plugging main power into new controller… nervously… did the usb firmware 5v thing but now it’s going to get full 12v through main terminal. I am sort of scared… and i don’t know why, i have volt modded video cards that cost twice as much. hacked up atx supplies into bench power and project power units. this trepidation makes no sense 
anyone else have a project stall and you just cannot make sense of the reason in the moment?
You gave no details on what you are hooking up, but I think 12v will fry any USB device.
Check your outputs with a volt meter
@NathanielStenzel most printer controllers can use 5v over USB cable power to upload firmware, and need 12v or 24v for functioning motors and heaters. Sorry I did not think that needed explaining here.
@Panayiotis_Savva Did that, did every possible check about 3-5 times over a few days… finally hooked it all up just now, runs perfectly. The hesitation was just weird, a feeling of dread, but it went away once I decided I had done all I could and if crap blew up on me it would not be for laziness or impatience.
@AlohaMilton you had me thinking 12v was coming through the USB cable and I was saying that would be a bad idea. I built my printer from a kitand the whole thing is powered via 12v with some parts of the board getting 4 or 5 different 12v wires. It is an ATX power supply setup. Go figure. I believe the board has a jumper to switch from usb power to 12v power. If your board has such a jumper, make sure you have it set right.
12v from the usb will let out the magic smoke. But if you hook 12 or 24v into the power terminal on the board, as long as it is rated for it (only applies to 24v since not all support it) you will be fine. Voltage is dropped down when supplied to the multi controller.
What board are you using
I had that same feeling when i spliced an old pc power cord to use on my cheap chinese power supply the first time. I think i tested the wires 12 times each because i really did not want to smoke or blow anything up. Scared the willies out of me, but it worked fine. Im usually pretty good with piwer stuff, even ac, but not sure what it was about that day.
Nathaniel, roger that 12v through the USB would be a shocking turn of events!
Griffin, It is a Duet 0.8.5. Its running fine now thanks for the help.
Michael, totally understand that is how it was for me, checked everything 10 times and wonder what might have been missed, then flip the switch. The correlation of ‘I got this’ with fires and water damage does not go unnoticed as one gets older…
I think for me it was just ‘be patient’ and ‘OMG want this thing to be running’ in total conflict making me feel nervous.