View Full Version : Warning: Don't open your power supply unless you know what you're doing.
Richard
08-04-01, 08:15 PM
I know I already replied to the thread about watercooling power supplies, but I can just see some kid running his hand over some charged capacitors and getting a heck of a shock.
FerrariF50
08-04-01, 08:18 PM
Why did you get shocked??? I opened up mine about 3 weeks ago to clean the dust out. WOW my whole desk had dust all over it... Not sure if it helped with temps.
Richard
08-04-01, 08:22 PM
No, I've never been shocked. I'm just trying to pass along some advice that I've been given. People have been shocked many times, because of carelessness or lack of experience. I tend to agree with learning from other's mistakes.
Thelemac
08-04-01, 09:06 PM
Agreed. This goes for monitors, too. Or you can open them up and just not touch anything. That'll keep you pretty safe, too. Though it's best just not to open them at all. That way lightning cat can't jump in or anything. :)
TeKkDrOnE
08-04-01, 09:48 PM
42? The meaning of everything in the universe? ;)
Thelemac
08-04-01, 11:36 PM
That's it exactly!
Cowtown
08-05-01, 12:10 AM
Cripes I thought this kind of thing just went without saying. I have a deep and complete fear/respect for electricity! We have an understanding, I don't mess with it unless I have to and it does the job it is supposed to do! ;)
*spazzed*
08-05-01, 01:57 AM
Now you tell me!!!!!!!!! j/j
I've gotten a small shock from the caps in my PSU, but then again, I've been shocked by many other things. The sparkplug wires in my van is one example :D
I looked at all the capacitors of my PSU and the heaviest one was rated 4400 micro farad at 16v. I don't think a capacitor with a capacity of 4400 micro farad's at 16v can kill someone. Touching it would be an unpleasant surprise I believe, but I surely doubt that it is able to kill. I once got shocked by a 400v wire running to an industrial motor, and even that I survived. Your body has a certain resitance wich is nearly the same for all voltages. My point is that you need a fairly high voltage to send a lethal current through someone's body. With 16v however this won't work. You can get shocked, you can't get killed. Watch out for capacitors rated above 200 volts though. I haven't seen numbers about that, but it could be a different story...
Allways work safe if you do something, noone can stress this enough :D
Let me teach you all something REALLY important about electricity. It's fast. And it hurts. Unless you know what you're doing, DON'T PLAY WITH IT! If you crack open any electronic device without proper training, you're taking your life into your own hands. I'm not telling you not to play with it, but if you do, and you kill yourself, don't come here and whine about it! It's your own fault.
I agree that you need the training to play with electricity. I have a degree in electronics so I know what I'm talking about.
I personaly think that someone who killed himself won'tl come here and whine about that though.
You make it sound like it's impossible for someone who hasn't had any training in electricity to open up a PSU and see which parts are running hot. If you don't know it, then you'd better be carefull while handling it. This doesn't say you may not handle it at al...
This is just ment to be informative and in no way to flame anyone or something.
Richard
08-05-01, 12:40 PM
Which is why it says in the subject, "unless you know what you're doing."
I'm not suggesting that people not experiement. Just that they should try and educate themselves on the components before tinkering with them.
Ya dig?
[Oc]acaridans
08-05-01, 12:41 PM
Originally posted by [Oc]Wa11y
Let me teach you all something REALLY important about electricity. It's fast. And it hurts. Unless you know what you're doing, DON'T PLAY WITH IT! If you crack open any electronic device without proper training, you're taking your life into your own hands. I'm not telling you not to play with it, but if you do, and you kill yourself, don't come here and whine about it! It's your own fault.
And to note, even the people that know what there doing or think they know what there doing, should take the exact same percautions as everyone else, overconfidence is just as dangerous....In my automechanic days I got a little to confident with and igniton system, Wally is right it hurts. Everyone please be carefull
I doubt that there are good electricians out there who haven't been shocked ever. If you work with electricity all day, things like this happen...
Richard999 : I took the "unless you know what you're doing." as unless "you have the needed training:". Now that's cleared up I agree with you totally, I just took it the wrong way :D...
Capacitors can be very fun but very dangerous. My good bud and I spent a few moths fooling aound with capacitors making cattle prods and other such devices. The best prod we made wase from an old startrek phazor. It had 4 220v capacitors from disposible cameras, a custom charging circut, a tiny cooling fan and gold plated prods sticking out the front. All this was powered from 2 700ma Nickle Metal Hidride AAA batteries. The prod was so powerful it would leave schorch marks and 2 divits in a hardened steel screw driver. The effect was like a little bolt of lightening lighting up the room for an instant. The second coolest prod we made was stuffed inside one of those little Milk Dud boxes that only holds 3-4 pieces of the candy. This little devil had 2 220v capacitors, a very tiny charging circut and 1 N battery to power it. This prod did almost as much damage as the bigger prod but in a much smaller package. We never had any use for our projects but it was very fun to goof aound with. Remember to be very careful when working around capacitors and other electric devices. It isn't the voltage that kills its the amperage.
