# How to test a PSU without components?



## Dazzeerr (Jan 30, 2010)

Is there any way to do this? I want to check it's deffinitely not faulty before selling.

Power supply is a OCZ StealthXStream 500W.


----------



## PohTayToez (Jan 30, 2010)

You can power up a PSU just by using a paperclip to jump the green wire and any black wire on the 24pin connector.  If it starts up and continues running, then it's probably good.  Of course the only way to be sure of 100% functionality is to power up a computer with it.


----------



## Machin3 (Jan 30, 2010)

Hmm, that helped me out PohTayToez because I was wondering myself how to start a PSU with components.


----------



## linkin (Jan 30, 2010)

Hey guys. not to threadjack, but I tried to test my psu by jumping the green and black wires with the power plugged in. i plugged the psu into some fans in my system, switched everything on and nothing. (only used 2 molex connections, nothing else plugged in)

is it safe to assume the PSU is dead?

I've already bought a replacement. (it's in the mail :S)


----------



## PohTayToez (Jan 30, 2010)

As soon as you jump the green and black the PSU's internal fan should start spinning which indicates that it's outputting power.  If that's not happening then something is definitely wrong.


----------



## Dazzeerr (Jan 30, 2010)

Thanks very much PohTayToez 

And not a problem at all linkin!


----------



## tyttebøvs (Jan 30, 2010)

Turning on the psu without any load is not a very good idea


----------



## linkin (Jan 30, 2010)

PohTayToez said:


> As soon as you jump the green and black the PSU's internal fan should start spinning which indicates that it's outputting power.  If that's not happening then something is definitely wrong.



okay, thats a start. although when i plug the power cable into the psu, it "buzzes" which i think means the power is arcing over to the psu, but as you said the fan isn't spinning so yeah...


----------



## PohTayToez (Jan 30, 2010)

tyttebøvs said:


> Turning on the psu without any load is not a very good idea



I've been doing it for about seven years now and never had a problem.  It's a pretty well known trick and I've never heard of anyone blowing a power supply doing it.


----------



## MacBook (Jan 30, 2010)

PohTayToez said:


> I've been doing it for about seven years now and never had a problem.  It's a pretty well known trick and I've never heard of anyone blowing a power supply doing it.


For short term testing, yet.  But you don't want to leave a PSU on for an extended period of time with no load.


----------



## johnb35 (Jan 30, 2010)

With one of these.

http://www.newegg.com/Product/Produ...der=BESTMATCH&Description=power+supply+tester

I have the Rexus PST-3 and it works very well.


----------



## PohTayToez (Jan 30, 2010)

MacBook said:


> For short term testing, yet.  But you don't want to leave a PSU on for an extended period of time with no load.



I'm sorry, but _why_?  I don't believe that there is any evidence to suggest that running a power supply with no load it any worse for it than running it with a load.


----------



## tyttebøvs (Jan 30, 2010)

Such switch mode power supplies cannot work properly without a load, because of their design. You might see them just shutting off right away if there is no load.


----------



## tyttebøvs (Jan 30, 2010)

The specs will often tell you both a maximum and a minimum load of the rails.


----------



## MacBook (Jan 30, 2010)

PohTayToez said:


> I'm sorry, but _why_?  I don't believe that there is any evidence to suggest that running a power supply with no load it any worse for it than running it with a load.


Switched mode power supplies have an absolute limit on their minimum current output. They are only able to output above a certain power level and cannot function below that point. In a no-load condition the frequency of the power slicing circuit increases in speed, causing the isolated transformer to act as a Tesla coil, causing damage due to the resulting very high voltage power spikes. Switched-mode supplies with protection circuits may briefly turn on but then shut down when no load has been detected. A very small low-power dummy load such as a ceramic power resistor or 10-watt light bulb can be attached to the supply to allow it to run with no primary load attached.


----------



## TFT (Jan 30, 2010)

MacBook said:


> Switched mode power supplies have an absolute limit on their minimum current output. They are only able to output above a certain power level and cannot function below that point. In a no-load condition the frequency of the power slicing circuit increases in speed, causing the isolated transformer to act as a Tesla coil, causing damage due to the resulting very high voltage power spikes. Switched-mode supplies with protection circuits may briefly turn on but then shut down when no load has been detected. A very small low-power dummy load such as a ceramic power resistor or 10-watt light bulb can be attached to the supply to allow it to run with no primary load attached.



It's usual to mention if it's a copy/paste quote from somewhere like Wiki.


