[Hallicrafters] SR-400A AGC Pumping

[Bill Gerhold]

This is very similar to a AGC problem or modification for the Collins KWM-2
tranceivers.  The Collins bulletin basically adds a (2) new caps for a fast
rise time and a slower decay time.

Your situation sounds very similar.  The KWM problem while a design
characteristic, was described exactly as you are describing the SR-400A.  A
popping sound type AGC action.  

I had this same problem in my SX-111.  Very fast "S" meter and audio action.
I tracked down the capacitor involved, and just basically paralleled a high
value cap and the "S" meter and "Pumping" AGC was resolved to my
satisfaction.

K2WH