I created a backup site of the excellent Microphonium Schematic Archive. The sdiy.com domain that it resides at is up for sale and the rest of the site returns 404 errors or domain for sale pages. I tried to make it a little easier to read (less color), and little more search engine friendly. The files vary from PDF to GIF to JPG – and from photocopy to CAD schematic. Hopefully the archive has the mic you are looking for.
I plan on adding my collection of schematics and files soon, so check back often.
If i missed any links, you find an error, or would like to contribute a schematic to the archive, CONTACT me.