Some of these schematics were already posted, some weren't, but here's a link to downloads
of many metal detector schematics.
There are two downloads, look for the download links on the left of the following page (annoying geocities page, watch for popups)
Some of the schematics include the FISHER CZ6, TESORO SILVER SABRE, WHITES PI-1000, SURFMASTER PI, and PI-BEACH DETECTOR. Enjoy!