wicked1, once you're done unplugging/switching off ALL the breakers also remember to unplug your cable (if you have cable TV that is). This is a long shot but defective coupler there could also result in you getting shocked if your ground connection is faulty so your "ground" is actually floating.
Other than that you got plenty of good suggestion that should keep you busy for a while
Other than that you got plenty of good suggestion that should keep you busy for a while
For almost 25 years ago I played with a breaker-less ignition system I built around a BU208 HV transistor from a scrapped TV, had everything connected on the lab desk to test the circuit.
Left the circuit for a while with the function generator left on at a very low rate of 2-3 Hz and wide duty cycle charging the coil with full energy, came back and got close with one hand on the centre of the coil (the HV output) and got a very nice experience, jerked couple of times like h*ll, 230 VAC is absolutely nothing in comparison I can ensure!
Left the circuit for a while with the function generator left on at a very low rate of 2-3 Hz and wide duty cycle charging the coil with full energy, came back and got close with one hand on the centre of the coil (the HV output) and got a very nice experience, jerked couple of times like h*ll, 230 VAC is absolutely nothing in comparison I can ensure!
Way back when I was in high school I worked as a tech at a company building computerized medical equipment. I had to get to the backplane on one of the systems so I had the front panel off and was down on my knees with my upper body inside the cabinet when my head hit the exposed contacts on the AC breaker switch that was mounted on the side of the cabinet. Of course I had turned the power off, hadn't unplugged it though. 120VAC skull to knees got my attention.
Years later a guy I worked with was doing ESD testing on a unit and got his zipper a little too close to the unit under test. We could hear the "yeowwwwwwwwwwwwwwww f*** f*** f*** f***!!!!!!!" all the way at the other end of the building.
Years later a guy I worked with was doing ESD testing on a unit and got his zipper a little too close to the unit under test. We could hear the "yeowwwwwwwwwwwwwwww f*** f*** f*** f***!!!!!!!" all the way at the other end of the building.
In grad school I worked with a APFIM (Atom Probe Field Ion Microscope) which required periodic calibration of the high voltage supplies. 50kV. This was a two person job as the voltage supplies and control console were seperated. My advisor had on several occasions advised me that when working with people on critical tasks to always ask a question that requires a negative response before proceeding to the next step.
Mr Wu. was my assitant that day and was responsible for operating the control console while I took measurements off the back of the power suppy with my voltage divider. We had just finished the 50kV supply and per the procedure I had asked him if the power supply was off. He said "YES" so I moved the divider to the next power supply and repositioned myself. As I sat back down, I felt a small bite through my jeans. Thinking that I had sat on a tack or sharp object I looked, didn't find anything and sat back down again. This time it was different. By the time I realized what had happened I had dented the heat register with my body and kicked the power supply cabinets several feet across the room. I had been bit by 50kV in my buttocks. Luckily it was capable of generating only a few milliamps. It was enough of a jolt that I was sore for several days after from the sudden muscle contraction but also from slamming against the heat register.
Moral of the story is that people in general are polite and will respond in a positive mannor even if they don't understand the question. Second lesson learned was to never "ASSUME" and always test to make sure.
Mr Wu. was my assitant that day and was responsible for operating the control console while I took measurements off the back of the power suppy with my voltage divider. We had just finished the 50kV supply and per the procedure I had asked him if the power supply was off. He said "YES" so I moved the divider to the next power supply and repositioned myself. As I sat back down, I felt a small bite through my jeans. Thinking that I had sat on a tack or sharp object I looked, didn't find anything and sat back down again. This time it was different. By the time I realized what had happened I had dented the heat register with my body and kicked the power supply cabinets several feet across the room. I had been bit by 50kV in my buttocks. Luckily it was capable of generating only a few milliamps. It was enough of a jolt that I was sore for several days after from the sudden muscle contraction but also from slamming against the heat register.
Moral of the story is that people in general are polite and will respond in a positive mannor even if they don't understand the question. Second lesson learned was to never "ASSUME" and always test to make sure.
Let me tell you something funny as I noticed something interesting in your post many of us should pay a bit attention to.
