Symmetricom 5071A, Assembly And Service Manual

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2. Service
Assembly/Module Diagnostic Trees (Diagnostic Section 3)
95
A8 Diagnostic Tree
(A/M Subsection 3)
This subsection describes the A8 1 PPS Assembly diagnostic tree.
3.3.0. A8 Test Setup
1 Remove instrument power.
2 Mount A8 on the short extender board (05071-60051).
3 Disconnect the CBT cable from A2J2 (this ensures power up to Fatal Error
mode).
4 Disconnect coax cable from A8J3 and reconnect to 50
Ω
input of the
oscilloscope (use 50
Ω
feedthrough if necessary).
5 Apply instrument power and verify presence of an 80 MHz sine wave with at
least 0.6 Vp-p amplitude.
QUESTION: Is the waveform as described in step 5?
If Yes: Go to, 3.3.1.
If No: Go to, 3.4.1.0 (A9 Diagnostic tree).
3.3.1. A8 1 MHz Output Signal Test
1 Remove instrument power.
2 Reconnect cable marked A8P3 to A8J3 and reapply instrument power.
3 Use the SO-16 dip clip and the oscilloscope with a high-impedance probe to
examine the wave-form at A8-U41.2 and A8-U41.3.
The correct waveform is a 1 MHz square-wave with a logic-low level of less
than 0.5 Vdc, and a logic-high level of greater than 2.5 volts. The wave-form
on A8-U41.3 must be the complement of that on A8-U41.2.
(Use the rear-panel 1 MHz output to conveniently trigger the oscilloscope.)
4 Record your results.
QUESTION: Is the waveform as described in step 8?
If Yes: Go to, 3.3.2.
If No: Go to, 3.3.1.1.