What was the highest HT voltage you ever experienced?

[Refugee]

40 messages and we have not heard about one of those shocks where getting told off by the boss is actually worse than the shock itself.
I am thinking of those "nips" you get while working on a colour TV so that you hastily pull your hand out and catch the video board sending the tube to air.

The best one we had was at college in the physics lab. We were doing statics and the vandagraph generator was out. One student grabbed an expanded plastic foam tray and we ordered the little skinny guy with long hair to stand on it and connected him up.
His head looked like a giant hedgehog and he was hissing. The little shaded pole motor that drove the charge transfer belt struggled with the loading as the electric wind wafted off his hair and stunk the room out with ozone.

[hannahs radios]

I think that no one is glamorizing getting belts off things its a painful and horrible experience and yes I realize I was lucky to get away with it especially as I have a heart condition. The suits the grid men where are not earthed as such they form a Faraday cage of sorts so the current flows around the low resistance suit and not through the person wearing it although they say that they sometimes feel a tingle not surprising really

[paulsherwin]

Just to clarify, it is not acceptable to boast about receiving dangerous electric shocks, and if the mods thought that anyone was doing that they would intervene. Receiving an electric shock is always a mistake and certainly nothing to be proud of. The (relatively minor) belts I've received in the past have been solely down to errors or poor practice on my part, and I've tried to learn the appropriate lessons from the experiences.

Anybody who deliberately shocks themselves to show how macho they are needs psychiatric help

Unfortunately the modern trend to ban anything slightly dangerous has led some people to find other outlets, this includes electric shocks. Psychiatric help indeed.

It's not fun, it's not safe and by definition only survivors tell the tale.

[julie_m]

Whilst at university, in the late 1980s / early 1990s, I supplemented my income by repairing appliances -- though, having heard horror stories, I refused to touch TVs. Live chassis, thousands of volts -- no chance. I must have turned down a fortune in easy jobs like dry-jointed LOPTs. My loss was the TV repairers' of Handsworth's gain.

Then I got a job working on gas ignition controls ..... Powered by a capacitive dropper, and capable of producing a spark that could jump 10 mm. (that being the spacing across the secondary winding). The ignition capacitor was 0.47 μF charged from half-wave rectified mains. Using the formula Energy = .5 * C * V ** 2, that was only about 0.027 J.

That's slightly less than the energy that would be imparted by dropping a penny on your foot from a height of one metre (= 0.0035 kg. * 9.8 m/s2 * 1 m); but when I got the full force of it, it by hurt, for most of the rest of the afternoon.

[G6Tanuki]

Julie_m's comment reminds me of the dire warnings I received from a photographer in the 1970s when I was looking enviously at his "new, high-tech" inverter-based photo flash units (powered from a small 12V rechargeable lead-acid pack, connected to his camera by wires so the flashes could be placed appropriately).

75 Joules! You definitely wouldn't want to be connected to the sharp end of that. It made my cheap Instamatic and "magicube" flash look pitiful.

[TonyDuell]

I have only had a few shocks over the years and I am ashamed of every one of them (except perhaps the first, as I was a toddler at the time). When I get an electric shock it means that I have been careless.

As regards scary voltages, probably the scariest thing I work on regularly is not a particularly high voltage (around 350V). I am thinking of the switch mode power supplies used in minicomputers around 1980. The mains is smoothed by a pair of physically large electrolytic capacitors in series (the circuit, as ever, is a bridge rectifier for 230V mains input, a voltage doubler for 115V mains input).

The ones in my little VAX 11/730 are 3300uF each, and a quick calculation suggests each is storing about 50J of energy. The PDP11/44 is worse with 4500uF capacitors (about 69J each) and the output is fed to barrier strips on the top edge of some of the PCBs. So remove the PSU cover and there's a lethal voltage on screw terminals just waiting for you to brush into it...

[The Philpott]

I did have an experience when standing at my front door- lightning struck about 4 houses away. The pressure wave pushed my shirt back against my chest with an audible 'thwap'
It was at this point that I decided that was the closest I ever wanted to be to it.

[G0HZU_JMR]

The closest I've been to a lightning strike was about 100 yards or so and I happened to be looking in the right spot just as it struck. The sense of power was amazing and the sight of the thick pulsing bolt was also amazing. I wasn't close enough to feel a pressure wave or anything like that but it was a memorable experience.

