I have a U-48 #110 in my shop for repair that has been modified to use an AC701k instead of a VF-14. The power supply is an NG #3943, but appears to have been modified to something like an NN48a. It also has a pattern select switch on the PSU, not a potentiometer. My guess is that the AC7-1k mod makes this mic more like an M249b. The capsule assembly, #296, has 2 patterns on the selector switch, Cardiod, and the letter F in a circle.
Any idea what this beast is and what schematics would be most appropriate ?