I just picked up a used AKG C414 B-uls off eBay. It appears to be in great condition. I am digging the sound and I am planning on replacing the electrolytic caps with films. However, upon taking it apart, I noticed a spot on the capsule that looks like it is rubbing off. This is my first time working on a mic as far as upgrading components on a circuit so I am admitting ignorance. Could someone tell me what exactly has rubbed off here and is this an issue going forward? I don't notice any sound problems. I took a picture of it for everyone to reference. Thanks for any help here.
It's hard for me to see (my eyes ain't what they used to be) even with the pic blown up. At first, it appeared as though it was just a larger piece of the gold sputtering that all 414's have, but then I wondered if maybe at some point, someone might have foolishly tried to clean it with something they shouldn't have used...
The bottom line is that your mic works and sounds great, so I wouldn't worry about it, and, as I said, it might just be a larger piece of gold used for sputtering the diaphragm.