Exchanging the device boards in the 5074, 5079, 8079-002, and 8093-002 expansion units

Removing and replacing the device board DB1 and device board 2

Power off the expansion unit (see Powering off an expansion unit).
Disconnect the power cord from the expansion unit.
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).
From the front of the expansion unit, do the following:
1. Remove the EMC access plates from the disk unit enclosures that are located in front of the backplane that you are replacing. (For location information, see Locations — 5074, 8079-002, and 8093-002 expansion units.) 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.
Remove the retaining screw that is holding the DASD board assembly to the frame.
Pull the DASD board assembly out until it slides off the guide pins, then rotate the DASD board assembly 90 degrees. Record the locations of the cables that are located on the backside of the board assembly, and then remove them.
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 DB1 or right-hand device board 2 DASD board 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 crisscross in the center of the tower.

Figure 1. Device board cabling
Remove the DASD board assembly.
Install the DASD board assembly by reversing the removal procedure. After exchanging an item, go to Verifying the repair. This ends the procedure.

Removing and replacing the device board (DB3)

Power off the expansion unit (see Powering off an expansion unit).
Disconnect the power cord from the expansion unit.
Open the rear cover (see Exchanging the covers in the 5074, 5079, 5094, 5294, 5096, 5296, 8079-002, 8093-002, 8094-002, and 8294 expansion units).
From the rear of the expansion unit, do the following:
1. Remove the EMC access plate that is located directly above the card enclosure. Press the surfaces of the two latching mechanisms together, and tilt the top of the cover away from the frame to remove it.
2. Remove the cables from the disk unit controller cards (IOAs) that are located inside the PCI card enclosure and record their card and port locations.
3. Remove the screws that hold the tower card enclosure to the frame.
4. Pull the tower card enclosure partially out of the frame while lifting the cables clear of the enclosure.
5. Press the release mechanism that is located along the top right side of the enclosure and carefully slide the enclosure towards you. Make sure that the cables are clear of the enclosure.
6. Remove the tower card enclosure from the frame.
7. Remove the screws from the EMC access plate that is located inside the frame and directly above the power distribution board.
8. Remove the EMC access plate.
9. Reach through the opening and remove the cables from the backside of the base DASD board assembly (DB3).
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).
From the front of the expansion unit do the following:
1. Record the removable media locations and then remove them by pulling out on the handles that are located on each side of the unit.
2. Remove the control panel by pulling on the handles that are located on each side of the unit and sliding it partially out of the tower. Then, unplug the cable from the rear of the control panel (see Exchanging the control panel in the 5074, 5079, 8079-002, and 8093-002 expansion units).
3. Unplug the control panel cable from the base DASD board assembly (DB3).
4. Remove the two retaining screws that are located inside of the removable media enclosure (the top right and lower left corners).
5. Remove the removable media enclosure.
6. Remove the EMC access plates from the disk unit enclosures that are located in front of the backplane (DB3). For location information, see Locations — 5074, 8079-002, and 8093-002 expansion units. Press the surfaces of the two latching mechanisms together and tilt the top of the cover away from the frame to remove it.
7. Record the disk unit locations 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).
8. Remove the screws that hold the disk unit enclosures to the frame.
9. Remove the retaining screws that are located inside the disk unit enclosure.
10. Remove the disk unit enclosures.
11. Remove the screws that hold the center support bracket and shelf for the disk unit and removable media enclosure to the frame.
12. Remove the support bracket and shelf.
13. Remove the base DASD board assembly (DB3).
Install the base DASD board assembly by reversing the removal procedure. After exchanging an item, go to Verifying the repair. This ends the procedure.