After quite some time fb2 is now logged in. This took a long time.
The control box for the south path FSS has been moved to the rack to sit along side the North path control front end.
I bought a longer 37 strand ribbon cable and crimping Sub-D connectors from digikey. The new cabling means that the electronics can now be operated from rack near the FB2 box location. Previously the two PDH loops were powered from two separate sets of power supplies on opposite sides of the lab. The electronics for both paths are now powered from the same set of power supplies with the same grounding. This should at least make diagnosing noise common to the loops a little easier.
I have not been able to test whether we are able to get back to lock because fb2 has not recovered from a ~1 week power down. I had unplugged everything to make more AC sockets available, swapping out the two small power boards in the rack with one long one. In the process of wiring up the south path electronics and changing the AC routing I pulled on some wires that turned out to be just hanging out the side of the rack bare: sparks came out. Its taken me a while to rewire and double check the DC lines within the rack. I have removed a number of HV lines that are not powering anything. This should be safe again.
fb2 has been turned on for a few hours now and is showing no signs of life on the monitor. I've tried plugging in a second monitor, still bad. If its not up by tomorrow, might need to investigate further.