Some cases come with power supply unit pre-installed for you. Likewise, if the case you are using has been used before, it may have a power supply already installed. In that case, you only need to make sure it is an adequate unit for the computer you intend to build. Also, if you are building an ATX machine, you must make sure that the power supply is an ATX power supply.
If the power supply is not already installed, you will need to install it now. Here’s how:
- Take the power supply unit and line it up for placement into the PC case. The fan should blow toward the rear and the wires should face forward.
- Insert the PSU into the case. Sometimes this takes a little maneuvering to get it into position.
- Once the unit is in place, check the back of the case and make sure the holes on the rear of the PSU line up with the screw holes on the case. If they do not, you may need to turn the power supply over.
- Using your screwdriver, tighten the PSU down using standard chassis screws.
- Make sure the voltage is set correctly. There is a little switch on the back that lets you switch between 120 or 220 volts. In the United States, its 120. If you are in a country overseas, its most likely 220. If you use 220, make sure the cord is rated for it. It should say on the side of the cord. Its easiest to just check this now while you’re thinking about it.
The information is not complete. I am trying to find out whether the fan should be facing up or down, but find here only “The fan should blow toward the rear”, which is not helpful, as this refers only to one type of fan that points to the rear. Most of the power supplies nowadays are of the model that has a fan that points upward/downward and I am trying to find out how it should be placed.
I assume that you are talking about a large fan on the top of the power supply. This fan should face inwards towards the middle of your case. It should never face the top/bottom wall of your case.
it can be facing the outside if the case has got a vent for the fan to blow out to cases that have this fuction have better cooling becase the hot air from the psu is blown out of the case
also, on many psu’s, the large fan (120mm or so) sits facing the cpu, to assist the cpu fan in drawing off hot air from the heat sink
It should be placed with the fan on the bottom.Facing up doesnt help much.Most power supplies have 2 fans.One at the rear blowing out and the bottom fan i beleive suck up through the power supply so the hot air blows out the back of the power supply.This way it removes alot of hot air from inside the case.That is how mine is set up.
Heat Rises… fan up in most cases
Yes well this is a tutorial on building a pc so i would think some discussion about the type of power supply unit. e.g my son is going to buy a mod case with a few extra led fans and lights and well u know all the rubbish stuff, where do they all plug into do i need a special power supply etc
Nope, this stuff is all connected using 4-Pin Molex as far as i know, and every case has those. You might want to get a PSU with a slightly higher wattage because the mods will use some watts.
Yes it should all run from 4-pin molex plugs. Case mods (Lights etc.) commonly use very little wattage: A common cold-cathode tube 5-15 watts, fans about 5 to 10 watts if that, LED lights a fraction of a watt. – It’s very unlikely that you’ll need a better PSU.
If you don’t have enough molex plugs you can buy 2 and 3-way splitters for very little $.
The fan can face upwards /forwards (toward boards) without any troubles at all. The fan on the top of the power supply is not going to push air, it is going to pull, so it will never do anything but help. As for the fan on the back, most still have this, as it is the exhaust fan. It will be on the switch panel face of the PSU’s box. It is best to find a supply that properly fits your case, and has all the correct wiring/fan arrangement/size factor to fit your application. This way, it is a simple mounting and plugging in to get going on the rest of your build.
I have a quick question. If I get a powersupply that is a 500 watts and my computer doesnt need it will it hurt it? or is it ok to have?
No problem, the power supply will use as much as it needs, if your pc uses 80 watts, it wil feed 80 watts. If your using more than the PSU can provide, you got problem though.
David: I know this is a little late, and you probably already have this information, but for future reference if you get a power supply that’s more than is needed, it won’t hurt anything. If anything, it should allow the power supply to run at a lower rate, which should improve it’s efficiency (and lifespan).
About the positioning of the power supply, and which way the fan should point – that’s going to be determined by the screw holes in the case, isn’t it? I mean, if the holes only line up one way, that’s the way it goes in. Or are there power supplies that are made “upside-down”?
more power the better David
Power supplies are rated a certain wattage because that is the maximum wattage the power supply should ever be required to put out. If you have a computer that uses 350W and you have a 750W supply it won’t hurt it one bit. The supply will only put out 350W even though it is rated for 750W. What matters is that the supply maintains the correct voltage outputs. The current drawn, and therefore power output, will be determined by the impedance of your system.
