How to Easily Test a Computers Power Supply with Simple Tools

If your computer is not turning on or working properly it may be the ATX power supply is at fault. This video teaches you how to remove it from the computer and test it using only an inexpensive multimeter.
There should be +12V, +5V and +3.3V DC output lines on every working ATX power supply. If any of these values stray too far beyond its proper value (half a volt or more), you probably have a power supply issue and it should be replaced. For example, if your +5V line is measured at only +4.1V, your PSU isn't delivering power as it should and that indicates a problem.
We also have a video that teaches how to use an inexpensive power supply tester and where to get one here: • Computer Power Supply ...
If you do not have a multimeter to measure voltages you can get one for as little as $5 if not free, as Harbor Freight Tools often publishes coupons for a complimentary unit just for visiting their store.
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How to Easily Test a Computers Power Supply with Simple Tools.

[@danf1572]

Best explanation of testing power supply and using volt meter on KZbin. Exactly what I was looking for. Must watch.

[@dyoung411]

Excellant, it's a great help. Thanks for providing a straight forward process, explained well.

[@dlgang]

Excellent introduction to testing power supplies! Good job with the video!

[@TrehanCreekOutdoors]

Great help to have a consolidated chart that show so many power supply configurations. Thanks for sharing!

[@mjb12141963]

Paperclip told me what I needed to know. Thank you.

[@ZackyDog]

The paper clip test worked. Thanks!

[@hankus253]

Got my touch pad wired and installed, per your video instructions. Installed limit switches on the X and Y axis. Today I finished building the table I plan to set in on. And within the next day or two, hope to have it running provided the sun doesn't come out and make me want to do something else. :)

[@indiracassie2657]

gr8 video, im teaching my class voltages, this helped alot. Thanks

[@W1llN4sh]

Nice picture of the different connectors and colour coded voltages, 👍🏻

[@eloctocs13]

Great stuff Steve. Your channel has helped me a bunch. Scot

[@JohnJBurnettJr]

Thank you making this video. I found it very helpful.

[@leonardjohnston4116]

Excellent demonstration and a calm explanation - thank you!

[@ernststavroblofeld1961]

The video starts at 5:53

[@GuruBrew]

+Ernst Stavro Blofeld Really? Maybe it started off were it was watch partially before.

[@ernststavroblofeld1961]

+GuruBrew Well, before 5:53 there is no testing as stated in the title. However, what, in your experience, is the third most likely part to fail in a PC-PSU, after the fuse and the capacitors?

[@jerymie6708]

thank you.

[@iltis3012]

Well explained,Thank you so much. Keep up the good work.

[@kerrycamargo4475]

Thank you for telling me about clip for power source!!!!!! was ready to give up!!

[@paulvogdes2367]

Excellent! You showed everything I need to know. Looks like I need a new PSU.

[@enufots4621]

Does the power supply tester (not the multimeter) provide a load test? Instead of a molex HDD drive connector I have sata power cables and it's very hard to get a voltmeter probe into those connectors for measurements. Do you think testing all the voltages on the larger motherboard connector is good enough? Thanks!

[@jaswik2023]

This was actually helpful

[@Phrophesy]

Excellent video. Thank you.

[@davidgiffordsr.930]

I agree with other comments, Very good technically speaking and also wanted to mention, Great video clarity, and orientation, Sound loudness good, clarity of speech also very good as well. Oh, the diagram was a nice plus.. Thank you very much.

[@shaheedpetersen6231]

Thanks. very informative. Straight forward. helped me stacks.

[@Bayhuntr]

On your diagram the PCI 6 pin express I’m getting 12 V 12 V and 22.8 V. Across the three sets of pins. I also noticed that one of my video ports is blackened on the where is connected to the motherboard. Is that 22 V an issue?

[@kemueltavarez4857]

Great job. Thanks man

[@boowonder888]

I got this working on 2 newer power supplies. The older ones (early 1990's I estimate) wont turn on by connecting black and green. It would be a big coincidence if they were al broken, wouldn't it? Which wires should I try to connect next? I got an older one that rates just 65Watts and has an on/off switch, I want to use that one for my projects so bad!

