Symmetricom 5071A Assembly And Service Manual

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5071A Primary Frequency Standard

Assembly- Level Service

Manual

Rev. B, July 3, 2007

Part Number: 05071-90040

Assembly- Level Service Manual

This manual describes how to service the Symmetricom 5071A Primary Frequency Standard. The information in this manual applies to instruments having the number prefix listed below, unless accompanied by a "Manual Updating Changes" package indicating otherwise.

SERIAL NUMBER PREFIX: US4538 AND ABOVE

Some sections of this manual refer to using the ‘5071A Profiling software’. This revision of the manual no longer supplies a 3.5-inch floppy disk with this software. To obtain a copy free of charge visit our web site at

http://www.symmttm.com/products_pfr_5071A.asp and follow the links to

“Software and Drivers”. The latest revision of the Profiling Software (Symmetricom P/N 05071-13501) can then be saved to your computer hard disk. This software is only available for use with a Windows®-based PC.

There are a limited number of 5071A replaceable parts available. The 5071A Primary Frequency Standard is a very precise and complex product and Symmetricom strongly recommends that they be sent in for repairs and postrepair performance testing. However, there are some assemblies, such as the Cesium beam tube that we do sell should you wish to perform this in your own facility. We require that you have a copy of the 5071A Assembly-Level Service Manual (P/N 05071-90040) before doing any repairs or parts replacements.

Although Symmetricom Global Services (SGS) is always available to help when you have questions, they cannot be expected to provide troubleshooting assistance when you are repairing the 5071A - That is the purpose of the 5071A Service Manual.

5071A Primary Frequency Standard

Safety Considerations and Warranty

©Copyright Symmetricom, Inc. 2006

Manual part number 05071-90040

Safety Considerations

General

This product and related documentation must be reviewed for familiarization with this safety markings and instructions before operation.

This product is a safety Class I instrument (provided with a protective earth terminal). If this instrument is used in a manner not specified by Symmetricom, the protection provided by the equipment may be impaired.

Before Applying Power

Verify that the product is set to match the available line voltage and the correct fuse is installed. Refer to instructions in Chapter 1 of this Manual.

Before Cleaning

Disconnect the product from operating power before cleaning. Clean only with lightly damp cloth and mild detergents. Do not get unit wet.

Safety Earth Ground An uninterruptible safety earth ground is recommended from the mains power source to the product input wiring terminals or supplied power cable. The terminal is located on the rear of the unit near the AC input receptacle.

Warning Symbols That May Be Used In This Manual

Instruction manual symbol; the product will be marked with this symbol when it is necessary for the user to refer to the instruction manual.

Indicates hazardous voltages.

Indicates earth (ground) terminal.

OR Indicates terminal is connected to chassis when

such connection is not apparent.

Safety Considerations and Warranty

Indicates Alternating current.

Indicates Direct current.

Rack Mounting

The Model 5071A Unit is designed for mounting in a standard 19-inch (48.26 cm) rack. Follow the rack manufacturer's instructions for mounting the Model 5071A Unit while observing the following guidelines:

 Elevated Operating Temperature: If the Model 5071A Unit is installed in a closed or

multi-unit rack assembly, the ambient temperature of the rack environment may be greater than the Model 5071A Unit's Maximum Operating Temperature of 50°C/122°F. Install the Model 5071A Unit in an environment that is compatible with the Model 5071A Unit 's operating temperature range, which is 0 °C to 50 °C, or 32 °F to 122 °F

 Mechanical Loading: Mount the Model 5071A Unit so as to avoid uneven mechanical

loading that could cause hazardous conditions.

 Circuit Overloading: Observe the power ratings on the Model 5071A Unit 's nameplate

and the additional load the Model 5071A Unit may place on the supply circuit. Overloading the supply circuit may adversely affect the supply wiring and over-current protection.

 Reliable Earthing: Maintain reliable earthing (grounding) of rack mounted equipment.

Pay particular attention to supply connections other than direct connections to the branch circuit (e.g., use of power strips).

CAUTION ________________ Damage to equipment, or incorrect measurement data, may result from failure to heed a caution. Do not proceed beyond a CAUTION sign until the indicated conditions are fully understood and met.

Whenever it is likely that the protection has been impaired, the instrument must be made inoperative and be secured against any unintended operation.

If this instrument is to be energized via an autotransformer (for voltage reduction) make sure the common terminal is connected to the earthed pole terminal (neutral) of the power source.

Instructions for adjustments while covers are removed and for servicing are for use by servicetrained personnel only. To avoid dangerous electric shock, do not perform such adjustments or servicing unless qualified to do so.

