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Electric Shock
- Thread starter Spkrdctr
- Start date
I was testing a power module and it blew up due to overheating. A snubber capacitor flew out and stayed on the floor a while as I investigated the power device that blew.
I go take a break and pick up the cap off the floor - bad idea. I can still feel that tingle I felt in my finger when I think about that incident. This was some 5 years ago. Circuit was operating at 1150Vdc before that shit blew.
Company sent me to the ER to get checked out (standard procedure where I work). Doc asked me a few questions, checked my heartbeat and let me rest for 30mins, checked again and back to work I went.
I go take a break and pick up the cap off the floor - bad idea. I can still feel that tingle I felt in my finger when I think about that incident. This was some 5 years ago. Circuit was operating at 1150Vdc before that shit blew.
Company sent me to the ER to get checked out (standard procedure where I work). Doc asked me a few questions, checked my heartbeat and let me rest for 30mins, checked again and back to work I went.
Seen a few?
Is that just bad luck, or is seeing several people killed just part of a career in your line of work?
I bought a nice, fairly new leather and canvas tool bag from a guy that saw a coworker electrocuted on the job he was in training for. Figured he would train for a different job...
antennaguru
Senior Member
One of the only times I ever got shocked was when a friend brought me his mono block SET tube amplifiers to fix because they were blowing all but the most expensive 300B tubes. I asked him when the last time he used it was, and he told me at least two weeks ago. As I was opening the first one up I got belted from the plate supply that had no bleeder resistor, and had been holding a charge for two weeks. It wasn't a bad shock but it did make me curse the designer of the amplifier. I told him that the designer was irresponsible to not have bleeders so the amp would need those. Then on taking measurements and comparing them to the 300B data sheet I saw that they had far too much voltage on the plate - which explained why so many brands of tubes couldn't stand up to that voltage. I installed appropriate dropping resistors as well as bleeders, and sent him on his way with his working amps.
I have worked on amplifiers with 2.5 - 3.5 KV plate supplies and never had an issue, including using an HV probe to take hot measurements for meter calibration. I also replaced a main electrical panel for a friend that was unable to get an electrician to do it. His was a small house and I swapped his very old and problematic screw-in fuse main panel for a modern breaker main panel while it was hot, and there was no issue doing the work carefully and methodically (don't ask me how to do this, as I won't tell). I think the key is that it's fine to work on hot electricity when you know it's hot and you are careful. However, don't get surprised!
I have worked on amplifiers with 2.5 - 3.5 KV plate supplies and never had an issue, including using an HV probe to take hot measurements for meter calibration. I also replaced a main electrical panel for a friend that was unable to get an electrician to do it. His was a small house and I swapped his very old and problematic screw-in fuse main panel for a modern breaker main panel while it was hot, and there was no issue doing the work carefully and methodically (don't ask me how to do this, as I won't tell). I think the key is that it's fine to work on hot electricity when you know it's hot and you are careful. However, don't get surprised!
syn08
Senior Member
Was about 14, Anno Domini 1972, building a tube amp with EL34 push pull. I got a steel painted (gray) chassis and scrapped the paint where the power supply elco’s were screwed. Amp was working great, with some hum, though.
Not good enough, while holding the chassis I touched the elco’s aluminum cases. An about 1.41*220=310V shock that I vividly remember today.
Not good enough, while holding the chassis I touched the elco’s aluminum cases. An about 1.41*220=310V shock that I vividly remember today.
Weeb Labs
Addicted to Fun and Learning
I have thankfully never received a shock from the mains.
As a child, I once disassembled a disposable film camera and accidentally bridged the flash capacitor legs with my fingers. It was a 10uF capacitor and charged to about 290V, which was brief but rather excruciatingly painful.
As an adult, I have occasionally been bitten by flyback transformer secondaries in CRTs. These typically output approximately 20KV of ripply DC and are current limited to a couple of milliamps. Painful but quite harmless as the voltage immediately plummets.
As a child, I once disassembled a disposable film camera and accidentally bridged the flash capacitor legs with my fingers. It was a 10uF capacitor and charged to about 290V, which was brief but rather excruciatingly painful.
