hi, i took out my power supply and saw there was a fan attached to it, the fan screws go from the inside out, and i they are screwed in from the core of the power supply. I need to take the fan out, or inspect it because its not working. But on the power supply, it says, do not open.....so if everything is unplugged and its sepparated from the computer, can i open the casing? and if i do open it, should i not touch anything? THANKS
can i get electricuted with power supply?
- Thread starter JoeFaheyx
- Start date
Nohr
Diamond Member
It can still be dangerous, but so long as you're careful not to touch anything other than the fan and the psu case you'll be fine. Get the fan unscrewed, peel off the label and put a drop or two of oil in there. That usually takes care of it. You will void your PSU warranty when you open it, btw.
Also, wrong forum. This should go in General Hardware.
Also, wrong forum. This should go in General Hardware.
Mermaidman
Diamond Member
- Sep 4, 2003
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DANGER DANGER DANGER!! Yes-You can get electrocuted because the PS has capacitors in it. This is evident when you unplug a PC and the motherboard will still show power for a second or so (if your mobo has a built in LED, etc) Make sure all the stored energy is discharged before you open it up.
Nohr
Diamond Member
Ha Ha Ha !!! This gave me the laugh of the day, a little 3 volt transistor radio has capacitors in it also, think that it may electrocute you???? A crystal set has capacitors, can you get electrocuted from it also??? As a afterthought a cpu has probably 10 thousand or more capacitors and I have never heard of anyone getting electrocuted from one.
FUNNY
Bleep
Take a 1000microF capacitor, charge it (~24V) and then discharge it on your self
See how FUNNY it is
The cap's vorking voltage, and thus it's voltage potential will determine if you get a shock. A capacitor charge of 24V is not much voltage. For example, try grabbing the two posts of an automobile battery (12V), or the batteries used in an electric wheelchair (most are 24V systems) if you have access to one. Automobile batteries can easily source over 400 amps, but you won't feel anything.
A cap's rating in farads determines how much charge it can hold. (C=Q/V). But if the voltage exceeds the cap's vorking voltage rating (WVDC), the plates will short and/or the dielectric will break down.
On the other hand, a cap charged to house voltage can be a shocking experience. But unless you have a bad heart (or use a pacemaker), it will not harm much less electrocute you. Power supply filter caps can easily range around 160 VWDC (for a full wave rectifier). Most circuits today put bleeder resistors across the filter caps which discharge the caps fairly rapidly.
An old lab trick back in the days of tubes (yeah, I go back that far) was to charge a cap to plate voltage levels, typically 150V to 300V, call out "here, catch", and toss the charged cap to another person. Many old techs and EE's have had a shocking experience catching a capacitor!
I know 24V is low but it still may give a tingle or two
I can?t really encourage some one to shock him self with 220V now can I?
I just can?t see some one making fun of something that can potentially hurt you
Also some PSUs that don?t use ?standard? transformers but rather rectify using
?induction? (term used loosely) may operate at 1000+V
JoeFahey - I see you have posted two topics regarding power supplies and potential danger. (I just scrolled to the next page.)
Obviously, you do not have a background in electronics and are concerned. However, you can safely dismantle your power supply. Note the safety precautions others have posted: unplug the PSU, partial discharge by pushing the PC's power button with the unit unplugged, and keep your fingers out of the circuitry.
You can easily discharge a cap by jumpering its two leads together, assuming you can access them. A jumper wire with two aligator clips is the simple way, but lacking a jumper wire, you can use the blade of a screwdriver (hold the screwdriver by the insulated handle). Or just wait awhile for the caps to discharge; the circuit design will determine how long it takes to discharge a cap.
You may get shocked which may be a scary experience the first time it happens, and rather unpleasant the next time. Highly unlikely to be harmful much less lethal, but use common sense and some safety precautions.
Obviously, you do not have a background in electronics and are concerned. However, you can safely dismantle your power supply. Note the safety precautions others have posted: unplug the PSU, partial discharge by pushing the PC's power button with the unit unplugged, and keep your fingers out of the circuitry.
You can easily discharge a cap by jumpering its two leads together, assuming you can access them. A jumper wire with two aligator clips is the simple way, but lacking a jumper wire, you can use the blade of a screwdriver (hold the screwdriver by the insulated handle). Or just wait awhile for the caps to discharge; the circuit design will determine how long it takes to discharge a cap.
You may get shocked which may be a scary experience the first time it happens, and rather unpleasant the next time. Highly unlikely to be harmful much less lethal, but use common sense and some safety precautions.
