schematic search for bounty hunter

I’m looking for a schematic for an old Bounty Hunter metal detector. This one is a model RB5 made by PNI inc of Tempe Arizona.
From my searching there must have been 2 manufacturers of the Bounty Hunter.
This thing worked when I put it away so its probably something simple but I can’t find it.
Anybody have a source for old metal detector schematics?