MAP21F0 UEPO loop good LED should be off

The primary power supply (PPS) UEPO Loop Good LED should be off when the UEPO switch on the rack operator panel is in the off (tripped) position.

About this task

The UEPO switch has two sets of contacts, one set of contacts for each PPS. Each set of contacts has a two wire UEPO loop cable that goes to the PPS sequencer module J4 connector. When the UEPO switch is on (normal operation), the circuit is closed and the LED should be lit. When the UEPO switch is tripped off, the circuit is open and the LED should be off.

Procedure

  1. Ensure that the rack operator panel UEPO switch is in the off (tripped) position.
  2. At the front of both PPS, observe the UEPO LOOP GOOD LED. Find the condition that applies:
    • The LED is lit for both PPSs, go to step 3.
    • The LED is off for one PPS and lit on the other PPS, go to step 4.
    • The LED is off for both PPSs, go to step 5.
  3. Each PPS has a separate UEPO loop so the only failure that would affect both PPS would be the UEPO switch not being fully off (tripped). Do one or more of the following:
    • Disassemble the operator panel as needed to fully inspect the mechanical operation of the switch.
    • Unplug the UEPO loop cable from the PPS sequencer module J4 connector cable. Observe the PPS UEPO LED, if it is off the UEPO switch needs to be replaced. If it is lit, the PPS needs to be replaced.
    • Unplug the UEPO loop cable from the PPS sequencer module J4 connector cable. Use a volt/ohm meter to measure the continuity of between the two pins of the cable. The cable should be open (infinite resistance). If it is not, replace the UEPO switch assembly.
  4. At the rear of the PPS with the UEPO LOOP GOOD LED that is lit, unplug the UEPO loop cable from the PPS sequencer module J4 connector. See Figure 1.

    Is the UEPO LOOP GOOD LED off?

    • Yes, the UEPO switch assembly is failing and needs to be replaced. If the customer allows the storage facility to be powered off, replace the UEPO switch FRU with the power off. If the customer cannot allow the storage facility to be powered off, see MAP2180 UEPO switch replacement (Models 94x, 95x, 96x).
    • No, go to the next step.
    Figure 1. Sequencer module J4 connector
    Rear view of PPS. Sequencer module J4 connector
  5. Does this rack have battery enclosures installed, as shown in Figure 2?
    • Yes, go to the next step.
    • No, the PPS is failing to UEPO when the UEPO loop is open. Replace the PPS.
    Figure 2. Battery enclosures
    Three battery enclosures
  6. At the rear of the PPS with the UEPO LOOP GOOD LED that is lit, unplug the cable from the PPS sequencer module J6 connector. See Figure 1.

    Is the UEPO LOOP GOOD LED off?

    • Yes, the problem is either the battery communication cable that was unplugged or one of the battery module enclosures to which the cable connects. Go to the next step.
    • No, the PPS is failing to UEPO when the UEPO loop is open. Replace the PPS.
  7. Connect the cable to the PPS sequencer module J6 connector.
  8. Trace the cable and unplug it from one battery module enclosure.

    Is the UEPO LOOP GOOD LED off?

    • Yes, reconnect the cable and replace the battery module enclosure that was disconnected.
    • No, reconnect the cable and repeat this step for the next battery module enclosure. If the cable has been disconnected from all battery module enclosures and the UEPO LOOP GOOD LED is still on, replace the cable.