Exchanging device board DB1 and device board 2 in the 5094, 5294, and 8294 expansion units

Use this procedure to remove or replace a device board 1 and device board 2 in the 5094 and 8294 expansion units.

1. Power off the expansion unit (see Powering off an expansion unit).
2. Disconnect the power cord from the expansion unit.
3. Open the front cover (see Exchanging the covers in the 5074, 5079, 5094, 5294, 5096, 5296, 8079-002, 8093-002, 8094-002, and 8294 expansion units).
4. From the front of the expansion unit, perform the following:
   1. Remove the EMC access plates from the disk unit enclosures that are located in front of the board that you are replacing (see Locations — 5094, 5294, 5096, 5296, 8094-002, 8294, and 9194 expansion unit). Press the surfaces of the two latching mechanisms together and tilt the top of the cover away from the frame to remove it.
   2. Record the locations of the disk units and then remove them from the disk unit enclosures that you just uncovered.
      Attention: The disk units are sensitive to electrostatic discharge (see Working with electrostatic discharge-sensitive parts).
   3. Remove the screws that hold the disk unit cage assembly to the frame.
   4. Remove the two retaining screws that are located inside of the disk unit cage assembly (the top right and bottom left corners).
   5. Remove the disk unit cage assemblies.
   6. Remove the screws that hold the DASD shelf to the frame.
   7. Remove the DASD shelf from the frame.
5. Remove the retaining screw that is holding the device board assembly to the frame.
6. Pull the device board assembly out until it slides off the guide pins, then rotate the device board assembly 90 degrees. Note the locations of the cables that are located on the backside of the board assembly, and then remove the cables.
   Note: Both ends of the ribbon cables are marked LH or RH, indicating that one end of the cable is plugged in to either the left-hand device board 1 or right-hand device board 2 assembly. The other end of the cable is plugged in to either the left-most (LH) or right-most (RH) DASD controller card. The cables will cross in the center of the tower.
   Figure 1. Device board cabling

   
7. Remove the device board assembly.
8. Install the new device board assembly by reversing this remove procedure.
9. After exchanging an item, go to Verifying the repair. This ends the procedure.