Evan found that when common gain is changed, DC offset also changes as well. I'm still looking into the problem.
a part of schematic, the driving signal was sent in through test port (the switch was flipped from off to test), so the signal came through PD line in this page.
We still cannot lock RCAV with TTFSS, so I'm checking the box 2009007 (#7).
Common Gain - DC offset problem
DC offset vs input drive. DC offset is calculated from (Vmax + Vmin) /2 from a sinusoidal signal input. The signal was taken from TP4. The behavior is very non linear and it is impossible to make a table for an appropriate offset level vs common gain setting.
What to do next?