It isn't the voltage that kills its the amperage. I agree but you are much more likely to get to the lethal currents with higher voltages. If you see capacitors for more than a hundred volts KEEP OFF! For lower rated ones: be carefull!
wild_andy_c
08-05-01, 01:20 PM
Originally posted by Richard999
I know I already replied to the thread about watercooling power supplies, but I can just see some kid running his hand over some charged capacitors and getting a heck of a shock.
Good call Richard
I agree with all of you. One way to help prevent shock is to discarge the psu before opening it. What I do is turn the psu off then tru to turn the comp on it will try to start and then stop
You can even just pull the plug while the computer is running, that will also discharge any capacitors.
Finally we are getting to a safe way of tampering with PSU's :D
Rob Cork
08-05-01, 02:33 PM
Someone here mentioned you could sometimes get rid of fuzziness in old monitors by discharging the caps at the back. They suggested using a screwdriver with a wire going to ground wrapped around the metal shaft. I don't see any problem with that in principle, but it does still feel a bit ghetto :)
Anyone used that trick, and could you use it with the caps in the psu? I don't see why not, but I don't claim to have any electronics training so there could be something I've overlooked/don't know :)
Originally posted by Rob Cork
Someone here mentioned you could sometimes get rid of fuzziness in old monitors by discharging the caps at the back. They suggested using a screwdriver with a wire going to ground wrapped around the metal shaft. I don't see any problem with that in principle, but it does still feel a bit ghetto :)
Anyone used that trick, and could you use it with the caps in the psu? I don't see why not, but I don't claim to have any electronics training so there could be something I've overlooked/don't know :)
Sing along, everyone!
Ghetto Supastar!
That is what you are!
Coming from afar!
Reaching for the stars!
Woudn't that do the same thing as hitting the degauss button? Or is degaussing something different?
funnyperson1
08-05-01, 03:09 PM
i opened a psu once...and i touched everything :(....thankfully this power supply was designed to work with a 486 and therefore i was saved by the fact that it had been laying around for five years.....shwoooh....
Car Audio caps are the worst, very high discharge and recharge rate. I know of a guy that touched the terminals to his tongue. Sure, a 9V will shock you, but a car cap burned a hole through his tongue. It only takes 1 Amp to kill you though. Putting into perspective, 1 Amp will drop a horse.
Tithulta
08-05-01, 03:39 PM
always be aware of electric fences as well...never smooth wet cement near them....installed batting cage near one...smoothed the wet cement with my hands and mean while backed into the fence...MAN talk about being surprised!
when working with electricity I've always taken great care....it's those times I'm not working with it directly that its biten me in the @rse. :D
Godfodda
08-05-01, 03:43 PM
Originally posted by Quaky
. My point is that you need a fairly high voltage to send a lethal current through someone's body. With 16v however this won't work. You can get shocked, you can't get killed. Watch out for capacitors rated above 200 volts though. I haven't seen numbers about that, but it could be a different story...
Allways work safe if you do something, noone can stress this enough :D
I believe this is incorrect. Voltage isn't what kills. Amperage is. These two are inversely proportional. You standard house plug can fry your arse easily. I've heard it said that it's more dangerous than a 220 or 440. And about the capacitors, I've heard tales of screwdrivers being blown apart when used to discharge them... these weren't huge capacitors, either. Gotta watch this stuff.
supraway
08-05-01, 04:44 PM
Voltage on the capacitors isn't exactly what you need to be worried about, it is the farad rating and amperage the capacitor puts out. I used to charge up 10000 micro farad capacitors with a 9 volt battery, and touch door knobs with them. The shower of sparks was way cool. The ones you have to be careful of are the caps in monitors, they are the powerful suckers. They will easily kill you in a matter of milliseconds. I have been shocked by the ones in PSUs before, it was just VERY, VERY, VERY uncomfortable. Shocked myself with a TV once, and it seriously felt like my heart stopped. I found myself halfway across the room, staring at the ceiling and my friends looking down at me. They had apparently dragged me over as I was "unaware" of what was happening for a minute. I would love to mess with one of those car amp capacitors, though. 1 farad ratings!!! They could honestly blow a frog a block away. Not that I ever would though :).