[@Mr4thetruth]

Great info, thanks :)

[@PorkyJones]

Nice video - thx!

[@ROSTOCKBEL]

Hi always come back to you always very useful information my problem is my PC boots up and everything seems to be ok in the tower but Monitor is completely dead will not even light up not showing anything

[@gmungaming9763]

Big help thank you !

[@MHM4V3R1CK]

This was a great help! Thank you!

[@paultuffin5781]

Simple instructions, simple clear test....all good thx.,

[@gregmyers1220]

XSimple test on your power supply. Well made video.

[@mscir]

My power supply has no green light on the outside near the ac plug when it is plugged in. I opened it up and found that D103 is completely blow up and fried. Do you know if a power spike would blow D103?

[@itzgilbert4765]

when i test it with a paper clip it works but hwen i put it in the p1 motherboard it has a low sound and no funs spin but i think something with my mother is wrong because it doenst send the power to my computer

[@curtyahnke5378]

good teaching and learning. if meter probes are too big, insert a finer wire, and touch that wire with the probe.

[@bamber2808]

Great Video

[@joshgehman232]

I don't see any blown capacitors in my PSU. I opened it up and cleaned the dust out. I don't have a soldering iron or a multimeter :(

[@edsmith7392]

Great video. Thankz

[@karandeepsingh8635]

Nice work! Subed!

[@Kattmat]

Some PSUs actually don't have a fan running by standard, like those BeQuiet PSUs that fans are off until a certain temperature is reached.

[@Pyridox]

A lot of supplies need a load on the +5v side in order to function.

[@c.rutherford]

I connected the green wire to several black wires, and the power supply won't turn on. Helpfully, the power supply has NO on-off switch in back either. Does this mean its dead? The PC started rebooting endlessly this afternoon. I shut it off and restarted and it came back up, so I ran out and bought a backup drive and started backing up the PC. It got to 1% and then the PC turned off, never started again.

[@Cotocon1]

Great Vid! Thanks - Question: I'm getting a reading of 11.33 on my +12v is that too low ?

[@pinkukumar2575]

Yhks

[@CybernatonEvolution]

My PSU shows double the voltage values and my PC basically doesn't show any signs of power at all when I connect it even when I tried breadboarding. I honestly don't know if it is the PSU or the motherboard.

[@Brincandopabajo]

Thanks!

[@Livetoscream]

My Negative 5 Read Positive 5 volts. Everything else was fine... should I replace it?

[@gianandreimarco4331]

Was the power switch working? I need it for my assignment

[@gearup603]

Pin 8 PS_PWRGOOD use for what and how the connection?

[@fckinnonstick9919]

Thumbs Up! Thanks :)

[@lessopinion9707]

ATX supply's are notoriously noisy electronically, I have tried to use then to power audio equipment with no luck. Show us how to clean them up electrically for use as a audio PSU. Like your stuff!

[@Layarion]

Could I just attach 3 fans to the PSU to get an acceptable load test?

[@afjachannel6895]

tqvm sir... :-)

[@NOUFALkakkad]

Thanks sir

[@Layarion]

Could I just get a massive resistor to load test it?

[@plastic1492]

Mine passed all the voltage checks > i had another one to try and it worked fine > my symptoms were i had to push the start button in 3 or 4 times and it finally started > also every so often the p.c. would shut down on it's own . thanks for the video ..

[@Mandy_39]

How long would it take before shutting down

[@hankus253]

Steve just a thought. If testing under load is more telling of a power supply's condition, would it be okay to use one of the unused power plugs going to a disk drive to gain access to the +12V and +5V , for a really simple and quick check? Those connectors have Yellow, Black and Red on them. The 3.3V would still require unplugging the mother boards 20/24 pin power connector to get at, but you would at least get 2 of the critical 3 voltages tested without unplugging anything.

[@GuruBrew]

Could work i suppose but the load would have to be enough to taxi the PS on all voltage lines. How is the CNC coming along?

