User's Manual

Initial Power Up – continued
PRELIMINARY
SC 4812ETL BTS Optimization/ATP
08/15/2000
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Table 2-4: Pre–power DC Power Distribution System Test
Step Action
1 Physically verify that circuit breakers on the ACLC (Figure 2-4) and DC PDA (figure Figure 2-5), and
all battery shelf circuit breakers (Figure 2-3), are OFF.
2 Visually ensure that all AC rectifier modules (Figure 2-3) are not powered (DC, Power, and bar graph
LEDs are not lighted).
3 Inside the battery compartment, measure the voltage between the + (red) and – (black) battery bus
bars. There should be no 27 Vdc present.
4 In the cabinet RF and LPA compartments, unseat all circuit boards/ modules (except CCD and CIO
cards) in the SCCP shelf and Linear Power Amplifier (LPA) shelves, but leave them in their respective
slots.
5 Inside the battery compartment, measure the resistance between the + (red) and – (black) battery bus
bars. Verify that the resistance measures >
500 Ω.
S 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).
6
On the DC PDA, set the Main Breaker #1 (Internal) to the ON position by pushing it in, and repeat
step 5.
* IMPORTANT
If, after inserting any board/module, the ohmmeter stays at 0 Ω, 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.
7 Repeat step 6 for Main Breaker #2, and each LPA circuit breaker.
8
! CAUTION
Verify the correct power/converter modules by observing the locking/retracting tabs appear as follows:
–
(in +27 volt systems)
Insert and lock the PS1 DC–DC converter module into its slot, and repeat step 5.
S A typical response is that the ohmmeter will steadily climb in resistance as capacitors charge, finally
indicating approximately 500
Ω.
9 Repeat step 8 for the PS2 converter module and all remaining modules in the SCCP shelf.
10 On the DC PDA, set the LPA 1A–1B circuit breaker to the ON position by pushing it in, and repeat
step 5.
11 Repeat step 10 for each of the three remaining LPA circuit breakers.
12 Seat all LPAs into their respective slots in the shelves one at a time. Repeat step 5 after seating each
LPA.
S A typical response is that the ohmmeter will steadily climb in resistance as capacitors charge,
stopping at approximately 500
Ω..
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