I've only got one 'extra high voltage' work experience and that was when I had to check the insulation resistance of some cables for a transmitter. The check was done at 35kV and the PSU was a chunky 19" rack unit. I can't remember how much current it could deliver but I think it was (maybe) 25mA. I was supposed to stand on a thick rubber mat and wear some evil smelling (and very old?) rubber gloves to do the test. When I did the test I could hear the HT hissing with a sound like drawing in air via your top teeth. Luckily, it all passed and I was very careful not to get a belt off it.

My only other experience is a passive one and I got to look inside the PSU for a marine radar transmitter. Presumably this would normally be in a big boat but this one was on land in a large hut. It was so big you could walk around inside it to service it but I refused to go in past the entrance. One look inside was enough to spook me and it looked like something from Dr Who with all the pointy insulators. I wasn't prepared to take the risk it really was switched off and discharged so I declined the full tour

If you allow lower voltages and high current then my record is working at the business end of a 440V 300A power supply. Yes, three hundred amps. I even got to start up the generator as this PSU was also in a large hut. When it started up I think it had some kind of self test routine where it switched in a full load briefly and the dials went to 300A several times. That was scary to see and hear. The output distribution cables were as thick as my wrists and I had to connect up a high power 'soft start' unit to the output of all this and switch it on.

[Herald1360]

Not sure why 300A cables would need to be that big. Or is that 3+N+E in one bundle? Individual cores would only be about 70sq mm.

[Biggles]

Regarding near lightning strikes, one day a few years back I was at work, and up on the moors, having my lunch break in the works pickup when a storm broke. Now as I had heard many times you are meant to be safe inside a vehicle, I ignored the bangs and flashes overhead. This went on for quite a while until I happened to catch sight of a direct hit to ground a little bit too close for comfort. That was enough excitement for one day I decided and made a sharp exit to lower ground. I have never seen lightning strike like that before or since and I don't think I want to. We regularly have blackened Krone connection strips in cabinets after a storm but once cleaned up it doesn't appear to cause any lasting damage.

[Andrew2]

We seem to have taken a detour into lightning strikes, so here's my story. About ten years ago I was standing in our back garden one evening with my neighbour while there was a thunderstorm approaching. As it got closer, I became aware of a kind of 'tightening' of the air and that familiar 'cooling draught' that you get near an HV source.
Then there was a creaking sound that made me very worried indeed, especially as my 40 ft vertical aerial (for 160m for like minded people out there) was still at full height. I grabbed his arm and told him 'just come in here a minute', and at that moment there was a huge bang and flash at the corner of the block of houses (probably about 60-70 yards away), followed by the sound of car and house alarms.
The next day I took a walk in that direction and noted that the corner of one house was severely damaged and the communal area which was normally criss-crossed with washing lines was bare, and the grassed area had been turfed up and was looking 'fried'. Telephones were inoperative for two days. A close one!

[Refugee]

I had a close lightning strike while driving a the outside lane of a big A road during a storm. There was a blinding flash that made the car shake quite violently.
The next day was when I spotted a dent in the front wing where some of the rubbish it had thrown up had gone into my path. I used to look at the safety barriers for the burn mark but was not able to spot it. It might have hit the end of speed limit sign as it was close by but again no burn mark.
Lightning does some pretty odd things at times.

[Stylo N M]

Hi,

I think I was lucky NOT to be here at home (perhaps it was fate) it was the 31st of March 1999 (AFAIR) I was going round to a friend's flat regularly at the time, I can't remember if I had heard a forecast or not, but anyway I may have taken a small transistor radio with me, or I may not (to see if I could detect any crackles on MW)

Anyway about just after midnight, I pulled back his kitchen curtains and saw a faint flash, so I said to my friend,"I think I would like to pop back home. So anyway all the way home there was a raging thunderstorm but sort of in the distance, not directly over us. I had a real odd feeling, don't know what it was like a premenition, something wasn't quite right.

I rang mum but got no reply, anyway we pulled up on the drive, it was pouring with rain as I unloaded a piece of wood, which was the flat side of an old kitchen cupboard, which I wanted to make a shelf with, to put yet anouther radio up on. The storm was moving away, i opened the front door, to see my mum standing at the top of the stairs, facing me holding a light bulb in her hand!

I said whats up, she said the bulb has blown in the bedside lamp, so anyway I didn't think much more, but the next day found the phone was dead, video recorder dead, the TV colour screen marked in the bottom left hand corner (you could only see this when the TV was on a pink patch) later found the tuning cover, of my portable TV upstairs under the bed! (must HAVE blown off), a mains socket with fused together switches, a scorch mark under my TV on the unit it stood on, and much later down the line, tiny black holes at the edge of the skirting board.

