Danger to people other than yourself!!!
Had a sketchy moment yesterday.
I was testing some well used 13E1 I acquired. I had a couple of power supplies rigged up one at 250V and another for bias at -100V. I'd been messing around for an hour or so when my wife came in and very nearly lent on the bech to talk to me. She was a bit shocked when I shouted NOOOOOO!! But certainly less shocked than she could have been.
Moral of the story, always let whoever is about know what you are doing and the dangers. This could not only save their life but also your own.
Cheers
Matt.
Had a sketchy moment yesterday.
I was testing some well used 13E1 I acquired. I had a couple of power supplies rigged up one at 250V and another for bias at -100V. I'd been messing around for an hour or so when my wife came in and very nearly lent on the bech to talk to me. She was a bit shocked when I shouted NOOOOOO!! But certainly less shocked than she could have been.
Moral of the story, always let whoever is about know what you are doing and the dangers. This could not only save their life but also your own.
Cheers
Matt.
Anyone who works on a bench in a house alone or with family, partner or mobile phone distraction should have a "dead mans" homemade pedal switch to sever the B+ supply or feed to it. It may seem a bother working with one but without it, sooner or later one will get caught out. I made mine up from an old sewing machine floor control.
richy
richy
A "Danger - High Voltage" sign on the bench will go a long way toward scaring them off.
Very good safety advice. Must this pedal have a foot on it at all times? Does the power go off when you take your foot off the pedal? Clueless.
My bench has an "e-stop" or emergency stop installed. There are two, one either side. The dead man's switch is a great idea.
The only trouble I see is that any DC power source no matter what voltage will have capacitors which store charge. So even on my bench hitting the mushroom doesn't make it safe.
Cheers
Matt.
The only trouble I see is that any DC power source no matter what voltage will have capacitors which store charge. So even on my bench hitting the mushroom doesn't make it safe.
Cheers
Matt.
When you have worked, as I have, with a "cherry picker" on live 550kV power lines, that is what I call High Voltage, Ultra High Voltage is like the Vandergraph Generator! DC voltages are the worst for danger because one cannot 'Let Go' the power makes the muscles contract. At least AC will throw you off.
I agree partly, I work with 11KV day in day out. It only takes 50V and around 30mA to cause fibrillation and this happens very very fast probably less than a cycle at 50HZ. So AC or DC just as dangerous.
Cheers
Matt.
Cheers
Matt.
It's also important to keep one hand in your pocket when working with high voltages.
Or at least be mindful of the facts before going in. Your hand, your foot, your elbow etc.
I know a guy who has a rather debilitating injury to the muscle in his forearm from a shock. Obviously it didn't kill him but he probably involuntarily lashed away and cut himself badly.
Cheers
Matt.
I know a guy who has a rather debilitating injury to the muscle in his forearm from a shock. Obviously it didn't kill him but he probably involuntarily lashed away and cut himself badly.
Cheers
Matt.
Yes, that's a good point. Some of the danger is from an involuntary reaction to the shock.
The main reasoning behind that post wasn't my good friends misfortune. Is was to be aware of the facts first. Testing is key here but even testing is a danger, the whole idea of testing introduces dangers. We all do it regularly and probably don't even think about it. There are no safe tests but tests allow us to know the danger. Bit of an oxymoron really. Perhaps electricity or just danger should be left alone? Now that's not the human way.
Cheers
Matt.
Cheers
Matt.
I remember my much younger days.
I decided to build a valve/tube pre amp.
I built it then turned it on.
Didn't work so I unplugged it and touched the circuit.
Of course I got huge belt from it.
It really shook me up.
I found a fault so fixed it.
I powered it up again and it still didnt work.
So this time being clever I discharged the capacitor.
I touched the circuit and got a huge belt again.
I had forgotten to turn it off !
Its amazing that this year I have been in electronics 34 years.
What's more amazing is that I am still alive.
I am much more careful these days.
I add LED's to high voltage circuits to show when they are charged.
When working on SMPS I use a isolation transformer.
I decided to build a valve/tube pre amp.
I built it then turned it on.
Didn't work so I unplugged it and touched the circuit.
Of course I got huge belt from it.
It really shook me up.
I found a fault so fixed it.
I powered it up again and it still didnt work.
So this time being clever I discharged the capacitor.
I touched the circuit and got a huge belt again.
I had forgotten to turn it off !
Its amazing that this year I have been in electronics 34 years.
What's more amazing is that I am still alive.
I am much more careful these days.
I add LED's to high voltage circuits to show when they are charged.
When working on SMPS I use a isolation transformer.
For SMPS work I use an isolated differential probe. I don't really like using an isolation transformer on the equipment under test as it leaves unknown fault paths and has to be carefully thought out first. Certainly use an isolation transformer on your test gear but be very aware of the dangers.
I have just started boxing up my GM70 amp as I'm happy with it now. I thought about LEDs on each of the four caps in the two stacked power supplies. Trouble is even a very efficient LED uses around 5mA which becomes significant dissipation in the dropping resistor. I used neons, they go out around 80V across the cap which disappears rapidly after that plus they use micro amps. I have not looked at the noise they make yet but as the caps impedance even at 20Khz is in the milliohm range I am sure it's fine.
Cheers
Matt.
I have just started boxing up my GM70 amp as I'm happy with it now. I thought about LEDs on each of the four caps in the two stacked power supplies. Trouble is even a very efficient LED uses around 5mA which becomes significant dissipation in the dropping resistor. I used neons, they go out around 80V across the cap which disappears rapidly after that plus they use micro amps. I have not looked at the noise they make yet but as the caps impedance even at 20Khz is in the milliohm range I am sure it's fine.
Cheers
Matt.
I think most of us probably feel the same way. I once got hit by 480VAC briefly, and you won't ever forget that, if you're still around afterward.
Not sure about you guys, maybe there should be a new sticky? Something like "safe test and measurement"
Cheers
Matt.
Cheers
Matt.
I feel bad for laughing at that, but i know how easy it can happen.
I had a wake up call a while back working on an amp. Unplugged it from the mains and turned my soldering on to warm up. When i came back 15 minutes later i proceeded to unsolder the wiring from the transformer and nothing was happening. Thought that was odd so checked the iron to find it was stone cold. Only when i looked down at the mutiblock again i realized i had unplugged the soldering iron and left the amp plugged in, and i had just tried to unsolder the primary side of the transformer. Check, double check, and measure for good measure!