[AMRadio] Shocking Experiences


Michael D. Harmon mharmon at att.net
Thu Jan 22 02:11:37 EST 2009


Hi,

I had to throw in a couple of my past experiences to add some variety.  
Back when I was a kid of 14 or 15, my radio-TV "elmer" showed me how to 
use an NE-2 neon bulb and a resistor (220K if I remember correctly) in 
an old ball-point pen to make a little probe you could use to find the 
"hot" side of an AC power cord or receptacle.  You make a probe out of a 
piece of #12 copper wire, series thru the resistor, on to one side of 
the NE-2.  The other side of the NE-2 goes to the clip on the old pen 
carcass.  It works great for its intended purpose.  One day I was having 
trouble with my dad's TV.  No HV.  I wanted to see if there was any 
drive to the flyback to determine if it was the flyback or not.  I 
figured that there ought to be enough HV to ionize the neon in the 
NE-2.  I held the pen by the probe end and stuck it in there next to the 
plate cap on the HO tube.  There was plenty of HV to ionize the NE-2.  I 
couldn't figure how I got from the back of that TV to my sitting 
position against the wall about 6 feet away!

Back in 1993, an electrical storm went through the area where I was 
living at the time.  I had everything grounded pretty well - a big 2-0 
cable across the back of the operating table, clamped to a 6' piece of 
old 6V Motorola mobile radio power cable, and running to an 8' copper 
ground rod right outside the shack window.  About 5:30 one morning, I 
was awakened by a loud arcing sound followed by a sizzle.  Fearing the 
worst, I ran down to the basement and into the shack.  The shack stunk 
like ozone, and I went over to check my gear.  When I got closer to the 
SB-220, the smell was much stronger, so I leaned over and looked behind 
it.  Nothing.  Then I raised it up and saw a big black charred spot 
about the size of a saucer on the desk beneath the amp.  I had to go to 
work, so I left it for later.

When I got home that night, I noticed that the 220V shack breaker in the 
breaker box was tripped.  I reset it, and it immediately tripped again.  
I went into the shack, unplugged the amp, and set it on the bench.  When 
I pulled the case off, the inside bottom of the case was charred and 
smokey, and covered with shiny flakes of metal.  The terminal strip 
where you change the primary wiring from 110 to 220 was charred almost 
beyond recognition.  I replaced the terminal strip, plugged in the amp, 
and very cautiously reset the breaker.  The breaker stayed on.  I 
switched on the amp.  So far so good.  I fired up the HF rig and 
switched to the dummy load.  I put some power intop the amp and tuned it 
up.  Still OK.  I cranked up the HF rig and brought the amp up to full 
power.  Everything seemed OK.

This experience taught me several things.  There's no substitute for a 
good ground.  Because the amp was well grounded, the surge went as far 
as the terminal strip, arced to the case, and stopped there.  The 
carbonized terminal strip acted like a conductor just as if it were a 
piece of copper.  I now unplug my gear when I'm not operating.  I had 
always disconnected and grounded the antennas, but now I unplug things 
from the power line as well.  Yes, the police department and the radio 
stations stay on the air through all kinds of weather, but they have 
deep pockets to replace destroyed gear and install cad-welded mega 
ground systems.

When I was in college, I worked summers in a factory not far from home.  
There was an electrician there who fixed the equipment and replaced 
light bulbs, etc.  The wiring in the place was pretty lousy, and there 
were bare sockets with shades hanging on wires coming down from the 
ceiling with big old 300 watt bulbs to light the place (somewhat).  When 
a light went out, it could be the bulb, or it could be that gravity had 
finally taken its toll on the dangling wires.  Anyway, the old guy would 
drag out his 15 foot rickety wooden stepladder, climb up and replace the 
bulb.  If the bulb came on, fine.  If not, he would unscrew the bulb, 
stick his finger in his mouth, and then reach in and touch the center 
contact on the socket.  If he got a tingle, he knew it was another bad 
bulb, rather than a loose connection in the wire.  One day the old man 
was home sick and a light went out.  One of the young hotshots who was 
always bragging about this or that had watched the old man check out the 
lights, so he dragged out the ladder, climbed up, and unscrewed the 
bulb.  As I said the ladder wasn't too stable, so the hotshot reached up 
and grabbed hold of the dangling socket with his left hand, wet his 
right index finger, and stuck it into the socket.  There was a loud 
yell, and a popping noise and half the lights in the place went out.  
The guy came flying off the ladder as it collapsed beneath him, landed 
on half on the floor and half on the remains of the ladder, broke his 
collarbone and dislocated his shoulder, not to mention a nasty burn on 
his finger.  I think he got fired because he wasn't a union electrician!

Mike, WB0LDJ


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