[Milsurplus] FW: [ARC5] Carbon mic pops

[Michael Hanz]

Hue's questions are salient.  It would also be useful to know which 
specific equipment you copied the circuit from.  It may have a history 
of the problem you have experienced.

On 11/30/2016 5:52 PM, Hubert Miller wrote:
>
> 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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