The issue of the 9 MHz amplifier box [1] was solved. The box is now back in the R2 rack and working fine.
I tested the box at the EE shop and it was very healthy. Then it turned out that the exterior signal cable was flaky even though Rich had replaced its N-connector by a new one yesterday because we had suspected it at the beginning. We swapped the cable with a temporary one and everything worked fine. The temporary cable will be replaced by an LMR cable at some point but we will go with it for now to carry out the demodulation chain and photo-diode calibration tests.

[1] LHO alog 5846 "9 MHz amplifier box pulled out for testing"