Recently (at least since we started using the new SOFT offsets for the new TCS pre-loading) the OMC alignment dither loops ran away during power-up to 20W, leading to an OMC-SUS saturation. So we dug a little deeper:

- The loop that runs away during power-up to 20W is H1:OMC-ASC_ANG_Y_OUTPUT, driven by dither lines.
- So we set the QPD offsets to match the dither alignment at low power (2W), and increased the power running on the QPD for OMC alignment. That worked fine and did not saturate the OMC SUS.
- Indeed the QPD OMC alignment produced 5% higher optical gain at 20W (!, that does translate into range - 80Mpc at 20W into the interferometer).
- We switch back and forth between QPD alignment and dither alignment (stopping short of saturating the OMC SUS), and repeatably saw more optical gain on the QPDs
- Just to verify that it is not a dither SNR problem, we increased the dither line strengh. This just confirment that the dither alignment has an offset (i.e. pulls us away place with less optical gain).

So, we are forced to conclude that the simple dither alignment somehow is affected by non-arm carrier light. It might be time to revive the idea of a beacon alignment.

For now I commented out the dine in the OMC_LOCK guardian that switches to dither alignment.