As an adult, I have occasionally been bitten by flyback transformer secondaries in CRTs. These typically output approximately 20KV of ripply DC and are current limited to a couple of milliamps. Painful but quite harmless as the voltage immediately plummets.
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- Thread Starter
- #47
Electricity proves the old saying "Respect is earned". Once it bites you, it has earned respect! The funny part is when people don't learn and get bit over and over.......
- Thread Starter
- #48
I was a police officer when I was a youngster starting out. I saw them after the actual electrocution. I pretty much arrived to just supervise the clean up, which is the ambulance taking them to the morgue. The char broiled lady, and the boy were pictures after the fact because I wasn't working that shift. I didn't think it appropriate at first but now I feel it is ok. Here is the charred woman story.
If you ever have the chance to notice, you see that almost all small hand held vibrators are run by batteries. It is a huge safety issue. The woman was way back then (1980?) using a corded vibrator and it shorted somehow. Well, the fuse never blew so she was slow cooked for days. Family or friends wondered what was going on and the officers on shift had to do a safety check. Needless to say a 15 amp fuse or breaker that doesn't blow or trip allowed her to slow cook beyond what I would say was possible. If I didn't see the photos I would never have believed it. Strange things happen in real life!
Balle Clorin
Major Contributor
- Joined
- Dec 26, 2017
- Messages
- 1,347
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I am an amateur and experimented with a power supply feedingn an electronic breadboard. I got the power supply as a leftover from a control room at work.
Someting did not work and I wanted to check the fuse. It was in this kind of hole with at knoib that can be screwed out abd then to pull the fuse straigh out. As I touched the bare end of the fuse tube, a got a shock and the power in the house went down and I was sitting in darkness but OK.
It was my fault not no turn off the power, but why was the fuse socked design such that pulling the fuse out of its hole connected me to live power?
Someting did not work and I wanted to check the fuse. It was in this kind of hole with at knoib that can be screwed out abd then to pull the fuse straigh out. As I touched the bare end of the fuse tube, a got a shock and the power in the house went down and I was sitting in darkness but OK.
It was my fault not no turn off the power, but why was the fuse socked design such that pulling the fuse out of its hole connected me to live power?
TrevorD
Member
- Joined
- Dec 14, 2021
- Messages
- 25
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- 30
When I was about 14 years old we had a record player/radio a bit like this:
A few times I got a belt off the bastard thing when touching the WOODEN frame around the turntable. My dad had one of those neon screwdrivers and I pushed the tip into the wood - lit up like a Christmas tree.
"Wood is not a conductor".........Bollocks!
A few times I got a belt off the bastard thing when touching the WOODEN frame around the turntable. My dad had one of those neon screwdrivers and I pushed the tip into the wood - lit up like a Christmas tree.
"Wood is not a conductor".........Bollocks!
Rip City Dave
Active Member
I was walking on carpet, then touched a doorknob and ..... BAM!
- Thread Starter
- #53
OMG! Don't even get me started on lightning. I fixed a boatload and a buttload of equipment from lightning striking buildings. You just made your own little baby lightning strike. It is an interesting topic though.........
Way too many to relate, and some very sad (injuries and deaths). I still have a scar on my wrist from a TV anode arc that leaped to my watch (which I usually removed at work, stupid). A sadistic parts store owner was known to charge a big axial cap, bend the leads back over the case, and toss it to folk for the shock effect. The usual tales of rooms filled with bits of foil and plastic from wiring a big electrolytic backwards. Etc.
Lightning, many tales, but the scariest I recall was a storm moving in whilst my boss and I were trying to finish erecting a TV antenna tower. We saw it in the distance, then a lightning strike hit the ground still very far off, but all the hair on our bodies lifted. Fastest we ever got down -- tied off the antenna to the tower and dropped! Then the time I waited out a mountain shower at home and after it moved east, with clear blue sky overhead, went to light the charcoal in the grill for supper. A bolt hit a tree about 50' away, out the blue, and showered the deck (and me) with bits of bark. Broiled steaks in the oven that night...
