Killed My Modem?

I think I killed my modem, but want to see if anyone agrees.

Rearranged the apartment and used the wrong AC adapter for our modem. Accidentally used the one from an external hard drive, as the tips are exactly the same. The modem wants 12V 750mA, and the drive adapter was 12V 1.5A. I didn't think that would be an issue as the modem seemed to work fine last night after switching back to the correct adapter.

Today I am getting nothing but problems. Internet connection cuts out for long periods of time. Not entirely but super freaking slow. On a 30mbit connection I get maybe 1KB download.

Windows error report said modem problem. Pinging my router gets 1ms with no loss. Pinging the modem gets huge loss, 75%+, going to do a more thorough ping to see how much its dropping.

At the same voltage I figured there wasn't an issue with using the wrong adapter, but I've done power cycling, got to the modems webpage and told it to do a factory reset and still having issues.

Any ideas, or just stuck with buying a new one? And it isn't the cable as I'm watching tv without issue, and pay my bill in full every month early.

This is frustrating as it seems intermittent.

Swapped cat6 cables and all of a sudden out of 100 pings I get 0% loss. Switch back to the cable that was in there, 100 pings 0% loss. Thought I had found the issue. ARGH.

I doubt you damaged your modem with that PSU - the V rating is a constant and can cause problems if you have the wrong one. The Amps is the max that the PSU can supply - the device (modem in this case) draws whatever power it needs. If you had done it the other way around, attached a 1.5a device to a 0.7a PSU then things would be different - but it'd have been the PSU you killed, not the device in all liklihood. It kinda sounds like it could be a dodgy RJ45 port and the slight movement in the cable is enough to make or break a connection. Personally I'd want to eliminate every possibility first, including that the problem might be the RJ45 on your PC.... THEN spend money...

Ya, I figured as much with the power adapter, it was just that it was the only variable that had changed.

The RJ45 cable that was swapped was the one from the modem to the router. PC is connected via wireless, and I tried several PC's in the house. All had similar connection issues and packet loss rate.

I found it strange that it would work for hours then cut out for half hour then come back again. It is tucked behind my TV, so there is absolutely no movement there to wiggle the cable. Temps are fine as the room is air conditioned and there is a fan behind the TV.

Maybe I just plugged the cable in poorly. Have to wait and see. The intermittent problem makes me concerned it may be something more.

Any other ports on the modem? What about bypassing the router?

The modem is a Motorola SB5101, and the router is a WRT320N. So, only one RJ45 and one USB port on the modem.

After I replaced the cable everything seems fine, but I will wait to see if it reoccurs as it was an intermittent problem that happened every few hours.

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Originally Posted by NightrainSrt4

The modem is a Motorola SB5101, and the router is a WRT320N. So, only one RJ45 and one USB port on the modem.

After I replaced the cable everything seems fine, but I will wait to see if it reoccurs as it was an intermittent problem that happened every few hours.

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It could be everyone on your street with the same cable service downloading the entire internet...that would slow it to a crawl as well. Check to see if it's happening around the same time of day each day.
The internet at my place of work is dsl and suffers from other subscribers downloading everything they see as if it won't be there tomorrow. The software we use only works when it's connected to an off-site server, so no internet means nothing happens. If only those in charge would put in a T1...:(

If it was Comcast's infrastructure that shouldn't affect being able to ping the modem successfully.

Even with their infrastructure getting pounded, if I've got no inbound/outbound traffic, I should be able to ping the modem to my hearts content and still get 0 packet loss, not 75% out of ~500 pings done that afternoon.

So far it is alright. I'm going to chalk it up to bad rj45 connection until it happens again.

Quote:

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Originally Posted by NightrainSrt4

If it was Comcast's infrastructure that shouldn't affect being able to ping the modem successfully.

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My bad, I somehow didn't realize it was your modem you were pinging.
The cables aren't stretched taut are they?...Or bent sharply as Cat cables do have a maximum bend radius. I know a guy that wrapped the excess cable tightly around a small diameter bar on the back of his desk and tied it off tightly...he couldn't figure out why his connection would fail or deliver corrupted files. I told him if he tied knots in his cable the packets wouldn't be able to fit through it!:banana:

Haha, nope, no major bends. It does 270 degrees over ~2 meters.

ARGHH! Doing it again. Unplugging and replugging the rj45 did nothing this time; must have been a coincidence.

100% packet loss pinging the modem.

WTF. Power cycling does nothing.

EDIT: Maybe there is something just wrong with that cable. Switched to another cable and it is working fine again. Guess we will see tomorrow if it happens again.

You rearranged your place. Did you plug into a different cable receptacle? Does it work perfectly (without intermittent) failure in the original receptacle? (If so, could be bad in-wall wiring.)

Perhaps you've moved an electrically noisy item (flourescent lighting, radio transmitter, 1000W PC mod, etc) and it's now producing EMI or crosstalk across one of the lines between your computer and your ISP?

I assume you've tried any reset switches already ...
Use a continuity meter to check all your cables.
Use an electrical contact cleaner on all the RJ pins and leads.

I doubt you've cooked it; if you did then it wouldn't work at all. I second what's above, 1.5A is just the maximum rating the wall wart can handle before melting ... Something like a 12V lead-acid battery will suck as many amps as it can while recharging, something like a modem with an embedded microcontroller cannot.

I'm assuming you don't overclock your modem. But maybe it's sitting in a new location where airflow is a problem and it's overheating? I'm assuming you didn't drop or bang it while moving things?

Those are my best guesses. Of course, it could just be your ISP or cable techs mucking around, or they've tapped one home too many into your end-of-the-line feed ... who knows.

Sorry I hadn't seen this before.

I haven't noticed it happening since. Everything was put back in the same spots, just a different location in the room. I only have one cable input in the apartment, so that didn't change.

Forgot to mention they were digging up the road, pipes, water lines, power lines, etc. out front of the apartment complex and another huge set of buildings that were erected right next door were doing electrical work at that time. There also was a huge influx of tenants leaving and new ones coming into our complex, so maybe a lot of crap was going with Comcast canceling old services and setting up new ones. *shrug*

Hasn't happened since that week. Then again I didn't swap back the original rj45 cable either. Who knows what fixed it.