i got zapped just last week with my 807 tube amp, found out the last owner removed a bleeder resister. i was runing a new heater
wire when i grazed a foot long 600v cornell dublilier, needless
to say i saw white light for a second. now all my amps get a grounded cord and i allways discharge the caps no matter how much of a hurry im in
it hurt
not as bad as a arking flyback but still hurt
wire when i grazed a foot long 600v cornell dublilier, needless
to say i saw white light for a second. now all my amps get a grounded cord and i allways discharge the caps no matter how much of a hurry im in
it hurt
not as bad as a arking flyback but still hurt
wow
You people have scary stuff to tell, really.
I've got some nice little stories to tell as well.
Like the first time I got zapped was in Italy, where I also had my last experience with live stuff.
The first time was in Italy, switching on the lights. There used to be those little bulbs inside of the switch to let you see where they are in the dark. Somehow that bulb/switch was damaged an I got buzzed. I was like 8 years old, but I can still remember the feeling it gave me. Surprised, but still curious. Nothing really happened, except fore a huge blister on my finger.
When I was a little older, a friend's father gave us a broken lawnmower. We took it apart and put the motor in a vice. We also attached a propeller to the motor, donno what we wanted it to do...the idea still makes me laugh.
Well, we where not tall enough to reach the workbench while standing on the floor, so put a wooden box there, on which we stood. We did not have a switch, so Thomas, my friend, decided to directly connect the mains-wires to the motor's contacts.
The following scenario is still in my head: he somehow screwed it up and I saw light, like the flash when you short something, developing around his hand. The same moment the lights went out, and it went dark (we where in the basement). But the afterglow of the arc let me see him fly off that wooden box through the air two meters at least. I was really sure that he was dead (everything was so dark and silent), but the wooden box and the fact that he got into the "circuit" with only one hand must have saved his live. He was passed out for a few seconds and had a numb feeling in his hand for a few days. Plus his knuckles hurt.
Well, and one month ago we where in Italy and stayed in some appartement with a gas-stove. They had these electric ignitors, like you have with piezo-lighters. But mains-fed, no earth-connection.
I was checking out the part where the gas comes out to see if any old food or something stuck to it, and a friend of mine pushed the ignition button.
An arc of considerable length cought the pointer of my right hand and I felt the muscles of my whole upper body contract. I couldn't hear anything for a second or two and my ellbow's joint hurt for hours.
When I work on live equipement (testing and stuff), I sometimes wear rubber-gloves (like the ones a doctor wears) when it comes to the high voltages. We built a ionic-tweeter and I never got a buzz. Seems like theses things can insulate fram 900v at least.
And yes, 20 mills kills. The 2Mohm you measure are DC. But the Na-K stuff (also the Na-Cl) in your body is a good conductor, just your skin is not really conductive. I think that's why your joints hurt so bad after getting a real buzz, because the liquid in there is really conductive which results in a larger current.
Plus you sure have got some impedance. Mains-frequency is almost rated at heart-frequecy, that makes things more dangerous (that's what people say and believe). But I don't know anything about the AC-characteristics of the human body.
One last thing: I am really scared of large capacitors. I've accidentally shorted one last week. I was sure it was empty, but the charge stays in there for many, many hours if the cap is big enough.
I don't want to imagine what happens if you shoert them with your fingers...
You people have scary stuff to tell, really.
I've got some nice little stories to tell as well.
Like the first time I got zapped was in Italy, where I also had my last experience with live stuff.
The first time was in Italy, switching on the lights. There used to be those little bulbs inside of the switch to let you see where they are in the dark. Somehow that bulb/switch was damaged an I got buzzed. I was like 8 years old, but I can still remember the feeling it gave me. Surprised, but still curious. Nothing really happened, except fore a huge blister on my finger.
When I was a little older, a friend's father gave us a broken lawnmower. We took it apart and put the motor in a vice. We also attached a propeller to the motor, donno what we wanted it to do...the idea still makes me laugh.
Well, we where not tall enough to reach the workbench while standing on the floor, so put a wooden box there, on which we stood. We did not have a switch, so Thomas, my friend, decided to directly connect the mains-wires to the motor's contacts.