[@AntonioSalazar-db1eb]

@@GuruBrew testing under load seems like a proper test indeed.

[@biologicalstatistics3320]

I am not having a problem with mine, but this seems a pretty simple tutorial to learn for kicks.

[@yumpinyiminy963]

FYI - Some new efficient CPU's fan(s) will not run until a certain power draw or temp is reached. Check mfg spec sheet.

[@cncbuss1]

Thanks Steve. I've learned something new today. My Dell computer turns off by itself and is difficult to turn back on again. I will need to troubleshoot my power supply. Would a faulty PS be the first thing you would suspect? Could it be the power switch?

[@GuruBrew]

I find that power switches seldom cause problems. Your power supply may be going but might be hard to check if it only happens at random times with a load. Might also be a heat related problem (like fan problem) especially if its a laptop

[@boowonder888]

what happens when you accidently cross the wires.. will the short circuit kill the ps or will it just shut off? The low voltages cant destroy the ps, can they?

[@NBryanBlack]

Seeing that the voltmeter does not test the PSU under load, wouldn't it be better to test the terminals from the back of the connector while the computer is (trying to) run? If you have thin probes (or paperclips connected to your probes) you can touch the terminal through the back of the connector. Yes, you have to be careful not to short your probes together, but since the PSU is still sealed, there shouldn't be any lethal voltages present-worst case is + and - 12volts. Wouldn't that solve the "under load" dilemma? Maybe test in vs. out of circuit to see the difference? Any reason not to do it this way?

[@jsc3417]

the computer really isn't at a 100% duty cycle even when it is running 'heavy' applications. In most cases, the voltage drop can be so quick that a DMM won't even able to catch it, the best way is to use a digital O-scope, with 10ms per division, trigger at 10% below nominal voltage while stress test the PC. e.g. if you insert the probe into the 12V+ feeding into the GFX card, if at anytime during the stress test, the o-scope is triggered due to voltage drop below 10.8V, the PSU is likely having regulation issues.

[@rpdigital17]

13:10 I just tried to figure out yesterday, why Dell Optiplex 390 PSU does not start. When I tried to move the case top back, I got shocked 225 VAC for a fragment of second. That was not pleasure at all! So beware! The problem was in rectifier ic, that was shorted, the + and - outputs were shorted, so PSU ground was hot. Today I used my tester-screwdriver, it did show me, that all radiators and electrolytic capacitors were hot. All the transistors did not show anything to the diode test,so they may be also burned down. But be careful with the dead PSU, it may be still alive in the bad way!

[@elamriti]

wat about a at psu ? in a 486

[@techie146]

thanks😙😙

[@yambo59]

Good video, though as he says this is not under load - anyone not aware should know this kind of test tells you voltages and give some idea of basic rail stability in an UNLOADED state, not under load. I do these same tests and ive had them look ok until I start placing the supply under load and if say the unit has capacitors going out or a power mosfet transistor acting up under load you may not even see the fluctuations. But theres only so much the average person can do with a multimeter, proper PS testing is done with equipment far beyond our scope -- but its still a good idea to know as much as you can about your PC's power supply, you may get lucky and catch a fluctuating, no volt, low or high voltage rail or some other anomaly and you can bet if its not looking good on a multimeter it certainly wont be doing any better under the load of your favorite game. I only say this so someone that may be having problems with their PC acting wonky and they think it might be the power supply assume because it reads right with a multimeter all is well, there could still be issues. I have a 500 watt supply right now that was running the computer it was in seemingly OK, but as luck would have it I found a deal on a PS I wanted to upgrade to, and out of curiosity I opened my old one up and though it seemed to be running ok two capacitors were showing signs of starting to bulge and leak, felt like I dodged a bullet there as caps are one of the electronics industries most common components to fail and sometimes cause a very expensive light show as it and your motherboard etc. go all 4th of july. All this said, it certainly does no harm to have a look at your rail voltages. BUT I DO NOT encourage opening a PS case because its very dangerous especially if you dont know what NOT to touch. I only do it after making sure ive bled all the caps off by UNPLUGGING the power supply and plugging in my power supply tester, turning the switch on and letting it sit for about an hour or even over night to help bleed off the caps into the tester. Theres enough voltage in these things to seriously hurt you, so if youre not qualified dont even try it, have a tech savvy person look at it or just replace it and call it better safe than sorry.

