Rebuilding Mic Elements

Hello Steve,
  Looks like a topic ripe for rampant digression.

In the Turner mic that I did years ago (the one I gave to you) I simply heated and removed the aluminum diaphram very cleanly. I then took one of the Mouser (Kobitone) small crystal MICROPHONE elements and began a disection. First I removed and discarded the OEM diaphram. Step two involved trimming the drawn steel cup that forms the shell to a suitable thickness. Leads were placed and soldered from the Kobitone replacement and the Turner terminals. Now the Kobitone is set in epoxy with the crystal stirrup center offset by one stirrup width. At this point I Cyano-glued the Turner stirrup to the Kobitone strrup so as to duplicate the postion it held in the original Turner configuration. Now the diaphram is Gorilla glued in place with the stirrup tip slightly protruding as it always had. The stirrup was also glued with a dap of partially thickened by pre drying Gorilla Glue.

  As you well know, it works just fine.

  As far as the Astatic 77 , I have several of those. More often than not, when shipped they arrive with the element flopping around within the case ! The mounting "adhesive" has long since turned to a dry clay like crud. At that point a secondary problem often presents itself. Seems, as luck would play the .002" element coil leads are often severed by sharp corners within the case as the element bounces about . Often they are severed when crushed between the fibreboard lead out backing and the sharp corner they are impacted against.
  With a little patience, good magnifiers and a ton of luck the leads may be repaired.
A little more ingenuity will lead you to suitable rubber and adhesive to effect a remounting of the element that should last another 50 years. I recently bought 2 Astatic 77s that once belonged to the legendary Roy Orbison. Both of them were DOA with the bouncing element syndrome. I also had tow others that were not working from open coil damage. The Orbison Mics were just the incentive to get me to attempt repairs. After finding near identical problems on the first two and successfully restoring function I had the confidence to undertake the "O" mics. They too responded well and are now in my son's mic collection.

The 77 as you know has an impedance selection switch and allows low, medium and high impedance matching. It important to use the proper terminal connections as well. If you need them, I have made some tools up that allow for clean removal and tightening of both the impedance switch recessed nut and the tilt position split drive nuts. Let me know if you would like to borrow them. That way you won't have to risk damage from a slipping screwdriver or other mis-applied substitute "tool" !

  Good luck Steve.

Gary 'LB