The photodiode amplifiers for the fiber transmitted and rejected beams were not behaving as expected. Changing the gain had seemingly no effect on the read voltage. The first problem was that the two diodes were crosswired in the slow controls system. However, this did not fix the problem, and it is the same for the IR DC power. It looks like the gain settings are not getting applied to the concentrator. The main suspects are the 5V supply, DC_6, in the end 2 chassis, or another of these DB37 cables with pin 19 conveniently left unconnected. This supply is used to power the binary IO terminals for auxiliary concentrator 5. It also controls the gain in the REFL PD DC path.