[Milsurplus] [ARC5] Carbon mic pops

[Hubert Miller]

What’s the voltage available to the mic element BEFORE the microphone is switched in, has mic current flowing?
In other words, does it soar with no ( mic ) load?
-Hue

From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of hwhall at compuserve.com
Sent: Tuesday, November 29, 2016 10:45 PM
To: arc5 at mailman.qth.net; milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] [ARC5] Carbon mic pops

Attached is the schematic of the mic circuit & amp that I'm looking at. The mic internal wiring looks like just a set of PTT contacts in series with the carbon mic button + the small cap across the mic button.

The primary of T-4 has no current thru it until one of the mics is keyed, then suddenly current flows thru primary & carbon mic, inducing a transient in T-4 that appears as a loud initial pop in the headphones. I don't see how they prevented this pop from happening every time a mic was keyed.

By hitting Send I'm about to remind myself whether these forums allow images attached.  :-\
Wayne
WB4OGM

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