[Hammarlund] HQ-170 AVC Problem

[Byron Tatum]

Hello-
    Thanks to all for your time here. Possibly someone here may be able to help 
me with these AVC problems in my HQ-170.
            1. There is a slight low freq modulation in all 3 AVC switch 
positions, giving a slightly raspy note, on both the calibrator or signals from 
a known good external source. It disappears when the AVC is turned off, and I 
have a nice T-9 note.
            2. When I switch to AVC SLOW the pitch of the note changes slightly, 
as compared to either the MED or FAST positions.
 Here is some background info-
            a) I have tried quite a few tubes in all of the osc (6C4, 6BE6), 
product detector (12AU7A), and AVC (6BV8, 6AV6) positions and and problem 
persists relatively unaffected.
            b) The third mixer V-5 (6BE6 455 KC to 60 KC converter) has been 
disconnected from the AVC bus and the free end of 220K AVC feed resistor (from 
pin #7) grounded.
            c) The second 60 KC IF amplifier V-7 (6BA6) has been added to the 
AVC bus by lifting the grounded end of R-32, 470K, and connecting it to the AVC 
bus bypassed to ground with 0.02 uFD disc cap.
            d)  The power supply has new electrolytics.
                                                                        Thanks, 
Byron WA5THJ