[R-390] AGC problem

[Bill Abate]

My 390A is almost finished its restoration.  Looks pretty good and works 
well.  Well, except for SSB reception.  If I try to tune in a ssb signal 
I get a lot of distortion in the audio and the signal can't be tuned in 
properly.  If I try the old method of max audio gain and reduced RF 
gain, all is well.  Of course this is not the way other R-390A's work. 
BTW, AM reception is pretty good but has some distortion in the audio.

I figured that the AGC was not working properly so I ran the AGC test in 
the manual.  I adjusted the ,local audio for 1.7V of audio with 5 
microvolts of RF.  I then increased the RF sig gen to 1000 microvolts 
and the audio output went to 20 volts.  Its supposed to increase to 3 
volts, so I found the problem.

The problem is I can't seem to find the cause.  I have AGC voltage on 
pin 2 of v506 (AGC line).  I got these AGC voltages with my sig gen:

5 mv    ->     .04VDC
50mv    ->     -.2 VDC
500mv   ->    -3.8 VDC
5000mv  ->    -7.1 VDC
50000mv ->    -9.6 VDC

I also found the AGC voltage on all the tube grids it was supposed to 
control.  The only thing I can conclude is that the AGC voltage is 
insufficient but the manual does not say what the voltage should be with 
varying inputs.  At least I could not find it.  I also tried slow, med 
and fast AGC and the results were the same.

Anybody have data on the AGC line?  Any ideas as to the cause??

Thanks,

Bill, K3PGB