Hi Colin I’ve had a couple of 504 who insisted they were controller and I manually made them NCon in the set up. You’re right this isn’t in the 504 manual but I think I pressed the display key as I powered the unit on and then cycled through the few choices - this is the way you get to that part of the config for a 501 for instance so kind of makes sense? If not display key then try others held as you power the unit up with the mains switch on the back. 501 manual is the reference for which keys change options etc….

Hope that works for you.

Richard

Main system; 861v8 ID41, DSP8000SEU fronts with DSP5500 centre and DSP7000 rears (all in lovely silver) 504, HD621
Second system 861v4 ID40 LPS, G98DH, 504, HD621, 2x DSP5200 with DSP5200 centre
MD600 tucked away in study. Lots of other Meridian!