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iii

Safety Considerations and Warranty

Safety Considerations (contd)

WARNING:

BODILY INJURY OR DEATH MAY RESULT FROM FAILURE TO HEED A WARNING. DO NOT PROCEED BEYOND A WARNING SIGN UNTIL THE INDICATED CONDITIONS ARE FULLY UNDERSTOOD AND MET.

AVERTISSEMENT:

LA BLESSURE PHYSIQUE OU RESULTAT DE MAI DE MORT DE L'ECHEC POUR FAIRE ATTENTION A UN AVERTISSEMENT. Ne PAS PROCEDER AU DELA D'UN SIGNE ANNONCIATEUR JUSQU'A CE QUE LES CONDITIONS INDIQUEES SONT ENTIEREMENT COMPRISES ET SONT RENCONTREES.

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WARNING:

THE MODEL 5071A UNIT SHOULD ONLY BE PLUGGED INTO A GROUNDED RECEPTACLE. SYMMETRICOM RECOMMENDS THAT THE CHASSIS EXTERNAL GROUND BE CONNECTED TO A RELIABLE EARTH GROUND.

ANY INTERRUPTION OF THE PROTECTIVE GROUNDING CONDUCTOR (INSIDE OR OUTSIDE THE INSTRUMENT) OR DISCONNECTING THE PROTECTIVE EARTH TERMINAL WILL CAUSE A POTENTIAL SHOCK HAZARD THAT COULD RESULT IN PERSONAL INJURY. (GROUNDING ONE CONDUCTOR OF A TWO CONDUCTOR OUT-LET IS NOT SUFFICIENT PROTECTION.)

AVERTISSEMENT:

RELIER CET APPAREIL À UNE PRISE DE COURANT AVEC CONTACT ADEQUATE DE MISE À LA TERRE. SYMMETRICOM RECOMMANDE QUE LE CHÂSSIS SOIT RELIÉ À UNE TERRE FIABLE.

N'IMPORTE QUELLE INTERRUPTION DU CONDUCTEUR FONDANT PROTECTIF (DANS OU HORS DE L'INSTRUMENT) OU DEBRANCHER LE TERMINAL DE TERRE PROTECTIF CAUSERA UN DANGER DE CHOC POTENTIEL QUI POURRAIT AVOIR POUR RESULTAT LA BLESSURE PERSONNELLE. (FONDANT UN CONDUCTEUR D'UNE DEUX SORTIE DE CONDUCTEUR EST LA PROTECTION PAS SUFFISANTE).

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Safety Considerations and Warranty

Safety Considerations (contd)

WARNING:

FOR CONTINUED PROTECTION AGAINST FIRE, REPLACE THE LINE FUSE(S) ONLY WITH 250V FUSE(S) OF THE SAME CURRENT RATING AND TYPE (FOR EXAMPLE, NORMAL BLOW, TIME DELAY). DO NOT USE REPAIRED FUSES OR SHORT CIRCUITED FUSEHOLDERS.

AVERTISSEMENT:

POUR LA PROTECTION CONTINUÉE CONTRE LE FEU, REMPLACER LE FUSIBLE DE LIGNE (LES FUSIBLES) SEULEMENT AVEC 250V FUSIBLE (LES FUSIBLES) DU MÊME COURANT ÉVALUANT ET TAPE (PAR EXEMPLE, LE COUP NORMAL, LE DÉLAI). NE PAS UTILISER DE FUSIBLES RÉPARÉS OU CIRCUITED FUSEHOLDERS COURT.

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DC Power Supply (VDC Operation Model) Installation

 Use a 15 Amp DC circuit breaker in series with the DC power source.  Do not connect the unit directly to a DC power source without the breaker.  14 AWG (1.5mm

power source hookup.

 The Unit Chassis must be grounded for proper safety.

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WARNING: ENSURE THAT A DISCONNECT DEVICE, SUCH AS A SWITCH, WITH THE APPROPRIATE VOLTAGE/CURRENT RATING IS PROVIDED WHEN CONNECTING A DC POWER SOURCE TO THE VDC OPERATION MODEL.

AVERTISSEMENT: S'ASSURER QU'UN DÉBRANCHER L'APPAREIL, TEL QU'UN COMMUTATEUR, AVEC LE CLASSEMENT DE TENSION/COURANT APPROPRIÉ EST FOURNI EN CONNECTANT UNE SOURCE DE POUVOIR DE DC AU MODÈLE DE CONFIGURATION DE VDC.

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Acoustic Noise Emissions

LpA<47 dB at operator position, at normal operation, tested per EN 27779. All data are the results from type test.

Geräuschemission

LpA<47 dB am Arbeits platz, normaler Betrieb, geprüft nach EN 27779. Die Angagen beruhen auf Ergebnissen von Typenprüfungen.

Electrostatic Discharge Immunity Testing

When the product is tested with 8kV AD, 4kV CD and 4kV ID according to IEC801-2, a system error may occur that may affect measurement data made during these disturbances. After these occurrences, the system self-recovers without user intervention.