HardWarrior
Diamond Member
- Jan 26, 2004
- 4,400
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- 81
A PSU will KILL you, even unplugged. If you're not comfortable with the process, I'd suggest you get the fan replaced by a tech.
Jeff7
Lifer
- Jan 4, 2001
- 41,596
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Wait a second, you are saying that a 12V car battery is harmless????
The lower the frequency of power, the more dangerous it is. Tesla Coils put out very high frequency power at very high voltages, but low amperage - that power flows right over your skin and you won't feel much of anything. House current is lower - 60Hz. It is dangerous. DC power has a frequency of 0. It is extremely dangerous. Now put 400 amps behind it and there's a big problem.
You can get shocked from low voltages - try a 9V battery. Low voltage and low amperage. But you'll still feel a shock.
A PSU can kill you if handled improperly. Do not listen to these "EE's".
Be extremely careful not to touch those capacitors.
Be extremely careful not to touch those capacitors.
You guys are making a mountain out of a mole hill.
JoeFahey just DON'T touch the caps inside the PS and you should be fine. If you are really concerned just put on a pair of playtex gloves when you remove the fan to lessen the chance you will get shocked. I have yet to hear a story of a technician getting killed by replacing a fan in a PS. Just be careful and use good common sense.
JoeFahey just DON'T touch the caps inside the PS and you should be fine. If you are really concerned just put on a pair of playtex gloves when you remove the fan to lessen the chance you will get shocked. I have yet to hear a story of a technician getting killed by replacing a fan in a PS. Just be careful and use good common sense.
DAMN. seems like people don't know what exactly to warn about.
The power supply in the computer isn't the same type of thing used in TV's and other electronic equipment. It's a switching power supply, so that the capacitors still can hold quite a charge, but it's not the same thing as reaching into a Microwave.
What to watch out is NEVER EVER OPEN A POWER SUPPLY WHILE IT IS PLUGGED IN. Lots of times those big metal heatsinks are HOT, and I don't mean in tempurature. Those mosfets need to be cooled down so they are screwed into the heatsink and the fan blows on the heatsink to keep them cool.
However that big metal heatsink is ALSO PART OF THE ELECTRICAL CURCUIT. Having them plugged in means they have electricity is possibly flowing thru those heatsinks.
If your worried about those capacitors , just discharge them. If their is no electricity in them they can't shock you.
What I do is unplug them and then just switch the computer on quickly. If there is any residual voltage the computer will very breifly try to start, like the fans will get a quarter turn in before they shut off.
Also all modern motherboards have 5 volts flowing thru them at all times if they are plugged in. Even if they are "turned off". That is part of the ATX specification. It's for stuff like power-on-lan and other things. (that's why you should always have the computer unplugged when you work on it. Those PCI cards will still have 5 volts active in them at all times, possibly).
So just by leaving the stupid thing unplugged for 10-15 minutes or so minutes will make sure that it's depleted.
Or if that' is still not good enough for you then you do the same thing you do when you work on TV's and Microwaves:
You find a little 2k ohm / 25watt resistor. On one end you attach a long wire with a allagator clip on one end. You attach that end to a ground. Hold onto the resistor with small pliers with rubber grip or while wearing rubber gloves. then you touch the other side of the resistor to the ends of the capacitors, one by one, holding them their for a couple seconds. The energy will quickly discharge thru the resistor and the resistance will make sure that it's done safely and it isn't going to damage anything delicate.
Then after your done probing the caps with the grounded resistor then take your screwdriver with the nice rubber grip and then go around shorting out the connections of the capacitors on stuff. If you get a spark then you know you didn't do the resistor thing right. If you don't get a spark then it's safe to touch it.
That way you NEVER EVER have to worry about being shocked. No worries, no problem.
The power supply in the computer isn't the same type of thing used in TV's and other electronic equipment. It's a switching power supply, so that the capacitors still can hold quite a charge, but it's not the same thing as reaching into a Microwave.
What to watch out is NEVER EVER OPEN A POWER SUPPLY WHILE IT IS PLUGGED IN. Lots of times those big metal heatsinks are HOT, and I don't mean in tempurature. Those mosfets need to be cooled down so they are screwed into the heatsink and the fan blows on the heatsink to keep them cool.
However that big metal heatsink is ALSO PART OF THE ELECTRICAL CURCUIT. Having them plugged in means they have electricity is possibly flowing thru those heatsinks.
