2. Service
Assembly/Module Diagnostic Trees (Diagnostic Section 3)
90
A2 Cesium-Oven Diagnostic Tree
This functional subsection describes the A2 cesium-oven diagnostic tree for
the 5071A Primary Frequency Standard. Performance of these tests is
indicated by the presence of either a self-test or fatal error that reports a
cesium-oven fault.
3.1.4.1.0 Cesium-Oven Resistance Test
1 Remove instrument power.
2 Unplug cable from A2J2.
3 Use a DMM to measure the resistance between cable pins 8 and 15.
QUESTION: Is the resistance between 200 and 250 k ?
If No: Recheck results and DMM, then replace CBT.
If Yes: Go to, 3.1.4.1.1.
3.1.4.1.1 Cesium Oven-to-Ground Test
1 Use a DMM to measure the leakage resistance between cable pins 15
and 11.
QUESTION: Is the leakage resistance at least 10 k ?
If No: Recheck results and DMM, then replace CBT.
If Yes: Go to, 3.1.4.1.2.
3.1.4.1.2 Cesium Oven Monitor Test (Current Off)
1 Remove instrument power.
2 Remove A2 CBT Controller.
3 Install long extender board (05071-60052) into A2 slot.
4 Reapply instrument power.
5 Use SCPI command syst:print?.
(Terminal-to-instrument via RS-232C data communication required.)
QUESTION: Is CBT Oven Err: between 0.5 and -0.5C°?
If Yes: Go to, 3.1.4.1.3.
If No: Remove power, replace A7, and retest.
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