[ARC5] Carbon cartridge replacement circuit

[jeepp]

Helmets after about 1960 will generally be dynamic, tequiring an adaptpr such as the MX-1646.  Roanwell was a major supplier.  The old M-52/UR mic element was probably the last carbon element used on Mil helmet lash-ups.  This mic snaps in a metal clip.  The dynamic mics will have a small 2-pin plug.  I have a bin with the H-78 type dynamic mics and I'll have to DC ohm them out. BTW, the grey and black elements you have will 99% certain be Lo-Z dynamic.  Jeep  K3HVG


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-------- Original message --------
From: J Mcvey via ARC5 <arc5 at mailman.qth.net> 
Date: 4/27/17  15:03  (GMT-05:00) 
To: Roy Morgan <k1lky68 at gmail.com> 
Cc: ARC-5 List <Arc5 at mailman.qth.net> 
Subject: Re: [ARC5] Carbon cartridge replacement circuit 

One quick and dirty way to tell is to test it "in circuit" . Carbons need a voltage present to operate. dynamics are diaphragms with a magnetic pickup, like a speaker in reverse. ( in fact yo can use a speaker as a mike, but not a very good one). Put your ohm meter in diode mode and tap the terminals of the mike. if you hear a static sound, it's either crystal or dynamic. Cabon won't make any noise.
However, others may know better than I, but I think the military  went to electrets in the 70's. Those need a bias voltage to work also, but much less current than a carbon. They will read 1K or better
Failing all of that, a part # or schematic will tell the story...
 

    On Thursday, April 27, 2017 1:51 PM, Roy Morgan <k1lky68 at gmail.com> wrote:
  

 J,
I have more than one microphone used in Navy planes (helicopters) in the 60's and 70's.  I am not sure if these are carbon microphones or dynamic ones (we did use little inline amlifiers at about that time with some of the lip mikes we had.)
Can you give any hints as to how to determine which is which?  Resistance maybe? One is gray and another one or two are black.  They mounted on the helmets.
Oh yes, I will look on them for some sort of nomenclature - I bet I'll find something.
Roy

On Mon, Apr 24, 2017 at 9:06 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
Hello all ,
I finally got this drawn up and published.This circuit will produce up up to  about 4 vpp without clipping.It has  more than enough gain to produce maximum modulation without yelling into the mike.Enjoy;



https://www.mcveyelectronics. com/images/stories/pdf_files/ electret_carbon_rpl.pdf
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-- 
Regards,
Roy

Roy Morgan
k1lky since 1958



     
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