There's no offset adjustment. You'll have to do as I did with changing and gain matching Q1-4 of the main amp board to lower offset which may or may not also fix your static issue. Read the info in post #1 under the heading Input Signal Transistors.
Yes, I had read your entire post, but I noticed that your offset was not bad, so just didn't know if you didn't adjust it because you didn't need to or if it was because there is no adjustment. Your response answers that. I did do some DC voltage measurements for Q1-4:
E, C, B (should be -0.6, +28, -0.05 V according to the schematic)
initial readings:
Q1: -0.34, +27.1, +0.35V
Q3: -0.34, +28.1, +0.36V
Q2: -0.64, +27.1, -0.16V
Q4: -0.64, +28.1, -0.16V
R9: -14.3V one side, -0.15V other side connected to emitters of Q1, 3.
R10: -14.3 V one side, -0.6V other side connected to emitters of Q2, 4.
So, starting out emitters of Q1 and 3 are low, and Bases are not good. Q2+4 are good.
After about 5 minutes I took readings again:
Q1: -0.02, +27.1, +0.61V
Q3: -0.015, +28.1, +0.62V
Q2: -0.53, +27.1, +0.07V
Q4: -0.53, +28.1, +0.09V
R9: -14.3V one side, +0.049 on side connected to Q1, 3 emitters.
R10: 14.3 V one side, -0.53V on side connected to Q2, 4 emitters.
Q2, 4 look good, I assume a low positive voltage on the bases is ok/normal?
Obviously Q1, 3 got worse. Is this indicating Q1 & 3 are bad, or something else?
I noticed you used transistors you had in stock, if you were to order replacements now, what would you order?