Let me start by saying I know very little about networking issues. Hopefully, at the end of this, someone can tell me what the next step is to diagnose my problem. I live in jacksonville, Florida, and have Comcast as my broadband provider, using a Motorola SB 5120 cable modem, provided by ComCast. I know that ComCast has been having some problems with their service lately and that may be part of my problem. I've had broadband for just over a year, and other than some problems when I first got it, it has been working without a hitch for a year. Over the last couple of weeks my broadband connection would go out, with the Receive and Send lights on the cable modem blinking, and the Online light being dark. I tried unplugging the power supply to the cable modem for a minute or two, and then plugging it back in, but the modem would not reconnect. I called ComCast, but other than saying their service was down for a while, or offering to send someone out to look at it, that was about it.
Here's what I did find out. If I disconnect my cable modem completely and take the modem and the power supply (AC) cord into my attic, I can plug the cable that supplies my house directly into the modem and plug in the power supply cord, the modem will connect and all four lights (Power, Receive,Send Online) will be on (not flashing). I takes about2 or 3 minutes to disconnect the modem, carry it into the attic, and plug it in, which seems to "reset" the modem. I can then disconnect it, take it back to my computer room, hook it up, and it will work for fine for a few days, or until the next service interruption by ComCast.
One thing to note about the way the modem is connected to the cable supply in the attic. The cable comes into my house into the attic, and then goes into a cable amplifier. It was an Electroline model 2400 4 port amplifier. When I first got broadband, the cable modem would sometimes lose the connection, (the send and receive lights would flash, and the online light would be dark). So I hooked the cable going to the cable modem directly into one of the Out ports on the Electroline model 2400 4 port amplifier. The cable that goes from the amplifier to my cable model is 50 feet long. I've had no problems for a year. However last week when I went to check the connection I noticed that the Electroline amplifier was really warm, almost hot to the touch, too hot to really hold in your hand comfortably. It was about 75 degrees F. outside, and the attic was a little hotter, but not nearly as hot as the amplifier was. After a couple of times of connecting the modem in the attic (to "reset" it), I bought another 4 port modem off of eBay. It was a Scientific Atlanta "new in the box" amplifier. (Note: both the Electroline and the Scientific Atlanta amps were 1 GHz amplifiers, and amplify 7dB). I replaced the old one with the Scientific Atlanta amplifier, and this worked fine for about 4 or 5 days. Then there was some kind of interruption, and I had to go back into the attic, and hook the modem up directly to the cable coming into my house and the modem "reset" itself.
OK. After all that explanation (sorry it was a so long), can anyone answer the following for me, (please)?1). What's going on here and how do I fix it? Any insight would be greatly appreciated. 2). Can a cable amplifier go "bad". It was only two years old. 3). If a cable amplifier is really warm, borderline hot, is that operating normally? 4). Do I need to get another amplifier and put it right in front of my cable modem? 5). Can you put more than one amplifier on a line to your cable modem? Is that OK? 6). Is 50 foot to long a run for cable when used for a broadband connection. 7). Maybe best question of all. Is the reason that the cable modem will connect when hooked up directly to the cable coming into my house because the signal is stronger there than after it comes out of the cable amplifier and goes down a 50 foot length of cable to my computer room? Is there something I can use, or buy, that will test the strength of the signal? Something that doesn't cost a fortune, and an average guy can use? 8). Is there something that others are aware of that is happening with ComCast that may be causing this?