Actually it’s not a good idea to have a power supply too large. Power supplies typically are most efficient when operating at around 50% of the rating. So calculating how much your PC pulls and buying a PS twice that is the best bet. This also gives you some headroom should you add or upgrade components in the future. PS ‘s can also behave poorly when operating way below their peak wattage.
I have a dynex 400 W, the fan is on the top of it, but it doesnt match the screwing of my tower. If i turn it upside-down though, it matches up with the screws, and the fan faces down. Is it bad to have the fan facing down towards the bottom of the tower?
Roxas; a rather late reply: I’ve only just read this article. (There’s so much valuable content on PC Mech it would take years to read it all it seems.)
If your fan faces down towards the bottom of the tower; it means that it should be drawing air from the inside of the case, over the components inside the PSU, and blowing the heat that they emit out of the outlet on the back of the case.
Provided that the air direction is from the inside of the case, through the PSU itself, and to the outlet and the world outside, you should have no problems.
I have installed the PSU and I have installed the rest of the hardware, but when I turn the switch “on”, the computer won’t start. Do I need to configure the PSU so that the motherboard can run? In fact, the PSU fan doesn’t start either. What can be done?
Protocliptik: When you set the PSU switch to “on”, it applies power to the motherboard but it doesn’t cause the system to actually start running. To do that, you need to proess the Power/ON button on the front of your case. Once you do that, your PC should hum into life (sound of the PSU, hard drives, optical drives, CPU, and case fans all whirring into action).
Note: Some motherboards have an LED on the board which indicates that power has been applied (see your motherboard documentation). If you want to verify that power has been applied after you set the PSU switch “on” and before you press the Case Power switch, then check this LED.
You may want to check the wiring of the pc.If the connection is in the wrong position it will cause the pc not to start.Try reversing the power connection of the switch.It may be connected backwards which will keep it from starting.Its a quick thing to do to know if you power supply is good.I think i did it once and i had the connection backwards and it wouldnt turn on.Try it or double check the manual to see if you have it right.If im wrong someone please tell me.
I got a new HD that was Serial ATA and has that kind of power plug instead of the old 4 pin style. I did not have a power cable converter to hook it up to my old power supply. I got a power supply from my Brother in law that had the right kind of power cable to use until the converter comes from monoprice. I hooked everything up (MB, Video card, DVD drive and the new HD.) My old ower supply was 300w this new one is supposed to be 600w. However it can only seem to power either the DVD drive or the motherboard. Am I right in thinking this PSU is faulty?
Chris; without actually seeing it and testing the power supply’s outlets that is difficult to answer.
Use a voltmeter to check the PSU’s outlets. If you get no reading whatsoever on one or more of the outlets then you may assume that the PSU is indeed faulty.
Hi Sharon,
I am new at building a PC, have changed parts before, video, memory and ect.
I just bought a Ultra Power supply tester, I plugged in my motherboard connector into it all the light were on except the -5 volt light does this mean i have a bad power supply???
Also, having a problem finding exact location for the LED switch and PW switch on my mother board. I have a gateway computer with ht2000 motherboard made by ECS model #mcp61am. Can you help with this connection.
Thanks for you help!
ray bloom
Hello ray. ‘Sorry for the late reply; but I don’t check the entire comment list of PC Mech every day
(‘Sorry to start off a bit sarky.)
- Anyway; moving on: The absence of a -5V supply is becoming quite commonplace recently on a number of boards. – Not having a -5V supply probably won’t be any type of cause for concern in 9 out of 10 cases.
With regard to the location of the connections for your “LED switch and PW switch” I’m afraid I can only advise you to check your motherboard’s manufacturer’s documentation.
David:
The power supply may have alot of power but it will only use as much as the computer needs to run. It will let it use less power which will greatly increase the lifespan of the power supply.