[@marinmilosevic7708]

Thanks for remaining me after 7 years brake of foxing.

[@fatihtasdemir7812]

mine 2 power supply running won't. how to repair?

[@graygamingps4503]

I've ordered Skyrim and I'm really considering getting a Raedon HD 5750 graphics card and I need to find out what my PSU is so I k ow whether its providing enough for the card. Will the wattage be written on the side of the PSU without having to take it out of the PC? Thanks

[@elizabethparnell4724]

but can it run skyrim

[@graygamingps4503]

+Ryan P Everything else on the PC is enough to run Skyrim. I am sure the GPU will run it

[@aryanmasterrace4295]

+GrayGamingPS4 the wattage should be written on the PSU. same for the voltage lvl, and aci ratio

[@Waltriani]

So GuruBrew it's really necessary to disconnect all cables and take the psu out to test? I was hoping not. My son's computer is not turning on and the psu is one of this modern psu that has lots of cables and even the graphic (video) card is powered by a cable. So, it's a good amount of work to disconnect all to take the psu out. Thanks for the video anyway.

[@tuunaes]

If you don't mind risking PC's componenents to possibly wrong voltages/high ripple only that 24 pin ATX power cable of motherboard is needed.

[@Waltriani]

Ok, thanks. I ended up taking the psu out and testing. It turned on with the wire shunt/paperclip test. I tested all voltages and they were ok (5V, 3.3V, 12V , -12V...). But the computer still won't turn on. No sign of post, beeps, black screen, nothing. There is a stand by led on the motherboard lit, when I turn on the psu, but nothing happens when I press the power on button.

[@tuunaes]

Also measure 5V standby rail. (purple wire) Indicator on motherboard tells only that 5Vsb is enough above 0V to light it, but not enough to fry that LED. If 5Vsb is going bad problems in starting PC are typical: In early stage it might need more than one power button press/waiting after plugging cord to wall. With symptoms obviously worsening the more PSU's capacitors fail. When PSU gets power from wall it constantly provides that 5Vsb to motherboard. When power button is pressed motherboard then tells PSU to start fully. ("connecting green wire to ground") After starting and with voltages inside margins PSU then gives "power good" signal to motherboard triggering boot up process. I've once seen also empty "BIOS"/RTC clock battery on motherboard (likely CR2032) causing such problem so that would be one cheap thing to check. Also you could try starting with only essentials (motherboard/graphics card) connected to PSU and no drives connected to motherboard to bracket possible locations of problem. But list of PC's components and full model name&number of PSU would be useful. Besides bad reliability some worst PSUs can be literal fire hazards. And PSU tends to be the spot where too many people go cheap. If there's no special reason to suspect PSU if case has reset button switching its cable with power button would be way to make sure power button isn't faulty. Though if there's enough contacts visible in connector multimeter would as well tell if power button works. (should be ~0 ohms when pressed)

[@DKTechYT]

My fan moves only an inch, is it dead?

[@stargatefever]

i have s friend who had had to replace his psu 4 times..what could be causing them to keep burning out

[@1pcfred]

+stargatefever His PC may be drawing more current than the power supplies he is trying to use. Not every PC PSU can output even the current it claims it can. Or they are rated with loads on each individual rail, but not all rails at once. Manufactures state a lot of things to make their products seem better than they actually are.

[@lighttheoryllc4337]

Good info though

[@TheShadowBullet11]

I know I will sound really dumb fro asking this, but if you touch the paper clip while the power supply is on and under load will it shock you? Again I am so sorry that I have to ask this I just don't know....

