How clean is my power supply

[Beo]

I have a pile of wall warts of various ratings, and a Small Wart I built from small bear. I rewired an 18v wart to work with a small Behringer mixer which I bought used without a power supply... it's working well. I'm thinking ahead about using a wall wart as positive ground for a FuzzFace/Octavia project.

What is the best way to evaluate how clean the power is from these various sources. I have an oscilloscope... should I simply look at 60Hz frequencies and it's multiples and look for spikes? If I want to add filtering, is the oscilloscope the way to analyze the effectiveness? Or is real world application the best test? In which case, which circuit is a good one to use as worst case susceptibility to noisy power?

[Pablo1234]

I would say use a load to draw expected current from the supply and then look at it. check for voltage level changes with and without load, AC signal levels and switching noise.

[DavenPaget]

Try looking at the scope when the PS is at full load , there you know how "clean" it is .

[Beo]

Try looking at the scope when the PS is at full load , there you know how "clean" it is .

Thanks for the feedback. I'll have to line up some power resistors or higher watt pot for testing this. I suspect a standard 1/4W resistor will pop testing at higher current, athough I haven't fried anything yet pedal building.

[Mark Hammer]

I say you invite Kim and Aggie over, and have them give it the once over:  http://www.channel4.com/programmes/how-clean-is-your-house

[frank_p]

http://www.youtube.com/watch?v=uNNNJ29xeFE

end of the vid.

you don't have to be a geek to see ripple on your scope...

[DavenPaget]

Try looking at the scope when the PS is at full load , there you know how "clean" it is .

Thanks for the feedback. I'll have to line up some power resistors or higher watt pot for testing this. I suspect a standard 1/4W resistor will pop testing at higher current, athough I haven't fried anything yet pedal building.

Or just use a automotive lamp if it is only 12/9v . Some of them can really go to 60 over watts .
Easy way out .

[DavenPaget]

http://www.youtube.com/watch?v=uNNNJ29xeFE

end of the vid.

you don't have to be a geek to see ripple on your scope...

Unless you're blind ( then again , how do you see capacitors numbers ? )
You really shouldn't say you can't see ripple ... A perfect power supply is a flat line .

[frank_p]

then again , how do you see capacitors numbers

You test (the caps, not the entire power supply) with a square wave, a current limiting resistor and a diode to cut out the negative part.

You really shouldn't say you can't see ripple ... A perfect power supply is a flat line .

I don't understand what you mean...
If I see ripples, I see ripples; if I don't, I don't.