Master Reset 220, 320, 420, 555, 580
Press and hold Mute and Volume Up buttons on the front panel for 5 seconds until PS-0 Flashes on the display then immediately release those buttons and press Volume up and Go from PS-0 to PS-1 and let the PS menu time out.
Then repeat the process but this time go down to PS-0. This will delete any learned remote from the 220/320/420. The standard current factory reset procedure where you hold the input button down does not work on the 220/320/420/555/580