Voltage an AMPS!
0.01volts can kill you, 1 volt can kill you 20,000,000 volts can kill you...just as easily as each other.
If you are stepping into valve equipment, don't go for high powered amplifiers above 10watts for starters.
Build a one-sided 150-250volt amp for practice and work your way up..
At least this way I can stick my head out and say that you may not have such a great a chance of arc-ing or short-circuiting anything onto your hand or straight to chassis through insulation as easy as you would 600v+
Plasma however is another thing, when you turn on a heater or a light, you can sometimes see a bright flash through the switch plastic, this is arcing, this is dangerous, it can cause burns or fires.
Even though it is only 240volts, it is arcing to a certian extent a few mm away from each contact. The higher the voltage the wider this arcing occours, This is why those 240volt relays you see all over radioshack ither have a limited amperage rating or limited voltage rating, and why you cannot use them for any voltage higher, same goes for switches.
Essentially as voltage is increased the length at which arcing will occour is increased also.
This is why Tesla coil insulation and internal capacitor insulation
is so crucial at such high voltages.
When you use point-to-point wiring in a valve amplifier it is very good practice to prevent wiring making contact to each other by slightly shortening the wires so they do not 'relax' back onto the chassis, however it would be stupid to make ANY wire so taught from one point to another that it can heat-up at the stretched points and melt, then once it has broken off or exploded at the weak point, it WILL touch something conductive!! further damaging everything else associated with it both by fire and short-circuit..VERY bad for any high-voltage high-powered amplifier!!!
So lets say you have a single wire carrying 500volts at 500mA
That's 250watts! so if your insulation at ANY point along the wire from point-A to point-B (even if it is a single millimeter of insulation it won't matter at all, infact the smaller the contact area the higher the chance of melting!) is not rated at being able to carry that Ohm-age aka Resistance it WILL break down if it touches a chassis or anything that leads back, eventually, to it's power source. INCLUDING if YOU! are a part of that line.
Also duration plays a certian role, lets say it takes 1/4 of a second for 250watts of electricity to burn through your skin, in that time the amount of power would probably have increased going through your hand from 250mW to 250watts!
(Going upon memory)
You can forget that insulation is even there, because if the insulation isn't rated to the voltage you use, you're gonna have a wild ball of molten steel/copper/silver to deal with later on.
I tend to prefer saying that Ohms kills, however a highly-resistive circuit can also kill so, meh.
EC8010: Yes it is perfectly okay for wiring to touch a chassis but only if the insulation is up to the task! You don't just go down to a local shack and buy 250volt wiring for a 500volt job, because the insulation usually isn't the same.
Readers discretion is advised in taking my practices and using them, I'm too young for a law-suit..
I'm passing on what my father has taught me.
If anyone objects to anything of this I will notify a moderator immediatley and ask him to delete my post.
0.01volts can kill you, 1 volt can kill you 20,000,000 volts can kill you...just as easily as each other.
If you are stepping into valve equipment, don't go for high powered amplifiers above 10watts for starters.
Build a one-sided 150-250volt amp for practice and work your way up..
At least this way I can stick my head out and say that you may not have such a great a chance of arc-ing or short-circuiting anything onto your hand or straight to chassis through insulation as easy as you would 600v+
Plasma however is another thing, when you turn on a heater or a light, you can sometimes see a bright flash through the switch plastic, this is arcing, this is dangerous, it can cause burns or fires.
Even though it is only 240volts, it is arcing to a certian extent a few mm away from each contact. The higher the voltage the wider this arcing occours, This is why those 240volt relays you see all over radioshack ither have a limited amperage rating or limited voltage rating, and why you cannot use them for any voltage higher, same goes for switches.
Essentially as voltage is increased the length at which arcing will occour is increased also.
This is why Tesla coil insulation and internal capacitor insulation
is so crucial at such high voltages.
When you use point-to-point wiring in a valve amplifier it is very good practice to prevent wiring making contact to each other by slightly shortening the wires so they do not 'relax' back onto the chassis, however it would be stupid to make ANY wire so taught from one point to another that it can heat-up at the stretched points and melt, then once it has broken off or exploded at the weak point, it WILL touch something conductive!! further damaging everything else associated with it both by fire and short-circuit..VERY bad for any high-voltage high-powered amplifier!!!
