No, neither servo engaged. Just got lucky with initial setting. I played with the offset trim and was able to go up to around 25V and then easily down to 0 with a bit of drift.
BTW, I did not populate the IC for the opto, just the OP27. Is the OP27 Servo 1 as labeled on the board? And is this the one that does not require the 10V to trigger, so I can just adjust to close to 0 and let it do its work?
EDIT: I just finished dialing in balance and offset. Turns out the offset was not as good as I though initially. The balance was WAY off, at 75V. It appears that balance impacts offset, because after getting balance to 0, the offset was then off about 20V, but easily got that down to 0 also. On both boards, I am able to get balance to < 100mV with a bit of drift over time, and offset to < 500mV, again with minor drift over time. Both servos turned off (header not connected). I am now going to re-check the 17ma setting for the 4 outputs and let it run for about an hour. Then, depending on the thermal state, I will move up to 20ma and redial all the settings. One thing I will say is the amps put out a LOT of heat!! Really surprised by how much. Massive heat sink got warm all over after just 10-15 minutes of testing.
EDIT2: I put the jumper on Servo1, and it works quite nicely!! The offset varies +/- 200mV around 0, but holds that range pretty well so far! Does the servo also help with balance? I did not think it did, but for some reason balance is also staying much more stable, going up and down within 200mV of 0. I think I am ready to listen to music. Finger crossed.
EDIT3: We have music!!! And it sounds really, really, really great! First impression compared to the SRX-Plus is more clarity to the bass (sharper, punchier) and more clarity in the treble. I jumped a couple times hearing some high treble parts I had not really noticed before in a few songs. Everything just sounds sharper and more technical, if that makes any sense. I need to listen more, but there appears to be more sound stage as well. I am using SR-507s. I can't wipe this smile off my face.