If your worried about those capacitors , just discharge them. If their is no electricity in them they can't shock you.
What I do is unplug them and then just switch the computer on quickly. If there is any residual voltage the computer will very breifly try to start, like the fans will get a quarter turn in before they shut off.
Also all modern motherboards have 5 volts flowing thru them at all times if they are plugged in. Even if they are "turned off". That is part of the ATX specification. It's for stuff like power-on-lan and other things. (that's why you should always have the computer unplugged when you work on it. Those PCI cards will still have 5 volts active in them at all times, possibly).
So just by leaving the stupid thing unplugged for 10-15 minutes or so minutes will make sure that it's depleted.
Or if that' is still not good enough for you then you do the same thing you do when you work on TV's and Microwaves:
You find a little 2k ohm / 25watt resistor. On one end you attach a long wire with a allagator clip on one end. You attach that end to a ground. Hold onto the resistor with small pliers with rubber grip or while wearing rubber gloves. then you touch the other side of the resistor to the ends of the capacitors, one by one, holding them their for a couple seconds. The energy will quickly discharge thru the resistor and the resistance will make sure that it's done safely and it isn't going to damage anything delicate.
Then after your done probing the caps with the grounded resistor then take your screwdriver with the nice rubber grip and then go around shorting out the connections of the capacitors on stuff. If you get a spark then you know you didn't do the resistor thing right. If you don't get a spark then it's safe to touch it.
That way you NEVER EVER have to worry about being shocked. No worries, no problem.
Why does no one ever agree on this topic?
So it takes just a few minutes for a PC PSU (say 300W) to discharge on it's own?
So it takes just a few minutes for a PC PSU (say 300W) to discharge on it's own?
What's the difference? I never know where to post. Problem installing your webcam? You could ask in video, periphs, GH, tech support, software, or OT... GH & periphs need to be merged. And they're all tech support.
Slightly OT, I lightly oiled the motor in my home CD player with sewing machine oil, trying to stop it from 'cutting out', but it made it completely inoperative. Any idea why?
Mermaidman
Diamond Member
- Sep 4, 2003
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Do be careful with a PC PSU. There are large capacitors which are charged to high voltages. Typically 360-370 V (That is not a typo). In the case of Active PFC PSUs, the main capacitors are charged to even higher voltages (380-400 V).
These voltages at least as dangerous, and probably more, than main electricity.
However, the total energy stored in the capacitors is small - and will dissipate rapidly when the mains supply to the PSU is interrupted. If there is a standby power LED on the mobo, this may remain illuminated for 5 or 10 seconds after the PSU is unplugged from the mains. Then the LED dims, often accompanied by a chirp from the PSU as the electronics try desperately to keep the output voltages up, as the capacitor voltage plummets towards zero.
If you leave the PSU unplugged from the mains, but plugged into a load (like a mobo) then the charge should dissipate to safe levels within a few seconds, and dissipate completely within an hour. If you want to be sure, then you can discharge the caps with the techniques listed above (ideally using a resistor).
NOTE THAT THE ABOVE DOES NOT APPLY IF THE PSU IS FAULTY. A Faulty PSU may be able to charge the caps, but not discharge them - a lethal charge could remain for minutes, hours or days (depending on the fault). DO NOT OPEN A FAULTY PSU UNLESS YOU ARE COMPETENT TO HANDLE AND ASSESS THE SAFETY OF, AND DISCHARGE HIGH VOLTAGE CIRCUITS.
You are very unlikely to get a shock from a working PSU that has been disconnected from the mains for more than about an hour - though of course, some care is needed. In particular, care when reassembling is essential to avoid any stray metal, or screws that may contact high voltage components, and to make sure that a good seal is made to prevent debris or fingers from getting in.
Anyway, some other points:
What is this supposed to prove? Such a capacitor charged to 24V is completely harmless. Indeed if you pick one up by the terminals you probably won't even feel it (unless you pick it up with your tongue - in which case it will give you quite a bite, but won't do you any harm). I have worked with 30 V circuits, sometimes with bigger capacitors - I certainly don't recall even getting a tingle from the supply (or caps). Voltages below 48V are classified as Safe Extra Low Voltage (SELV) - essentially, SELV voltages are sufficiently low, that an injurious accident is exceptionally unlikely. The circumstances required for injury are difficult to achieve - generally needing electrodes penetrating the skin, or a large area of skin wrapped in metal foil.
These voltages at least as dangerous, and probably more, than main electricity.