----------



## bomberboysk (Jan 30, 2010)

MacBook said:


> Switched mode power supplies have an absolute limit on their minimum current output. They are only able to output above a certain power level and cannot function below that point. In a no-load condition the frequency of the power slicing circuit increases in speed, causing the isolated transformer to act as a Tesla coil, causing damage due to the resulting very high voltage power spikes. Switched-mode supplies with protection circuits may briefly turn on but then shut down when no load has been detected. A very small low-power dummy load such as a ceramic power resistor or 10-watt light bulb can be attached to the supply to allow it to run with no primary load attached.



Modern power supplies do not need a true load in order to maintain a minimum output. One shining example of this is the fan integrated into the power supply, which is run off of the +12v dc output of the power supply, and that alone can be anywhere from 3-10W draw.


----------



## MacBook (Jan 30, 2010)

bomberboysk said:


> Modern power supplies do not need a true load in order to maintain a minimum output. One shining example of this is the fan integrated into the power supply, which is run off of the +12v dc output of the power supply, and that alone can be anywhere from 3-10W draw.


Typically power supply fans are fairly silent and rotate at lower RPM's then your average case fan, and the one's I've found typically draw between 1-5W.  Still, it's not ideal to operate them without any additional load for an extended period of time, as I explained in my previous post.


----------



## ganzey (Jan 30, 2010)

MacBook said:


> Typically power supply fans are fairly silent and rotate at lower RPM's then your average case fan, and the one's I've found typically draw between 1-5W.  Still, it's not ideal to operate them without any additional load for an extended period of time, as I explained in my previous post.



doesnt matter if they are silent, they still draw power. and 5w is considered a load


----------



## tyttebøvs (Jan 30, 2010)

It all comes down to how the psu is built. They are not all the same. They have different "minimum load" requirements. Some are also built to handle "zero load". It all depends on the psu in question.


----------



## ganzey (Jan 30, 2010)

MacBook said:


> Switched mode power supplies have an absolute limit on their minimum current output. They are only able to output above a certain power level and cannot function below that point. In a no-load condition the frequency of the power slicing circuit increases in speed, causing the isolated transformer to act as a Tesla coil, causing damage due to the resulting very high voltage power spikes. Switched-mode supplies with protection circuits may briefly turn on but then shut down when no load has been detected. A very small low-power dummy load such as a ceramic power resistor or 10-watt light bulb can be attached to the supply to allow it to run with no primary load attached.



http://en.wikipedia.org/wiki/Power_supply#Switched-mode_power_supply


----------



## MacBook (Jan 30, 2010)

tyttebøvs said:


> It all comes down to how the psu is built. They are not all the same. They have different "minimum load" requirements. Some are also built to handle "zero load". It all depends on the psu in question.





ganzey said:


> doesnt matter if they are silent, they still draw power. and 5w is considered a load


Exactly, and some are 5W, while others may be near 1-2W which isn't enough of a load, and then some don't need any load.  



ganzey said:


> http://en.wikipedia.org/wiki/Power_supply#Switched-mode_power_supply




It just proves my point.


----------



## ganzey (Jan 30, 2010)

MacBook said:


> Exactly, and some are 5W, while others may be near 1-2W which isn't enough of a load, and then some don't need any load.
> 
> 
> 
> ...



that you can copy and paste? lol, jk. but wikipedia isnt exactly the most reliable source


----------



## MacBook (Jan 30, 2010)

tyttebøvs said:


> It all comes down to how the psu is built. They are not all the same. They have different "minimum load" requirements. Some are also built to handle "zero load". It all depends on the psu in question.





ganzey said:


> doesnt matter if they are silent, they still draw power. and 5w is considered a load





ganzey said:


> that you can copy and paste? lol, jk. but wikipedia isnt exactly the most reliable source


While a few articles are questionable, topics like this are generally correct.  And they are usually more up to date as the community adds to the articles to keep them up to date.


----------



## PohTayToez (Jan 30, 2010)

MacBook said:


> It just proves my point.



Congratulations.  You quoted a Wikipedia article which references a patent from 1995.  Of course, it might be worth mentioning that the patent in reference is for a method of designing power supplies which creates a constant load above the minimum.  This patent also references another patent from 1984 which does the same thing, but is less efficient.  I think it's pretty safe to say that modern power supplies can be powered on with no external load without danger of damage.


