15. TSEC/KY-57 INPUT POWER CIRCUIT.
a. Situation 7. When performing EPC step 40 (TSEC/KY-57 Input Power),
the KY-57 power switch is turned to ON. The A-RT call lamp does not light
and alarm beeps are not heard in the handset at J5.
This symptom may be
caused by no power to the KY-57.
To confirm power, measure voltage 5.2
volts DC at the KY-57 (turned on) audio connector pin A to pin C (If KY-57
is turned OFF voltage measured at the audio connector pin A to C will be 30
volts DC). If no voltage is measured, the KY-57 input power circuit is bad.
Tracing the KY-57 input power circuit identifies the following possible bad
items of equipment: J-3513/U, CX-13061/U, CX-13063/U, HYP-57, and KY-57
(Figure 51).
Figure 51.
KY-57 input power (possible bad items).
b. General test procedures. You must determine the type of tests and
the location of the test points, to identify the actual bad item of
equipment. Troubleshooting techniques for this type of defect are voltage
measurements, followed by continuity measurements (Figure 52).
c. Test procedure 27. The first voltage test point (TP1 of Figure 52)
is between pins N(+) and G(-), plug P2 on the CX-13061/U.
Pins N and G,
through the CX-13061/U and the KY-57, provide a ground for the J-3513/U K-5.
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