Ok. So the fan points into the case. But I am considering buying a Cooler Master HAF 932 case which has places for both bottom mounted (default) and top mounted PSUs, and there are grated vents both directly below the expected location of the bottom mounted PSU and directly above the top mounted PSU. I assume that in this case I would install the PSU on the bottom of the case with the fan on the bottom (facing AWAY from the motherboard). This way it would suck cooler air in from outside the case and exhaust it out the back. Right?
P.S. Any suggestions for a good, reasonably priced PSU for an intel i7 system i’m building? I’m looking for 650-700W and hoping to spend about $100 but will spend more if necessary.
I can’t quite get my head around what you mean about sucking cooler air in from outside and exhausting it out the back; probably because I don’t feel that well and it’s late at night here.
A PSU suggestion for you: Click here.
is a 500W PSU enough for most modern games?
That depends upon your graphics card: If you’re running multiple graphics cards, such as Crossfire, I suggest something meatier just to be on the safe side.
It all depends upon the wattage that your entire box is using too: Calculate the total peak wattage used by all components using Ohm’s Law<, and fit a power supply, the maximum rating of which exceeds that figure by around 30% at least. – That way you can’t go wrong.
The video card is a Sparkle GeForce 9400 GT. Not sure on the wattage required on it…
‘Nice card.
Now I’m going to add another variable to the equation: After you’ve asessed the total peak wattage of the rest of your system using Ohm’s Law… If it comes to less than 200W, then I would imagine that a 500W PSU would be OK with that card. – Provided that it’s a good quality PSU with a 500W continuous rating; rather than a 500W peak rating: A cheap PSU with a 500W peak rating might not be able to do the business: it might not be able to supply the required power continuously. (Assuming that you’ll be playing Crysis etc at full resolution.) When the power-drain peaks it might not have what it takes – Maybe causing a BSOD even.
In conclusion then: A good quality 500W PSU should be just right. Anything less may well cause problems.
I’m building my first PC and found this article to be wonderful! I do have a quesiton about the orientation of the PSU though. I building an HTPC, and the case has a vent on the wall next to the spot for the PSU. Should I line up the PSU to draw nice cool air in from this vent instead of drawing air from inside the system? I’m asking because that’s how I have it oriented, and I’m having system stability issues. Would this might help?
In my opinion no; because if you’re drawing room-temperature air in from outside then where is the hot air going? If it’s going inside the case then you’ll need a large number of cooling fans to compensate, your CPU cooler will be taking in part hot air and will have to work a lot harder, and your motherboard will get hotter faster, as will your RAM, graphics card…blah.
…Unless you can mod your case so that the PSU draws in air from outside and blows it back out. – In which case I suggest adding an additional case fan to extract the air that would have been extracted from inside the case by the PSU.
I know this thread seems dead but was looking for similar info to that which the first poster was referring, my understanding is that you can have a 1 fan psu with the fan on top blowing the PSU heat straight up (thereby taking advantage of basic thermodynamics, ie, heat rises) but you either have to get a case that supports this or is modded to have a hole at the top of the case for your fan. you could do it 2 fan as well I suppose (one on bottom sucking air in and then the top blowing out) but I have never seen one like this, does it exist? the vent grates for the 1 fan PSU are still on the back though so that would create a draw to pull system heat back in from the exhaust fans. lastly any good clear acrylic PSU’s out there?
OK, My original post to this thread was on March 30 (see above). Since then I have built my computer and learned a lot. The big fans on the top (or perhaps bottom) of the power units always blow IN to the power supply and the air is exhausted out the back of the PSU. If the PSU is mounted at the top of your chassis, the big fan points down toward the motherboard. It will suck in hot air from the chassis and exhaust it out the back. This will help keep the chassis cool but will subject the PSU to warmer air (probably not a problem). If you do a bottom mounted PSU the fan again points toward the inside of the case sucking from the case out the back of the PSU. HOWEVER, if you are lucky enough to have a case that has vents directly above a top mounted PSU or directly below a bottom mounted PSU than you can do the exact opposite and mount the PSU with the fan pointed to the vents so it sucks air from outside the case then out the back. These cases are always the higher end gamer cases that will typically have side vents and extra fans.
