Adjusting Infinity IRS servo controller

I don't have any specific info on that Genesis servo, but based on my experience with the Infinity servo, I would suppose that one pot is gain and the other offset.  I adjusted mine for as close to zero dc bias as I could get and the the gain for unity.  You will have to try them to see which one does what.  You will also need access to an oscilloscope and probes.

and how do I set this up without an oscilloscope?

Multimeter I have! (and the plastic "screwdrivers")

Let me know!!!!

Could you share insights on how to measure and set levels?

I have the same situation, I have my LF Gain at -10 to have a good balance between LF and Mid/Hi Frequencies

It may be possible to do this with a DMM.  Use DCV setting to adjust offset and ACV to adjust the gain.  Since you can only monitor gain or offset individually, it will be an iterative process.

Has anyone looked at the input / output phase on their servo?

I have two on the bench and it looks like they both have a 90° phase shift.  Makes the 180° knob or the ± phase outputs kind of useless.  Yes, those do flip 180° but that means its either +90 or -90 out of phase.

These are SN's 350 and something around 850.

How about knob removal?  Do they just pull off?  The signal gets noisy on one when you touch the knob.  Grounding the pot fixes.  I'm guessing they didn't remove the anodizing on that pot before installation.

Anyone know of a replacement for the power switch?

How close are low voltage rails.  Both of these have about ±17 rather than 15.