MCE Maintenance

Notes on Winchester (Power) Connectors

• The thumb screws on these connectors provide a secure mating. However, they can be difficult to connect. The following points may help:
  • Do not use a screw driver on the thumb screws, it is very easy to break the thumb screw shaft
  • Hold the connector in one hand and support the weight of the cable while mating the connectors
  • Alternate tightening the 2 screws one revolution at a time
  • Attempt to keep the 2 mating connectors parallel

Notes for SPIDER Subracks

• Additional weight saving may be achieved as follows:
  • The rear panels on the subrack protect the backplanes from foreign objects but may be removed prior to mounting the subracks (the rear panel is not part of the RF enclosure)
  • The feet may also be removed if the subracks are not on the bench (on the bench, the feet provide proper airflow to the bottom of the subrack).
  • The top panel protecting the heat pipes can be removed (in flight configuration, these panels are on the bottom)

• Some issues that may need further investigation
  • The heat fins between the cards in the subrack are intentionally loose for easy fitting, a spot of glue where then meet the Card Guide Stiffener Rail would eliminate the rattling of the loose fins
  • The white panel that covers the front of the subracks was designed for the normal orientation of the subracks before we realized that SPIDER mounts them upside down. The existing covers are usable either by inverting the cover and cutting a new hole for the clock card connectors or using them as designed and covering the opening with aluminum tape. New cover panels could be built but it doesn't seem to be necessary.

MDM Mating Problems

Some problems have been encountered when mating the MDM connectors. The issue is that some connectors appear to bind and either not mate or not mate smoothly. We think that we have duplicated the problem at UBC but the issue requires further investigation at the SPIDER cryostat. It appears that the subrack and mounting flange are more flexible than is desirable. When mating the MDM connectors the mating is causing the subrack to distort. If the following mating procedure is followed then connectors can be mated consistently.

1. Position the subrack MDM connectors so the T on the filter box and T slot on the subrack are flush. This is the fully mated position. A half a turn past this point and the box will encounter the retaining screw which halts further motion in the mating direction (clockwise).
2. Back off, counter clockwise, on the shaft exactly 3 turns.
3. Attach the subrack to the cryostat using all 8 mounting hole. If possible also attach the Heatpipe Frame to the crystat as well. The Heatpipe Frame attachment should considerably reduce the distortion when the subrack is mounted. Check closely that everything is flush.
4. Mate the MDM connectors by turning them 3 turns clockwise using a torque wrench set to 10 in-lbs. If the maximum torque is not reached at 3 turns then it is likely that some distortion has occurred. It is safe to continue turning up to 1 additional turn or until some resistance is met. The resistance will be the mechanical stop of the box hitting its stop screw.
5. At this point in our investigation it appears that the last connector mated encounters the most resistance because the assembly is distorted most at this point. We suggest one of two ways to overcome this. Either turn each connector 1 turn at a time then go back to the first connector and repeat the process until all are fully mated. Alternatively if one connector is consistently harder to mate, then mate that one first.

As a result of over-torquing during repeated mating cycles, the split rings on the shaft, which set the limits of travel of the filter boards, can shift. These can be easily restored to the correct position; see Connector Mating System Maintenance.