Yes, the "Paperclip trick" need be employed when not using the MB plug, which sends the on/off signal. Example...On Corsair Power Supplies, you jumper the green pin & any black pin on the 24 pin MB connector. The on/off switch usually only allows the computer to actually send the on/off signal, and this bypasses that, and makes it so the power switch on the back actually turns the power supply on/off. I myself will be snipping the wires a bit from the plug, and wire-nutting them together.
I'm sure there will be hundreds of noobs plugging in their machines & flipping the switch, wondering why their machines wont work, crying DOA on the miner, when this is the problem, but not really a problem at all. Hope this helps alleviate some of that. Good luck.
More info here: https://www.youtube.com/watch?v=YyPWWusHndA
You'd rather hope that KnC would supply at least this info to all buyers as they do say the rigs are plug in and forget them. In fact all info regarding rigs that appears here should at least be emailed to buyers. Not everyone frequents forums after all.