[R-390] AGC Slow - Moment of silence

[Larry H]

It looks like the problem with the circuit is the charge time of C551 when switching the AGC into the slow position.  This causes the agc line to be pulled + for a second while C551 charges.  Even if it had zero leakage, one end is switched from ground to B+ potential, causing the problem.
I came up with a fairy simple solution to this problem.  Add a 10 meg to 20 meg resistor to the AGC switch contact 8 to ground.  Remove the wire that goes to that same contact and add a 20 mfd cap (call it C590) in series with that wire to contact 8.   This will maintain a charge on C590 all the time and will have very minimal affect on the operation of the AGC circuit.  I know that this will reduce the effectiveness of the slow position a little, but I don't think you will notice it.  Use the largest res that will overcome the leakage in C590 (should be very low), but I don't think it should be less than 10 meg.  See this schematic.
     http://s32.postimg.org/6310y6av9/IMG_7198s.jpg
I've been using this for a while and have not noticed any issue with it.
Regards, Larry