I assume Mr. Wu is a Chinese, I have some experiences with Chinese and communicating with them, I even know very brief Chinese language too, do NEVER ask them a question where they have to say NO because when Chinese are negating they say always YES! I am NOT joking!
One can see it from another point of view, when a Chinese answer yes it means he/she is insisting with you, let's say we ask something like "don't do that because it's dangerous" and they would answer YES because for them it means "Roger that".
(Oh, and those who didn't understand "Roger that" check Urban Dictionary: roger that or watch any American war movie.)
Cheers Michael
What is the possibility that the slab surface itself is sitting some volts above ground? Do you have a furnace or other machinery (washer/drier/dehumidifier) sitting on the wet basement floor that is not grounded properly? (The slab is conductive, but not a good conductor.)
Another possibility is that the slab is a better ground than the house ground system in which case you might want to get that fixed. I would think this unlikely, but you should have it checked if you cannot identify the source of the problem. This is a job for an electrician - local electrical codes should have provisions to deal with prevailing soil conductivity issues. The city I live in just outside Boston actually requires 2 six foot (in soil) ground rods placed no more than a few yards apart and bonding to the water mains per local code.
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I was working on a bad termination for the AC motor operated pressure outflow valve on a 757. I had already made the mandatory trip to the cockpit to placard the control panel and open the system breaker. I got in position to do the job lying on the aircraft structure under the aft galley floor.
When I cut the wire there was a blinding blue flash as the jaws of my wire cutters became incandescent, then the free hot end of the wire fell neatly between the ring finger and social finger of my right hand and I became a powered device causing the circuit breaker to pop. The very same circuit breaker that I had opened and collared ten minutes earlier. 115 volts @ 400Hz gave me a blister between my fingers, a very sour demeanor, and a temporary loss of vocabulary control. I climbed out and ran to the cockpit intent on murder. When I reached the cockpit I found the circuit breaker collar on the centre console, the breaker it had been on was open, but my intended victim was no where to be found. The miscreant in question no doubt heard the ruckus I was making and left in a hurry.
Scott
When I cut the wire there was a blinding blue flash as the jaws of my wire cutters became incandescent, then the free hot end of the wire fell neatly between the ring finger and social finger of my right hand and I became a powered device causing the circuit breaker to pop. The very same circuit breaker that I had opened and collared ten minutes earlier. 115 volts @ 400Hz gave me a blister between my fingers, a very sour demeanor, and a temporary loss of vocabulary control. I climbed out and ran to the cockpit intent on murder. When I reached the cockpit I found the circuit breaker collar on the centre console, the breaker it had been on was open, but my intended victim was no where to be found. The miscreant in question no doubt heard the ruckus I was making and left in a hurry.
Scott
Great Thread
My interactions were from a time before I made tube gear.
I worked at a transformer company years ago (1981) in production test and I did a lot of HV (AC) and Hi-pot (DC) testing manually. After you've tested a few hundred little transformers you get careless or drowsey and somtimes you'd get tested too!
That'll wake you up...
I remember I used to bike to work back then and one day it was raining so my pant legs were wet. My chair was metal on an un-insulated conrete floor. You could feel your mistakes all the way down to your ankles! Luckily all this gear was current limited to micro-amps.
The biggest one was when I worked at a place with 550V/3-phase power and I had the task of balancing the loads on the three phases. I was embarking on a voyage of discovery in the main panel and was about to measure the voltage of one phase (550V) with a handheld DVM (Keithly I think). Luckily I wasn't holding the meter in my hand so I could use the probes. The meter turned into a flashbulb. (Yes it was on the right setting and it was a 750VRMS meter.) The whole facility blacked out. One of the guys came
running down stairs and saw me looking like a ghost standing next to a smoldering lump. He was very concerned and said "Are you OK?". I said "Yes" and then he laughed his a** off. "You should see the look on you face!" he said.
That was a scary one. Now I keep one hand in my pocket whenever I have to reach into any gear and I always have a spare DVM on the main cap in the supply just to know when it has discharged to a safe level.
Stay safe
Matt
My interactions were from a time before I made tube gear.