The following scenario is still in my head: he somehow screwed it up and I saw light, like the flash when you short something, developing around his hand. The same moment the lights went out, and it went dark (we where in the basement). But the afterglow of the arc let me see him fly off that wooden box through the air two meters at least. I was really sure that he was dead (everything was so dark and silent), but the wooden box and the fact that he got into the "circuit" with only one hand must have saved his live. He was passed out for a few seconds and had a numb feeling in his hand for a few days. Plus his knuckles hurt.
Well, and one month ago we where in Italy and stayed in some appartement with a gas-stove. They had these electric ignitors, like you have with piezo-lighters. But mains-fed, no earth-connection.
I was checking out the part where the gas comes out to see if any old food or something stuck to it, and a friend of mine pushed the ignition button.
An arc of considerable length cought the pointer of my right hand and I felt the muscles of my whole upper body contract. I couldn't hear anything for a second or two and my ellbow's joint hurt for hours.
When I work on live equipement (testing and stuff), I sometimes wear rubber-gloves (like the ones a doctor wears) when it comes to the high voltages. We built a ionic-tweeter and I never got a buzz. Seems like theses things can insulate fram 900v at least.
And yes, 20 mills kills. The 2Mohm you measure are DC. But the Na-K stuff (also the Na-Cl) in your body is a good conductor, just your skin is not really conductive. I think that's why your joints hurt so bad after getting a real buzz, because the liquid in there is really conductive which results in a larger current.
Plus you sure have got some impedance. Mains-frequency is almost rated at heart-frequecy, that makes things more dangerous (that's what people say and believe). But I don't know anything about the AC-characteristics of the human body.
One last thing: I am really scared of large capacitors. I've accidentally shorted one last week. I was sure it was empty, but the charge stays in there for many, many hours if the cap is big enough.
I don't want to imagine what happens if you shoert them with your fingers...
The worst stories are the ones where the teller is no longer here to do the telling. And that happens too often. I still get the willies when I see posts that read something like, "I don't know much about electronics and have never built anything before. But I bought all the parts for an 845 SET amp and I have some questions on troubleshooting the power supply..."
Yannow, not much to tell here. About five years ago, I was developing a 3.0KV supply for a project. The AC section consisted of a 12.0V(dc) to 1150V(ac) inverter running at 14KHz. I had the output connected to a voltage divider with 2.2MEG in series with 100 ohms, to o'scope the output waveform. Upon reaching over I pulled a spark from the voltage divider chain.
Not any worse than touching a door knob after walking across a wool carpet on a frigid winter day. NBD.
As for mains voltage and higher, nothing to report.
Not any worse than touching a door knob after walking across a wool carpet on a frigid winter day. NBD.
As for mains voltage and higher, nothing to report.
A few years back we were servicing one of our 50watt UHF LPAs. I had the cover off and the interlocks disabled and ran my forearm across the main filter cap.
Felt cruddy the rest of that day.....
We have Pulsers at work that will simulated E1 and E2 EMP pulses, big Marx Banks on the outputs..... I haven't messed up with any of them yet...
We call this one Spanky-
Felt cruddy the rest of that day.....
We have Pulsers at work that will simulated E1 and E2 EMP pulses, big Marx Banks on the outputs..... I haven't messed up with any of them yet...
We call this one Spanky-
Attachments
About 2 years ago working on a preamp, had it unplugged and attached a 50K 10W Clarostat WW resistor that I have for discharging power supplies to which i have attached 6 inch leads with alligator clips on either end, waited about 2 minutes then put my hand inside and zap! around 300V. My wife was just walking into my office and called me at the same time and I remember answering yyyyyyyyyyyooooooooowwwwwwwwwww with a vibration like tone in my voice. After years of faithful service the lead on one end of the resistor had broken free from flexing but I could not see because of the heatshrink tubing around it.
Years ago I always used to measure to see if voltage was present but had stopped and just used the resistor. Of course I have gone back to measuring again.
Complacency can kill.
Andrew
Years ago I always used to measure to see if voltage was present but had stopped and just used the resistor. Of course I have gone back to measuring again.
Complacency can kill.
Andrew
1986, summer, Massachussets, 25,000Vdc. Twenty-five thousand.