However, the total energy stored in the capacitors is small - and will dissipate rapidly when the mains supply to the PSU is interrupted. If there is a standby power LED on the mobo, this may remain illuminated for 5 or 10 seconds after the PSU is unplugged from the mains. Then the LED dims, often accompanied by a chirp from the PSU as the electronics try desperately to keep the output voltages up, as the capacitor voltage plummets towards zero.
If you leave the PSU unplugged from the mains, but plugged into a load (like a mobo) then the charge should dissipate to safe levels within a few seconds, and dissipate completely within an hour. If you want to be sure, then you can discharge the caps with the techniques listed above (ideally using a resistor).
NOTE THAT THE ABOVE DOES NOT APPLY IF THE PSU IS FAULTY. A Faulty PSU may be able to charge the caps, but not discharge them - a lethal charge could remain for minutes, hours or days (depending on the fault). DO NOT OPEN A FAULTY PSU UNLESS YOU ARE COMPETENT TO HANDLE AND ASSESS THE SAFETY OF, AND DISCHARGE HIGH VOLTAGE CIRCUITS.
You are very unlikely to get a shock from a working PSU that has been disconnected from the mains for more than about an hour - though of course, some care is needed. In particular, care when reassembling is essential to avoid any stray metal, or screws that may contact high voltage components, and to make sure that a good seal is made to prevent debris or fingers from getting in.
Anyway, some other points:
What is this supposed to prove? Such a capacitor charged to 24V is completely harmless. Indeed if you pick one up by the terminals you probably won't even feel it (unless you pick it up with your tongue - in which case it will give you quite a bite, but won't do you any harm). I have worked with 30 V circuits, sometimes with bigger capacitors - I certainly don't recall even getting a tingle from the supply (or caps). Voltages below 48V are classified as Safe Extra Low Voltage (SELV) - essentially, SELV voltages are sufficiently low, that an injurious accident is exceptionally unlikely. The circumstances required for injury are difficult to achieve - generally needing electrodes penetrating the skin, or a large area of skin wrapped in metal foil.
hello everyone, let me clear all this up, i had rubber gloves on (dish washer gloves) and i slowly experimented with what i could touch. I could replace the fan, ( with sometimes bumping my hand on the cap) with good rubber gloves... its a small issue.... as farmer cal said, just use common sense
I also woulkd like to apologize for starting all this
I also woulkd like to apologize for starting all this
Mermaidman
Diamond Member
- Sep 4, 2003
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gsaldivar
Diamond Member
- Apr 30, 2001
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Originally posted by: Mermaidman
No big dealNo need to apologize.
I agree - there's no need for apologies.
With any tech-oriented forum, there are always plenty of people who are "experts" in their fields. The simple fact that we have thousands of them here means that even simple questions can often turn into pissing matches among the gang here.
Despite some of the egos, you'll find that many of the people here really are the among BEST in their field. You'll get used to it.
Welcome to Anandtech JoeFahey!
:beer:
The capacity of the capacitor does not enable it to charge any more voltage than any other cap. The only difference is in the time element involved in the discharge cycle.
I know of no I repeat NO manifacture of powersupplys that does not put beeder resistors across large capacitors expecially those in series to equalize the voltage drop across the capacitor and when the input voltage is removed they discharge at a very fast rate.
If AC is used to charge the 1000 mfd cap it will charge to the peak voltage of the source and not the RMS of the voltage applied, when charged with DC it will only charge to the voltage applied because there is no peak to peak voltage in DC. The caps in a power supply are in the filtering circuit to remove the AC rippple that may be on the DC and this is on the DC part of the supply so cannot charge to more than the DC voltage applied, in the case of a switched supply is around 19 volts before regulation.
I was not owned by the statement quoted, 24 volts DC is not now or ever has been dangerous, the only way to get even a shock from the PS is to leave it plugged in and get into the primary side of the transformer to get a pretty good jolt but not fatal or harmfull and this is not likley as the wire is insulated and the connections to the supply hardware is not out in the open.
I think there are to many on this board and others that think they know things that they dont and give poor advice.
To the origonal poster, dont worry you will not get killed from changing the fan in your supply,
I have designed, built, repaired supplys from 1.5 volt to 25,000 volts so I am speaking from years of experience not just a person that has read someone else that was wrong and chose to repeat the wrong information.
OWNED?? I dont think so, the person posting this is ignorant of the workings of power supplies. Or the workings of capacitors.
Bleep
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