I worked at a transformer company years ago (1981) in production test and I did a lot of HV (AC) and Hi-pot (DC) testing manually. After you've tested a few hundred little transformers you get careless or drowsey and somtimes you'd get tested too!
That'll wake you up...
I remember I used to bike to work back then and one day it was raining so my pant legs were wet. My chair was metal on an un-insulated conrete floor. You could feel your mistakes all the way down to your ankles! Luckily all this gear was current limited to micro-amps.
The biggest one was when I worked at a place with 550V/3-phase power and I had the task of balancing the loads on the three phases. I was embarking on a voyage of discovery in the main panel and was about to measure the voltage of one phase (550V) with a handheld DVM (Keithly I think). Luckily I wasn't holding the meter in my hand so I could use the probes. The meter turned into a flashbulb. (Yes it was on the right setting and it was a 750VRMS meter.) The whole facility blacked out. One of the guys came
running down stairs and saw me looking like a ghost standing next to a smoldering lump. He was very concerned and said "Are you OK?". I said "Yes" and then he laughed his a** off. "You should see the look on you face!" he said.
That was a scary one. Now I keep one hand in my pocket whenever I have to reach into any gear and I always have a spare DVM on the main cap in the supply just to know when it has discharged to a safe level.
Stay safe
Matt
Neither is the racing stripe that went down my back from the output of a 120 watt marine radio. I was out on a sailboat with some high school budies in persuit of some lobster in Biscayne Bay. We had just climbed back in the boat after about an hour in the salt water. I was leaning against the back stay, a 1/4 inch stainless steel cable that guys the mast and doubles as the radio antenna. This was in the late 60's and the marine radios of the day used AM modulation on the HF bands (2.1 MHZ). One of the more intoxicated idiots on the boat thought that it would be funny to key the transmitter. 120 watts (real tube power) at that frequency both burns and shocks. The involuntary muscle spasm that resulted sent the diving knife in my hand into Low Earth Orbit. The diving knife happened to belong to the idiot on the microphone. It took almost a year for the scar to fade, and Mr. Idiot was not permitted to go out with us on the boat any more.
It was probably similar to the look on my wifes face after she measured the ohms in the wall outlet. The meter spit parts right through the plastic case.
My mother in law's house had a similar leak somewhere. The house was built in 1921 and wired with two conductor cloth covered wire (ground, what ground). Her husband (now deceased, so I can't ask him) made several additions to the house and rewired much of it himself. I have noticed the tingle when touching things in the basement while standing barefoot on the concrete floor. Removing fuses from the box changes the amount of the zap, but doesn't make it go away. Killing all power to the house does stop it. The zap is much worse on a rainy day. I gave up trying to find it years ago.
When I was there last it rained for a week. The phone would not work. Verizon wanted a bunch of money if a tech had to go into the house, so I set out to fix it. The rats nest of phone wires all came together at a very old Western Electric box in the basement. I started disconnecting wires until the buzz in the phone stopped. It was a pair of wires that went out underground to a detached garage. Sherri's mom doesn't need a phone in the garage so we left the wires unhooked. I discovered that there was no more zap in the basement either. I bet that someone ran the phone and power wires to the garage either in the same pipe, no pipe at all, or worse.
Like most here I've had a few moments, a few I recall from my younger years..
One I recall which I didnt get a shock from... Mum and Dad were out on the farm and at the tender age of 7 I decided I could hook a light up to a power point, very carefully I managed to strip the insulation back and quite successfully attach it to a 3 pin plug, plugged it in and BANG!, the light exploded and the rather warm brass light bayonet went flying apart.
What I didn't count on was that the light ws only 12v, scared the hell out of me but unfortunately did nothing to curb my curiosity.
No-one could explain the mystery burn in the hallway carpet
Another incident where I think I was 8 or 9, Dad was in the neighbours paddock helping repair a fence, there was a temporary electric fence erected that stood approx 2 feet high, I had a few shocks from fences before so I dropped to the ground and crawled commando style under it, stood up, BAM!, I stood up directly under the wire and had it stretched over my head.
