[Milsurplus] FW: [ARC5] Carbon mic pops

[hwhall at compuserve.com]

I'll take all those ideas for testing.  I hope to make as little change to the original wiring as possible.  But the present pop is so loud that it renders the system nearly unusable - no one today would stand for that level of pain.
 

 Wayne
WB4OGM

 

-----Original Message-----
From: Hubert Miller <Kargo_cult at msn.com>
To: milsurplus <milsurplus at mailman.qth.net>
Sent: Wed, Nov 30, 2016 3:52 pm
Subject: [Milsurplus] FW:  [ARC5] Carbon mic pops



1.      You know that if the AC 6v rectified supply to the mic circuit has no unkeyed current and no regulation, the DC is going to soar up to 8-9 volts, right?
A zener across the 50 uF cap would lessen the inrush current.
2.      The microphone current <10 mA seems a little on the low side but that may be irrelevant.
3.      I would try  a cap at the top side ( microphone side ) of the primary of T-4. The cap will key-up charge to the same voltage as the 50 uF and will
        ( maybe! ) slow the inrush current by means of its stored charge. I would try 0.05 uF which is about 3000 ohms at 1000 Hz. You don’t want to go
       higher than 0.1 uF.
 
Worst case, a cap across the secondary of T-4 or worser case, even a zener clipper here.
This is just my thinking. I don’t have a clue why it was designed like that or if what you’re experiencing is “normal” for that equipment.
 
I have a Bendix intercom amp ( non-JAN nomenclatured ) which maybe i’ll have a look at to see how it’s wired.
-Hue

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