This was back when I was a designer of high-res CRT displays. We always had open chassis everywhere. I was going to replace the high voltage supply and forgot to turn it off. Went into the anode cap with a screwdriver and my elbow in contact with metal chassis.
Needless to say, it hit hard. The resulting arm jerk hurled the screwdriver across the lab right above some guys head. The scream must have been pretty loud, as a lot of folks came a runnin'. I was on the floor. My arm recovered in about ten minutes, with only a residual pain for a couple weeks (probably dead tissue inside).
In hindsight, probably pretty lucky it wasn't the other arm touching chassis.
jh
This was back when I was a designer of high-res CRT displays. We always had open chassis everywhere. I was going to replace the high voltage supply and forgot to turn it off. Went into the anode cap with a screwdriver and my elbow in contact with metal chassis.
Needless to say, it hit hard. The resulting arm jerk hurled the screwdriver across the lab right above some guys head. The scream must have been pretty loud, as a lot of folks came a runnin'. I was on the floor. My arm recovered in about ten minutes, with only a residual pain for a couple weeks (probably dead tissue inside).
In hindsight, probably pretty lucky it wasn't the other arm touching chassis.
jh
I was repairing a record player, which had the controls (including mains switch) on the same panel as the turntable. Before making adjustments, I carefully removed the WRONG mains plug.
Picked the panel up with fingers round the switch, and the current made my hand contract and hold it tighter - I couldn't let go! I eventually managed to kick the wall switch off, and suffered no ill effects apart from a minor skin burn, but have ever since been careful to trace the cable back to the wall...
Picked the panel up with fingers round the switch, and the current made my hand contract and hold it tighter - I couldn't let go! I eventually managed to kick the wall switch off, and suffered no ill effects apart from a minor skin burn, but have ever since been careful to trace the cable back to the wall...
Just remembered another more recent one.
An early 1950s TV, which clearly hadn't been used for years (cobwebs, thick dust on outside of cab, broken rubber insulation, etc.) Wasn't worth restoring, but the tube was worth keeping, as it was a rare model. Usually, I'd carefully discharge the final anode, and leave the shorting link for several minutes to make sure, but this obviously had no charge left after years of neglect
You guessed it, of course - I pilled the anode cap off with my fingers, and received an uncomfortable belt for my trouble - not severe, but it amazed me that the charge could remain so long!
Stupid thing is that I had for once put goggles on just in case the rimband-less tube imploded.
An early 1950s TV, which clearly hadn't been used for years (cobwebs, thick dust on outside of cab, broken rubber insulation, etc.) Wasn't worth restoring, but the tube was worth keeping, as it was a rare model. Usually, I'd carefully discharge the final anode, and leave the shorting link for several minutes to make sure, but this obviously had no charge left after years of neglect
You guessed it, of course - I pilled the anode cap off with my fingers, and received an uncomfortable belt for my trouble - not severe, but it amazed me that the charge could remain so long!
Stupid thing is that I had for once put goggles on just in case the rimband-less tube imploded.
Usually, I'd carefully discharge the final anode, and leave the shorting link for several minutes to make sure, but this obviously had no charge left after years of neglect
It probably wouldn't have any charge left after so many years. However, an open capacitor can charge up simply from ions normally present in the air. Depending on the environment, that can build up some astonishing voltages.
It's always a good idea to dead-short capacitors, especially big ones, if you're going to be storing them for any length of time.
It probably wouldn't have any charge left after so many years. However, an open capacitor can charge up simply from ions normally present in the air. Depending on the environment, that can build up some astonishing voltages.
It's always a good idea to dead-short capacitors, especially big ones, if you're going to be storing them for any length of time.
Had the top off an amplifier, needed to plug it in. Grabbed the mains lead in left hand, grabbed the inside of the amp (where the plug goes to) with the other. Plugged it in and got a strange 50Hz vibration through my index finger. The finger was across live and neutral, so the fuse didn't go. Nothing since.
Hi guys,
scary moments indeed....
For a lot of you lucky moments as well as there were quite big discharges.....
I had some stupid moments of my own, and yes, some of them were the result of being quite unexperienced at the time....