So lets say you have a single wire carrying 500volts at 500mA
That's 250watts! so if your insulation at ANY point along the wire from point-A to point-B (even if it is a single millimeter of insulation it won't matter at all, infact the smaller the contact area the higher the chance of melting!) is not rated at being able to carry that Ohm-age aka Resistance it WILL break down if it touches a chassis or anything that leads back, eventually, to it's power source. INCLUDING if YOU! are a part of that line.
Also duration plays a certian role, lets say it takes 1/4 of a second for 250watts of electricity to burn through your skin, in that time the amount of power would probably have increased going through your hand from 250mW to 250watts!
(Going upon memory)
You can forget that insulation is even there, because if the insulation isn't rated to the voltage you use, you're gonna have a wild ball of molten steel/copper/silver to deal with later on.
I tend to prefer saying that Ohms kills, however a highly-resistive circuit can also kill so, meh.
EC8010: Yes it is perfectly okay for wiring to touch a chassis but only if the insulation is up to the task! You don't just go down to a local shack and buy 250volt wiring for a 500volt job, because the insulation usually isn't the same.
Readers discretion is advised in taking my practices and using them, I'm too young for a law-suit..
I'm passing on what my father has taught me.
If anyone objects to anything of this I will notify a moderator immediatley and ask him to delete my post.
Thanks, Tony. Fascinating stuff. I note that most of the precautions are to protect against arcs and minimise the effects of burns (synthetic fibres melt into the wound, whereas natural fibres burn away). This has just reminded me that jeans are a no-no in the firework industry, apparently they exacerbate burns.
Layberinthius: I'm afraid you are adrift on a few points. Insulated wiring contacting an earthed conductive chassis is perfectly OK. Electrical safety is amazingly complex. It's easiest to sum it up by saying:
If in doubt, don't.
Layberinthius: I'm afraid you are adrift on a few points. Insulated wiring contacting an earthed conductive chassis is perfectly OK. Electrical safety is amazingly complex. It's easiest to sum it up by saying:
If in doubt, don't.
Tony: thanks for the post. Funny it doesn't say to work with one of your hands tied behind your back 
.
John, I still haven't figure out if you're for real or you're pulling a leg on the people that have kindly more than answered your questions. Anyway, read again:
"51 to 600 volts
• Barricade, if necessary• Safety Glasses"
I really think you should barricade.
Guilherme.
.John, I still haven't figure out if you're for real or you're pulling a leg on the people that have kindly more than answered your questions. Anyway, read again:
"51 to 600 volts
• Barricade, if necessary• Safety Glasses"
I really think you should barricade.
Guilherme.
I have long lost count of the hi voltage caps experiencing the privilege to discharge through my body. Is this not the more physical part of the hobby? Like experiencing really low bass with your bones
Still, the complete (?) absence of horror stories in DIY is quite remarkable, especially compared to the real life stories i used to hear (and witness) when i worked at a research facility (lots of hi-voltage laser related stuff). And those were well educated professionals!
Still, the complete (?) absence of horror stories in DIY is quite remarkable, especially compared to the real life stories i used to hear (and witness) when i worked at a research facility (lots of hi-voltage laser related stuff). And those were well educated professionals!
The absence of those horror stories has much to do with the solitary nature of the hobby and the rather permanent results of mishaps, not with any intrinsic safety.
Tony, I'll add my thanks to you. Also, we use lock-out/tag-out to make sure that someone doesn't accidently power up a circuit while someone else is working on it. Diyers should do the equivalent if there's any chance whatever that someone else may be in the area. "Hey, SY, what's this button for?" ZZZZZAPPPPP!
Tony, I'll add my thanks to you. Also, we use lock-out/tag-out to make sure that someone doesn't accidently power up a circuit while someone else is working on it. Diyers should do the equivalent if there's any chance whatever that someone else may be in the area. "Hey, SY, what's this button for?" ZZZZZAPPPPP!
I wanted to build this http://my.execpc.com/~n9zes/amps.htm but i am affraid power supply will be too dangerous, i can´t find power supply circuit, it is from Eric Barbour on Svetlana web page. I don´t want to build on el34, it is pentode, i have heard it hasn´t so nice sound like pure triode.
I have plans for a long-keyed mains switch on my set
I intend on placing it at the back and having an "always-on" 12volt baton transformer and regulation to run onboard IR remote controls (& future projects) and the final mains power-up paralleled relay...
So essentially the keyed-switch turns on the controls which turn on the actual supply via whatever utility I suit fit.
