(Topic ID: 41503)

Electrocution, and how to avoid it

By textrivers

11 years ago


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  • Latest reply 11 years ago by Foo
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There are 86 posts in this topic. You are on page 1 of 2.
#1 11 years ago

I'm fairly new to the hobby. I've just brought a Bally Dogies back to life and I've now started working on a Bally Sea Ray. The wiring in my Sea Ray cabinet seems much more iffy than in Dogies, and I find myself trying to track down problems by poking relays and jiggling cables and manually activating stepper solenoids, and it has made me think.

How do you deal with the risk of electrocution, and how serious is the risk? Are there any "best practices" I should know about? Are there places I shouldn't touch when the power is on? Should I try not to touch (for example) leaf switches with my bare hands? Should I refrain from licking the transformer?

#2 11 years ago

When in doubt - Try not to grap things with both hands to make a circuit with your heart.

#3 11 years ago

always keep in mind that the word "electrocution" came into being when the electric chair was invented... it was shorthand for "electric execution"...

#4 11 years ago

Think of it like this: All current is just trying to find it's eventual way to ground. If the machine is on and part of your body is touching something that is grounded and another part touches open current, your body becomes the quickest way to ground and it will attempt to travel through you to get there. Most voltages on a pinball machine outside of the main power supply areas aren't deadly, but it's still not good practice to send abnormal electric pulses through your body. They can still have their effects on the heart or nervous system.

#5 11 years ago

Don't have 2 hands in the machine at the same time, unless of course only one is yours...

#6 11 years ago

Not to poo-poo your concerns too much, but I don't believe I have ever heard of anyone getting seriously injured on a pinball machine. 110v is not horribly dangerous, and the stepped down voltage even less so. The biggest risk for injury is likely to your head: You get "bit" and jump up, knocking your noggin on the bottom of the PF.

Wear shoes. Don't poke around with the power on unless absolutely necessary.

Read this:
http://www.pinwiki.com/wiki/index.php?title=EM_Repair#Safety

#7 11 years ago
Quoted from MinusWorlds:

Don't have 2 hands in the machine at the same time, unless of course only one is yours...

Good advice there....this is a good rule of thumb when I discharge monitors on video games. I always put one hand in my pocket when I ground the anode....30,000V coursing through my body is not a good thing.

Best to do your work with the machine off and then turn it on to test. High voltage can be present at the coils so watch out there. Leaf switches aren't a problem. Best not to lick the transformer...guess you could lick the used gum stuck to the bottom of the machine tho.

#8 11 years ago

110 is more dangerous then higher voltages.......!

#9 11 years ago
Quoted from scottc:

110 is more dangerous then higher voltages.......!

Care to explain your logic on that one?

#10 11 years ago

Most things said already, but do make sure to inspect and repair safety ground. You'll find a lot of machines have had the 3rd prong broken off the wall plug.

#11 11 years ago

Use a magic stick to poke around. Not fingers
Also be sure the magic stick isnt metal

#12 11 years ago

Have you ever been hit? Voltage isn't what gets you, current is. I had 16000 volts put thru me working on a Neon sign in the mall when I was first out of school. Some jackass flipped the breaker while I was booting the sign. Very low current but watched that arc between my thumb and the sign. Chances are if you get hit by larger voltages then 110 like 480 v or more its going to have an explosion type effect which should blow you back and away from the short. 110 if circumstances are all wrong (or correct) will not blow you back it will pull you in. There are a million different scenarioes but just want the statement of 110 not being horribly dangerous to be stricken. Sure you can put your finger on 110 get hit and not really get hurt but if circumstances are correct...solid path to ground, especially water, its 100% deadly!

#13 11 years ago

Don't be afraid of electricity, just respect it.

#14 11 years ago

If you're unsure, get some of those surgical latex gloves, they're cheap. Wear those whilst you're touching the internals. Or unplug the game and be totally safe.
Really, on most games, it's only the transformer and mains fuse that are high voltage. Some Ballys are 50V but most games are only 25 - 30V. Lighting is mostly 6.3V. I touch the 50V switches in my bingo without any problems. Some contacts on pre 70s Gottliebs are mains, the coin door switch, the replay game start switch, the tilt switches and a few score motor and relay contacts so they need care when messing, best to unplug them. Wear shoes when messing.