[@1pcfred]

+Shadow Bullet No voltage coming out of a PC PSU should be able to shock anyone. It is all too low voltage. But the currents are pretty high, so if you plug the paper clip into the wrong leads that could cause quite a spark, if the PSU is on when you do it. It might be like trying to light a match between your fingers then too. Kinda hot, if you know what I mean. Maybe worse than a match? Electrical arcs are pretty hot stuff.

[@EastEndWatcher]

what if it doesn't have a green wire? a dell 250

[@1pcfred]

+EastEndWatcher Congratulations. You just learned why it is bad to purchase proprietary Dell hardware.

[@colinmaharaj]

6:31 not qupon, its coupon

[@hvacdr]

So i put my paper clip between ground and black and nothing happens. I plug it in and tried another cord that is for sure good. I know i got power. Im assuming i have a bad power supply. The computer worked fine a few days ago. Went to fire it up this morning and nothing happened.

[@GuruBrew]

Did'ent I say Green and Ground?

[@mitch19636]

Black is ground.

[@hvacdr]

Well the video was right in diagnosing my psu. But the bad news is my bad psu also took out the motherboard. Also a few fans had bad bearings and werent working. Im thinking the bad fans may have caused the problem.

[@wlorenzo1y]

hi how can I get in contact with u

[@ChrisD__]

wlorenzo1y You just did.

[@premielectronics9701]

In cpu where is fuse

[@seal3081]

my multimeter needles will not fit int he pins. What should i do?

[@ameyas7726]

seal3081 you don't need to fully insert, just touch the top metal part inside your probes can reach....alternatively get two alligator clip wires for each of your multimeter probes and use two more paperclips which will fit.

[@seal3081]

Ameya S actually i got it working a while back. Thanks though. Now all my power voltages are fine and the fans not working, so dunno why no power is going into the system.

[@ameyas7726]

seal3081 I heard multimeters are not 100% reliable tool to check PSUs...many times they will show normal output voltages when it's not so, as you will find if you checked the voltages on an oscilloscope. Or maybe it's a broken fan and your PSU is actually working!!!

[@seal3081]

Ameya S I have acess to an oscilloscope. If it shows up as normal, would you recommend getting a new power supply or not?

[@ameyas7726]

seal3081 I am really no expert but if the oscilloscope shows normal voltages for all the rails and still your PSU doesn't switch on when installed correctly in your PC motherboard...it could be a motherboard issue...to verify this get a spare new PSU (if you can, I think it's always handy to have a spare working one when you are self diagnosing your assembled PC at home, saves the trouble to run between different service centers), and see if it runs your PC....if not then it's definitely faulty motherboard.

[@christianfernandez7979]

I put the pin green and black it blows ahh not good

[@maxr382]

You should test the grey wire for 5volts. I had all my voltage go to spec, but grey was 4 volts not 5. Bingo~ fail!

[@davegregg1512]

Thanks for this. It’s my old Dell PC, no power at the motherboard. Has a terrific sound card so it’s still a useful old PC.

[@davevan8864]

t THANKS

[@gilian2587]

Power supply lead diagram 10:00

[@cyborg6294]

I think it is a lot better and safer way to work without a ring in the hand, correct me if i am wrong.

[@stevenbrown3002]

what the website i really want this video i am A Student ongoing my A+ and we are right on this topic now Power supplies so i will really this video

[@DeeegerD]

If you have to tell them how to take out the power supply and remove the case screws they really shouldn't be trying to fix anything ;)

[@ahsokatano6059]

+Digger D so true!

[@HKey_Root]

+Digger Don't recall in the vid any advice on fixing anything. "This video teaches you how to remove it from the computer and test it using only an inexpensive multimeter"

[@DeeegerD]

Philip Bedford If they have to be told how to take out the supply - they are also in danger of a shock from the capacitors... Best left to someone who's at least studied electronics as a serious hobby... Just saying.

