[mTakahashi, Ushiba]

Abstract:
We found MNH1 coil itself is electrically short to the cryogenic payload.
The place where the short occures seems to be inside the coil bobins, so we need to replace the coil to another new one.

What we did:
We measure the resistance at several point.
At the top chamber: ~50 ohm (should be about 110 ohm)
At the BF: ~35 ohm (should be about 40 ohm) 
At the PF: ~50 ohm (should be about 50 ohm)
From the above result, I thought electric short occures between BF and PF at first.

However, it turned out to be wrong because of the following measurement.
At BF when disconnecting at PF: NC

Then, I carefully check all pins one by one and found that pin #2 is short to the payload (resistance between pin #2 and the payload is about 2 ohm)
Also, to confirm the place where electric short occurs, we checked the clamping points of the cables.
Then, finally we found that short seems to occur at the coil bobin itself.
So, we need to replace it to new one.

[Tomaru, Ushiba]

We removed broken coil from the payload.
Also preparation of new one and check of the polarity was done but it has been not yet installed.

We will do it tomorrow.

[Tomaru, mTakahashi, Ushiba]

We reinstalled a new MNH1 coil to the IX payload.
After installation, we measured the resistance of MNH1 coil from the top flange.
Measured value is 110.7 ohm and seems fine (nominal value is about 110 ohm).

We also measured the IM heater resistance (6-7 pin: 130.2 ohm, 8-9 pin: 130.7 ohm).

According to these results, acceptance check document is updated.

[Ushiba]

Today, I checked all cables again after repairing of MNH1 and foundthat there are still some unhealthy caables.
P6-1 (MNH1 sensor & actuator): 7 pin is grounded (~18 ohm)
P6-5 (MNV1 sensor & actuator): foreward voltage of LED is strange (1.364 V while nominal is about 0.94 - 0.95)
P6-8 (MN & IM thermometer): 9 pin is grounded (~ 4 ohm)

Also, I found several port is grounded at 5 pin.
P6-2 (~0.8 ohm)
P6-5 (~1.7 ohm)
P6-6 (~0.9 ohm)

However, I thought it is not a serious problem because the 5 pin is not connected to anywhere inside the chamber.

[Tomaru, Ushiba]

We tried to confirm the broken point of IX problematic cables.
Followings are the result:
P6-1 (CRYO9): #7 pin of the cable between BF and PF are short to the suspension.
P6-5 (CRYO13): No trouble was found below BF port. Need to check tower side cable.
P6-8 (CRYO16): No trouble was found below BF port. Type-A tower cable is short to the suspension somewhere.

For P6-1 cable, since the place which is short to the suspension is almost the center of cable and cannot be repaired, we installed additional cable between PF and BF. (fig1).
As you can see in the fig1, old cable is now just put on the BF and not fixed, so we need to do it.
Also, cables is once clamped at the cable clamp on maraging wire between BF and PF but not fixed on the body of BF (see fig2).

In addition, we keep the connector of P6-8 disconnected (see fig3) because it is very difficult to access due to the BF dampers and one of the nuts to fix the connector was loosen.
So, to recover that cable, we need help of Type-A team.

Note: nut for fixing Dsub connector was now taped on the franges as shown in fig. 4 not to miss it.
The cryopayload has already released but BF has not, so we need to release BF if we would like to control the suspension.

[Takahashi, Sato]

We went to the recovery of cables for the payload. This is short summary of countermeasure.

• P6-1(CRYO9): New cable was fixed onto the bottom of BF. Old connector was attached to the side plate on BF.
• P6-5(CRYO13): Checked the rsistance of each wire between the BF and the feedthrough. They are almost the same (about 7Ω). Diode voltage became 0.5V in Pin1-6, and 0.9V in Pin3-8 after reconnection.
• P6-8(CRYO16): Pin9 is grounded inside the corrugate tube. This cable was swaped with P4-8(BF PM).

The following actions are attached as a cartoon.

• P6-8(CRYO16): Pin9 is grounded inside the corrugate tube. This cable was swaped with P4-8(BF PM).