Quite simple, Quite safe. at least this way I can place an all-in-one DMM LCD backlit display to actually show me what voltages are still in the circuit before and after I "activate" it.
I intend on placing it at the back and having an "always-on" 12volt baton transformer and regulation to run onboard IR remote controls (& future projects) and the final mains power-up paralleled relay...
So essentially the keyed-switch turns on the controls which turn on the actual supply via whatever utility I suit fit.
Quite simple, Quite safe. at least this way I can place an all-in-one DMM LCD backlit display to actually show me what voltages are still in the circuit before and after I "activate" it.
I am an Engineer with many years of experience designing, repairing and maintaining Broadcast transmitters.
I have worked on 26,000 volt transmitter power supplies (Gates/Harris MW-50) and have never received so much as a shock.
Why?
Because I am aware of the potential and I safeguard myself by discharging the capacitor bank before I reach into the equipment.
The simple truth is that you must respect electricity ... any electricity. If you don't understand the potential danger, stay away from it ... PLEASE!
I witnessed the electrocution of a fellow Engineer several years ago. He died because he didn't discharge a capacitor bank ... a 2500 volt Low Voltage supply in a 50,000 watt transmitter.
It was horrible.
I have worked on 26,000 volt transmitter power supplies (Gates/Harris MW-50) and have never received so much as a shock.
Why?
Because I am aware of the potential and I safeguard myself by discharging the capacitor bank before I reach into the equipment.
The simple truth is that you must respect electricity ... any electricity. If you don't understand the potential danger, stay away from it ... PLEASE!
I witnessed the electrocution of a fellow Engineer several years ago. He died because he didn't discharge a capacitor bank ... a 2500 volt Low Voltage supply in a 50,000 watt transmitter.
It was horrible.
Here's the guidelines I teach...
Here, only up to "C is allowed..nobody I teach is qualified for range "D".
Important notes: High voltage hazard C is a supply over 300 volts and under 750 that can deliver in excess of TEN milliamps..which is defined loosly as fatal.
Ten milliamps can be delivered by a car battery, if the skin is sufficiently wet. The current through the body is entirely derived from the skin resistance and the supply voltage. How the current travels through the body determines if it is fatal or not..
Ten joules of stored energy is also considered a hazard, specified as :
Estored=1/2CV2
or
Estored=1/2LI2
Cheers, John
Here, only up to "C is allowed..nobody I teach is qualified for range "D".
Important notes: High voltage hazard C is a supply over 300 volts and under 750 that can deliver in excess of TEN milliamps..which is defined loosly as fatal.
Ten milliamps can be delivered by a car battery, if the skin is sufficiently wet. The current through the body is entirely derived from the skin resistance and the supply voltage. How the current travels through the body determines if it is fatal or not..
Ten joules of stored energy is also considered a hazard, specified as :
Estored=1/2CV2
or
Estored=1/2LI2
Cheers, John
Attachments
I once had a drunken visitor fall into my DC coupled OTL amp (pic in project photo album section) while it was powered up. Fortunately, after determining that he hadn't received a shock or cut, I found that only about three or four 6AS7G's were squashed and the LS3/5A's it was driving at the time hadn't suffered either.
This rule, (using only one hand when working on equipment in operation) was introduced in the Swedish navy and is thought to give 2 advantages:
You are less likely to get a electric shock between your hands, (across your body) which should be the most dangerous way of getting electricity trough the body, (goes trough your heart).
The other reason is simple that is less likely to get a shock when using only one hand for work.
This work rule is very old and I dont know if it still enforced or indeed if the reasons for introducing it is valid but when I started working with radar performance monitors which involved work in some radar equipment I was told to use this method. I still try to follow this when working on high voltage tube amps, for me it is a habit.
Anyway I still think that if you are unsure about working with high voltage circuits then don't before you have learnt how to, preferably by some old hand with a lot of experience.
Regards Hans
metal man suits
Anybody know where one can get one of those metallic woven suits the high line workers use? Probably too expensive for DIY, maybe an opportunity for some enterprising minded person. Even, if one could just find the source for the metallic cloth, could get some seamstress to make you a snowmobile suit from it, or a jacket. Probably have to solder the seams though! I've seen woven magnet wire at the scrap metal yard, was used for decorative stuff, but used fine enamel insulated wire, ie. NG.
Or maybe could just make some metallic woven gloves with grounding straps.
