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

Russ wrote:

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,

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.

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.

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.

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

Russ wrote:

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.

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.