[ARC5] Carbon Mic Replacements

[J Mcvey]

The zener would go across the electret to protect it from the voltage exceeding it's upper limit. when the electret circuit conducts, it will draw more current than the zener and the zener will drop out of conduction.  The 18K is in series from the plus battery from the bc456 plug tip to the plus marking on the mike and the mike minus goes to "ring" on the mike plug. 
I think if you find an older electret in the junk box, probably  a 5V zener will be OK. I believe the older types were rated for up to 10V.I buy old mikes at ham fests for a buck or less and they are great sources of project and repair parts for other mikes.Generally, Icoms have electrets and yaesus are dynamic. 

    On Thursday, March 24, 2016 10:50 PM, Roy Morgan <k1lky68 at gmail.com> wrote:
 

 
On Mar 24, 2016, at 10:22 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:

> Just had a thought to check the voltage ratings sinvce this is a higher voltage application than where they are usually used (3.3-5v)

I am learning a bit here: I thought electret microphones were basically an open circuit, so do not draw current.  I have a couple here and intend to use them soon.

> Sure enough, some are rated as low as 2V, so putting a 2V zener or resistor across the module will help.

What “module” does the zener go across, the electret element?  (Wouldn’t that limit any audio the thing produced?)  Or maybe you mean the entire amplifier/adapter.

> I have used them with a 3300 ohm series resistor on 5V supplies with good result, so I am surprised by the 2V spec.

I need to understand a bit more before I hook one up.

Roy

Roy Morgan
k1lky68 at gmail.com
K1LKY Since 1958

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