FerrariF50
08-05-01, 08:10 PM
Well I want to add that I was working on a old tv before I dumped it and I had the whole thing open when it was on the back of the picture tube was exposed. Anyway I was about to fall over because I was in a crouching postison. And I fotgot allabout the back of the Tv and so My hand landed on the back of the PSB of the picture tube. To tell you the truth it really did not hurt. Not that I would do it again! But it felt like metal spikes going in my hand.. Not a good feeling!
Ooohhhhhh.... Electronics descusion..... Me like!!
Here's a little rhyme I picked up somewhere
It's the volts that jolts,
But the mills that kills...
For all of you out there, voltage can't to a darn thing to you. If the water ain't flowing, you won't get hurt. It's like standing in front of a dam. Stand by the gates all you want, but you won't get hurt. Once they open those gates though... Well, all that water rushing with you in the way, and you won't be a very happy camper.
Also, one amp is WAY more than is needed to kill a person. I read in my science book that at about 5 miliamps it hurts, and 10 (or 20) miliamps is the "can't let go" current. At 50 milliamps you won't be living no more if it goes through the heart. Thats only 0.05 amps!! (Corrections anyone for the exact numbers??)
Don't mess with caps unless you KNOW they are discharged. If you aren't sure, but still need to mess with em, make sure you wear some seirous insulation over your hands and such.
JigPu
FerrariF50
08-05-01, 10:20 PM
First of all why do I need to keep loging on to post anyway you are right it's really the amps that can kill you. My uncle was telling me a story one day back when he used to work at the power co. That a guy that worked their got shocked by 5,000volts but it never killed him.... Now if that was 5,000 amps I guess we would need to look in a 3 mile radus for his body parts..........
FerrariF50
08-05-01, 10:22 PM
nevermind fixed it
CrystalMethod
08-05-01, 11:15 PM
Originally posted by sieb
Car Audio caps are the worst, very high discharge and recharge rate. I know of a guy that touched the terminals to his tongue. Sure, a 9V will shock you, but a car cap burned a hole through his tongue. It only takes 1 Amp to kill you though. Putting into perspective, 1 Amp will drop a horse.
Yep, shocked the S*** outta myself the other day working on a friend's system. He never told me he had it installed. He just wanted me to hook up his new amp for his subs. Got a niffty burn on the knuckle of my thumb now. Hope it doesn't scar too much...
Crazy Jayhawk
08-06-01, 01:25 AM
Originally posted by TeKkDrOnE
42? The meaning of everything in the universe? ;) "Life, the Universe, and Everything." http://s.drunkencell.com/badrazz.gif
Godfodda If you have a resistor of 100 ohms, you apply 5v an 50v to it... Won't you have a 10 times higer and therefore more dangerous current with the 50 volts. I surely believe that the higher the voltage the more dangerous a capacitor is. If anyone can show me a scientific article proving the opposite I could agree until then I believe in my statement :D
Again, not to flame or anything, just trying to be informative...
Originally posted by Quaky
Godfodda If you have a resistor of 100 ohms, you apply 5v an 50v to it... Won't you have a 10 times higer and therefore more dangerous current with the 50 volts. I surely believe that the higher the voltage the more dangerous a capacitor is. If anyone can show me a scientific article proving the opposite I could agree until then I believe in my statement :D
Again, not to flame or anything, just trying to be informative...
Originally posted by Quaky
Godfodda If you have a resistor of 100 ohms, you apply 5v an 50v to it... Won't you have a 10 times higer and therefore more dangerous current with the 50 volts. I surely believe that the higher the voltage the more dangerous a capacitor is. If anyone can show me a scientific article proving the opposite I could agree until then I believe in my statement :D
Again, not to flame or anything, just trying to be informative...
As Ive understood superconductor has (in theory) zero voltage and infinite current. Voltage is generated by resistance, when the flow of electrons is resisted. Than larger resistor you have btwn the GND and 50V for example, Than larger voltage is born. Also the current is smaller. The basic electronics math proves that Voltage is opposite to current in scale.
U = R * I, than larger the R, than larger the U.
I = U / R, than smaller the R, than larger the I.
But this also proves that than larger the U (voltage), than easier to get larger I (current) over large R (resistance). If human R is 100kohm (btwn left and right hand) and the capacitor is 230V, the current would get to 230 / 100000 = 23mA where 110V capacitor would generate only 11mA. This is missleading as the resistance of your skin generates alot of heat and your resistance is likely to drop as soon as the current burns trough your skin. And I recall also the 50mA to be enough to kill.
Hope I got the facts right...
Ive also heard someone to die from 9V battery. He pinched his multimeter rods trough his thumbs. Skin seems to be the most resistant part of your body.