#15 11 years ago
Quoted from scottc:

Have you ever been hit? Voltage isn't what gets you, current is. I had 16000 volts put thru me working on a Neon sign in the mall when I was first out of school. Some jackass flipped the breaker while I was booting the sign. Very low current but watched that arc between my thumb and the sign. Chances are if you get hit by larger voltages then 110 like 480 v or more its going to have an explosion type effect which should blow you back and away from the short. 110 if circumstances are all wrong (or correct) will not blow you back it will pull you in. There are a million different scenarioes but just want the statement of 110 not being horribly dangerous to be stricken. Sure you can put your finger on 110 get hit and not really get hurt but if circumstances are correct...solid path to ground, especially water, its 100% deadly!

If you are dealing with 480 and cause an arc flash explosion you are getting blown back as a glob of melting goo. It is total myth that these explosions save people. The heat is radiant, it hits you instantly and is around 35000 degrees. The leading edge of the blast wave consists of gaseous copper which coats your skin and since gasping is a natural reflex it will also coat your lungs. Reality is a long way from the old wives tale.

#16 11 years ago

Im not talking about rackin in MCCs. But yes what has been stated is true above.

#17 11 years ago
Quoted from textrivers:

I'm fairly new to the hobby. I've just brought a Bally Dogies back to life and I've now started working on a Bally Sea Ray. The wiring in my Sea Ray cabinet seems much more iffy than in Dogies, and I find myself trying to track down problems by poking relays and jiggling cables and manually activating stepper solenoids, and it has made me think.How do you deal with the risk of electrocution, and how serious is the risk? Are there any "best practices" I should know about? Are there places I shouldn't touch when the power is on? Should I try not to touch (for example) leaf switches with my bare hands? Should I refrain from licking the transformer?

Lots of good suggestions for you in here. The two best are unplug the game or if you can't then poke around with something wood or plastic instead of your fingers. Anything under 50 volts is not going to harm you so use your voltmeter and check before you touch. The dangerous voltages are usually contained in the bottom of the cabinet but on some games you can find them on the coin door or in the backbox.

#18 11 years ago
Quoted from scottc:

Don't be afraid of electricity, just respect it.

Words of wisdom.

And after you have worked with electricity for a long time. Still be careful. Easy to make mistakes the more you work with stuff.

LTG : )

#19 11 years ago
Quoted from textrivers:

Should I refrain from licking the transformer?

Only if it is plugged in.

Ken

#20 11 years ago

If your dealing with DC touch with the back of your hand first.

#21 11 years ago

Thanks all, for the many words of wisdom. The transformer in Sea Ray steps 115v current down to 52v, but in practice our wall current is more like 124v and the machine voltage is around 56v. If I were to switch to the hi-tap lug I'm probably looking at ~60v. Guess I'll keep my shoes on and my hands to myself!

#22 11 years ago

Don't kill someone in a state with electrocution for a death penalty.

LTG : )

#23 11 years ago
Quoted from scottc:

Have you ever been hit? Voltage isn't what gets you, current is. I had 16000 volts put thru me working on a Neon sign in the mall when I was first out of school. Some jackass flipped the breaker while I was booting the sign. Very low current but watched that arc between my thumb and the sign. Chances are if you get hit by larger voltages then 110 like 480 v or more its going to have an explosion type effect which should blow you back and away from the short. 110 if circumstances are all wrong (or correct) will not blow you back it will pull you in. There are a million different scenarioes but just want the statement of 110 not being horribly dangerous to be stricken. Sure you can put your finger on 110 get hit and not really get hurt but if circumstances are correct...solid path to ground, especially water, its 100% deadly!

True, but voltage also directly determines the amount of current that can flow through you. In the case of the neon sign transformer those are pretty low current circuits. It explains why DMD fuses only need 250mA fuses or whatever it is, otherwise the circuit would destroy itself due to too much power. It's not completely ok to dismiss the fact that higher voltages equals potential for more current but there are exceptions.

#24 11 years ago

I've gotten zapped a few times, usually being lazy and not wanting to power off the machine and back on check that something like LED's look good or are working..

Now I try to turn off the machine whenever possible, and a lot of times, unplug it.

#25 11 years ago
Quoted from Crash:

True, but voltage also directly determines the amount of current that can flow through you.

Oh my how many times I've had to explain this. I'll take 100 car batteries in parallel, 12 volts at a potential 60,000 amps, and gladly grab both terminals right after I got out of the pool. Good old V=IR tells us we can change V, and we can change R, but we can't directly change I (Current). We can affect I by increasing V or decreasing R. This means either high voltage, or impaling ourselves with positive and ground. So short of skewering ourselves with electrical leads, it's the voltage that determines whether or not we get a fatal amount of current.

