[Takahashi, Sugiyama, (remote) Sato, Ikeda]

We checked the adjustable range of each filter with the FR.

• Releation between number of steps and the keystone height is shown in the plot.
• Adjustable range is summarized in the table.
• F2 FR has been stuck at the lower side during the operation. The filter itself is still working, but the height of keyston is out of the linear range of LVDT. The ballast on the BF cup was dcreased by 180g.
• F1 FR didn't work. We will investigate more.

[Takahashi, Sato, Sugiyama, (remote) Ikeda]

We tried to recover the F1, F2 FRs.

• Checked cable connection for the F1 FR. Pin #1 was grounded. We prepared for the stand alone driver and connected it to the F1 stteper motor through a #1-6 flip cable. Though we tried to move the stepper moter using some step methods, the FR didn't work.
• Tried to move the F2 FR again. We used the slow micro steps and the intermittent full steps. The FR came back alive! Set the keystone height to the mid point.

We tuned the IP more.

• Added a ballast ring (t=6mm, 2.7kg).
• Measured the TF (ACT-L to LVDT-L). Resonant frequency became lower than 50mHz.

Work on 2021.7.13

Investigation of F1 stepping motor ground fault.

To identify the F1 stepping motor cable, I removed the feedthrough (Port4) once. After that, I found a short circuit where the cable was fixed to the IP structure. (See photo: the sheathing was damaged in the area circled in red.  The ground fault was at the point indicated by the arrow.)

I took temporary measures to insulate the cable and tried to run the stepping motor. The motor was trying to move, and I could see vibration in the LVDT signal, but I could not change the keystone height. There seems to be a lot of mechanical resistance.

Where the cable is fixed in a similar way at the IP, additional measures should be taken to maintain the insulation. We will continue with the cable insulation and motor drive checks tomorrow.

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Resistance of F1 stepping motor (measured from feedthrough)
Pin 1-6, 9.0[ohm]
Pin 2-7, 9.2[ohm].
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[Takahashi, Sato]

Recovery of F1 FR

• Tried to move the F1 FR. We used the slow micro steps and the full steps. The FR came back alive! Adjustable height range of keystone was 66.5 +/- 2.4mm.

Tuning of F0

• Compressed six blades to 8mm, 12mm, and 14mm from 6mm.
• Measured the dependence between weight on the F0 and height of the keystone in each compression.
• Expansion of adjustable height range of keystone is expected.

[Takahashi, Sato]

1. Measured the dependence between weight on the F0 and height of the F0 keystone again after fastening the screws to fix the blades to the keystone more.
2. Fixed the ballast weight (total 48.15kg) on the F0.
3. Checked adjustable height range of the F0 keystone. It was expanded to +/- 3.6mm. The upper side is limited by the LVDT range. The lower side is limited by the FR blades which touch the TF base.

Data on the FR range measurements for BF, F1, and F0.