So it turns out 3com overvolts ...

[macklin01]

(Sorta')

I had my network screech to a halt about a month ago. (Like maybe a few bytes per second, collisions light constantly lit.) (3com home networking kit of a hub, 2 ethernet cards) Spent an entire day with tech support who finally told me it was what I knew it was -- hub failure.

Well, I finally got around to packaging up the hub today for the RMA. It was very warm to the touch, although there was plenty of space around it. (Maybe a foot of clearence generally.) Well, my curiosity was piqued, so I pulled out a digital thermometer. Over 40C after being unplugged for awhile. Well, I figure that has to be pretty hot for a hub, since my CPU socket isn't much hotter than that. So, I'm thinking it was definitely the hub.

So, just for the heck of it, I pulled out my multimeter to check the output of the AC/DC adapter that came with the kit. It was rated for 9V DC output, 1000 mA total. Well, guess what my meter read: 13.91V! 55% over the rated output!! Well, no wonder the thing died -- it was receiving a 150% of its rated input voltage for up to a year!!!

So I guess 3Com joins the ranks of over-volters, too. :)

Strange, eh?

-- Paul

[Mpegger]

Wall warts generally put out a higher voltage then what thier rated for. This is mainly because as soon as the proper load is applied, the voltage will drop.

However, even with no load that 13.9V seems way too high if its only a 9V adapter. The problem may be the power adapter frying the hub. If you didnt already, send back the power adapter with a note attached to test it.

[macklin01]

Thanks for the advice and the insight! I figure the overvolting may well have killed it, and even if it didn't, I wanted to eliminate the possibility of the adapter harming whatever they send back to me.

Actually I did send it along with a note. Reading the back of the wall wart (I like that. :) ), I see it was rated at 9V output at 1000 mA. The input of the hub was rated at 9V - 12V. So, at 13.91V, it was still 16% over spec. Not quite as bad, but that's 16% above the max stated tolerance, rather than, say, the mean. I wish I had tried putting a 1A load on it to see what it dropped to...

At any rate, it'll be on its way today ...

Thanks again for your insight! -- Paul