) gage wire is the minimum gage permitted by the NEC for DC

Safety Considerations and Warranty

Certification and Warranty

Certification

Symmetricom certifies that this product met its published specification at the time of shipment from the factory. Symmetricom further certifies that its calibration measurements are traceable to the United States National Institute of Standards and Technology (NIST), to the extent allowed by the Institute’s calibration facility, and to the calibration facilities of other International Standards Organization members.

Warranty

Symmetricom warrants Symmetricom hardware, accessories and supplies against defects in materials and workmanship for a period of two years from date of shipment. If Symmetricom receives notice of such defects during the warranty period, Symmetricom will, at its option, either repair or replace products which prove to be defective. Replacement products may be either new or like-new.

Symmetricom warrants that Symmetricom software will not fail to execute its programming instructions, for the period specified above, due to defects in material and workmanship when properly installed and used. If Symmetricom receives notice of such defects during the warranty period, Symmetricom will replace software media which does not execute its programming instructions due to such defects.

Symmetricom does not warrant that the operation of Symmetricom products will be uninterrupted or error free. If Symmetricom is unable, within a reasonable time, to repair or replace any product to a condition as warranted, the customer will be entitled to a refund of the purchase price upon prompt return of the product.

Symmetricom products may contain remanufactured parts equivalent to new in performance or may have been subjected to incidental use.

The warranty period begins on the date of delivery or on the date of installation if installed by Symmetricom. If customer schedules or delays Symmetricom installation more than 30 days after delivery, warranty begins on the 31st day from delivery.

Warranty does not apply to defects resulting from (a) improper or inadequate maintenance or calibration, (b) software, interfacing, parts or supplies not supplied by Symmetricom, (c) unauthorized modification or misuse, (d) operation outside of the published environmental specifications for the product, or (e) improper site preparation or maintenance.

TO THE EXTENT ALLOWED BY LOCAL LAW, THE ABOVE WARRANTIES ARE EXCLUSIVE AND NO OTHER WARRANTY OR CONDITION, WHETHER WRITTEN OR ORAL, IS EXPRESSED OR IMPLIED AND SYMMETRICOM SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OR CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, AND FITNESS FOR A PARTICULAR PURPOSE.

Safety Considerations and Warranty

Warranty (contd)

Symmetricom will be liable for damage to tangible property per incident up to the greater of $300,000 or the actual amount paid for the product that is the subject of the claim, and for damages for bodily injury or death, to the extent that all such damages are determined by a court of competent jurisdiction to have been directly caused by a defective Symmetricom product.

TO THE EXTENT ALLOWED BY LOCAL LAW, THE REMEDIES IN THIS WARRANTY STATEMENT ARE CUSTOMER’S SOLE AND EXCLUSIVE REMEDIES. EXCEPT AS INDICATED ABOVE, IN NO EVENT WILL SYMMETRICOM OR ITS SUPPLIERS BE LIABLE FOR LOSS OF DATA OR FOR DIRECT, SPECIAL, INCIDENTAL, CONSEQUENTIAL (INCLUDING LOST PROFIT OR DATA), OR OTHER DAMAGE, WHETHER BASED IN CONTRACT, TORT, OR OTHERWISE.

For consumer transactions in Australia and New Zealand: the warranty terms contained in this statement, except to the extent lawfully permitted, do not exclude, restrict or modify and are in addition to the mandatory statutory rights applicable to the sale of this product to you.

Assistance

Product maintenance agreements and other customer assistance agreements are available for Symmetricom products.

For any assistance, contact your nearest Symmetricom Sales and Service Office.

vii

DECLARATION OF CONFORMITY

In accordance with ISO/IEC GUIDE 22 and EN 45014

Symmetricom, Inc.

2300 Orchard Parkway

San Jose, CA 95131

Declares under our sole legal responsibility that the

PRIMARY FREQUENCY STANDARD

MODEL NO. 5071A

CONFORMS TO THE FOLLOWING EUROPEAN UNION DIRECTIVES:

Safety

73/23/EEC Low Voltage Safety as amended by 93/68/EEC

IEC 61010-1 EN 61010-1

Electromagnetic Compatibility 89/336/EEC Electromagnetic Compatibility

EN61326 EMC Requirements for Measurement, Control and Laboratory Equipment. EN61000-3-2 Harmonic Current Emissions EN61000-3-3 Voltage Fluctuation and Flicker Emissions

WEEE

Waste Electrical and Electronic Equipment Directive (WEEE) 2002/95/EC

For more information about Symmetricom’s WEEE compliance and recycle program, please visit the Symmetricom’s WEEE/RoHS website at http://www.symmetricom.com/About_Us/WEEE_RoHS_Initiatives.htm

RoHS Restriction of the Use of Certain Hazardous Substances Directive 2002/95/EC

This product falls under the category of Monitoring and Control Instruments Equipment (Category 9 as defined in Annex 1A of the WEEE 2002/96/EC Directive) which is excluded from the RoHS Directive 2002/95/EC (reference Article 2, paragraph 1) requirements.