#26 11 years ago
Quoted from Crash:

Care to explain your logic on that one?

i think he might be talking a bout when you freeze up a suffer a prolonged shock ??? not real sure though.

stay dry, ware shoes, dont be a good ground.

#27 11 years ago

Voltage isn't the real concern. It's amperage.

Effects can range from a barely perceptible tingle to severe burns and immediate cardiac arrest. Although it is not known the exact injuries that result from any given amperage, the following table demonstrates this general relationship for a 60-cycle, hand-to-foot shock of one second's duration:

Current level

(Milliamperes) Probable Effect on Human Body

1 mA Perception level. Slight tingling sensation. Still dangerous under certain conditions.

5mA Slight shock felt; not painful but disturbing. Average individual can let go. However, strong involuntary reactions to shocks in this range may lead to injuries.

6mA - 16mA Painful shock, begin to lose muscular control. Commonly referred to as the freezing current or "let-go" range.

17mA - 99mA Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death is possible.

100mA - 2000mA Ventricular fibrillation (uneven, uncoordinated pumping of the heart.) Muscular contraction and nerve damage begins to occur. Death is likely.

> 2,000mA Cardiac arrest, internal organ damage, and severe burns. Death is probable

#28 11 years ago

If you have a pacemaker, let someone else work on it.

#29 11 years ago

Dont whiz on the electric fence.

#30 11 years ago
Quoted from Rick471:

Voltage isn't the real concern.

The amperage is directly controlled by Voltage. You can't force more current through a circuit without increasing voltage or decreasing resistance. So unless you stab through your hand with a wire (lowering resistance) then Voltage is the only concern because it dictates current.

#31 11 years ago

If you dabble in electricity, you WILL get shocked. All you can do is be as careful as you can, and hope it isn't bad.

Every electrician I know at one time has been shocked, and I'm betting everyone who has done enough pinball work has felt some sort of shock at one time. I have.

#32 11 years ago

the further i read into this thread, the more it scares the sh!t outta me...

i guess it's doing it's job.

#33 11 years ago
Quoted from CodyF:

The amperage is directly controlled by Voltage. You can't force more current through a circuit without increasing voltage or decreasing resistance. So unless you stab through your hand with a wire (lowering resistance) then Voltage is the only concern because it dictates current.

I don't know about that. Amperage has always been known as the key factor. My understanding is that voltage is like a water pipe, and the current is like the water that flows. You could have a 1 foot diameter pipe allowing a trickle of water to flow, or a half inch pipe allowing gallons per minute to flow - it's not the size of the pipe, it's the rate of the water rushing in.

#34 11 years ago
Quoted from CodyF:

The amperage is directly controlled by Voltage. You can't force more current through a circuit without increasing voltage or decreasing resistance. So unless you stab through your hand with a wire (lowering resistance) then Voltage is the only concern because it dictates current.

Wrong. All 3 are important but voltage doesn't kill you. It's the amperage. 110 Volts + high resistance = low current = less danger.

110v + low resiatance = high current = high danger.

The probability of higher current due to higher voltage is probable but not the constant.

The constant in this argument is amperage.

Ohm's law.

#35 11 years ago

I work with electricity everyday and have been hit several times. Yes 110 can mess you up, but all the perfect variables have to be there. The main thing is not being able to get away from it. That's when you will get hurt. For example laying in a moist crawl space under a house with an ungrounded extension cable. Bad news! Say it has a knick in it you don't see and you crawl over that spot. Zap!

Arc flash as mentioned before is bad also, but for a arc flash to be bad enough to hurt you it has to be in a confined space. Like an electrical panel. It's kinda like gun powder. If you lay some gun powder out on the ground and light it. It's not a big explosion. You pack gun powder in a pipe with a cap on one end and you put your face at the other end..... Bad news! Basically the electrical panel is the pipe and the open door is the uncapped end of the pipe. Arc flash will cook you inside out! Not to mention the exploding copper coming at you.

#36 11 years ago
Quoted from Atomicboy:

I don't know about that.

Oh I know about it V/R=I (Voltage)/(Resistance)=(Current). It's easy to change voltage and easy to change resistance, but you absolutely can not change current without changing the other two. If your body is 100k ohms resistance from fingertip to fingertip and you get hit with 100 volts you're going to have 1mA of current running through your body no matter what. Now this can change over time if, say, the 100v is from a capacitor that is discharging, or if your skin is physically getting burnt (this lowers resistance).

