Jepp charts specify the PRIMARY aid to be used for navigation in the top right corner of the approachp plate. Its my understanding if that aid is unservicable, your not legal to do that particular approach.
Say ABC is an NDB at 10nm and DEF is one at 4nm. If ABC is the Primary Designated Aid then ABC must be servicable in order to do that approach. If ABC is out you cant legaly use DEF on its own.