Yamamoto, Ushiba, Aso

We went to the X-end to check what happened.

It turned out that the breaker to provide the AC power to the PDs was off.

The diagram below shows how the various components are connected to the power line.

FFU: Filter Fan Unit for the TMS area
SX-5: Wall power outlet, to which the transmission PDs are connected.
LED: The LED lighting for the TMS area

When we arrived at the X-end, B1 was off and S1 was on.
Therefore, nothing was powered.

We then turned on B1. Then all the components were powered.
However, the PD signals were still strange.
We power cycled the PDs using the switches on the PD bodies.
Then the oscillations went away and the green flashes were visible.

We disengaged S1 to turn off the LEDs. However, we cannot turn off the FFUs without shutting down the PDs. So we left the FFUs running. Probably, the FFUs were on during the O4 observation.

After this work, Ushiba-kun confirmed that the X-arm can be aligned well with the ADS.

I think this incident was caused by a very confusing connection. As shown in the photo of B1, it seems Akutsu-san was also annoyed by this problem in the past. We put an additional notice that turning off this breaker results in the shutdown of the PDs.
However, a better solution is to connect the PDs to, not SX-5, but to a DGS power outlet. We have one near S1.

B1

S1