I built my i7 system with a Cooler Master HAF 932 case and a Cooler Master modular 700 W PSU. I cannot say enough good things about that case. For $160 it is totally awesome. The PSU is mounted on the bottom with the fan pointed DOWN sucking in air from vents under the case made specifically for this. (The case is elevated about an inch on sturdy legs or wheels so air can enter from the bottom.) The case stays cool, cool, cool, and the PSU gets cool air straight from the outside of the case (not warmed up from all the other heat producing components in the case). This case come with two intake fans (side and front) and two exhaust fans (top and back). The PSU acts as a separate intake and exhaust fan for itself. It also has special holes for liquid cooling if that is your thing… If you want to see a video of this case search for it on the compusa.com website.
I have a question about power supplies…
IF THE POWER SUPPLY IS NOT CONNECTED TO ANYTHING..and you plug the power cord into the back
does the fan in the power supply run? It would seem logical to me that it should but I just bought a new
power supply and wanted to check it before I put it in the computer so I connected power cord,checked the voltage selector…etc and made sure the outlet was alive but the fan does not come on in the power supply.
Does the power supply have to be connected to the mb/cpu to work?
Hi Bill
The ATX power supplies in use these days are switched on and off by the motherboard when it shuts down and starts. Therefore simply plugging the power cord into the socket won’t in itself make the PSU start, run the fan, etc.
Having said that; there is a way to trick the PSU into thinking that it has been switched on by the motherboard. For more information on this I suggest you see my blog article which is part 1 in a series of 2: ” How to Test a Power Supply Unit: Part 1. Testing Voltage Output. That article gives you full details of how you can test a power supply for (unloaded) output without connecting it to a motherboard. Best of luck.
What kind of motherboard should I get that would fit an Intel quad core q6600 and a modtek alien x case?
I’ve heard good things about the Gigabyte 8I915PL-G and the Abit IS-10, But im no expert… so what should i do?
Both of those boards are a bit dated; supporting slower and more expensive DDR 400 RAM and Intel Pentium processors. – So yesterday.
If you’re an Intel geek I would suggest Gigabyte GA-EX58-UD3R iX58 Socket 1366 7.1 Channel Audio ATX Motherboard that supports the latest i7 processors and much faster DDR3 RAM.
Incidentally; I thought it strange your asking about a motherboard in a power-supply article – ?
Reading your question again; and not getting carried away with myself, I would alternatively suggest, for the processor that you mantioned, Gigabyte GA-X48-DS4 iX48 Socket 775 8 channel audio ATX Motherboard, which could do the trick nicely; provided that it fits in the case that is.
I have a question. I know it may seem kind of dumb but I’d rather ask it then make more work for myself later. Okay so if my motherboard needs a 24 pin PSU and the powersupply that I am looking at is 20+4 pin will it be compatible? I saw a picture of the 20+4 pin and it has 24 pins, so I assume it will be compatible, but I just want to make sure.
It’s not really a dumb question at all Tim: It’s a valid point to ask about, and no doubt something that will benefit others to know.
In answer; yes, a 20 + 4 pin PSU is fitted with a 20-pin P1 connector + a 4 pin P1 connector extension in order that it can be compatible with both the older boards that only have a 20-pin P1 socket, as well as the newer boards that have a 24-pin P1 socket. Plug in the 20-pin connector first, and plug the 4-pin connector in afterwards.
“Which end do I plug the 4-pin into?”
The P1 socket will only fit both connectors together 1 way, unless you use too much brute-force; (NOT advised.) so experiment and see which arrangement goes together easily. There might even be instructions that came with your motherboard and/or PSU?
“There are 2 (or 3) 4-pin connectors on the low-voltage wires from my PSU: Which one do I plug into the P1 socket?”
The case with some PSUs is that there are 3 x 4-pin connectors. You’ll notice that 2 of those 3 connectors look exactly the same. – Those are both the VLT (Very Low Tension) connectors which power the CPU. Most [AMD] boards have only 1 socket that these will plug into, and it’s situated nowhere near the P1 connector, so you won’t accidentally plug the wrong plug into the wrong connector unless you’re very absent-minded. 1 of the 2 will simply not be used unless your board has 2 individual processors or something like that.
