(WARNING BURNED SKIN)Don’t bypass capacitors

Even the one rule that always hold one hand behind your back when testing high voltages with a meter does not always work. I used to repair spas, The husband of this spa called so out I went. Usually, the first thing one does is take ones hand and dip it in the water to check for purity and temperature. Got a jolt and threw me 10 feet. Checked the GFI with the meter using the precaution of using one hand. Got another jolt, fortunately not as bad. The completed circuit must have gone through my shoes on the wet concrete. Still not sure how. Replaced the GFI and then found a short in the heater element and replaced it. The lady of the house came out and asked me why I had to fix the spa. I asked her if she had been using it. She said that she had been. Amazed, I then asked her if she felt anything when she got in. And she said she felt a tingling, but thought that was normal for how a spa worked. She must have had the hide of a walrus. Good thing, you can imagine what kind of lawsuit that would have been.
 
cathead said:
More than ouch... Lucky to be alive is more accurate. A lot of folks with that much skin affected just don't make it.
Your skin is the largest organ in your body.
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they tried real hard and almost succeeded in killing 2 or 3 times, twice they overdosed me on morphine, luckily they caught it in time, then they misread the chart and administered a sulfa based drug, even though my wrist band stated an acute allergy. A couple of mishaps, but in all, the care was excellent, I got the therapy and medical care I needed to function somewhat normally, everyday since then. one of there real big concerns was infection, with so much raw surface exposed.
 
cathead said:
Back in my younger years, I assembled a Van de Graff generator that was a great source of fun and interest.
It worked really well in the dry air in the house in the wintertime as I remember, a great toy for science minded kids.
My experiences with high voltage in tube transmitter projects and linear amplifiers has had it's share of excitement
as well and I too DO NOT work with both hands in the midst of high voltages. I could share a few experiences
too but am leery to expose these stories to the world on the internet.

Edit: OK, i changed my mind and have one story I can share. Back in the day I built a small one transistor
oscillator that emitted a very high pitched tone. The whole thing was about the size of a man's watch. We
took it to school and buried it under the teacher's desk and all was fine till towards the end of the period
when we were supposed to be quiet for a time to read. The high pitched tone permeated the room and
it was a lot of fun. I don't remember if the teacher ever caught on but those of us who knew about what was going
sure had a good laugh. We couldn't stop laughing that day.
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Funny, in middle school, I made a Van de Graff generator. Must have had a dome about 12" in diameter. My dad made me calculate the capacitance of the dome and the stored energy. The stored energy appeared to be sub-lethal. He was prescient.

One evening, I had the generator on and commented on the tiny blue specks on the dome. The room was slightly darkened and you could see the corona from specks of dust on the dome. I made the mistake of pointing to it with my right hand as I spoke. A 36" blue spark jumped to my fingertip and passed through the right hand side of my body to ground. Simultaneously, every single muscle on the right side of my body contracted. Fell over on my side before I was even aware of what happened. Stunned on the floor, with half of my muscles aching from the violent contraction, I heard laughter. Yep, dad teaching his son a lesson... All I can say is, good thing it wasn't my left hand as the current would have passed through my heart. Have to say, I've got a healthy respect for all high voltage now.
 
This thread is starting to scare me.

I’ve always said that the self-preservation gene doesn’t kick in until about age 30, but Buffalo21’s story is haunting.

Something that awful and that random is horrifying. I honestly can’t imagine working in a burn ward, much less being a patient in one. Horrifying.
 
My last dealings with capacitance, Me bumbling around with my new to me Sabertooth 2 x 24 volt dual motor controller board for my (still a project remote control lawn mower)
I hooked up another voltage controller to it on each side between the controller board and the motor to tame down the amperage draw and boof instant fire, not real good on the petrol lawn mower it was attached too. Other than a pucker moment it all turned out ok.
Of course a new 2 x 32 amp 24 volt motor controller on its way from Sabertooth as I type.
Those capacitors burn real nice!
 
sycle1 said:
My last dealings with capacitance, Me bumbling around with my new to me Sabertooth 2 x 24 volt dual motor controller board for my (still a project remote control lawn mower)
I hooked up another voltage controller to it on each side between the controller board and the motor to tame down the amperage draw and boof instant fire, not real good on the petrol lawn mower it was attached too. Other than a pucker moment it all turned out ok.
Of course a new 2 x 32 amp 24 volt motor controller on its way from Sabertooth as I type.
Those capacitors burn real nice!
Click to expand...
me and my friends plug them into electric cords hide behind garage doors and plug in the cord it makes a loud bang sometimes but always lots of smoke.
 
Capacitors can be fun. especially big ones.
At a place I once worked at we used very big capacitors. Electrolytic capacitors can explode if connected backwards. They can explode with considerable force. The power unit we made was a 10GA steel box approx 18 x 18 x 12. A cap connected backwards would turn this steel box into an almost perfect sphere when it exploded inside. About once a year I would get to do a demonstration for all of the new people that were wiring machines up to impress the importance of correct connections. I would run a long cable out to the parking lot and connect a cap to the cable, then come back into the plant to connect the cable to a power supply with reverse polarity for the cap. Switch on the power and watch everyone jump as that cap exploded like a stick of dynamite. Every time it left a hole in the asphalt parking lot. But I had fun. Be careful with capacitors, some are polarity sensitive and can bite hard if you upset them.
 
Okay, one more capacitor story.

A nameless startup I used to work for back in the '90s sold a datacenter product worldwide. I was responsible for the technical side of sales in Japan, mostly through one fairly large OEM. The Japanese are very meticulous when it comes to quality and hardware. During the OEM's evaluation of the product, they complained that the capacitors we'd chosen to use on our power supplies were sourced from a company with very poor quality control and insisted that we replace them.

Our ops people were incensed and felt the OEM was overstepping their bounds. They refused to change the component and said we would stand behind the overall quality and safety of the entire product.

About a year or two later one of the power supplies failed at a very large and well-known car manufacturer (they only make cars and trucks, not toy yachts). There weren't any injuries or actual flames, but it did fill the datacenter with quite a bit of smoke and supposedly nearly caused a HALON dump. It caused a big stink in every sense.

And, of course, root cause analysis showed that it was those exact capacitors that had failed due to poor manufacturing tolerances at the supplier's facility. We had to fly out our operations VP to fall on his sword. Not a fun meeting.

I was out there with a team of people not long afterward swapping out entire systems for newer models provided for free. Those ended up being very expensive capacitors.
 
Rex. you brought up a good point. We all like to save money. However, when it comes to electrolytic capacitors, go for a good brand and try to get the newest. These caps do have a shelf life. I used to work on all types of electronic equipment. One of the first things that went out in old tube equipment that were over 25 years old were the electrolytic capacitors in the power supply. Usually, we replaced them all. Sure made a difference. I sure like these brushless DC motors, but I always wonder about the lifespan of the electrolytic caps in the circuits. This may be a good topic to pursue.
 
Are modern capacitors made better than the ones in old tube equipment? Is the shelf life longer?
At the rate the things are advancing in the RC brushless motor field, these only need to live for a few years before the controller will be replaced due to obsolescence, or the need to have the latest and greatest.

In the RC club I belong to I get picked on for running a 12 year old transmiter.
 
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