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2. Service

Assembly/Module Diagnostic Trees (Diagnostic Section 3)

A2-Mass-Spectrometer Diagnostic Tree

This functional subsection describes the A2 mass-spectrometer 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 mass-spectrometer fault.

3.1.3.1.0 Mass-Spectrometer Resistance Test

1 Remove instrument power.

2 Unplug CBT cables from A2J1 and A2J2.

3 Use a DMM to measure the resistance across A2P4 CBT cable

pins 1 and 4.

QUESTION: Is the resistance greater than 200 k?

If Yes: Go to, 3.1.3.1.1.

If No: Recheck results and DMM, then replace CBT.

3.1.3.1.1 Mass-Spectrometer Test (Current Off)

1 Remove instrument power.

2 Replace A2 CBT Controller with long extender board (05071-60052).

(Do not insert A2 at this time.)

3 Reapply instrument power: instrument will go to Fatal Error.

4 Use SCPI command syst:print?.

(Terminal-to-instrument via RS-232C data communication required.)

QUESTION: Is Mass spec: between -0.5 and +0.5V?

If Yes: Go to, 3.1.3.1.2.

If No: Remove power, replace A7, and retest.

3.1.3.1.2 Mass-Spectrometer Monitor Test (+ Current On)

1 Place a 10 k resistor between pins 1 and 37 on connector XA2P2

(48-pin connector on extender card).

2 Use SCPI command syst:print?.

(Terminal-to-instrument via RS-232C data communication required.)

QUESTION: Is Mass spec: between 9.5 and 11V?

If Yes: Go to, 3.1.3.1.3.

If No: Remove power, replace A7, and retest.

Symmetricom 5071A Assembly And Service Manual

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