The AM Forum

A worker survived being shocked by 2,000 volts of electricity for about 30 seconds. John Zimmerschied, 35, was working inside an electrical box when the accident happened about 9:30 a.m. Friday

http://www.local6.com/news/4941608/detail.html (http://www.local6.com/news/4941608/detail.html)

Don,

It's pretty amazing that he survived that.  Surely he was pretty far from an Earth ground of any sort.  Even at that it is really odd someone could endure that for 30 seconds.

So far, all I have ever been exposed to was in the bias supply on my 450tl finals.  About -450 DC.  I was standing on carpet barefoot and had my other hand behind my back as I always do when I get close to the juice.  Still, it dazed me pretty bad since I had my hand inside the rig trying to neutralize the final and couldn't get out of the hole I had my arm in.  The plate voltage (3200 VDC) was NOT on, but still, a really stupid thing to do...

Live and learn is a lot better than die and learn, as the later makes no difference to the victim.

BTW, hope to work you again when I get things going.  I've missed hearing your voice from the Woodlawn, Tennessee spot on my dial.

73,
Brian

The worst jolt I ever got was in November, 1960.  It was election night, and I had stayed up late listening to the Kennedy vs. Nixon election returns on the  radio, and decided to work on my transmitter.  It was about 2 AM, and everyone else in the house was alseep. Lacking a solid ground connection, when the modulation transformer windings shorted between primary and secondary, it put the whole modulator unit at full +1000 plate volts above ground.  I was holding the mic in one hand and went to adjust the transmitter with the other.  As soon as I touched the transmitter, I got the full plate voltage from one arm to the other.  My hands were frozen to the mic and to the transmitter and I could not let go.  I managed to jerk away, and pull the mic cord right out of the connector.  That's most likely the only thing that saved me.  I fell over backwards and broke a glass 6L6 that was lying on the floor, with my head.  I had some significant burns on my hands, and arm and chest muscles were sore the next day, but that was all the damage.  One thing that was probably the most frightening was that when I did get loose, my paralysed arms went completely spastic for a couple of seconds.  If that mic cord had not pulled loose from the connector, someone would have most likely found me hanging on the thing next morning.

Before that incident, I seemed to routinely get zapped with HV whenever I worked on the trasnsmitter.  Since then I have never been seriously shocked, and I often work around voltages as high as +3500 or more.  I suppose experience makes one a believer.

Wow, that's quite a jolt there, Don.

I had a similar path thru my arms and chest in 1971.  About 1000VDC also, and I could not let go of the chasis and plate choke. My chest and arms were paralyzed during the ~ 3 second shock, but my legs still worked. I ran backwards and the cables connected to the rig ripped it out of my hands. I hit the floor and felt a hard pulsating pain - like a major funny bone was slammed -  throughout my upper body half.

I had 3rd degree burns on one hand with open flesh hanging, but no blood. Instantly coterized. The other hand had a small set of dots like a snake bite, but  no real damage. I shud have gotten stitches on the bad hand, but did not. The wounds took months to heal and kept becoming infected. I still have tiny scars left there 30 years later.

As you, I've never been seriously shocked since. That learning experience probably saved my POTENTIAL life of carelessness in the future around HV.

T

WOW!!! You guys are making me think twice about starting that YC-156 linear amp project I've been planning which will have about 5kv on the anode  ::)

Whew!

These are the kind of stories that need to be heard by both the newbies and old-timers alike to remind us just how vulnerable we can be around our own equipment.  I am as guilty as anyone, having a sense of well being in what I do inside the rigs.  Too much confidence in myself and sometimes not enough caution.

I have most every QST back to about 1926, and have read many obits in them where hams were killed right in their own home, by their own pride and joy rig.  Never will forget the one about a ham still in contact with his BC610 hours later when his wife woke the next morning.  Plate voltage still going through his dead body.  Luckily, she knew enough about what was happening not to touch him.

Might be a good idea to devote a section on the website to SAFETY.  Could save a few lives over time.

I was working in a garage when I was a kid and exploded a Firestone snow tire. It launched me through the air and I landed on my feet. The bead snapped as I was inflating it. I couldn't hear or see for a short time from the shock.
I don't buy firestone to this day.

