🚀 go-pugleaf

Brian <bswindle@charter.net> wrote in message
news:3C27FF5E.337A678D@charter.net...
>    USB is great for printers, mice, cameras, etc... It just doesn't seem
> to work well with cable modems on a lot of computers.
>    I saw a PC a few weeks ago that developed a problem on the
> motherboard or powersupply (probably the power supply) that fed 110
> volts out the USB plug. The modem's USB port was dead when I arrived, so
> I got another modem and connected it to my laptop first, where it worked
> okay on USB (the PC had only USB connections - you couldn't pay me to
> take one of those). When I connected that new modem to the computer, it
> actually tripped the main breaker in that part of the man's house. When
> he reset the breaker, the USB port was dead. We tried one more modem and
> when we connected it, smoke came out of it and killed it's (modem's) USB
> port as well. I don't know exactly what was wrong with the PC, but it
> could have possibly electrocuted somebody if it had that kind of power
> on the USB port and a person grabbed the other end of the USB cable. The
> machine had a surge suppressor strip he had purchased with the computer.
> I don't know why it didn't trip the suppressor breaker, but it never
> did, and it ruined 2 modems USB ports.
>    I've never seen anything like that, but I will definitely be careful
> anytime I work around a USB device with any type of problem in the
> future.
>

There are a few possibilities, but this scenario is the most likely.  The
"hot" and "neutral" are reversed on the ac outlet that the computer or modem
was plugged into.  This is more likely to happen with 2-prong outlets that
3-prong grounded outlets.  If this happens, then the computer case will be
at 120v ac.  The shields in the computer cables are connected to the case,
so they too would be at 120v.  Unless you are grounded, you may never notice
that this has happened if you touch the case.  However, plug in a properly
grounded device (cable modem, since cable will be earth grounded) and POW,
tripped breakers, exploding computers, and more.  The breaker on the surge
protector didn't trip because the power went through the unprotected neutral
side, not the breaker protected power side.  A good surge protector would
have been showing a wiring fault when first plugged in.

In short (sorry, couldn't resist), the problem is most likely with the house
wiring, not the USB port.  It's very, very unlikely that 120v ac could be
present at the USB port and the computer still work.

Kent