To use your pipe analogy, Imagine your 1 foot diameter pipe coming out of a water reservoir. If you are getting 100 gpm (analogous to current) from your pipe and you want to get 200 there's two ways to do it. For one you can double the size of your pipe (lower resistance) or you can increase the pressure (voltage, potential difference) by raising the reservoir higher. In everyday electricity we don't really change our resistance too drastically, so our resistance stays within an order of magnitude of itself. That leaves only one other option to affect how much current can flow through us and that's Voltage. Do not underestimate voltage.

To explain why we can take a 10,000 volt zap from a capacitor or static shock, imagine your same water pipe example. We've got a reservoir that's a mile high and a pipe that's 10 feet wide. The only problem is our water tower only holds an 8oz glass of water. We get hit with a blast of water traveling at an incredible rate with nothing to stop it, but fortunately for us the amount of total water (measured in Joules in electricity) is so low that no harm is done.

#37 11 years ago
Quoted from Rick471:

The constant in this argument is amperage.

You are missing the point. You can't change the amperage without changing the voltage or resistance. You said yourself: Ohms law. In my earlier example a set of 100 car batteries can put out 60,000 amps at 12 volts but isn't really any more dangerous than a single battery. The resistance is high and the voltage is too low. The potential for high current is there, but that doesn't matter. If we bump the voltage to 120 volts you should start worrying.

This argument is like saying "It's not the strangulation that kills you, it's the lack of oxygen getting to the brain"... Technically true, but it's better to just avoid strangulation altogether because it is a direct cause for the latter.

The reason I'm so adamant about this point is because you discount voltage. VOLTAGE DIRECTLY AFFECTS CURRENT. HIGHER VOLTAGE WILL ALWAYS HAVE A HIGHER CURRENT. I don't want people feeling safe around high voltage because it is what causes high current and is inherently dangerous. Saying a high voltage source is "safe" because it's not high current is just stupid, electricity doesn't work that way says ohms law.

#38 11 years ago

Once touched the transformer (bally) with my elbow, 20 amp fuse blew, one thing i know it doesn't feel good

#39 11 years ago

any voltages greater than 42v can be life threatening according to my past radio amateur (ham) examination

Just found this 30 volts is the
commonly accepted value for the lowest voltage that can cause a dangerous electric shock.

But they failed to say to what a cat fish dog?

#40 11 years ago

My advice, if you think your teeth are a suitable replacement for wire strippers and your tongue is an analog for a DMM then stay away from electricity altogether.

#41 11 years ago
Quoted from 72Devilz:

and your tongue is an analog for a DMM

Haha, I'm not gonna lie, I've touched my tongue to a phone line to see which is which.

#42 11 years ago
Quoted from Wolfmarsh:

Haha, I'm not gonna lie, I've touched my tongue to a phone line to see which is which.

I touched my tongue to my slotcar track when I was about 10 and pulled the trigger. F-- would not recommend.

#43 11 years ago
Quoted from Wolfmarsh:

Haha, I'm not gonna lie, I've touched my tongue to a phone line to see which is which.

The op I worked for had a man who used his tongue for jukebox installations. He could tell speaker lines, volume control, 110AC, etc.

Of course he only lived to 40.

LTG : )

#44 11 years ago

I for one believe every adolescent child should experience the ol finger in the light socket trick at least once. I on the other hand took a liking to it and became an electrician.

Quoted from Wolfmarsh:

Haha, I'm not gonna lie, I've touched my tongue to a phone line to see which is which.

Yeah I did that once but there was an incoming call, never again!

#45 11 years ago

Dont touch the third rail

#46 11 years ago
Quoted from newmantjn:

Not to poo-poo your concerns too much, but I don't believe I have ever heard of anyone getting seriously injured on a pinball machine. 110v is not horribly dangerous, and the stepped down voltage even less so. The biggest risk for injury is likely to your head: You get "bit" and jump up, knocking your noggin on the bottom of the PF.
Wear shoes. Don't poke around with the power on unless absolutely necessary.
Read this:
http://www.pinwiki.com/wiki/index.php?title=EM_Repair#Safety

Then you knock the PF off the hold up bar and it knocks you out and you're trapped in a live machine.

But it's not the voltage as much as the current.

People have been killed with 28V when the current was high enough.

