[Amps] Be Careful Measuring those voltages.

[Roger]

Many years ago, as in the 50's I took a correspondence course on 
electronics. One of the first things we did was build a volt meter.  A 
few years later I needed to check the plate voltage on my HT-44 power 
supply.  If any on here remember that series, you measured the current 
across a resistor in the PS150.  The ends of the resistor are connected 
to meter jacks so you can just plug in the Simpson or what ever meter 
leads.  The voltage is in the neighborhood of 500 volts plus change (570 
IIRC).  At any rate I had to get up on the operating desk and reach 
cross armed over to the meter. Unbeknownst to me, my fingers had slid 
down to the probe tips although I didn't feel even a tingle. I didn't 
feel a tingle that is until I reached over to pick up the meter which 
had a metal, grounded case. In one arm and out the other.  I woke to 
find myself laying on my back on the tile covered, concrete floor. I was 
as out of breath as if I had just finished a marathon. I worked my way 
up into the big easy chair and sat there for about a half hour 
contemplating why I was still alive while I Also waited for my breath to 
catch up.

I had pitched head first off the work bench to land on my back which 
probably started my heart again or at least I think that is why I was so 
out of breath. Then I was also lucky  the fall didn't break my neck.  
There were burns on the ends of my fingers on the right hand and 
matching pits in the PS chassis.  To say my arms and chest were sore the 
next day would be an understatement.  IIRC it didn't even blow a fuse.

To top it off, a few years later, after moving to the old family farm 
and building a new home in the Breckenridge MI area I had something 
similar happen, but not by grabbing a PS. 

I had a 1/4 wave, 40 meter vertical in the West yard. The shack was 
located in the SE corner of the basement making it a good 120 to 150 
feet from the vertical.  At the base of the vertical was an 8' ground 
rod with bare copper radials fastened to it using a pipe clamp along 
with the coax shield. One of the radials had come loose. I bent over and 
picked it up, pulled it tight, and kneeled down to push the end of that 
wire which was grounded at the other end.  As soon as my knees touched 
the damp soil It had me.  Fortunately I was balanced on the balls of my 
feed and tipped over backwards. As soon as my knees broke contact it let 
go and I THREW the wire as hard as I could.At least I stayed conscious 
so I could enjoy getting my battery charged.
 
The station was grounded, but the old Yaesu FT-101B used a two wire 
power cord. An over generous solder joint (from the factory) allowed the 
hot wire to contact the chassis. As this was before ground fault outlets 
and circuit breakers were common probably the coax shield was carrying 
the majority of the current as the ground directly behind the station 
was higher and dry. I took my Simpson 250, laid it on the ground and 
reached out as far as I could to place the probes directly into the 
ground. One was about a foot from the grounding rod at the base of the 
vertical and the other about 5' to 6' out.  I measured over 100 VAC.

The station was tied into the house electrical ground so why it didn't 
pop the breaker? I don't know.


Even the lower voltages can sneak up on you and if the contact is good 
the results won't be.

73

Roger (K8RI)