After the NE motor problem detected  last Friday (elog #33267), we performed the following actions:

-  Mon 22nd -   we opened the hermetic flange on the upper part of the case hosting the motor  (Figs 1-2).  We inspected the internal cables and their soldering to the feedthrough, without finding any damage or failure. Also measuring the phase resistance from those wires, the short-circuit on the phase #2 has been confirmed  --> at that point has been evident the need of replacing the motor.  This was quite worrying due to the risk that in order to perform the motor replacement,  it could have been necessary to dismount the whole motor case, where the whole filter chain is hanged.  We evaluated the possible options of intervention, taking into account the duration foreseen for each option (ranging from half a day to  several days) and studied a way for an insitu replacement.

- Tue 23rd -   we performed the insitu replacement:  with some difficulties,  the motor was removed from the sealed case, and replaced with a spare one, purchased a few months ago  (Fig3, new one on the left, damaged one on the right  - Oriental Motor PK264-E2.0A).  Before mounting the motor, we feed it with the new motor driver, and checked its rotation  (thanks to F.Carbognani). The old motor was opened  (Figs. 4-5), and it was found that 4 out of 8 windings were in cc.  From the wire color, it seems a damage due to over-temperature

- Wed 24th -  we performed a quick check  by measuring the output of the "rotary encoder" connected to the hoist movement/position (actually it is a 1kohm multi-turn potentiometer installed inside the sealed case):  a variation of 2.8 ohms was measured in corrispondence of a motor movement of 5000 steps.   After, a final and longer check was performed by looking at the F#7 vertical positon by means of its vertical LVDTs, in corrispondence of a motor movement of 40000 steps forth and  back  (Fig6), hence with the evidence of the effective movement of the whole filter chain.

It remain to understand the cause of the failure, ie the reason of the temperature excess, considering that this motor has a Class B insulation (this means a Maximum allowed temperature of 130C).