There's a big difference between A/V equipment and computers.

Not really. In both cases there is a transformer isolating the power from
the load. I grant that the "switching" power supply used in PCs has a good
amount of circuitry (the "switches") before the transformer -- "they convert
the incoming AC to DC and then convert it to a higher frequency. At higher
frequencies the transformer can be made a LOT smaller. In switching input
also lets the power supply accomodate a very large change in input voltages
without problem. There is no good reason why "they" could not make a PC
power supply that made the PC as safe as your TV without relying upon a
ground.

Again, I point out that LG (the Korean company, formerly known as Lucky
Goldstar) now ships it's Chinese made room air conditions with a GFCI built
into the plug but with NO ground wire going to the chassis.

I also like to point out that you are somewhat safer if metal objects in
your environment "float" rather than be grounded. If your left hand is
resting on a well grounded object and your right hand touches something
electrically HOT, you may get a fatal shock. If your left hand is resting
on a "floating" metal object you might get a little "tingle" when your right
hand hits the HOT wire.

Tradition counts for a lot is setting standards. BUT, had cheap and
reliable GFCI technology been available when electric power was "new" it's
quite likely that "grounding" may not have been as important.

Well, at
least in Europe, I don't know much about US regulations.
Most A/V stuff has reinforced or double insulation. That's why they
have a plug without ground. Computers (except some laptops) usually
have only 'normal' insulation. A single fault in the insulation can
create a connection between the live pole and the cabinet. Without a
grounded cabinet, that could be lethal. With grounded cabinet, you just
blow a fuse.

True. Nonetheless, it's possible to make a PC power supply that is as safe
as that in your television or DVD player. The next time I have both a dead
PC power supply and a dead VCR I will open both up and see whether the PC
supply is any more likely to generate a HOT to Ground cross that the VCR.

In case of fire or other damage, the insurance company can give you a
hard time, if they find out that you have class I equipment connected to
a socket without ground.

Unless it was the cause of the fire, the insurance company will not say a
thing. Moreover, codes permit sockets with ground openings that are not
grounded so long as: 1) the circuit is protected by a GFCI; and 2) there
is a "not grounded" label applied. Read the installation instructions on
your GFCI (I may be making an incorrect assumption about GFCIs "over
there."). In the States, the insurance companies have better have a VERY
good reason to give your a "hard time." A company that drags its feet over
a payment risks paying fines to the regulators and risks being successfully
sued by the insured with truly massive "punitive" damages.



BTW: the 55 V you mentioned (115 V over here) is more than enough to
blow a serial or parallel port when connecting a grounded printer to a
non-grounded PC. For me, that's also a good reason to ground my PC.

No. It would be current limited. Likewise, if you rub your feet on the
carpet in winter and build up a 20,000 volt charge (which happens) you
likely would not fry something it you touch a signal pin. It's all a
matter of how much energy you can dump into the interface.

Your grounded printer would "ground" your PC. No harm, no foul.





--
Maurice