----------



## ganzey (Jan 30, 2010)

also, if you read the patent



> U.S. Pat. No. 3,524,124 discloses a system which switches a dummy load, a transistor, onto the output of a power supply in response to the output voltage of the supply rising above a predetermined level.



it was a patent to fix the problem (15 years ago) as stated above by pohtatoez


----------



## MacBook (Jan 30, 2010)

Yes, the patent was issued in 1995, however it is still in use today.  Gas engines have remained relatively unchanged over the past century as well.


----------



## ganzey (Jan 30, 2010)

MacBook said:


> Yes, the patent was issued in 1995, however it is still in use today.  Gas engines have remained relatively unchanged over the past century as well.



if it is in use, then that means you can run a power supply with no load because it will automatically compensate for there not being a load and create one. 

obviously you know little to nothing about car. "relatively unchanged". yea, they are still internal combustion engines, but they have had thousands of upgrades and modifications. 
a ford model t had a 2.9L 4 cyclinder with 20hp. now a 2.9 can put out over 500hp.


----------



## PohTayToez (Jan 30, 2010)

MacBook said:


> Yes, the patent was issued in 1995, however it is still in use today.



I'm going to go ahead and not refute you here.  Lets see if you can figure out why what you just said is hilarious.


----------



## MacBook (Jan 30, 2010)

ganzey said:


> obviously you know little to nothing about car. "relatively unchanged". yea, they are still internal combustion engines, but they have had thousands of upgrades and modifications.


It is still a gasoline internal combustion engine, the main concept has remained unchanged.


----------



## ganzey (Jan 30, 2010)

wow, you arent even worth arguing with



PohTayToez said:


> I'm going to go ahead and not refute you here.  Lets see if you can figure out why what you just said is hilarious.



hahaha, i think it may take a while


----------



## MacBook (Jan 30, 2010)

ganzey said:


> wow, you arent even worth arguing with
> 
> 
> 
> hahaha, i think it may take a while


A change from the gas engine is an electric engine is a significant change, not a gas engine to a gas engine with VVT and turbo.


----------



## PohTayToez (Jan 30, 2010)

Are really turning this into an argument about gas engines?


----------



## ganzey (Jan 30, 2010)

yea, but from this:





to THIS:





is quite a difference. not to mention the several computers that are used to control modern car engines.



PohTayToez said:


> Are really turning this into an argument about gas engines?



i think he is becasue he is wrong about the power supplies. but cmon, lets not argue. this is a friendly exchange of who is right and who is wrong.


TO OP---if you want to be ABSOLUTELY POSOTIVE that is works, just pop it into your computer and see if it works


----------



## MacBook (Jan 30, 2010)

Alright, I give up, there is no convincing you guys.  Yes they have changed lots of features of the engine, but the engine itself is still the same where it burns a mixture of gasoline and air to produce power.


----------



## PohTayToez (Jan 30, 2010)

Yeah, we're just too darn stubborn.  It's a personal problem I have.  I get all caught up looking at the facts and I always forget to relentlessly defend everything I say until irrevocably proven wrong at which point I'll change the subject or give up under the pretense that it's the other person that's being stubborn.  I'll try and work on that.


----------



## ganzey (Jan 30, 2010)

PohTayToez said:


> Yeah, we're just too darn stubborn.  It's a personal problem I have.  I get all caught up looking at the facts and I always forget to relentlessly defend everything I say until irrevocably proven wrong at which point I'll change the subject or give up under the pretense that it's the other person that's being stubborn.  I'll try and work on that.



i think i have that as well


----------



## MacBook (Jan 30, 2010)

Well the OP's question has been answered, so there is no point in posting here anymore.


----------



## PohTayToez (Jan 30, 2010)

Nice save.


----------



## linkin (Jan 30, 2010)

Actually, I what to know if because my PSU had no load when i tested it whether it is dead or not. if you need details ask me.


----------



## MacBook (Jan 31, 2010)

If it still worked until you turned it off, I can almost certainly assure you that it still works.


----------



## linkin (Jan 31, 2010)

it didn't work at all. no fans spinning. i plugged into two of my case fans, so that counts as a load, right?


----------



## PohTayToez (Jan 31, 2010)

If you plugged it in, jumped it, and nothing happens then yeah, it's toast.


----------



## linkin (Jan 31, 2010)

well it's a bloody good paperweight now. 

Thing is, it must have broken when i was carrying the case around. or when i actually turned off the pc and unplugged everything. jsut hope nothing else fried...


----------

