2. Service
Assembly/Module Diagnostic Trees (Diagnostic Section 3)
97
3.3.2.2 Clock Does Not Increment
1 Remove instrument power and replace A3.
2 Reapply power and observe display for time increment.
QUESTION: Does the time display increment correctly?
If Yes: Retain new A3 and retest.
If No: A1 may be defective, contact Symmetricom for further assistance.
3.3.3. 1 PPS Outputs Test
1 Reapply instrument power if required.
2 Use the oscilloscope with 50 input termination to check for 20 microsecond
pulses at a rate of 1 pulse per second at each of the three external 1 PPS
output connectors.
3 Verify that all 1 pps output levels are: pulse low level less than 0.5 volts, and
pulse high level more than 3.0 volts. Use a trigger level of 1.5 volts.
QUESTION: Are all 1 pps outputs present as specified in step 2?
If Yes: Go to, 3.3.4.
If No: Go to, 3.3.3.1.
3.3.3.1. 1 PPS Output Fault
1 Remove instrument power and replace A8.
2 Repeat steps 1 and 2 of procedure 3.3.3.
If Yes: Retain new A8 and retest.
If No: Go to, 3.3.5.
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