This morning the NNN NCal (Box 10 rotor R4-10) has been replaced by the NCal (Box 06 Rotor R4-17) which was installed on the NWN slot.

This NCal swap required the removing of the box top plate for the metrology target holder (in order to fit in the vertical support), as well as the swap of the bottom spacer( to provide the right twist angle).

During this change, it was noticed that the power supply channels for the NNN NCal motor (32 V channel 1) and North setup position sensors (5 V, channel 2) was broken. More specifically, it could not be turned off by the “output” button, and once the main power (red) button was cycled off/on, these two channels could not anymore supply any current. They have probably been damaged during the fast stop of the rotor that might have send back more current than the shunt regulator could stand. Therefore, the position sensor cable was connected together with the 5V photodiode cable, and the NNN motor power cable moved to the channel 1 of the NCal East power supply. However, the channels 3 and 4 of the North power unit are still working properly.

The four nominal NE NCals have been restarted with their usual configuration at 5:58 UTC.