MD421 Ground Disconnected

[panman]

You did not answer the question, what type of connector your mic has. does it have bass-roll-off ring? The things get more complicated, if your mic is a MD421HL(or HN). That would mean it has a High-Z transformer and the connections are not the same, because it can be wired low-Z or high-Z both. So. please, do the the proper measurements and answer the the stated questions and we can move on and see, to what extend you can be helped here.

 

[mmmmm]

Just measure the resistance between the lugs on the side(not the middle, but where the red wire is connected and the "third"). Should be around 210 ohms. Could be more or less. If no reading, the voice-coil is broken. The humbucking - you can separately measure between the middle(blue wire) and the right-lug("the third"), which you obviously did..

so a broken voice coil seems to be the case. But how did you know this? Do you by chance have a wiring diagram for it somewhere?

 

[mmmmm]

You did not answer the question, what type of connector your mic has. does it have bass-roll-off ring? The things get more complicated, if your mic is a MD421HL(or HN). That would mean it has a High-Z transformer and the connections are not the same, because it can be wired low-Z or high-Z both. So. please, do the the proper measurements and answer the the stated questions and we can move on and see, to what extend you can be helped here.

no it doesnt have a rolloff its actually a 521 blackfire but other then that it shouldnt matter that much. Do you by chance have any good papers/articles or whatever in regards to Hi-Z transformers in microphones, since i dont really know what that refers to in an electrical context. Also thanks for the help!

 

[panman]

so a broken voice coil seems to be the case. But how did you know this? Do you by chance have a wiring diagram for it somewhere?

Rob Finn already posted the diagrams. The wiring is the same as in MD421-U without the rolloff. Just click the attachement and you`ll see it! Unfortunately you don`t have any use for it, because your voice-coil is shot. That is not your level of repairs, but a job for a real expert.

 

[mmmmm]

Rob Finn already posted the diagrams. The wiring is the same as in MD421-U without the rolloff. Just click the attachement and you`ll see it! Unfortunately you don`t have any use for it, because your voice-coil is shot. That is not your level of repairs, but a job for a real expert.

I was hoping for a electrical schematic, not just which xlr connector does what. Ideally even with the acoustic properties FI converted but i suppose thats a bit too much to aks for... Also thank you for being dismissive and not giving me any way to research this further. No way of becoming an expert at something without learning about it beforehand.

 

[Khron]

I was hoping for a electrical schematic,

What more of an "electrical schematic" were you hoping for, that is NOT visible in Rob's post, right here?

And you seem to stubbornly refuse to even mention what sort of damn connector your mic has - that in itself kinda waives the right to complain or have that sort of attitude...



This is the wiring diagram of a Beyerdynamic M201 (with the RLC filter removed, for clarity). This is about as close of an "electrical schematic" as you can hope for. One was not shown earlier because i'm sure it was deemed much too trivial / simple / obvious.

The big round doohickey at the left is the voice coil; the squiggly line top left is the humbucking coil. The pin numbering corresponds to the XLR standard.

thank you for being dismissive and not giving me any way to research this further

There's not much left TO research. Repairing a microphone voice coil is no small feat, especially with the wire being maybe a quarter the thickness of a human hair, or even less, so unless you REALLY know what you're doing, AND you're (or at least "feel") qualified to remove the diaphragm without tearing it to pieces, repairing the voice coil wire (if it's even feasible), AND gluing the diaphragm back in its place, with the voice coil well-centered and not rubbing against either of the pole pieces........

No way of becoming an expert at something without learning about it beforehand.

Well, there's "learning", and then there's "being taught"...

Do you by chance have any good papers/articles or whatever in regards to Hi-Z transformers in microphones

https://www.coutant.org/578probe/index.html

Scroll down just past the image with the frequency response. That's an example of a mic with an isolation / step-up transformer (ie. even in the "low impedance" setting, it still puts out more signal than is provided at the input).

https://sengpielaudio.com/MD421HNoderHL.gif

Second wiring diagram from the right is the case for the MD421 HN or HL. Those use a "klein Tuchel" / DIN output connector, and are an example of high/low impedance output without an isolation / step-up transformer. Pin 2 is "common"; low-impedance output (straight from the voice coil) is available between pins 2-3; high-impedance output is available between pins 2-1.

 

[panman]

Also thank you for being dismissive and not giving me any way to research this further. No way of becoming an expert at something without learning about it beforehand.

I did not mean to be dismissive about research. You are free to go on taking apart your mic as you please. I just stated the plain fact, that you are not yet there to succeed in repairing the voice-coil. An expert would most likely be able to restore the capsule fully funktioning. You would only end up destroying it most likely beyond repair. That has come clear of your postings and no offence meant. How do I know? Well, have a guess, how I started my learning!MD421 is an expensive way, but I made it after an amount of failings and you might make it too in the end. Khron gave you a good portion of knowledge in his posting. Just go on and you`ll end up learning for sure.

 

[Evertide]

The voice-coil is moving if sound hits the diaphragm , were it is glued to.

2 small wires go to the lugs were the red and blue wires are soldered to.

In a very small chance here is a bad solder joint...

Re-soldering may help.

We al think 1 of the small wires is broken at the voice-coil...

At this point we all give up , and put the mic with the spare-parts.