Peter K, Gabriele

We were not able to close the ISS second loop. Every time the board was enabled, the output railed.

We checked that the commands to switch the board on and to select which photodiodes to use are correctly sent to the board. Also the variable gain and the reference voltage are sent to the board. Instead, it seems that the commands sent throught the other DB9 cable (boost on and integrator on) are not received. We don't know if it is a model problem or a DAC problem. However, those two commands are not relevant for the moment.

We discovered that when the board is powered up, the inputs are raised to about -11 V, regardless of the input. We traced the problem to the LT1124 used to buffer the inputs and send them to monitoring channels. Removing the LT1124 solve the problem. We checked that thae same happens with the other ISS servo board we have in the electronics lab. We don't understand this behavior. The AEI board is not bahaving in the same way.