent a request to have another outlet installed.
 

Weaselboy

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Jan 23, 2005
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signal to noise ration was 37 db
are there other measures to show good/bad connection issues?
could it be a defective modem?
i have sent a request to have another outlet installed.

37dB SNR is not bad. You can read more here about signal levels.

I don't think your cable modem is bad. Like I mentioned earlier the Motorola modems reboot when they detect a series of those T3 and T4 errors and I think that is what you are seeing. The cable co. is going to need to fix your line.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
ok, thanks. I guess i should still try to re-wire it tonight?
Do you think the additonal outlet for the office would help?
At this point im not really sure what to tell the cable company....and i really cant complain, as this is an employee account.
 

Weaselboy

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Jan 23, 2005
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ok, thanks. I guess i should still try to re-wire it tonight?
Do you think the additonal outlet for the office would help?
At this point im not really sure what to tell the cable company....and i really cant complain, as this is an employee account.

Swapping around those splitters like you said should definitely help. Maybe give that a shot and see if it helps.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
ok, so i did the switch, the modem is now directly split from the entry into the house. at first it looked real good (see the first screen shot with downstream at about -2 and up at about the mid 40's. It then rebooted (see error T4) and now its been up for a few minutes at ds -4 to -5 and up 51/52.

I have no idea whats going on. Why would i have gotten a t4 error with good up and down stream # s initially ?
 

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Weaselboy

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Jan 23, 2005
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Both those shots are pretty good signal levels. If you are still getting t4 errors at those levels there is a bad connection somewhere further up the line. I would call the cable co again and have a tech come out.

I went through this a few years ago and they finally found a bad connection a few blocks away.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
Another tech coming out sat. I just don't understand. Before when I split it in the office and levels were at 57 I didn't get this many t3 t4 errors. Not sure what the last tech did ?
I give up
Btw. Thanks for all your help
 

Primejimbo

macrumors 68040
Aug 10, 2008
3,295
131
Around
37 SNR is good, anything over 30 is workable. Now the more you split that line, the higher the Up Stream will go, and the lower the down stream will go.

The idea set up is for cable TV and cable internet is: line coming into the house to a 2-way splitter. 1 leg of the splitter goes to the modem and that's it. The other leg of the 2-way feeds all the TV's, that is the best set up period.

Now can the modem be bad? yes, I've seen it many times they start to go bad. Do you own it?
 

Knoodles

macrumors 6502
Feb 2, 2003
430
1
Gone to the Beach
OP. If you google T3 and T4 errors Comcast Motorola Surfboard you will see you are not the only one with this problem. Lots of suggestions but no real answers. Some have been dealing with it for years.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
37 SNR is good, anything over 30 is workable. Now the more you split that line, the higher the Up Stream will go, and the lower the down stream will go.

The idea set up is for cable TV and cable internet is: line coming into the house to a 2-way splitter. 1 leg of the splitter goes to the modem and that's it. The other leg of the 2-way feeds all the TV's, that is the best set up period.

Now can the modem be bad? yes, I've seen it many times they start to go bad. Do you own it?

yes, i do own it.
Last night i re-wired to have the cable from the street split 2 way. one to modem, other to another 2 way for the tvs. Got pretty good readings, but still getting t3/t4 reboots.
Can having a powerline adapter on the network (plugged into router) effect anything?
Im just trying to list things i have changed recently. Because for years before a few weeks ago. Before i added powerline and tried initially splitting teh cable coming into the office (one for modem/one for tv) it had been working pretty much flawlessly. No t3/t4 errors that i can tell. And that was with the cable coming in from the street to a 3way splitter. Is there any diagnositic stuff i can run on the modem to see if its malfunctioning?
I do have a tech coming sat, though i dont hold out much hope. I have been consistantly getting reboots about every 30 or so minutes.
It very, very agervating
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
so the tech came out last sat. did some stuff down the street to amp my signal? than ran a new line from the garage to the office. ---so far so good. my question is, would a powerline adatper have any effect on this? is the only part of my network i have yet to re-hook up. its a netgear powerline adapter into my router to a 4 port hub near my tv/ps3, etc.

thanks
 

Weaselboy

Moderator
Staff member
Jan 23, 2005
34,071
15,494
California
so the tech came out last sat. did some stuff down the street to amp my signal? than ran a new line from the garage to the office. ---so far so good. my question is, would a powerline adatper have any effect on this? is the only part of my network i have yet to re-hook up. its a netgear powerline adapter into my router to a 4 port hub near my tv/ps3, etc.

thanks

No, a powerline adaptor would not do anything to make those modem reboots come back.
 
Last edited:

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
No problem. I'm just so paranoid. Don't want anything to mess it all up again
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
quick question. So its been good for since the last tech came over. About 11 or so days. Just curoius though. I have seen two T3 errors in the logs over the 11 days. are some t3 errors expected/ok?
 

Weaselboy

Moderator
Staff member
Jan 23, 2005
34,071
15,494
California
quick question. So its been good for since the last tech came over. About 11 or so days. Just curoius though. I have seen two T3 errors in the logs over the 11 days. are some t3 errors expected/ok?

Yes... once in a while is normal. I get one or two a week. It is when you get a whole stream of them together that is causes the modem to reboot.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
ok, thanks. made me feel a little better. Just checked the logs, as i just got home. Looks like one more this afternoon. Just paranoid i guess....especially after not getting any the last 10 or so days.
 

brentg33

macrumors 6502a
Original poster
Mar 5, 2007
593
5
oh no, came home and in the logs we had a T4 and a reboot about 3 hrs ago...do you still get them from time to time?
 

Weaselboy

Moderator
Staff member
Jan 23, 2005
34,071
15,494
California
oh no, came home and in the logs we had a T4 and a reboot about 3 hrs ago...do you still get them from time to time?

Not often... maybe once a month or so. It usually is in the middle of the night, so I'm not sure if there is a problem of some sort, or if the cable co. is doing maintenance.
 
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