Getting bit by 115v in a pinball i

#47 11 years ago
Quoted from CodyF:

You are missing the point. You can't change the amperage without changing the voltage or resistance. You said yourself: Ohms law. In my earlier example a set of 100 car batteries can put out 60,000 amps at 12 volts but isn't really any more dangerous than a single battery. The resistance is high and the voltage is too low. The potential for high current is there, but that doesn't matter. If we bump the voltage to 120 volts you should start worrying.
This argument is like saying "It's not the strangulation that kills you, it's the lack of oxygen getting to the brain"... Technically true, but it's better to just avoid strangulation altogether because it is a direct cause for the latter.
The reason I'm so adamant about this point is because you discount voltage. VOLTAGE DIRECTLY AFFECTS CURRENT. HIGHER VOLTAGE WILL ALWAYS HAVE A HIGHER CURRENT. I don't want people feeling safe around high voltage because it is what causes high current and is inherently dangerous. Saying a high voltage source is "safe" because it's not high current is just stupid, electricity doesn't work that way says ohms law.

And conversely, I don't want people feeling safe with low voltage current thinking that low voltage it safe. Understand?

#48 11 years ago
Quoted from newmantjn:

Not to poo-poo your concerns too much, but I don't believe I have ever heard of anyone getting seriously injured on a pinball machine. 110v is not horribly dangerous, and the stepped down voltage even less so. The biggest risk for injury is likely to your head: You get "bit" and jump up, knocking your noggin on the bottom of the PF.
Wear shoes. Don't poke around with the power on unless absolutely necessary.
Read this:
http://www.pinwiki.com/wiki/index.php?title=EM_Repair#Safety

Then you knock the PF off the hold up bar and it knocks you out and you're trapped in a live machine.

But it's not the voltage as much as the current.

People have been killed with 28V when the current was high enough.

Getting bit by 115v in a pinball isn't pleasant, but won't kill you.

Early pinballs have some 115v sections, 6v for lights, and either around 30v and sometimes 50v AC.

Later EMs started using DC which can kick your butt a lot harder if it catches you right.

Everything they say about 1 hand is true.

You should try and not complete a circuit thru your heart.

The moral is try and not get shocked.

#49 11 years ago
Quoted from CodyF:

You are missing the point. You can't change the amperage without changing the voltage or resistance. You said yourself: Ohms law. In my earlier example a set of 100 car batteries can put out 60,000 amps at 12 volts but isn't really any more dangerous than a single battery. The resistance is high and the voltage is too low. The potential for high current is there, but that doesn't matter. If we bump the voltage to 120 volts you should start worrying.
This argument is like saying "It's not the strangulation that kills you, it's the lack of oxygen getting to the brain"... Technically true, but it's better to just avoid strangulation altogether because it is a direct cause for the latter.
The reason I'm so adamant about this point is because you discount voltage. VOLTAGE DIRECTLY AFFECTS CURRENT. HIGHER VOLTAGE WILL ALWAYS HAVE A HIGHER CURRENT. I don't want people feeling safe around high voltage because it is what causes high current and is inherently dangerous. Saying a high voltage source is "safe" because it's not high current is just stupid, electricity doesn't work that way says ohms law.

It is not nearly as simple as Ohm's law. Studying this is an enourmous field and the amount of variables involved are incredible. You cannot just plop Ohm's law on it and call it good. Just like the guy who touched his 16,000 volt Neon sign and was fine, figure that one out with Ohm's law...you can't. The power supply has a very large internal resistance so even though a voltmeter will show 16kV his volts drops to almost zero when he touches it but you don't see that when you do Ohm's law. Hidden factors are there. Hidden factors are there in any electric shock situation.

When dealing with AC, resistance isn't what we care about anyway, reactance is the key factor here so we go with impedence to factor in everything. Human impedence varies greatly from person to person and it drops extremely fast as you apply higher voltages to the skin. Your ohmmeter is only putting out about .7V and it reads 100K-1M Ohms depending. If you crank that voltage up to 120V your skin's impedence breaks down immediately and drops to 1000-3000 Ohms depending on the person...some of those people are immediately dead with just 120V going from one hand to the other. No wet skin, no puddle of water, just their natural electrical impedence is lower than other people's.

If you just used Ohm's law and nothing else you would calculate that with 100K ohms in your skin you would need 10,000 Volts to get to the .1 Amps needed to kill you. Certainly you know that you don't need 10,000 volts to kill someone.

#50 11 years ago

Cody said: HIGHER VOLTAGE WILL ALWAYS HAVE A HIGHER CURRENT

This is absolutely false btw...cmon man!

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