[@JourneyToTheTruthandTR]

My standards are higher. If you can't at least swap out a water pump in your vehicle you probably shouldn't be fixing anything. Computer builds and part replacement are simple tasks that require inexpensive tools and really no training. Just a little bit of reading. Start to finish is maybe an hour tops vs multiple hours or days when working on automotive repairs. I think it's obvious that this video is for newbies. The paperclip thing is funny because you can use it to start military Humvees. At least in the 90s you could. I believe J and K were the female pins you would place it in.

[@mr-salty6145]

what if my fan ain't running what do I do

[@Yon_Jon5715]

Is it connected to the PSU and (maybe) the motherboard? Your motherboard might have a "SYSFAN" plug, or something.

[@Yon_Jon5715]

oh, maybe you meant "it isn't running" as in " it isn't running when I'm trying to do the test". I thought it doesn't run in proper use.

[@tuunaes]

Measuring just voltages is never enough for checking suspect power supply even if it's done with PSU under load. Proper checking needs oscilloscope for measuring also ripple. And if PC doesn't start at first try after cooling down/having been without AC power, but starts to need increasing number of power button presses that's sign of PSU likely being dying... Caused usually by failure of garbage quality capacitors in 5V standby line. Cheap low quality PSUs can easily fry most of PC's components so those symptoms should always be taken seriously.

[@Yon_Jon5715]

My PSU wouldn't turn on its own orange light, when I plugged it in to the wall power. It would turn whenever it felt like doing so, lol, maybe hours after. Is that what you are talking about? Also, when I do get to start my PC, I cannot control my keyboard and it gives me a message that it doesn't see a hard disk or something(I forgot the exact phrase because I did it a while ago).

[@Yon_Jon5715]

"BOOTMGR is missing. Press Ctrl+Alt+Del to restart", was the message.

[@tuunaes]

If PSU has power indicator light which should tell its ready to start that woud be obvious sign. When PSU is getting power it constantly provides 5V standby to motherboard. Power button in case is connected to motherboard which then tells PSU to start fully. 5Vsb misbehaving can easily prevent that. Also 5Vsb provides some power to USB controller/ports so it going bad can break at least those causing problems with USB devices. Once PC is powered main 5V rail is used for power. But in typical cheap garbage capacitor PSU it's of course hard to know if much anything in it is anymore working inside tolerances of ATX specification

[@Yon_Jon5715]

It was an Etasis 750W. I don't know if that's any good. Also, 9 years old. Do you think it will have made any damage to other parts(Mobo Usb,disk drives,etc). I ordered an EVGA Supernova G2. Hope that's a good one.

[@tuunaes]

Etasis is one of the more capable manufacturers (actual manufacturer instead of just brand) so at least design wise it shouldn't be bad. Though that doesn't mean they might not have had some cheap series. (-5V being present in sticker would mean old junk design because that was dropped from ATX spec in ~2002) Anyway 9 years is quit long time if it's been in active use PC and especially if it has been kept in stone aged case with PSU on top sucking in heat from CPU and especially graphics card with non-reference cooler: Reference coolers of high TDP graphics cards exhaust heat directly out from case while custom coolers dump it into case. (ironically while failing electrolytic capacitors can still work after warming up heat is biggest factor affecting to their lifespan) So would definitely replace it already basing to its age. Unless it was (expensive) top end model already efficiency is notably better today. If also other parts are older one thing to try would be changing "BIOS"/RTC clock battery (likely CR2032) on motherboard. I've seen some real crazy symptoms from that battery being empty. Though that definitely can't have any effect to PSU's own "receiving power from wall"/"ready to start" indicators.

[@TheWalKXNG]

Hi.. I messages you on Facebook. Under the name Obeyy TJ... Can you read that and get back to me... I messages your fan page i think.

[@SuperBorg1]

throw away that old DDR1 machine

[@cyborg6294]

Why?

[@paulsimin-gv6jj]

we all know the obvious ! get on with it

[@inachu]

Gurubrew looks like you broke your nose a long time ago. Go fix it dude! Cheap to fix!

[@paulredmond5956]

That pc doesn't even have the correct power supply it's been using a 20 pin psu when the board is a 24 pin