You guys are very lucky to share these high voltage stories.
I once came close to the 4-1000A HV supply but felt the hairs on my arm stand up and pulled away. Close enough for my candy ass.

Yep, I know how you guys feel, I took 750 VDC across the arms working on my Drake TR-4 with a metal jeweller's screwdriver, like a complete idiot.

Kept the other hand behind me until I reached for my 4-cell maglite, which I knocked over onto the power supply just as the screwdriver slipped and hit B+. Locked all my arm muscles, eventually manged to pull back and break the circuit. Screwdriver wound up embedded in the ceiling. My sister came running upstairs when she realized the dimming lights and subsquent thump and loud profanities were both caused by me.

Fortunately, we all got hit by DC (and I deserved mine). If any of us were telling the same story with AC, we'd be probably be sitting on a cloud somwhere. This guy was beyond lucky.

--Thom
Killer Agony One Zipper Got Caught

Why would a.c. be more dangerous than DC of equivalent voltage?

I remember reading something about safety being an argument in the old Tesla vs Edison AC/DC debate.  Don't remember who said which one was more hazardous.

I recall a description of how an electric chair was homebrewed by a sheriff dep't electrician in a small Alabama town in the 30's.  He used a pole pig set up to deliver 2000 volts a.c.

Since this is a cathode driven design, there is no reason to poke around in there with it lit. Always use proper primary fuse sizing. It could save your a$$. Don't forget a properly sized safety choke also. Get some handcuffs for the high tension supply. 1 Jesus stick and 1 HD clipleaded line directly across the supply capacitor(s) (not chassis ground).

Hi Dave, A few questions... What are "Handcuffs" ?? I know what a "Jesus stick" is, (also called a "Chicken Stick"?) Does the safety choke go across the RF output after the blocking cap in case the blocking cap shorts? and what do you mean by a cliplead line across the supply cap? Bleeder isn't enough?

I think it has to do with the reason electricty kills in the first place. The reason the across-the-arms path is lethal is because it intersects the path carrying a ten microamp pulse that beats your heart. A sustained DC flow usually doesn't disrupt that. A sustained AC flow (following the same path) usually does. I don't know why, to be honest, but 60Hz probably confuses the hell out of your heart, if nothing else.

If you caught a momentary snap of DC (like discharging a cap), it would probably have the same effect as AC.

Anyone ever see the film that was shot during the AC vs. DC argument of a rogue elephant being put to death by electrocution? They tried DC first, and the elephant survived. They followed up with AC, the elephant was dead in a few seconds. They kept the power flowing just to be sure, and the elephant caught fire.

This doesn't mean DC is safe, by any means, but AC is a lot less safe.


I think that's where the elephant came in (or went out, as the case may be). AC mostly won the argument because it's much easier to step the voltage up-and-down as need be. Transferring huge volumes of power over imperfect conductors is more efficient when the power is mostly voltage, and it's more efficient to step AC down to a household level with a transformer than DC with some giant DC-DC converter.


Now that's homebrew! Or would that be jailbrew?

--Thom
Keep Away: One Zorched Ground Conductor

I'll never touch that DX-100 plate cap again!

(http://i.euniverse.com/funpages/cms_content/4635/images/bhd.jpg)

AC has an entirely different result on me than DC.  I've been tangled in regular AC house current many times, and I can feel the vibration of the 60 cycle wave, as many of you probably can too.  I'd rather have smooth DC any day if I had to make a choice.  AC seems to fire up my anger emotions more so ;)  Don't know why.  I seem to be looking for something to destroy with my hands moments after the attack of the sine wave monster.  Both can kill however...

Those are some hair raising stories. I'm glad I'm not alone.

Several years ago I got wacked by 2kV in a homebrew power supply.  I simply reached in to move a wire with my left hand. The back of my hand was resting on the chassis and I simply tweaked the position of a wire with my forefinger.  I doing so I wasn't paying attention to where my thumb was and it brushed up against a hot spot on the filter cap bank.  I received a very memorable jolt from the back of my hand to my thumb.  I remember clear as yesterday the flame that shot out of my thumb.  My thumb actually glowed briefly like those experiments in high school where they stick a pickle on two electrodes.  I had blackened skin on the back of my hand and a burnt black hole in my thumb. The fortunate thing was I moved my arm myself in reaction to what had happened. It wasn't a reflex action from current flow in my body.  My body's reaction to the shock was minimal.  No soreness in muscles other that my hand. No heart fluttering, nothing.  I guess having my left hand up against the chassis and my right hand in my back pocket and being on an insulated floor helped.

