[Milsurplus] FW: [ARC5] Carbon mic pops

[Hubert Miller]

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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