1) Turn off feedback to ETMY (the ETMY button on the LSC screen).
2) Put a 1 into the YARM->MC2 output matrix element on the LSC screen.
3) Turn off FM6 (comb), FM7 (0.1:10) on the MC2_MCL filter bank. This is to make the IOO-MCL loop more stable and to reduce the IOO-MCL low frequency gain.
4) Set the MC2-LSC gain to 0.5, turn the output ON, turn ON FM4 & FM5 & FM6 of the MC2-LSC filter bank.
5) Turn on the input of MC2-LSC and the arm should now lock.
6) After locking, set the MC2-MCL gain to zero. Hopefully with a few second ramp time.
(A comment by KA - c.f. this entry )