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Powersupply testing

I have a electronic load powersupply tester and was wondering how you go about setting it up? For a computer powersupply how would you set it. Do you set the resistance and for how much? How do you figure this out. Just measure the inputs on the computer? Does that give you a correct value? I need to set a 5 volt, 12 volt and 3.3 volt. Also do you set the amps or watts? So if it says 5 volts 12 amps. I just need to figure the resistance? and then set it for 12 amps? do I need to set the watts? Not much in the manual. They assume people know what they are doing. Also,

I have this powersupply that sometimes doesn't come on and sometimes does. If it isn't the solder joints how do you track this down? Anything in particular thing that determines what turns on the PS. It has a red LED and it will work a few times then not work. I take it to my bench and it comes on after turning the power on and off and waiting.

Thanks Uriah

Reply to
Russ
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Best way is with a DC current meter in series with each output. Then, slowly increase the current (decrease the load resistance) up to the full rated load of that output. Otherwise, set the load resistance for each output using the formula R = V/I. So for a 5v 30a output, the resistance would be 5/30, or 0.167 ohms. For 12v @ 12a it would be 12/12, or 1.0 ohms. It's easier with the meters, however.

Could be a number of things. I assume it is NOT an ATX PSU. Most switch mode PSUs need about a 1-2 amp load on the +5v to power up. This might be your problem if it is unloaded.

Reply to
UCLAN

Would measuring the 5, 12, 3.3, -5 VDC inputs give me the correct resistance setting also? If I measure the 5 volts I get 1.6 Ohms. If I measure the 3.3 VDV I get 35K Ohms. ( need to double check that one). The 12 gives me 500 ohms. Do I set the load tester to these settings when setting up the resistance? Or does this not take into consideration of any reactance in the circuit? The load tester has a setup for the amps and watts. You can set them at what every you want. Do I need to set these? I guess I would set the amps but what about the watts? Do I set that or just leave it at 0. It shows me the amps on the display of the tester. Thanks Uriah

Reply to
Russ

You've lost me. 5v/1.6 ohms is only 3.125 amps. 12v/500 ohms is only 0.024 amps.

If you have to manually set the ohms, use the formula I gave. If the tester has a current readout display, it must have an adjust knob. Start with the knob fully CCW, and slowly turn it CW until the current readout is at that output's full rated load. Be careful not to exceed the PSU's total rated power.

Reply to
UCLAN

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