Quote Originally Posted by printbus View Post
All I was getting at with the AC measurement is to put the meter in AC volts mode and look at the same power outputs from the power supply. It's not a good test, but it might reveal something. Ideally, the 12V DC output should read 0V AC. If the meter shows a considerable AC (ie, not fixed like good DC would be) component, the power supply might have issues.

My point on powering up RAMPS and LCD via the USB port is I wouldn't do that. I'm not saying you are - it's just one way that people can have unexpected current flowing through the USB.

Thanks for the clarification. I tested using AC volt mode and it does indeed show 0V. Thought I was doing it wrong.
How would I avoid powering over USB. Don't think I have control over it. I just ensure that I power on the power supply before connecting the printer to my PC