Originally posted by maha_x
U = R * I, than larger the R, than larger the U.
I = U / R, than smaller the R, than larger the I.
You need to know what kind of power supply you have. Constant voltage (very common), or constant current (eg. high-end battery chargers). A battery is a const. voltage source but with depleting reserves of ions, the voltage will drop with prolonged use. Voltages can also drop (RMS) according to how inductive or capacitive loads are (for AC only).
Yeah, most of that earlier stuff (math formulas) only apply for DC. This would be the case when touching a charged capacitor. When there is no network AC connected (for Gods sake, If you plan to open your PSU, unplug it!). Getting hit by AC can be more complicated matter.
The power source I was refering to was the capacitor, which is the most common zapper. anyhow, the point of my eariler posting was that indeed voltage is opposite to current.
killem1x1
08-06-01, 10:17 AM
I work on plasma cutting machines, and power supplies for my day job, and I've done some pretty dumb things, even last night. (See my other post PLZ HELP)
Anyway, about two months ago I was in our shop on a sunday night wiring up a 240v Plasma power supply, the lead was hanging from the roof so I was working with my hands stretched, I had to take the cover off the rec. to determine if the previous person had hooked up the stinger to the right place, and it wasn't so I changed the legs, then went to the ppsu, and wired it up. I wen't back to the "roof" section grabbed it to put the cover on and BAM! it knocked me down. I sat right back up, I was a little shaken, but it was nowhere close to what 110v had done to me in the past, where I had hurt for days on end all the way up my arm, this time my hand hurt a little, but it just scared me more than anything.
As to how I was shocked, I ASSUMED the breaker was off as this plug had not been used in forever. This is the worst mistake I think I've seen people make.
As the person who started this thread stated, ensure the power is unplugged, the breaker is off, the caps are discharged, something and everyhting before you play around. I consider myself lucky to be alive when I look back at some of the crazy things I've done to save a few minutes over the last 10 years, but next to lockout boxes, ensure that there is no power leads going to anything your working with, and if your working with power leads, ensure the breaker is locked out, or pulled!
;)
*spazzed*
08-06-01, 11:09 PM
Originally posted by sieb
Car Audio caps are the worst, very high discharge and recharge rate. I know of a guy that touched the terminals to his tongue. Sure, a 9V will shock you, but a car cap burned a hole through his tongue.
Try fooling around with the "super caps" that are used inline with a d-class amplifier......those thigs can feed upto 30 amps and store about 400amps(i think)@ 12 volts. They are used when you hit a really low note and the amp pulls, but the battery just isn't there. Now THOSE pack a jolt. never shorted one yet though......not going to either :D
Crazy Jayhawk
08-07-01, 01:27 AM
Now if you want to get a real shock, get a hold of one of those capacitors like they use on power lines and charge it up. The caps you find in your PSU are in the microfarad to millifarad range (not too high a capacitance) but the ones on power poles are often 1 Farad or higher.
This has been your pointless observation of the evening. Thank you and good night. :)
M@€$†®Ö™
08-07-01, 01:35 AM
I just take a Powerful AIrhose and Blow it out. Never got shocked pulling one apart. I know what I am doing :D
Maestro
FerrariF50
08-07-01, 02:50 AM
Most airhoses I use when you spray air out of it you can see a fine mist of water come out of it.
Originally posted by Maestro
I just take a Powerful AIrhose and Blow it out. Never got shocked pulling one apart. I know what I am doing :D
Maestro
Hmmm, got me thinking about homemade cattle prods...
Email me cjtune:cool: I'll let you know the detailed specs. Maybe I'll get some pics of the Milk Dud box if I still have it around.
CalCoolage
08-07-01, 11:19 AM
> And I recall also the 50mA to be enough to kill.
Those capacitors people mention must have a high voltage on them, otherwise they would do nothing much
The 12 volts used in autombiles would ordinarily not push enough current through your chest to stop your heart, the usual way of getting killed by electricity. However putting an 1/8 inch piece of sweaty flesh accross some terminals could well do some damage.
Big car audio amplliers generate more than 12 volts, so you can deafen the whole neighborhood.
Voltage is like pressure, and without enough "pressure" you can't get enough current flow to do much. 50 mA is tiny, so ordinarily there is plenty enough current available from a power source, excluding possibly tiny capacitors or the case of so-called "static" electricity.
Switching power supplies, like the PC power supply, have inductors in them, which generate voltages proportional to the current change. The circuits control this to generate the various voltages. You can get very high voltages when you either open or close a circuit, which you might do when fooling around inside.
AC is particularly dangerous because the peak voltage is 1.4 times the rated voltage.
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