Tweet
Hello there
I have a Shure green bullet microphone 520D (the old model) brought to me to have a look at and hopefully repair.I haven't seen this type before with the diaphragm going to a pin which in turn goes to an armature which rests inside a coil.It has 3 connections so you can either have low or high impedance and there is a 39k resistor across the high impedance connection apparently to help smooth the high end frequency response.
The center tapped coil is fine measures from memory approx 1K3 from white to black and white to blue with the resistor temporarily removed.
There is a very faint thin signal if you yell into it which you can hear in amongst the hum with the gain cranked up, If you handle the mic a bit roughly and bang it with your palm you can hear promising sounds with some bass frequency content but no change to what the diaphragm picks up which makes me think the armature picks up movement giving me false hope !
I think it must be a mechanical fault either the diaphragm is totally clogged and jammed so it can't move or perhaps the diaphragm is no longer connected to the center pin,
There are some sign of "white rust" and yes I have cleaned it with isopropyl alcohol which removed it.
I was just hoping some one may have had some experience with this mic.
Sadly the original capsule for this model is no longer made although Shure now make a dynamic mic with a DX suffix.
The attached "exploded parts" diagrams are not mine but I am grateful to the person who made them and unfortunately I've forgotten where I got them from.
EDIT: The Images are from https://greenbulletmics.net/shure-mi...ements/#dating