Another incident prior to the 2kV incident involved an 800VDC plate supply.  Similar situation where the back of my hand was on the chassis and I was poking around in a place where I shouldn't have been.  I brushed up against a hot spot with a finger and all I heard was click and felt nothing.  The ground fault circuit interrupter to the station tripped out instantly and killed the AC power to the rig.  I didn't feel a thing.  Lucky again.

After the incident with the flame shooting out of my thumb I am extremely cautious and think about everything I do around HV.  Glad I'm here to write this...

I got hung up as a Novice by touching my key and the plate switch on my Globe Scout.  I didn't know anything about the key being at plate potential when open, being the rig was cathode keyed.  I learned fast - that 6146 was at about 750vdc.

AC is supposedly more dangerous because it makes your muscles seize up so you can't let go as you supposedly can DC.  That's one story I remember reading as a kid.

The thousond volt jolt that I received was DC, and I couldn't let go.

Same here, my 750 jolt was DC and that rig muckled right on to me with a vengeance.

Given that our muscles are controlled by a weak electrical stimulus provided by our nervous systems, a strong electrical stimulus (AC or DC) simply outstraps our nerves, both motor and sensory. Your only hope for survival in a chest zorch is to yank back with whatever muscles can still copy your brain.

I would think getting a chest hit with AC would be something like being defibrilated 60 times a second until the circuit breaks.

Hey, isn't there at least one electrician in the house? I thought this was one of those things they taught in ZAP101.

--Thom
Killer Agony One Zipper Got Caught

Yep, a chest bang is the worst for sure.

The real problem is that in extreme cases, the heart muscles and surrounding body infrastructure go so spastic that they start ripping themselves apart - the fragile tendons and muscle tissue in critical areas. That alone can check someone out.  If that ain't enuff, if the dose continues with enuff current, the body fluids start to boil inside and you can literally blow up. Or at least pop some serious stuff inside. But that kinda current is usually reserved for line workers getting the big 3-phase HV doses on power lines..  Though, I'll bet 2kv with sustained contact on sweaty hands could do the same thing.

BTW, regarding an AC line fault protection circuit... The DC filter capacitors remain ass kickingly charged for some time [many seconds] even if the AC plug is pulled.  An AC fault protection circuit is good for AC protection only. Filter caps [DC] are still lethal.   

I imagine that fault protection is useless if someone came across the transformer AC secondary since there is no ground involved - since the secondary floats, right ???  I never measured voltage / currrent between one SECONDARY  leg and 220 ground.  Anyone knowlegable of this situation ?

T

Hi T,
All I know is at that time I felt a extremely brief tingle and the GFCI tripped instantly upon feeling the tingle.   

I do agree on a big full duty cycle PS as it probably wouldn't matter if AC was GFCI protected or not. There's one huge potential there and bleeders won't knock down the charge on the cap bank fast enough. One could be dead meat by the time they discharge. 

The rig I was messing around with had a dinky power supply as it was a slopbucket rig and I probably didn't have a "clean" connection between the 800V side and ground.  In any event, it did trip. Whether or not the trip-out saved me from serious injury, who knows. All I know is it did trip-off pretty much instantly.

Actually, I think the ground is involved with a secondary whether it is tied directly from the secodary or through a rectifier (assuming one is using a 3 pronged outlet and power cord).  All that is needed to trip a GFCI is a brief imbalance between the hot side and neutral through the ground.

 Don't know about a 220 setup however. Depends on how it's wired I suppose (3 wire or 4 wire).

B

Yep, looks like it worked FB for you, Bob.  Your lucky day... ;D

The only reason I brought it up was in case a newcomer comes across this thread in the future and misreads it thinking he could work on a transmitter or receiver without electrocution risk after having the latest fault protection circuit installed on his bench.