Like when i bought myself a variac, to be able to safely try out projects and such....i had a nice pre-amp including ps and had it hooked up to the variac....powered it up and wanted to change something for which i had to solder a ground.....so not in the least expecting trouble i turned down the variac and moved my soldering gun towards the ground.....
(which was effectively connected to the mains, by my auto-transformer!!)
Wow, what a bang and flash......green fire!
Luckily i didn't touch anything, but it did well teach me to ALWAYS unplug the variac, or buy an isolation transformer.
I always work with my right hand, when probing voltages and keep my handpalm of the same right hand on the chassis when possible (so the path to ground will be only through my hand).
One time i had a Dynaco gigant, which operated EL34's at 800V, i had rigged up some test and powered up the dynaco. At the time i had only one DMM, so that meant changing measuring wires every time.....
I got careless and switched them live, figuring that if i left the wires very far from the amp on my table it would cause no trouble.
It did.....because the insulation on one of the measuring wires had cracked (where it always bends)....so i grabbed B+.....pfew, everything was white for a second and my arm was a bit sour.....
Luckily no further ill-effects....
The last stupid thing was when working on a pre-amp....which needed to be modified, i replaced a lot of resistors etc. and had to change the grounding point.....which i had already taken loose.....
So, the pre-amp seemed finished and after checking quickly i powered it up....huh?? what strange voltages.....then i realised the ground wire and quickly shut the amp down....
(what comes now is utterly stupid and i still curse myself for it
)
I got the ground wire and prepared to solder it....so i took the wire, and another in one hand (it had to be lengthened a bit) and touched the ground wire with one of my fingers......and gave the ps the path to ground.....(you stupid peep peep peep )
it made me jump a bit in my chair....
These 3 examples show that no matter how often you solder something or try something out....ALWAYS follow the proper sequence.
-power down
-plug out
- bleed out
- change
- check
-check
-check, or go for a coffee, and then check.
- power on
- keep cautioned
As fas as accidents go, i keep my fingers crossed, i work with danger all the time, and most of the time i realize that very well....
these 3 accidents took place in a period of about 10 years
greetz,
Henk
scary moments indeed....
For a lot of you lucky moments as well as there were quite big discharges.....
I had some stupid moments of my own, and yes, some of them were the result of being quite unexperienced at the time....
Like when i bought myself a variac, to be able to safely try out projects and such....i had a nice pre-amp including ps and had it hooked up to the variac....powered it up and wanted to change something for which i had to solder a ground.....so not in the least expecting trouble i turned down the variac and moved my soldering gun towards the ground.....
(which was effectively connected to the mains, by my auto-transformer!!)
Wow, what a bang and flash......green fire!
Luckily i didn't touch anything, but it did well teach me to ALWAYS unplug the variac, or buy an isolation transformer.
I always work with my right hand, when probing voltages and keep my handpalm of the same right hand on the chassis when possible (so the path to ground will be only through my hand).
One time i had a Dynaco gigant, which operated EL34's at 800V, i had rigged up some test and powered up the dynaco. At the time i had only one DMM, so that meant changing measuring wires every time.....
I got careless and switched them live, figuring that if i left the wires very far from the amp on my table it would cause no trouble.
It did.....because the insulation on one of the measuring wires had cracked (where it always bends)....so i grabbed B+.....pfew, everything was white for a second and my arm was a bit sour.....
Luckily no further ill-effects....
The last stupid thing was when working on a pre-amp....which needed to be modified, i replaced a lot of resistors etc. and had to change the grounding point.....which i had already taken loose.....
So, the pre-amp seemed finished and after checking quickly i powered it up....huh?? what strange voltages.....then i realised the ground wire and quickly shut the amp down....
(what comes now is utterly stupid and i still curse myself for it
)I got the ground wire and prepared to solder it....so i took the wire, and another in one hand (it had to be lengthened a bit) and touched the ground wire with one of my fingers......and gave the ps the path to ground.....(you stupid peep peep peep )
it made me jump a bit in my chair....
These 3 examples show that no matter how often you solder something or try something out....ALWAYS follow the proper sequence.
-power down
-plug out
- bleed out
- change
- check
-check
-check, or go for a coffee, and then check.
