I have recently bought and begun using several wall warts that are specified as "switching power supplies" in 5, 9, 12 and 15 VDC. I have checked each one with a Fluke 36 meter for both DC output and any AC in the output. So far, all have passed testing and performed appropriately in service. Products were all "Made in China" and sourced from Amazon or eBay.
I mention checking with my Fluke 36 instead of my Radio Shack multimeters because of the issue we discussed here in a previous thread where the cheaper multimeters were giving screwy AC readings with DC power supplies - even batteries. So, if you only have a cheap multimeter and get the urge to check for AC in a DC power source, I suggest that you first try that meter on AC setting with batteries of the appropriate voltage, so that you will know if the meter is good for that test on the power supply. Peteski thinks the reason for the screwy readings has to do with the autoranging circuitry in the meters. It would really take a scope to do a rigorous test for AC. But, I don't think the issue is worth worrying about. (I only got into it before because we have an MRC power supply at our club that really is acting up and putting some AC on the rails, even when turned to zero speed - enough to light LEDs and make motors growl.)
