f. Test procedure 64. When measuring continuity on the MT-1898 J14 and
it has been determined the X-MODE OUT and X-MODE IN circuit is not open or
shorted, and the MT-1898 and J-3514/U are good, the R-442 is bad.
g. Test procedure 65. When performing EPC step 24, no rushing noise is
heard in the earphone or in the speaker. Rushing noise at either speaker or
handset confirms that the R-442, MT-1898 and J-3514/U (X-MODE OUT, X-MODE IN
circuit) is good. However, a short is in the system. Again, testing at MT-
1898 J14, as in test procedure 63, remove the R-442 from the MT-1898.
Measure continuity at J14 pin S (phone out) or pin F (speaker
out) to J14 pin A for the circuit that is not working.
If infinity is measured, the R-442 is bad.
If zero ohms is measured, a short exists within the system.
h. Test procedure 66. To test the system for a short, remove the CX-
7058/VRC from the AM-1780 J-510.
Remeasure at J14 pin S or pin F to pin A.
If infinity is measured, the AM-1780 is bad.
If zero ohms is measured, disassemble the MT-1898 and remove the
CX-7058/VRC from the J-3514/U J1.
Remeasure J14 pin S or pin F to pin A.
If infinity is measured, the CX-7058/VRC is bad.
If zero ohms is measured, remove P1 from J12 on the MT-1898.
Remeasure J14 pin S or pin F to pin A.
If infinity is measured, the J-3514/U is bad.
If zero ohms is measured, the MT-1898 is bad.
29. R-442 KY-57 KEYING ALARM CLEAR CIRCUIT.
a. Situation 15.
When performing EPC step 42b, the R-442 call lamp
does not go off and ALARM beeps do not stop when substation button on J-
3514/U is pressed and released. This indicates the KY-57 keying ALARM CLEAR
circuit is bad. This symptom is caused by an open or a short. Trace the
KY-57 keying ALARM CLEAR circuit to identify the following possible bad
items of equipment: J-3514/U, CX-13062/U, and KY-57 (Figure 98).
b. General test procedures.
You must determine the type of test and
the location of the test points to identify the actual bad item of
equipment.
Troubleshooting techniques for this type of defect are signal
substitution, followed by continuity measurement.
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