Marantz NR1506 - Manual (Page 180)

Maintenance Mode
Use when receiving maintenance from a Marantz service engineer or
custom installer. Ordinarily, this mode isn’t suitable for use by the end
user, only by a trained service technician or custom installation
professional.
NOTE
0 Only use this function if so instructed by a Marantz serviceperson or installer.
Contents Connections Playback Settings Tips Appendix
180
Front panel Display Rear panel Remote Index