preamp fault help needed please NAC122x

hoping someone can help Just tried to change the input of my preamp from cd to phono and the light showing the input went out and I couldn't select . The volume knob started going to full volume and back and then searched inputs and keeps repeating this procedure. I thought it might be the input cable from my Non-naim power supply so I have taken the power supply out the system and reinserted the dummy plug and wired it directly from my amp. Still doing it so unsure of next step.