Anybody know where one can get one of those metallic woven suits the high line workers use? Probably too expensive for DIY, maybe an opportunity for some enterprising minded person. Even, if one could just find the source for the metallic cloth, could get some seamstress to make you a snowmobile suit from it, or a jacket. Probably have to solder the seams though! I've seen woven magnet wire at the scrap metal yard, was used for decorative stuff, but used fine enamel insulated wire, ie. NG.
Or maybe could just make some metallic woven gloves with grounding straps.
I once saw a practical example of this in action. A good friend was working on his 'classic' british car and as he was messing with some wires the battery short-circuited through his steel watch strap. I couldn't quite get what happened as he suddenly started jumping around and violently shaking his hand in a desperate attempt to remove the red hot watch. Left him a lovely mark.
None of them metal gloves for me, thanks.
One great idea is to put bleeder resistors, say 220K, permanently across power supply capacitors. This tends to ensure the caps fully discharge.
First thing I do when working on any valve amps is put a 47 ohm 5W resistor briefly across all power supply capacitors in an amp.
Also if you are measuring voltages while the amp is on, use crocodile clip leads with your DMM. That way all you do is put the clips on, turn the amp on, read the voltage, and turn it off again. Very safe.
Also I don't like separate power supplies with tube amps. Too much energy stored in a box. Lose your ground connection and your amp chassis floats to B+ level.
First thing I do when working on any valve amps is put a 47 ohm 5W resistor briefly across all power supply capacitors in an amp.
Also if you are measuring voltages while the amp is on, use crocodile clip leads with your DMM. That way all you do is put the clips on, turn the amp on, read the voltage, and turn it off again. Very safe.
Also I don't like separate power supplies with tube amps. Too much energy stored in a box. Lose your ground connection and your amp chassis floats to B+ level.
Given the right circumstances, enough amps to go along with the volts and your butt is fried. Therefore, any voltage could be a killer.
You have given me a very bad feeling here. My whole hearted suggestion is to avoid building ANYTHING at all and be content to purchase an already built product.
You have given me a very bad feeling here. My whole hearted suggestion is to avoid building ANYTHING at all and be content to purchase an already built product.
If you have ever been shocked across the chest then you know its far worse then just up the arm. I have had both!
Up the amr, sorry to say this but it wasnt all that bad, my arm just vibrated with a strange tigly sensation, it was not unpleasent
I should start to worry now lol, I dont have any intention of gettin shocked again.
Next time was as BAD as it can get my right arm was connected to +volts , my left completed the circuit to ground. I flew backwards a few feet, I was sitting cross legged on the ground and it was a hot day so I was sweaty. I didnt know what had hit me it fealt as if I had been kicked several times all over, I just sat there dazed for a few minutes thinking WHAT THE *&£$ was that.
This WAS a complete accident it was off my soldering iron the flex had become damaged, which I didnt know about so a few wires poked through the flex, so right arm on flex, left soldering touch the tip which is earthed and BAM.
Its a good thing I am was 18 at the time, so my heart is strong. I know that if I was older and had weaker heart I would not be here.
After being shocked for the 1st time I took extra care not to get hit again where the threat is obvious. I didnt have any idea that the sodering iron was bad. NOW im extra vigilant, im 19 For heavens sake, I dont want to die.
Beware of electricity it can kill.
Up the amr, sorry to say this but it wasnt all that bad, my arm just vibrated with a strange tigly sensation, it was not unpleasent
I should start to worry now lol, I dont have any intention of gettin shocked again.Next time was as BAD as it can get my right arm was connected to +volts , my left completed the circuit to ground. I flew backwards a few feet, I was sitting cross legged on the ground and it was a hot day so I was sweaty. I didnt know what had hit me it fealt as if I had been kicked several times all over, I just sat there dazed for a few minutes thinking WHAT THE *&£$ was that.
This WAS a complete accident it was off my soldering iron the flex had become damaged, which I didnt know about so a few wires poked through the flex, so right arm on flex, left soldering touch the tip which is earthed and BAM.
Its a good thing I am was 18 at the time, so my heart is strong. I know that if I was older and had weaker heart I would not be here.
After being shocked for the 1st time I took extra care not to get hit again where the threat is obvious. I didnt have any idea that the sodering iron was bad. NOW im extra vigilant, im 19 For heavens sake, I dont want to die.
Beware of electricity it can kill.
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