Lightning, many tales, but the scariest I recall was a storm moving in whilst my boss and I were trying to finish erecting a TV antenna tower. We saw it in the distance, then a lightning strike hit the ground still very far off, but all the hair on our bodies lifted. Fastest we ever got down -- tied off the antenna to the tower and dropped! Then the time I waited out a mountain shower at home and after it moved east, with clear blue sky overhead, went to light the charcoal in the grill for supper. A bolt hit a tree about 50' away, out the blue, and showered the deck (and me) with bits of bark. Broiled steaks in the oven that night...
I was awoken at ~3am one morning feeling kinda weird. I went for a pit stop and found my hair was statically charged and we where having a very close thunderstorm. My arm and leg hairs where standing up and my head hair was a bit frizzy. So I went out on the patio deck and turned on the lights and saw the cloud cover/ceiling/fog was maybe 50 feet over the house and there was lightning and thunder occurring often all around me. I figured the energy cell/lightening/cluster must be very close so I went back inside and went back to bed. I've lived in a 3500 feet elevation mountainside city with very radical lightening and when it occurred it was like being in the clouds with the lightning. My uncle who lived in the same mountain city had his prune tree split in two from lightning and that was about 15 feet from the house. He said it scared the cra*p out of them when it hit it was so loud.
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- Joined
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I had the exact same experience many years ago when our baseball team was warming up in the outfield by the big scoreboard. Just a few dark clouds rolled in but no one was worried because there hadn’t been any signs of lightning before hand. Well, all of a sudden BAM, lighting hit the scoreboard. Many of us fell to the ground just from the shear suddenness of it all. No one was hurt, but we all talked about how we could feel the hairs on our body perking up just milliseconds before the hit. We still talk about it 40 years later.
I had to laugh at some of these stories: not because they are funny, but because I experienced the same thing!
Back in electronic technician school, the class was working on small B&W TV sets; we each had one on our workbench. Having complete my assignment, I stepped back to admire my work and backed into my neighbor's fly-back transformer with my elbow. I let out ta WHOOP! and the entire class erupted in laughter.
Last year's whoops was a little more painful. Someone above lamented getting zapped by power supply caps because the builder of the amp had omitted the bleeder resistor. I never omit the bleeder resistor after watching a choke input supply head for 700V ( with 600V caps) before the the tubes conducted.
Anyway my latest amp build was having a problem with one channel modulating the other through the power supply. I turned out that I had omitted a decoupling capacitor for that stage, despite it appearing on the schematic I had drawn. So I initially installed a couple of diodes on the plate supply, one for each channel to separate them from the shared feed. In this instance, I was going to change an output tube that had a plate cap, like an 807. I lifted off the plate cap and must have brushed my hand against the internal conductor. I was shocked by the voltage (about 400V) stored in the output tube plate supply capacitors: the diodes had prevented the voltage from draining down to the bleeder resistor. That was a stunner and a reminder to be careful and attentive at all times.
Back in electronic technician school, the class was working on small B&W TV sets; we each had one on our workbench. Having complete my assignment, I stepped back to admire my work and backed into my neighbor's fly-back transformer with my elbow. I let out ta WHOOP! and the entire class erupted in laughter.
Last year's whoops was a little more painful. Someone above lamented getting zapped by power supply caps because the builder of the amp had omitted the bleeder resistor. I never omit the bleeder resistor after watching a choke input supply head for 700V ( with 600V caps) before the the tubes conducted.
Anyway my latest amp build was having a problem with one channel modulating the other through the power supply. I turned out that I had omitted a decoupling capacitor for that stage, despite it appearing on the schematic I had drawn. So I initially installed a couple of diodes on the plate supply, one for each channel to separate them from the shared feed. In this instance, I was going to change an output tube that had a plate cap, like an 807. I lifted off the plate cap and must have brushed my hand against the internal conductor. I was shocked by the voltage (about 400V) stored in the output tube plate supply capacitors: the diodes had prevented the voltage from draining down to the bleeder resistor. That was a stunner and a reminder to be careful and attentive at all times.
If you ever feel hair standing up in a storm immediately get inside (inside a car is good), or if that is not possible, get yourself *very* close to the ground.
For me when I experienced the hair standing up stuff I was so intrigued and amazed by the storm that it took me a minute or two to get my butt back inside the house. I suppose I looked like one of those idiots in a movie that everybody is annoyed at for being near the forthcoming death and not having the sensibility to get outta there.
