Re: Non-magnetic screwdrivers



Toby wrote:

> When I work on a PC, I keep the IEC cable connected to the mains but
> turn the socket switch to OFF. That leaves the earth connected, so I can
> easily keep myself earthed by touching the chassis.

Another alternative is, on your typical four-way mains block, to plug
the 3-pin plug in upside-down (using the earth pin only).

Of course, this rather depends on your local earth being earth, and not
wired to live by some maniac electrician, or not connected at all, etc.
If the earth is not actually connected to earth fairly locally, as has
happened in a few large sites, the earth pin on the plug can actually
quite a few volts away from your local earth potential. It is
particularly unwise to work on copper cabling that runs from another
building that may be on a different mains circuit than you (For
instance, on a telephone pair, the 'A' wire is allegedly 0V and the 'B'
wire -48V, but that 0V is relative to the exchange's ground, not yours)

In a lot of places, earth and neutral are pretty much the same thing.

When dealing with static, however, it is not the earthing that is
important. It doesn't matter if the machine has a case potential of two
million volts w.r.t. earth, provided that YOU have the same potential.
Having an external earth connector only provides any protection if both
you and the system are connected to it.

You can generate several kilovolts of static potential in a few seconds,
merely through the action of moving about, rubbing against various
fabrics. You could do computer maintainance in the buff, but it tends
to put customers off. (Well, most customers anyway, depending on their
outlook and particular taste, see comp.sys.maintainance.nudist for more
information).

If you don't have an anti-static wristband ('Zap-Strap') your best bet
is to maintain contact with the PC case in some way at all times while
handling components. Bare arms leaning on the case helps, as does
handling components in sensible ways (don't pick up pci/agp cards by the
edge connector, use the mounting bracket instead; handle hard drives by
the sides, or the end furthest from the IDE connector (because there's
rarely any PCB up that end these days).

Static damage is real, and it is also insidious, in that it may not
wreck something, merely shorten it's life. It's also a fact that some
somponents are more susceptible than others. This doesn't answer the
question as to why Redstore package their plastic wall boxes in
anti-static bags though.

Jim
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