ZAPPER (Health Hazard?)

[harvey]

Here are some tidbits:

- The "Zapper" was initially built as a work-around (not solution) for the
verdigris problem. Unlike other work-arounds which are still used, any
endorsement for this application has been withdrawn. In case that was
unclear...

- For a change, it's the inventor, not the user (us) who withdrew
endorsement for using the device on center pins. Francis Mehaffey does NOT
recommend using the zapper on center pins.

- The entire device must be considered a disclaimer: "For Professional
Use". As a byproduct of it's very function, it could be considered fair
game for the OSHA crowd, and for good reason.

- Like the electric chair, it's the amperage, not the voltage doing the
work. The implication of this is that the secondary windings must be able
to withstand a direct short (intermittently), without overheating and
burning the insulation from, and thereby shorting or opening the
transformer's secondary windings.

- This would seem to exclude a typical light duty potentiometer as a
regulating/adjustment device. A heavy-duty wire-wound resistor (ceramic
housing) would be more appropriate for sharing and/or bypassing this much
amperage and the related heat. Anything less 'becomes' the fuse.

- Similarly, the entire thought of built-in safety (fuse) would be
self-defeating. A fuse is, intentionally, the weakest link, meaning it
would always fail as soon as the electrodes (blades, probes, whatever) were
applied to a part. In abstract, the "part" becomes the fuse on the output
or secondary side of the transformer, but in the case of a [disqualified]
center pin or regulating screw, these are far more resistant to melting
than any fuse, fusible link or circuit breaker. The potential -- amperage
-- is therefore shared between the part ("load" in electro-speak) and the
windings of the transformer.

- The transformer should have a *minimum* of a 1-amp rating. More is okay,
in fact better, but at the expense of weight, size and cost. Less will
guarantee the transformer become toast (or worse). The fact that the
secondary is 12 volts is more a matter of  cost and current availability.
The 12 volt variety are easier to find with this kind of amperage rating;
likewise are less expensive, and may be found in reasonable sizes and
weights. In the old days, powering the filaments of dozens of vacuum tubes,
finding a 6-volt transformer (or portion in the event of multi-taps) with
this kind of amperage capacity would have been more common than  today.

- As mentioned by someone, the prongs may be fabricated from spring steel.
Satisfactory materials include metal strapping, traditional soundboard
steels, and hacksaw blades. Working with these materials is different than
other forms of steel, and is beyond the scope of this reply. The portion
that separates the blades may be any non-conductor -- wood, Plexi,
bakelite, etc.

- I wouldn't be overly concerned with 12 volts at 1 amp or so. I've
encountered much higher potential when blindly reaching under the dash of
my car. However, like other hard lessons, I learned not to wear rings and
metal watch bands while reaching under the dash (!)

- The *primary* side of the transformer is another story, and anyone is
fair game. The results depend on a number of things: the person being
grounded or not, standing on concrete or other moisture retainer, touching
another object to complete the circuit, and many other possibilities. In
this case, the person becomes the path of least resistance, not necessarily
the fuse.

harvey


At 10:59 AM 9/15/98 -0700, you wrote:
>I've built, and burned out a couple of "Zappers" over the years using them
>on all kinds of things both piano related and not... 
>
>And "No," just because I've burned a few out, doesn't mean that I've been
>out there charring flange bushings and birdseyes instead of repinning.
>
>Let's just say that I'm fond of experimentation, and leave it at that.
>
>Anyway, long ago,  I was told by someone who worked on electrical doo-dads
>for a living, that the Zapper, ala Mehaffey was a "potential death trap."
>
>I didn't ask him why at the time, because, knowing nothing about
>electricity, I didn't want to appear ignorant.
>
>Now, years later, I'm still mostly ignorant about electricity, but have
>learned just enough to fool around with it and get myself killed.
>
>I think that simply going down to Radio Shack, buying the appropriate
>transformer, wiring it up with a plug on one end and shorting it across a
>tight center pin on the other, could be dangerous if not lethal should that
>transformer choose to burn out, fusing the internal widings together
>somehow, and connect you directly into the power grid.
>
>After all, the thing works by creating a short circuit across the center
>pin thus heating it up, but everything involved gets hot especially the
>windings in the transformer itself.  This is what fuses are in your home
>wiring to protect against...(sort of.)
>
>Anyway, I could be wrong here folks, and perhaps John Fortiner, Larry
>Fisher, or some other electrical wizards on the List could set me straight,
>but I believe that the simple "Zapper" described in the paragraph above is
>potentially dangerous if not modified somehow...
>
>Please help me out here as I'd love to continue experimenting without
>killing myself...
>
>
>	Richard Wagner RPT