Cool power supply tester

[superdave]

thanx. Just ordered one and some brass thumbscrews.

 

[SuperCyrix]

<< You go take your power supply, set up a video camera, strip some wires, and flick them together. Then tell me if they don't spark up. I'm fairly positive these computer PS's pump out enough amps to cause some good fireworks. >>



As a matter of fact, thats exactly what we all do everyday when we turn on the ATX powersupply. We connect the +5V terminal directly to ground and our computer boots up. But don't tell that to the Power Supply or one day all of our computers might start catching fire.

 

[Zach]

<< >And if you want to test a PS, get a multimeter.

I have a multimeter, how do I test it with a mulitmeter?

Please help. >>



Check the voltages..

 

[MighTiVo]

An ATX power supply relies on a logic circuit on the PC motherboard to turn it on. Once you plug the power supply into an outlet the ATX power supply only provides a Voltage StandBy supply of +5V (VSB) 720MA current to the motherboard through pin 9 on the power connector. That current is for power on circuits and LAN cards to monitor network activity for WOL support. The pushbutton located in front of ATX case sends a signal to the mothboard power on circuit, which in turn sends a signal to the ATX power supply to turn on the full power.
The shunt between green and any black described above is equivilent to this PowerSupply ON signal which is connected to pins 14 (PS-ON) and 15 (COM) on the motherboard and only allows a small amount of current to drain pulling a very basic logic circuit to ground which causes the power supply to enable and no sparks will fly.

Running a switching power supply for a period of time with no load could damage it so do this at your own risk, but you shouldn't have any trouble at all.
The only real side effect might be that the Grey Pin 8 (PWROK) will not be supplied without a proper load on the +5V and +3.3V rails. If your power supply seems to be working yet your MB won't boot, this cicuitry may be the trouble as it is used to indicate to the MB that the Power Supply is up and running with all rails have reached their threshhold.

 

[mikeford]

Maybe its perfectly safe, but I don't care to use a $125 motherboard and a $150 processor to &quot;test&quot; some $15 powersupply I buy at the swapmeet or something. This little tester is quick and effective at weeding out problem power supplies, so that makes it well worth $8 to me.

One caution about using a multimeter, or any other kind of probe in a running computer, is to be very carefull not to short adjacent pins with the test probes.