How to Start PSU without Motherboard?

Hi there,

Just bought a new water cooling set up for my pc, i would like to leak test this before putting it in my case for obvious reasons.

How Should i start my PSU without it being connected to the Motherboard?

I'm sure it can be done but not too sure how to.

Thankyou!

 

You have to fake out the on/off switch while supplying a load...

Check this out:

www.metacafe.com/watch/729606/how_to_test_your_computers_power_supply_psu/

 

No offense to Caliban but I recommend you AVOID following that video guide. The reason is because there is nothing that requires PSU makers to follow any color-code standard for PSU wiring. The ATX Form Factor Power Supply Design Guide requires specific voltages on specific pins, but only "recommends" specific colors. And not all PSU makers follow the recommendations. Therefore I urge you DON'T follow that tutorial as the green wire may not be the right one, and you may end up shorting out the supply.

Here's my canned text on testing supplies, which explains how to fake out a PSU so it will start:

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronic repair facilities.

Fortunately, there are other options that are almost as good. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

As mentioned, swapping in a known good supply is a tried and trued method of troubleshooting used for years, even by pros. Remove the "suspect" part and replace with a "known good" part and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply.

 

Good tips however the PSU testers may say the psu is good due to the fact it doesn't put enough load on the PSU and some falling psu's fail under small load. I do agree it's better then the multimeter and alot easier as well as much safer to check voltages.

 

Which is exactly why I said,

 

Well, just trying to help burrell: he/she's trying to test a water cooler, not the power supply...

I'll have to question that one: I've replaced power supply fans on numerous occasions, no problem...

 

I understand and appreciate that. But that does not change the fact that color codes are not standard.

As have I - but,

Therefore, repairing a PSU, to include replacing a failed fan, should be left to a trained technician.

 

I agree, that not ALL psu manufacturers will use the same colour coding, BUT I'm sure that they will use the same pin layout.....?

So for example it could be the 3rd and 4th pin on the right from the top, with the mobo clip facing a certain direction.

Would following this method be safe?

Burrell

 

Burrell, You are correct that the pin layout will be the same in all psu's regardless of the color of the wires. And for just the sake of seeing if a power supply will spin up, that method is safe but that is about all it's good for I would think..............

 

In my first post in this thread, I said,

The question is, safe for what? Will you get electrocuted? No. Well, assuming the PSU is not damaged or seriously faulty, and you don't open the PSU case where deadly voltages exist. Can you tell if the PSU fan spins up? Yes. But will the voltages be safe for anything you connect to the PSU, such as your new water cooler? Maybe not. Once again, simply shorting two pins does not put a realistic load on the PSU. In fact, a paper clip presents a direct short - or zero ohms for no load whatsoever. And without proper loading, a PSU is very likely to produce out-of-tolerance and unstable voltages which may, or may not put an excessive strain on any device connected to it. At least with one of those testers, a 10 ohm load is used which should allow the PSU to produce stable voltages, although they may still not be within the required +/- 5% or 10% tolerances.

It is also important to consider the quality of the PSU under test. I would expect a PSU from Antec, Mushkin, Corsair, PC P&C or any of the others power supply brands listed under the "Good" column of PC Mechanic's PSU Reference List to be well made and more tolerant of these "abnormal" loads - ASSUMING it is not damaged and is otherwise working properly. But sadly, way too many supplies found in computers today are generic, off-brand or no-name supplies that may have been made under horrendous conditions by underaged :cry :mad, unskilled, forced labor in some remote part of China or a 3rd world country under the direct supervision of greedy factory owners and corrupt government officials - and assembled using components made under similar conditions in the next village up river. Too many naive, or overly budget conscience builders try to save money by buying the cheapest PSU they can find. That's a mistake. And sadly, many cases (even from quality makers) are sold with cheap PSUs "tossed in" just to make the case sale. Today's digital electronics need a good quality, stable power source.

 

@burrell:

The paper clip thingy has nothing to do with loads - all it's for is to provide the PSU with a signal simulating an on/off switch...the water cooler wil provide the load...

If your PSU has been working fine, then you shouldn't have to worry about testing the cooler - just plug it in, and leak test the thing...

 

@Cailban

Thankyou, i thought so but was just checking!

 

The water cooler does NOT provide a proper load. A proper load is one that presents a realistic load not only for the +12V, but also for the +5V and +3.3V required volages. The water cooler, which I am assuming requires +12V is NOTHING compared to what would be realistic since the +12V is used to supply power to all the fans, all the drive motors, and is the main power source for the biggest power consumer, the graphics card.

So while the paper clip method may work for testing for leaks and fans, it is not good for the PSU to run without a proper load. And since the load is not proper, the supplied +12V may not be within the +/- 10% tolerances.

You are right that the paper clip used to simulate pushing the power switch, but my point is beyond that, it offers no loading.