In fact, even with fault protection, if someone were to stick their hands across the wall AC outlet, they would still be fried. The 120-0-120 circuit doesn't know the difference between flesh and copper...  ;D    It works for special circumstances, like when you come in contact with the AC line and the other hand [or foot] touches the Earth ground like a puddle, plumbing, the rig chassis connected to the AC green neutral wire or whatever - consumer variety stuff. When working on a rig, out of 100 lethal points in there, maybe 5 will trip out and then only if your other body part is touching that third point wire/earth ground.  ie, You don't want to come across the 800VAC transformer secondary leads, even the transformer primary or input to the rectifier stack [still AC] and expect it to trip off.

I guess my point is that these protection circuits create a false sense of security for newbies just getting into the hobby...  just wanted to make that point for the archives.

73,

T

Hi Tom,
Yes, indeed a very good point and not only for newbies but for others as well who are unfamiliar with certain aspects of AC fault protection.

3rd of 3

"Switch to Safety"

One of the ARRL's better campaigns.

Here's what I found to be a very haunting story, one that still, even after a few years, can get to me.

A local ham was working on his amplifier.  His wife was in another room, and heard a god-awful crash coming from the radio room.  She rushed in to find her husband lying on the floor.  He looked at her and said,

"I just electrocuted myself", and then it was all over.

(Shudder)

The worst I ever got was about 750 volts.  I was troublshooting an HX-20.  I'd taken off the plate cap of the 6146 and turned it upside down to keep the final inactive.   Then (real smart), I turned the rig over a held in on my lap, wearing shorts.  (DUH!)  When the inevetible contact happened I jumped up to get it off, dropping a brandy-new radio on the tile floor.  I was OK and so was the radio, nothing broke, but I had a scar on my thigh a while.

My 4X1's got 6 kV on the plate.  I never even thought about taking off the top cover until I saw the HV meter go to zero. 
(shudder again)


And the Drake story above...I didn't get the HV, but I got the LV.  I was also using a metal jeweler's screwdriver to adjust the cans and guess what?  They had the LV (300v? something like that) on them.  But then, that's just "low voltage". 

On a coal mine tour in Scranton, PA, the guide told us about the electric mine trains.  He said that DC was, actually, safer because if you got shocked, it tended to throw you in one direction or another, but AC didn't throw you, just just stayed where you were and vibrated.

And speaking of AC...when I was young I noticed that "funny" feeling when you got across the 110v.  A couple of times I did it on purpose.  I also know electricians who will use their fingers to see if a circuit's live or not.

And finally...I commute on the New Haven line of Metro-North, and their catenary supports say "Danger - 11,000 volts".  Does anyone know if that's what's on the catenary itself, or is that referring to the other feeder wires up higher?  The insulators on the catenary sure look like they're good for 11kv.  I guess there's lots of stuff in the cars to protect the riders from that.  The other branches of Metro-North are either 700 or 600 volts.  The third rail is marked 700 volts, but the cars say 600 volts.  Maybe a 100v drop between the third rail and the car?   


Switch to Safety

73,

Paul

I'm going with fear as the best protection!  :P

Don't trust a bleeder. You do want to watch any Voltmeter to see if the bleeder is working but don't trust that. A safety choke goes right where you said. Across the R.F. output. If the blocker shorts or if it develops a carbon trace then the high Voltage will be DC connected to ground and will take the supply offline through a fuse. Handcuffs are a permanant Jesus stick that goes across the capacitors. This assures that the discharge steps have reached a certain point in the process of making the amplifier safe to work on. Capacitors that are shorted with a shorting stick can recover chemically and will sometimes develop plenty of Voltage. Clip them with the handcuffs. The goal is not to zap the supply capacitor(s) in the first place. You really want them to discharge all the way to a couple hundred Volts through the bleeder. I like to hit them and see a small discharge assuring that the bleeder was working and my safety connection is OK. Don't try to discharge the capacitor when it is anywhere near supply Voltage!!!. This is dangerous and can damage certain types of caps not to mention flying molten metal particles. Do not trust chassis ground as a place to discharge capacitors. Some amp designs use meter multipliers in the negative lead. If someone has worked on a commercial amplifier before and shorted a capacitor bank with some energy then the resistance for the meter multiplier can be damaged. Same for previous amplifier glitches such as gas discharge or parasitics. Also check the plate blocker and even padder caps in the output tank. Plate blockers can store a nice jolt also depending on the design of the amp.
Proper fusing in the supply primary along with a glitch fuse in the secondary can save a life. Lots of homebrewers leave the secondary fuse out. It needs to be treated like an M80 when you get up to YC-156 Voltages!
     The advice seen in older handbooks is worth repeating especially after seeing so many personal accounts of shocks. Frankly I'm yellified to see this.
Don't work on this stuff when sleepy, pre-occupied, had a fight with the (X)yl, pissed off at something, been drinking or likely to be interrupted. The rest of the family should know how to shut the station down if your hide gets across the supply.
The best way to get a$$hole teenage drivers to slow down is to take them to the impound yard and show them a fresh no-head-Fred car with some gory pieces of hair stuck between the safety glass and Crimson stains. Maybe I should post the whole W2WME electrocution story (as told to me) here.