It was 30 years ago but I remember it like yesterday.
Tinkering in dads shed I recall charging up a 750,000mfd 16v capacitor with a 12v battery and discharged it with a large screwdriver, the capacitor exploded and blew a huge chunk out of the screwdriver, there were fibres and foil everywhere, nothing larger than a bottletop remained.
I'm amazed I wasn't blinded.
One I recall which I didnt get a shock from... Mum and Dad were out on the farm and at the tender age of 7 I decided I could hook a light up to a power point, very carefully I managed to strip the insulation back and quite successfully attach it to a 3 pin plug, plugged it in and BANG!, the light exploded and the rather warm brass light bayonet went flying apart.
What I didn't count on was that the light ws only 12v, scared the hell out of me but unfortunately did nothing to curb my curiosity.
No-one could explain the mystery burn in the hallway carpet
Another incident where I think I was 8 or 9, Dad was in the neighbours paddock helping repair a fence, there was a temporary electric fence erected that stood approx 2 feet high, I had a few shocks from fences before so I dropped to the ground and crawled commando style under it, stood up, BAM!, I stood up directly under the wire and had it stretched over my head.
It was 30 years ago but I remember it like yesterday.
Tinkering in dads shed I recall charging up a 750,000mfd 16v capacitor with a 12v battery and discharged it with a large screwdriver, the capacitor exploded and blew a huge chunk out of the screwdriver, there were fibres and foil everywhere, nothing larger than a bottletop remained.
I'm amazed I wasn't blinded.
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when I was around 13 or 14 the lights went out at my house during a heavy rainstorm. This was a regular occurrence in heavy rain and I was soon to find out why. It was usually my job to run down to the basement and reset the main breaker, and so I did it.
FLASH!
Suddenly I am lying on the damp floor of the basement about 5 feet from the breaker box and my right arm and hand are tingling like mad. I don't remember a sound, but my parents said it sounded like an M-80 going off.
Turns out that when they built my parents house in the 60's they didn't shellac the fabric covered mains wires going into the house. Instead the just painted them with house paint. For many years, it turns out, they had been acting as a wick bringing water right into the box. When I reset the breaker I apparently bridged the circuit and zappo. It took a week before we had power again. They had to put new modern wires from the peak of the house and down into a new breaker box, since the old was completely rusted out in the back.
Gave me a healthy respect for electricity, that's for sure.
FLASH!
Suddenly I am lying on the damp floor of the basement about 5 feet from the breaker box and my right arm and hand are tingling like mad. I don't remember a sound, but my parents said it sounded like an M-80 going off.
Turns out that when they built my parents house in the 60's they didn't shellac the fabric covered mains wires going into the house. Instead the just painted them with house paint. For many years, it turns out, they had been acting as a wick bringing water right into the box. When I reset the breaker I apparently bridged the circuit and zappo. It took a week before we had power again. They had to put new modern wires from the peak of the house and down into a new breaker box, since the old was completely rusted out in the back.
Gave me a healthy respect for electricity, that's for sure.
Another possibility I once encountered is a fault in underground service equipment e.g. a transformer pad nearby. This can create a potential difference between the plumbing, the electrical ground, and/or the slab. This was repored in a subdivision where people were getting shocked in their basement showers.
As for electric fences, they cycle on and off about once every few seconds. Not realizing this, I once briefly brushed the fence wire with a fingertip to see if it was hot. Not feeling anything, I proceeded to push the wire down and put one leg over the fence... just as the fencer cycled on
oh Im glad I am not alone.
The most dangerous I have had was in a flat I used to live in. The local morons had decided that a new path was needed. It was a TT system and they pulled the earth rod out. The old girl below me had a down to earth imersion heater in her hot water cylinder, nice. My misses said that she was getting shocks from the washing machine!!!! On investigation it turned out that the loop impedence was about 2R (Fluke loop impedence tester) between my sink and the drum of the washing machine. Needless to say I was not too happy about this and it was sorted sharpish.
The second most life threatening and also stupid incident was when I used a black rubber tube to listen for corrona on an antistatic blower thing (Meech)
I had a 15Kv whack in the earhole. Rubber contains carbon black. It is conductive. I was working in a rubber factory. Yes I feel very stupid.