Other PSUs have only 2 x 4 pin connectors: 1 for the VLT supply to power the CPU, and the other as an extension of the 20 – pin P1 connector. The trick is to first plug in the one that supplies your CPU in this case (It’ll be extremely difficult to plug the wrong one in there.); which leaves only one more, which must be the P1 extension. – The wires to the P1 extension are usually bunched tgether with the 20-pin P1 connector’s wires anyway; so it is usually fairly straightforward.
Remember: if it won’t go properly, don’t force it. – That applies to everything with regard to computers: I have the T-shirt from my early days.
If you have to force it then I will put money on the fact that you’re doing something wrong. Step back, have a cup of tea/coffee – and a smoke if you smoke, then return to it, think, and try again in a different manner.
Please help I installed a new dynex ATx 400 watt power supply to put in my old hp pavilion 500 computer. It has all the same connectors to reconnect my floppy and cd rewrite drive. I got the power connected also with the 24 to 20 pin adapter. My problem is with the fan. My old bested ATx 1523d power supply had a connector labeled fan c but the new one does not will that matter? I do not want to try to power it on because I’m concerned that it could damage something. Do you have any advise. Im new to this and now using my itouch to try to find an answer.
According to this page:
“NOTE: This unit is wired with the connectors above. Your power supply may not have all of these connectors. In that case, the unused connectors can be tied off with no problem. The important thing is to ensure that this unit has at least the connectors that are connected to your motherboard and peripherals with one exception. If the original has a P7, P9 or FAN/C 3 Pin connector…no problem. The replacement unit operates without this connector and it is not supplied.”
Just to add: Bestec is to power supplies today what Skoda was to cars in the 1980s. – I just thought it worth mentioning.
I’ve got a AM3 socket Gigabyte m/brd and it has a 24 pin power connector and also an 8 pin connector. the diagrams look as if the 8 pin connector is just two 4 pin connectors side by side.
My PSU has a 24 pin connedctor and only 1 4 pin connector. Should i be looking for a different PSU? Or, will the board work OK with just one 4 pin connector.
‘Maybe you’ll need a new PSU: Maybe not. Post a link to the motherboard data and I’ll probably be able to tell you. As yet I have been given no idea which model of board is in question.
I have a red car. What engine would be best for it?
(Someone’s going to say “A red engine”. Wait for it…
)
mobo is Gigabyte GA-MA790FXT-UD5P see
http://www.gigabyte.com.tw/Products/Motherboard/Products_ComparisonSheet.aspx?ProductID=3005 for summary and
http://www.gigabyte.com.tw/Products/Motherboard/Products_Spec.aspx?ProductID=3005 for spec.
soory if the original question was vague.
The PSU i’ve had recommended is ATX V2.2 compliant – this seems to be the update to the spec to add the8 pin connector
PS – probably the best engine is a deisel!
That is one nice board!
I think you answered your own question; but read this anyway.
(I am so envious of you having that board!)
the tech guys where i bought the board say that it “should” work with the old style PSU with the 4 pin connector in one end of the 8 pin socket. I don’t fancy trying that so i’ve bought a PSU with the correct connectors.
thanks for you help and advice.
Roger
So what is the difference between having a psu with a single 12v rail and one that has multiple 12v rails?
Extra 12v rail(s).
Well I get that, but is there an advantage to having more/les rails? Will it be more of a hassle to install and use a PSU with multiple rails than to get a PSU with one rail?
There is one thing that alot of people do that i never understood.They spend a bunch of money on ther parts and when it comes to a power supply they usually buy a cheap power supply.Its a part of your pc that is very important.If anything you need to spend over a hundred bucks on a good psu.You may get one a little cheaper but its not a good decisionThen they wonder why their machine doesnt work very well.Spending a grand or so on good parts and 30 dollars on a psu is stupid in my book.Most people dont realize how important the psu is.My buddy built his pc and used a case with one included.It was a cheapo 30 dollar psu.He wondered why his board shorted out and stopped working.It aslo took out his video card .I have pounded it into his head and the next build he did he did the same thing.Im just waiting for it to happen again.He just cant get it through his thick head and i just dont understand.It will happen soon and he will be doing the same thing again.Building a new pc.