- power on
- keep cautioned
As fas as accidents go, i keep my fingers crossed, i work with danger all the time, and most of the time i realize that very well....
these 3 accidents took place in a period of about 10 years
greetz,
Henk
Lessee..
Was working on an old Telequipment scope once,had it on it's side,put my hand down on the counter to lean over and see if the tubes were heating up.. and an arc jumped atleast an inch from the focus pot to my thumb. Hurt like a SOB,and left a black crater in my thumb for a couple weeks. IIRC the HV supply was labeled 1080V.
Was playing with a HeNe power supply once,was trying to feel how hot the ballast resistors were getting. The supply was unplugged,but those caps still held a hell of a charge..Not sure how,but I managed to get it across both arms. It felt like I was hit in the chest with a baseball bat. My whole body jumped,like you see when they hit someone with a defib. I immediately started checking myself for a pulse.
That one was the scariest. I was rattled and shaky for a couple days.
Got into contact with the -590V supply in my RA-100 amp. It hurt,some swearing.
Been shocked countless times by flybacks,120V mains,ignition coils,etc. When you tinker as much as I do it's bound to happen eventually. (and I am careful around HV)
The above three were the most memorable though.
Was working on an old Telequipment scope once,had it on it's side,put my hand down on the counter to lean over and see if the tubes were heating up.. and an arc jumped atleast an inch from the focus pot to my thumb. Hurt like a SOB,and left a black crater in my thumb for a couple weeks. IIRC the HV supply was labeled 1080V.
Was playing with a HeNe power supply once,was trying to feel how hot the ballast resistors were getting. The supply was unplugged,but those caps still held a hell of a charge..Not sure how,but I managed to get it across both arms. It felt like I was hit in the chest with a baseball bat. My whole body jumped,like you see when they hit someone with a defib. I immediately started checking myself for a pulse.
That one was the scariest. I was rattled and shaky for a couple days.
Got into contact with the -590V supply in my RA-100 amp. It hurt,some swearing.
Been shocked countless times by flybacks,120V mains,ignition coils,etc. When you tinker as much as I do it's bound to happen eventually. (and I am careful around HV)
The above three were the most memorable though.
I remember as a kid recasing my zx81 computer from its crappy plasti case to a metalbox. I took the offboard power supply which was in a nice insulated plastic wallwart and stripping the case suppergluing it to the metal case. Whilst poking around to get it working after the "rebuild" I pushed at the power transformer - I got a strange buzzing which travelled up my arm. Unfused mains - not clever. Nearly bought the big one there but lived to tell the tale.
Quite a few minor shocks since then, but always on the seconary side - once through the chest - nasty feeling.
I decided to decomission my first valve amp because it was a parafeed RH807 with a +B of 900V, didn't trust myself with that one.
Shoog
Quite a few minor shocks since then, but always on the seconary side - once through the chest - nasty feeling.
I decided to decomission my first valve amp because it was a parafeed RH807 with a +B of 900V, didn't trust myself with that one.
Shoog
Apart from a lamp post in a caravan park when I was 12 (which gave me a funny tingling feeling which at the time I didn't realise was an electric shock) and holding onto an electric fence (again when about 12 or 13 which gave my arm a good belt, I've had two DIY close calls.
The first was with my first amplifier. The volume control was a pot out of an old unit that also had a switch on it (which I was using to switch the mains). I was holding onto the grounded case with my right hand and can't remember what I was doing with my left hand, but my left thumb came in contact with the 240V active on the power switch (I didn't know what heat shrink was, was 17 at the time)... for a couple of seconds I was thinking why is my thumb hurting and what is that strange pulsing going up one arm across my chest and down the other... Then I realised I was getting a 240V electric shock so quickly pulled my hands away. I had a hole about 2mm deep (and completely white) in my thumb, but apart from that no other ill effects.
The other time was much more scary. I was playing with an old valve car radio which had an intermittent fault (again was about 17)...... I quite incorrectly made the assumption that as it was running off a 12V car battery that it was completely innocuous and couldn't possibly be dangerous... I didn't know at the time that valves required 600V and that the can labeled vibrator was converting the DC to AC so that it could bump up the voltage to the required levels. There seemed to be some sort of bad joint, so I was pressing on components (with my finger doh) trying to find which one had a problem. Something I touched was live and my goodness it gave me a belt! The only shock I've ever had that caused muscle contraction. I never touched that radio again...
