...on one of the ADF boxes is U/S.
No, not necessarily.
If audio station ident is heard, the ADF receiver is functional.
If the ADF pointer is 180 degrees to the desired direction, it is the resolver, not the receiver.
Now, if one has installed one of the older Collins ADF sets, where
manual direction finding was possible (many 707's for example), then proper pointer orientation can be determined without the resolver.