Something like that happened to me in Vo-Tech school when I was about 17. My instructor and I were both squatting behind an old Setchell Carlson color TV. I had the high voltage probe, and he had the foot on top of the AC line that ran under a metal cover screwed to the floor. When my knee touched his, the 20,000V shock caused both of us to jump up and backwards, clear over a 36" high double workbench with a 50" high center partition. We both landed on our backs on the other side of the workbench. Luckily we were not hurt. I still can't figure out how we survived that jump without any broken bones or permanent spinal crackers.
Neither of us could have ever jumped backwards that high and that far if we were simply trying to win the Olympics, but a 20,000 volt encouragement will spring any muscles that are currently tensed much faster and harder than can be done without.
And this happened just one day after watching the government-sponsored safety movie entitled "Curiosity Killed the Cat" which was about the effects on a cat from drinking out of a 100 VDC-charged metal milk bowl versus a 100 VAC-charged metal milk bowl. Anybody else ever see that one? I am sure it is banned now; there was no PETA in those days.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pat Goodyear
Sent: Monday, August 19, 2013 11:23 AM
To: [log in to unmask]
Subject: Re: [TN] Refreshment
Brings back a memory or two, aligning a FOCRT on a Honeywell Visicorder
that had been dropped, I had repositioned the tube. I didn't have a
mirror to watch when I focused the tube so I laid down on the workbench and reached across the chassis to adjust the beam gain and focus.
Picture this, the workbench had a shelf that my head was under, it was a
maple benchtop and shelf. I brushed the hv lead as I was adjusting,
they guys watching said I made 3 cycles after they stopped laughing.
My arm hurt for a week.
pat
On Mon, Aug 19, 2013 at 8:49 AM, Ed Popielarski wrote:
> Yes, James. I learned first-hand how much that hurts.
>
> This was back in the late '70's (ears still quite wet) when I had
> taken a job debugging arcade games in the NY Metro area. I had just
> finished repairing 5 square color CRT displays and set them up in a
> row from a common composite video source to align the guns. What I
> didn't notice was one of the 5 tubes was rotated 90 degrees, so the
> first few had the 2nd anode below the CRT, but the one "oddball" had
> it positioned right where my arm could make contact while reaching
> over to adjust the horiz. & vert. size pots on the rear of the
> chassis. I thought someone hit me with a door (huh?) and found myself
> on the floor salivating like a mad dog. Apparently, the dielectric
> strength of the rubber cup isn't high enough for this maneuver. OUCH!
> Never did that again! (remember the electric fence analog earlier!)
>
> Ed Popielarski
> Engineering Manager
>
>
> 970 NE 21st Ct.
> Oak Harbor, Wa. 98277
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>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of James Head
> Sent: Monday, August 19, 2013 8:20 AM
> To: [log in to unmask]
> Subject: Re: [TN] Refreshment
>
> When I used to work for Toshiba at the TV plant in Plymouth we were
> meant to break the tube necks before disposing of CRTs but we thought
> it was more fun to put them in the crusher unbroken and watch the old
> crusher shudder. We once had a high-end special 44 inch tube. We
> wheeled it out and very carefully lifted it up to place it gently face
> down in the crusher on its own, pushed the green button and hurried
> away. There was a low thumping bang and the whole cage around the
> crusher rattled. Crushing flat panels was not as exciting.
>
> We used two large screw drivers to discharge the tube before working
> on a set. Holding both screw drivers like sheers so they touched each
> other, we touched one screw driver on the ground side of the tube and
> wriggled the other under the anode cap. I had a few 35 kV shocks
> though when I forgot to only hold the screwdriver by the handle
> (doh!). Fortunately I remembered to hold them correctly the one time
> when I tried to discharge a tube where the TV was still switched on -
> although we used 1:1 isolation transformers I suspect that it still
> could have been very painful.
>
> James
>
> James Head BEng CID+ MIIE MIET
> Senior PCB CAD Engineer
> Crowcon Detection Instruments Limited
> 2 Blacklands Way
> Abingdon Business Park
> ABINGDON
> OX14 1DY
> Telephone: 01235 557700 extension 289
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