User Manual

Pre–Power Up Tests – continued
2-2 1X SC4812T–MC BTS Optimization/ATP 5/21/04
DRAFT
Table 2-2: DC Power Pre–test (BTS Frame)
Step Action
3 For –48 V configurations ONLY:
Verify the resistance on the –48 V bus:
– Remove the Power Supply Modules (PSMs).
– Verify that the resistance from the power (–) feed terminal with respect to the ground terminal on
the top of the frame measures >
500 Ω (see Figure 2-3).
Verify the resistance on the +27 V bus:
– Remove PSM#1 or the filler panel.
! CAUTION
Do not put probes inside Elcon connectors.
– Place the Digital Multimeter probes on the mounting screws on the Elcon connector (bottom two
Elcon connectors).
– If reading is < 500
Ω, a short may exist somewhere in the DC distribution path supplied by the
breaker. Isolate the problem before proceeding. A reading > 3 M
Ω could indicate an open (or
missing) bleeder resistor (installed across the filter capacitors behind the breaker panel).
4 For +27 V configurations ONLY:
Verify that the resistance from the power (+ or –) feed terminals with respect to the ground terminal on
the top of the frame measures >
500 Ω (see Figure 2-3).
– If reading is < 500
Ω, a short may exist somewhere in the DC distribution path supplied by the
breaker. Isolate the problem before proceeding. A reading > 3 M
Ω could indicate an open (or
missing) bleeder resistor (installed across the filter capacitors behind the breaker panel).
5 Set the C–CCP breakers to the ON position by pushing them IN one at a time. Repeat Step 3 (for
–48 V) or Step 4 (for +27 V) after turning on each breaker.
NOTE
If the multimeter stays at 0 Ω after inserting any board/module, a short probably exists in that
board/module. Replace the suspect board/module and repeat the test. If test still fails, isolate the
problem before proceeding.
6 Insert and lock the DC/DC converter modules for the C–CCP shelf and into their associated slots one
at a time. Repeat Step 3 (for –48 V) or Step 4 (for +27 V) after inserting each module.
– A typical response is that the ohmmeter steadily climbs in resistance as capacitors charge, finally
indicating approximately 500
Ω.
! CAUTION
Verify the correct power/converter modules by observing the locking/retracting tabs appear as follows:
STPN4009B
PWR C–CCP 4812 +27V
7 Insert and lock all remaining circuit boards and modules into their associated slots in the C–CCP shelf.
Repeat Step 3 (for –48 V) or Step 4 (for +27 V) after inserting and locking each board or module.
– A typical response is that the ohmmeter steadily climbs in resistance as capacitors charge,
stopping at approximately 500
Ω..
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