Indeed, the power supply is one of the most important parts of any PC build (others being motherboard and GPU). If you don’t have a proper supply, it simply won’t work, or even worse, it could outright destroy other parts (or, worst case scenario, put the house on fire). Also, wattage really doesn’t matter. 520W with enough amperage on the right rails is enough for everyone.
Hey GreatEmerald
Once again I agree that a decent-quality PSU is always a good thing: However, if the PSU used is a bad-quality PSU then it’s most-likely that it won’t be able to continuously supply the wattage that it’s rated at.
While in numerous cases it has been known for a cheapo PSU to fail when its rated wattage is continuously demended from it, and in rare cases for it actually to blow up, it’ll most likely just not be up to the job expected of it and therefore will fail to provide the required wattage, causing a blue-screen-of-death or something similar.
Whilst this may strain other components, it is unlikely in itself to cause damage. What will cause damage is when the poor-quality PSU finally ‘decides’ that it can’t handle any more strain of being asked to continuously supply more wattage than it is actually capable of doing, and internal components fail causing voltage-spikes on the supply-rails, which in turn damage the sensitive MOSFET-based integrated circuits (chips).
Furthermore you state: -
“Also, wattage really doesn’t matter. 520W with enough amperage on the right rails is enough for everyone.”
…So you would say. then, that a person running a quad-core 45nm-fabricated processor, with 5 hard-drives in a RAID configuration, using quad-SLI graphics and playing Call of Duty at maximum screen resolution with a high-frame-rate only needs a 520-watt PSU? Maybe they’d be playing for a whole minute if they were extremely lucky.
What do you mean about “520W with anough amperage”? – At 520 watts the amperage is dependant upon the voltage: -
At 1.5 volts the amperage is 520W/1.5V = 346.667 amps.
At 5 volts the amperage is 520W/5V = 104 amps.
At 12 volts the amperage is 520W/12V = 43.334 amps.
According to Ohm’s Law those amperages are fixed values at those preset voltages at a wattage of 520 watts. – However, if the PSU were a cheap and nasty model that was rated at 520W peak-output, then the 520-watt output could not be maintained continuously, and the wattage would drop off, resulting in a proportional-reduction of the current (Amperage) supplied to the circuitry, which would cause some part to function inefficiently and disrupt the program, causing possibly a BSOD or some other type of failure.
Hey Leigh
I’ve not been back to this thread for a while as I assumed that nothjing else was going on here: It’s good to see that there’s life in it yet.
While I agree that making sure that the PSU used in any computer you build is a good and reliable quality product is a necessity; especially if you’re building for someone else, the quality of the PSU is not linked in any way to short-circuits on the (mother)board: It’s just as likely to have a short-circuit on a motherboard if you’re using a top-quality $1000 PSU as it is to have a short-circuit on it if you’re using a $10 chinese-made no-name PSU. A short-circuit is a short circuit: It’s where two or more different, usually opposing polarity, currents meet, due to either something separating them coming adrift so that the two meet, causing heat to build up and burn something out, or something having electrical conductivity dropping across the two or more differing currents/polarities and connecting them together, with the same result.
I would suggest that, if your friend’s (mother)board shorted and burned out, then it was due to either a loose screw or wire/piece of solder crossing two supply tracks, or simply bad (mother)board manufacture: In which case he should return it to the manufacturer for a refund or a new board.
I build my first PC(mid tower) a year ago, using a 450 w psu from Corsair. It has a lot of wires I don’t need. I am thinking of getting a different psu from Thermaltake that has the same wattage but, it’s a modular. Are Modular power supplies good?
As with all power supplies; it depends upon the make and quality of any given unit.
just hooked up new dynex ps to 6 year old compaq. sorry, not a tech wiz. have to text all this cause computer wont work. so nothing is happening. nothing turns on. i try and retry the connections, nada. how can i tell if the pu was really the problem?