I think that I am lucky. I'm sure it would have killed some people (either of those). when I was in year 9 at school I was the only person in the class who didn't get a shock off the vandergraph generator, and was certainly the only person who could hold my finger in the direct line of the spark throwing coil (only feeling mild prickling in my finger). Maybe I have higher resistance than normal, but it doesn't make me any less careful!! Those two experiences and one with some resivoir caps on a disconnected piece of equipment (a screwdriver flash type scare not a shock) were enough to teach me to be extremely careful whenever electricity is involved (whether the equipment is turned on or not!!!)
Tony.
The first was with my first amplifier. The volume control was a pot out of an old unit that also had a switch on it (which I was using to switch the mains). I was holding onto the grounded case with my right hand and can't remember what I was doing with my left hand, but my left thumb came in contact with the 240V active on the power switch (I didn't know what heat shrink was, was 17 at the time)... for a couple of seconds I was thinking why is my thumb hurting and what is that strange pulsing going up one arm across my chest and down the other... Then I realised I was getting a 240V electric shock so quickly pulled my hands away. I had a hole about 2mm deep (and completely white) in my thumb, but apart from that no other ill effects.
The other time was much more scary. I was playing with an old valve car radio which had an intermittent fault (again was about 17)...... I quite incorrectly made the assumption that as it was running off a 12V car battery that it was completely innocuous and couldn't possibly be dangerous... I didn't know at the time that valves required 600V and that the can labeled vibrator was converting the DC to AC so that it could bump up the voltage to the required levels. There seemed to be some sort of bad joint, so I was pressing on components (with my finger doh) trying to find which one had a problem. Something I touched was live and my goodness it gave me a belt! The only shock I've ever had that caused muscle contraction. I never touched that radio again...
I think that I am lucky. I'm sure it would have killed some people (either of those). when I was in year 9 at school I was the only person in the class who didn't get a shock off the vandergraph generator, and was certainly the only person who could hold my finger in the direct line of the spark throwing coil (only feeling mild prickling in my finger). Maybe I have higher resistance than normal, but it doesn't make me any less careful!! Those two experiences and one with some resivoir caps on a disconnected piece of equipment (a screwdriver flash type scare not a shock) were enough to teach me to be extremely careful whenever electricity is involved (whether the equipment is turned on or not!!!)
Tony.
When we were kids, my grandfather sold his TV Radio shop and the new owner wanted transistors only, this was 1975-6, So granpa gave us some nice old tube radios for our rooms and also a black tube tester with lots of interesting dials and knobs, and sockets.
(what was he thinking?
) Of course my 4 years younger brother about 9-10 years old war the first to find the high tension, when he tried to get a bulb to light. He screamed and jumped straight in the air, as his right hand was hit by a blue flame. Had to sit down for a little while but was fine by the time our mother came home from work. I didn´t have any idea of what kind of tension or current we were playing with, but now I sure would have loved to have that tube tester. 
(what was he thinking?
) Of course my 4 years younger brother about 9-10 years old war the first to find the high tension, when he tried to get a bulb to light. He screamed and jumped straight in the air, as his right hand was hit by a blue flame. Had to sit down for a little while but was fine by the time our mother came home from work. I didn´t have any idea of what kind of tension or current we were playing with, but now I sure would have loved to have that tube tester. Construction workers as myself unfortunately in rainy WA state get shocked 3/4 of the year around as if we do not run our power tools in bad conditions we have no job,this has been the case for 25 years for me & sometimes it just gets to crazy bad to even work at all, especially under houses in which the new guys go thru hell as in flooded crawl spaces & running power tools. Cordless tools have limits & are mostly useless for seriouse work. Last time I got hit by a coupling cap in amp twice in 1 hr, I changed all habits when working on gear, that was the last time. I sure do feel for anyone that has to run power tools in the field in rainy areas.Most re-model jobs have no earth ground at all to recepticals & job must go on. I won't get into what I have seen for shocks as it does make me a little woozy..... well metal clamp light crawling in 2 foot of water....might be one of them.
Joe
Joe
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