Yes, the trains on MetroNorth and the rest of the old Penn Central system run in 11kv 25Hz AC.

Good  summary, Dave! 

You mentioned the secondary fuse.  ie, a fuse that goes in the ~5kv DC line before the amplifier.

What I did here is install a pair of 2" stand off insulators spaced about 2" apart. The HV plus lead goes in series here and the insulators are bridged with TWO fine strands from an RG-213 coax shield.  When the HV supply gets shorted, it opens up with a flash and the tiny wires evaporate. It's imporatnt to keep the insulators apart by two inches min cuz of the sustained arc that can occur.

It has saved my solid state diode bridge rectifier stack many times. In the past I've wiped out bridges, but not one has fried since installing this HV fuse.   

Ther most common short circuit reason?  I hate to admit it, but it's cuz  sometimes when finsihed working on the amp, I forget to take the handcuffs or Jesus stick off before firing it up ...  BANG!!  :o

T

Yes, thanks for the explain Dave... Yea Tom, I've come across that same thin wire HV fuse method during my recent amp info searching online.

I Guess "Handcuffs" could be made with some sort of metal bar on a hinge that shorts the filter cap bank.

....have you seen this homebrew YC-156 big mawl linear amp??

http://www.wv7u.com/yc156amp/yc156amp.html

Dayum.  This post oughta be put on the home page of this site!!!

Done this myself more than once. It shows how easy it is to forget and that all safety systems should be redundant.

Yup. MRI machine meets H.F. amp. Nice stuff.

And it's a point well taken, not only for those in our hobby, but for anyone working around high voltage. Coupled with that are dangers associated with bypassing protection circuits or a failure to design them into equipment in the first place.

I worked at one TV station that experienced an engineering fatality due to several of the reasons mentioned in this thread. Luckily the accident happened before my employment there, but I observed that it cast a long shadow over the company and everyone connected to it for many years afterward. Human nature being what it is, these types of accidents unfortunately seem to reoccur every years. I always cautioned any new technicians not to think about themselves, but to think about those they would be leaving behind if they ever considered taking a shortcut on safety procedures. I told them to think about their fellow workers who would have to pull the big switch or the empty eyes of the grieving widow and the fatherless kids. In the case of my station, the employee had bypassed safety interlocks and was working on energized equipment alone without another man providing a safety backup. There was actually a second worker in the building at the time, but he was in another room.  I'l spare the unpleasant details except to say that the second worker never heard the accident when it happened. He was alerted when the smoke detector went off.  The neighbors to the site were alerted when they heard the second man screaming. The nearest neighbors were 1/4 mile away.

We all know that there is no shortage of hubris among some hams. It's easy to become complacent and dismiss basic safety measures whether it be in the interest of time or because we think that somehow we are immune to danger. Somehow we never expect that the ultimate crapout will happen to us when we tempt fate and cease giving high voltage the respect it deserves. I'm not trying to dispense a bromide here, but hopefully to make someone think twice before he does something stupid. Life is far too short as it is.

73, Jim
WA2AJM/3

That's a scratch built amp. Pretty amazing. The only thing from an MRI machine is the surplus tube  ;)
Wish I had that much "scrap" aluminum to play with!

More electrocution banter. Good reading.

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