The first proper belt I ever had was when I was working in the local TV repair shop (sadly long gone) I got hold of 25KV in the back of a set. The old boy just laughed, he was right too, it was minimal current and it tought me a very good lesson.
I am a profesional sparks (hope not) by trade and have seen many, many really nasty incidents. People stealing earthing and copper in general from sub-stations(you know the types) I will say that there is no minimumum current or voltage that will kill. Its all on the circumstances.
People have been soaked in rain and struck by litenining, survived, only to die of the horrific burns.
Matt.
The most dangerous I have had was in a flat I used to live in. The local morons had decided that a new path was needed. It was a TT system and they pulled the earth rod out. The old girl below me had a down to earth imersion heater in her hot water cylinder, nice. My misses said that she was getting shocks from the washing machine!!!! On investigation it turned out that the loop impedence was about 2R (Fluke loop impedence tester) between my sink and the drum of the washing machine. Needless to say I was not too happy about this and it was sorted sharpish.
The second most life threatening and also stupid incident was when I used a black rubber tube to listen for corrona on an antistatic blower thing (Meech)
I had a 15Kv whack in the earhole. Rubber contains carbon black. It is conductive. I was working in a rubber factory. Yes I feel very stupid.
The first proper belt I ever had was when I was working in the local TV repair shop (sadly long gone) I got hold of 25KV in the back of a set. The old boy just laughed, he was right too, it was minimal current and it tought me a very good lesson.
I am a profesional sparks (hope not) by trade and have seen many, many really nasty incidents. People stealing earthing and copper in general from sub-stations(you know the types) I will say that there is no minimumum current or voltage that will kill. Its all on the circumstances.
People have been soaked in rain and struck by litenining, survived, only to die of the horrific burns.
Matt.
My first chock happened when I was about 6-7 years old. I had this old tube radio that had a phono input. For this input, it used a plug that fit nicely in the mains outlets, but one could open it in the back to connect the wires. One night I decided it would be a good idea to see what would happen if I took this plug and connected it to the mains outlet and placed my right index and middle finger on the two terminals in the plug with the power on... Let's just say I stuck to low voltage circuits for a while after that...
There was also one time in college where I was working on a 500 W switchmode supply for an audio amp. I used rectified 230 VAC for the primary side of the switchmode supply and I was being careful. I used an isolation transformer, and made a habit of checking the reservoir cap to make sure it had fully discharged before making any changes to the circuit. Well... One time I forgot to turn the power off and went to verify that the reservoir cap had discharged. Of course it hadn't, and I was instantly thrown back in the chair by the 315 V DC across the cap. The issue was that I was using some test probes for the voltmeter that took a banana lead in the end. Upon further inspection, it turned out that this kind of probes left just enough metal of the banana plug exposed to catch the meaty web between my thumb and index fingers. I got chocked hand-to-hand by 315 V DC. That's the first time I've felt the need to check my pulse after a chock...
Then there was the time I was messing with the series resistor for an LED situated immediately above the power switch in an amp I was working on. The amp was turned off, but the cord still plugged in. And the power switch was a DPDT switch... Well... I moved one lead on the series resistor and BANG!! it found the hot end of the power switch. The lights flashed and my dad stuck his head in with this half annoyed, half concerned expression on his face and asked "what are you doing!?". I don't recall my response if I had any. But I do remember being rather stunned sitting there with the remains of a resistor lead still in the jaws of the pliers I was holding. Thankfully, the pliers were insulated so no chock just loud noises and flashes of light...
~Tom
There was also one time in college where I was working on a 500 W switchmode supply for an audio amp. I used rectified 230 VAC for the primary side of the switchmode supply and I was being careful. I used an isolation transformer, and made a habit of checking the reservoir cap to make sure it had fully discharged before making any changes to the circuit. Well... One time I forgot to turn the power off and went to verify that the reservoir cap had discharged. Of course it hadn't, and I was instantly thrown back in the chair by the 315 V DC across the cap. The issue was that I was using some test probes for the voltmeter that took a banana lead in the end. Upon further inspection, it turned out that this kind of probes left just enough metal of the banana plug exposed to catch the meaty web between my thumb and index fingers. I got chocked hand-to-hand by 315 V DC. That's the first time I've felt the need to check my pulse after a chock...
