Too late, I read all of this too late... I already removed the black stuff. IPA took that black matter away like butter.
Anyway let's start from the beginning. Sorry for the shitty pic quality, next time I use my Canon 5D.
Pics of the entire board front and back after desoldering the wires.
The capsule does not look clean, I do not know if I have to expect here a mirror finish...
Here the "sharpie" region after the cleaning (ups
)
A few observations:
1) Since it is a little bit too dirty, I think it is an old used mic (yes I got it from from ebay)
2) the sharpie region seems a reworked area, the solder joint reminds me some hand job not a reflowing oven.
3) in the sharpie region there is a area no filling ground plane, it could be for minimizing capacitance beetween tracks, or for minimize current leak and/or dirt contamination...
4) Few component are for me a mistery (sorry for my ignorance)
- No. 1, 2, 3, 4 are strange capacitor? Audio stuff?
- No 5, 6 have a black line in the middle, WTF? Nerver saw something like this before.
Anyway if current leakage is a deal why not use a guard ring? Ohhh maybe there is one... do you see it too?
After reversing rev the board I will probably clean it with my ultrasonic cleaner... do not know if the coating was necessary for the proper function.... I mean it would have been for sure not a mass production process in that way. It has to be some rework jazz.
My bet some guy fixed it and put the black stuff to protect his job.... or to tell me now "yeah in this area was me"
It will be a lot of fun this weekend digging into this interesting board.
Rode eng knows how to build a mic...