It's a wonder I didn't come home to some sort of fire, as also the aerial spliter in the attic was fried, but no other damage. Then realised I had noticed a funny smell when I got home but couldn't associate it with anything just a weird smell. Anyway we must have been very lucky, maybe the oak tree on the front somehow saved the day, don't know, my neighbour at the time said he was stood outside, the dog ran in moments before the bolt struck, he said he felt it in the air.

The odd thing is, I do watch storms usually in relative safety, and 99.9 times they sort of seem to always go around our perticular area, and never come here, they're always either one side of us or the other, or they start here, and immediately go off elswere towords Sheffield, or they fizzle out when they get here.

So the day I could have seen a pearler, oh I wonder what if, knowing me I could have been in the wrong place at just the wrong moment. Funny thing is, mum never said much about it really, maybe the bang just woke her up and that was it, I think she mensioned it to a couple of people and that was about it.

Paul.

[bluepilot]

The worst shocks I have had are probably from the electric fence around the garden. Power cuts sometimes mess up the timer so it's on when it should be off. These things come in various strengths and ours is a sheep and deer strength one if that means anything. (Also works for wild boar).

The most frightening shock I had was many years ago when I was building the Television magazine colour TV project. I decided to put it in a larger cabinet than the one suggested. I had the IF strip on one side and the EHT board on the other. Both were pulled out on runners as I was trying to trace some fault. As I probed the IF strip I realised that sparks were coming out of my finger tips. For a couple of seconds I was very impressed and decided I must be turning into a super-hero or something. Then suddenly the penny dropped. Behind me I was leaning on the top cap of whatever valve it was on the EHT board. When I looked it had burnt a hole in my shirt and into my back. I never felt a thing and the TV didn't seem to suffer either but I was very careful after that.

As for shocking yourself deliberately, it does seem to be a daft thing to do. However it wasn't always like that. The Victorians thought electricity was a cure for almost anything:

https://www.doeandhope.com/products/...iant=281107502

We had one of these in the school physics lab. The teacher made the class stand in a circle holding hands with the people at the ends holding the electrodes. Then he gave us all a shock at the same time. I can't remember what that was supposed to demonstrate. I expect nowadays H&S would have something to say.

[ionburn]

That was my experience with a PL504 topcap straight through my knuckle to chassis Stuart. Except for a slight tickling sensation I didn't feel a thing. The body does not react to RF shocks which can make them far more dangerous than mains frequency!

[G0HZU_JMR]

Originally Posted by Herald1360

Not sure why 300A cables would need to be that big. Or is that 3+N+E in one bundle? Individual cores would only be about 70sq mm.

It was a big remote generator hut that had to distribute (underground) power across a large radar site and I was probably 100 metres away from the hut when connecting to the business end at my workbench. At the end of some of the benches was a huge metal junction box and you needed a fairly meaty spanner to make the connections. I also needed special authority and a key (and supervision) to access the junction box. It was 300A mean but I don't know what it could deliver in peak transients. It was presumably designed to cope with peak current with minimal voltage drop? It was for radar based stuff but I only used it to power a very meaty 3 phase soft start unit. I didn't need 300A for the stuff I was doing. The distribution cable going into the junction box was very thick. I didn't measure it but it was impressive.

[Refugee]

They still sell those medical shock machines for toning muscles.

[G0HZU_JMR]

I can remember getting a shock off a cattle fence when I was a small boy. It was on a school trip to a local farm when I lived in Bedford. I can't remember what age I was but probably about 7. The farmer told us not to touch the electrified fences. Obviously we all followed his instructions and kept well away from the fences. But then the farmer pulled/held down one of the fences to the ground so we could walk over it into another field.

So being about 7 years old this made us all a bit curious so the boys all experimented with briefly touching the fence (as a dare) to see if the farmer was fibbing about the electricity. After all, he was OK when he held down the fence? So we took turns in touching the fence when he wasn't looking. Sadly, I was the idiot who eventually grabbed and held the fence wire for a second or so and I got a very meaty pulse shock up my arm. It felt like someone had forced a rock to travel up inside my arm. I'm guessing that the farmer had special insulated wellies on that stopped him getting a shock?

[Refugee]

I got one from a farm electric fence by testing it with a neon screwdriver. Afterwards I had to retrieve the now recently overloaded neon test screwdriver from the mud.

I have my own somewhat less powerful electric fence to prevent seedling dig up problems in my veg plot. The shocks are uncomfortable enough that dealing with more than three or four weeds makes it worth going to switch it off for a few minutes.