[Elecraft] KPA500 Build

Fri Jul 8 22:42:00 EDT 2011

When I was 18 and had a handful of newly-issued FCC licenses that allowed me
to work as an aircraft electronics tech for Lockheed I knew other (older)
techs who were missing ring fingers - they had accidentally gotten their
wedding bands across the 28V DC power bus used in aircraft and the melting
band neatly cauterized and removed that finger. Unfortunately, it was
without benefit of anesthesia. 

One of them told me of a fellow missing his hand so he was no longer working
there. Yep, he had been wearing a metal watch band. 

A car battery can easily inflict similar injury. 

Since those days I have *never* worn jewelry around a DC supply. An punk
18-year-old newly licensed kid can actually learn good lessons :-)

Unfortunately, most 13 VDC supplies - even those fed by a car battery
through a few feet of #10 wires - probably won't be as considerate to the
victim. If they get across the supply it will fuse the ring (or watch band)
to the terminals and then slowly melt it through the flesh while the victim
is unable to pull free. That might take a minute or so. I was never
interested in experiencing that either. 

Ron AC7AC

-----Original Message-----
I was working on my car with my wedding ring on.  The car was turned off.  I
was reaching for something and put my hand into the space between the hot
side of the car battery and a tube.  I ALMOST WELDED MY RING TO MY FINGER.
There was hole melted into the ring.  I do not wear the ring any more for
safety sake.  Besides getting shocked wearing it I found that it snags on
things when gardening! 

Luckily I have been married to the same understanding woman for 43 years!! 

Don and Kevin are correct.  Low voltages can be very dangerous.  Better safe
than sorry!

Jack, AE6GC
****************************************************
I was at a Red Cross EOC during a training drill as an ECOM operator.  The
stack of radios were on a folding leg table with an aisle for people to pass
on the back side of all of those radios.  When I walked into the radio room
the first thing I saw were all the low voltage lines exposed to  
touch.  I kept telling the folks in control how very dangerous this was.   
They all wore wedding bands and watches which would have welded themselves
to the power lines.  They did not seem to understand.  "It is only 12
volts", they said.  "But at how many amps?", I responded.  They did not
understand the welding concept.  I searched the place and found a bunch of
tape which I used to cover all the exposed cables.  Even the other radio ops
did not seem concerned.  I wonder what they would have done if I had shorted
a screwdriver across one of the rigs?  Sometimes it is very difficult to
tell folks they are in danger and have them understand it.
    73,
       Kevin.  KD5ONS

On Fri, 08 Jul 2011 15:40:30 -0700, Don Wilhelm <w3fpr at embarqmail.com>
wrote:

>   Tony,
>
> Your cookie sheet is an OK idea, but it gives me cause to insert one 
> of my safety "hot spots".
> When working on a fully conductive surface, keep all power sources at 
> a safe distance (at least 1 foot greater than your reach).  That goes 
> for even 9 volt batteries and 13.8 power sources, and of course, the 
> AC receptacles.
>
> The AC voltage problem is easily recognized - high voltage can kill 
> you, but not as readily recognized is that low voltage can maim you - 
> suppose your watch or wedding ring comes in contact with a battery
terminal.
> Not only will flying molten metal happen, but your finger or wrist can 
> be very badly burned by the heat produced.
>
> Work as you see fit, but above all - BE SAFE - low voltage sources can 
> maim or even kill just as well as high voltage.
>
> There are no fully conducting surfaces in my work area - static mat, 
> yes, but metal sheets, NO!
>
> 73,
> Don W3FPR
>
> On 7/8/2011 5:07 PM, Tony Estep wrote:
>> Not only is a muffin tin an excellent parts bin, but a large cookie 
>> sheet is great for building SMT gadgets. It's conductive, so no 
>> static buildup, and the raised edges keep little parts from ending up 
>> on the floor. I got a muffin tin and cookie sheet at Walmart, $3.50 
>> each. If the shiny surface of the cookie sheet is too reflective, put 
>> a piece of black conductive foam on it.
>>
>> Tony KT0NY

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