Then there was the time I was messing with the series resistor for an LED situated immediately above the power switch in an amp I was working on. The amp was turned off, but the cord still plugged in. And the power switch was a DPDT switch... Well... I moved one lead on the series resistor and BANG!! it found the hot end of the power switch. The lights flashed and my dad stuck his head in with this half annoyed, half concerned expression on his face and asked "what are you doing!?". I don't recall my response if I had any. But I do remember being rather stunned sitting there with the remains of a resistor lead still in the jaws of the pliers I was holding. Thankfully, the pliers were insulated so no chock just loud noises and flashes of light...
~Tom
When I was younger I plugged a NE-2 bulb directly into the outlet to make it light up. A big BANG and flash followed..I wasn't shocked,but the neon bulb was vaporized,I never found any part of it,and there was a big black mark on the outlet..It suddenly dawned on me what the resistor was for. One of those "Ah-Ha" moments.
Excellent, I have also done the neon direct across the mains trick it also had my dad running up to see waht had happened. I replied "nothing" as all young uns do. He fitted an RCD to my bench when I was at school after that. Hes not as daft as I thought he was;-).
Anyway talking about all this, I had a nasty one yesterday. My mate phoned me saying his washing machine was knackered (seems to be a running theme, perhaps I should stay clear of the things) The pump was clearly intermittant. We dragged it out to his patio and I had a look after draining all the water in the usual manner of dragging the pipe off the pump. I had a look and found that one of the spades was all corroded, replaced it then said go on pug it in. It didnt work. I said turn it off then jumped in and had a mess about, WOLLOP I was on my **** on the lawn!! I shouted at him a bit saying he should have turned it off. Thing is he had, it turned out that the one socket in the whole house that was wired backwards was the one by the back door. I do electrical testing as part of my usual job and the first sockets you test are the ones that can be used outside. so I was surprised by this, especialy as he had only just moved in and it was a council place. Thinking about it, it was also the council that had ripped out the earthing at my old flat.
Matt.
it also had my dad running up to see waht had happened. I replied "nothing" as all young uns do. He fitted an RCD to my bench when I was at school after that. Hes not as daft as I thought he was;-).Anyway talking about all this, I had a nasty one yesterday. My mate phoned me saying his washing machine was knackered (seems to be a running theme, perhaps I should stay clear of the things) The pump was clearly intermittant. We dragged it out to his patio and I had a look after draining all the water in the usual manner of dragging the pipe off the pump. I had a look and found that one of the spades was all corroded, replaced it then said go on pug it in. It didnt work. I said turn it off then jumped in and had a mess about, WOLLOP I was on my **** on the lawn!! I shouted at him a bit saying he should have turned it off. Thing is he had, it turned out that the one socket in the whole house that was wired backwards was the one by the back door. I do electrical testing as part of my usual job and the first sockets you test are the ones that can be used outside. so I was surprised by this, especialy as he had only just moved in and it was a council place. Thinking about it, it was also the council that had ripped out the earthing at my old flat.
Matt.
Tubelab,
You should try an upturned glass with a burning toothpick inside in the microwave. Use an old microwave it really gives it hell. Also melts the glass after a while, although I think this is more a problem of impurities on the glass than the heat of the plasma If you forget the glass altogether the plasma rolls around the top and kills the microwave fast. good fun if a little distructive. Along the same lines, you can use the magnetron to pump a CO2 laser.
Cheers Matt.
You should try an upturned glass with a burning toothpick inside in the microwave. Use an old microwave it really gives it hell. Also melts the glass after a while, although I think this is more a problem of impurities on the glass than the heat of the plasma
If you forget the glass altogether the plasma rolls around the top and kills the microwave fast. good fun if a little distructive. Along the same lines, you can use the magnetron to pump a CO2 laser.Cheers Matt.
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