Note: The Model 5071A is compliant when supplied with or without the High Performance

Option. CE Marking first affixed 2007 We declare that the equipment specified above conforms to the above Directives and Standards.

28 March 2007 Robert Mengelberg Compliance Program Manage

Date Name Title Signature

viii

Contents

Assembly- Level Service Manual ............................................................................................i

Declares under our sole legal responsibility that the .......................................................viii

Contents...................................................................................................................................ix

Preface...................................................................................................................................xiii

Repair Strategy...................................................................................................................xiii

Text Conventions used in this manual................................................................................xiii

Instrument Identification ....................................................................................................xiii

Instruments Covered by This manual................................................................................. xiv

Manual Organization..........................................................................................................xiv

How to Order Manuals ....................................................................................................... xiv

1. Performance Tests – Verifying Specifications...................................................................1

Introduction ...........................................................................................................................1

Operational Verification .....................................................................................................1

Complete Performance Tests..............................................................................................1

RS-232 Verification............................................................................................................1

Test Record............................................................................................................................2

Equipment Required.............................................................................................................. 2

5071A Operational Verification............................................................................................ 5

Power-On Self-Tests and Servo Lock.................................................................................5

Rear-Panel Output Signal Checks.......................................................................................7

RS-232 Serial Port Verification..........................................................................................8

5071A Complete Performance Tests...................................................................................10

Test 1 — Output Signals: Harmonic Distortion and Spurious Signals Check..................10

Test 2 — Frequency Accuracy .........................................................................................18

Test 3 — Stability.............................................................................................................21

Performance Test Record..................................................................................................22

2. Service................................................................................................................................. 25

Introduction .........................................................................................................................25

Returning the Instrument to Symmetricom for Service....................................................... 26

To Provide Repair Information.........................................................................................26

To Pack in the Original Packaging Materials ...................................................................26

Pre-Troubleshooting Information........................................................................................27

Safety Considerations .......................................................................................................27

Recommended Test Equipment........................................................................................28

Repair Considerations.......................................................................................................28

After Service Considerations............................................................................................28

Service Accessories ..........................................................................................................29

Assembly Identification and Location..............................................................................31

Diagnostic Trees and Procedures.........................................................................................33

5071A Diagnostic Tree Organization...............................................................................34

Navigating the Diagnostic Trouble-Tree Sections............................................................34

Top-Level Diagnostic Tree Organization.........................................................................35

Top-Level Diagnostic Tree (Diagnostic Section 1)...................................................37

1.0.0 First Power On.........................................................................................................37

Contents

1.0.1.1.0 DC Input 1 and 2 Power Steering Circuit Check...............................................38

1.0.1.1 Digital Supply Voltage Check..............................................................................38

1.0.1.2 A3 Microprocessor Fault ......................................................................................38

1.0.2 DC-Supply Test/Log-Record Examination..............................................................39

1.0.3 Power On Fatal Error Check .................................................................................... 40

1.0.4 Instrument Self Tests...............................................................................................40

1.0.5 CBT Warm Up.........................................................................................................40

1.0.6 Servo-Lock Warning State.......................................................................................41

1.0.7 User-Input/Output Checks.......................................................................................41

1.0.8 5071A Profiling .......................................................................................................42

1.0.9 Delayed Failures, Warnings, and Messages.............................................................44

Power-on Fatal-Error Diagnostic Tree (Subsection 1) .....................................................45

Self Test Diagnostic Tree (Subsection 2) .........................................................................47

Warm-up And Fatal Error Diagnostic Tree (Subsection 3)..............................................49

Warning Message Diagnostic Tree (Subsection 4)...........................................................57

I/O Diagnostic Tree (Subsection 5) ..................................................................................60

CBT Performance Evaluation (Subsection 6)...................................................................61

Advisory Messages (Subsection 7)...................................................................................65

Functional-Group-Diagnostic Trees (Diagnostic Section 2) ............................................... 66

Power-Supply Diagnostic Tree (Functional Group Subsection 1)....................................67

Analog-Signal Chain Diagnostic Tree (Functional-Group Subsection 2) ........................74

RF-Chain Diagnostic Tree (Functional-Group Subsection 3) ..........................................77

C-Field Diagnostic Tree (Functional-Group Subsection 4)..............................................81

Assembly/Module Diagnostic Trees (Diagnostic Section 3)............................................... 82

A2 CBT Controller Diagnostic Tree (A/M Subsection 1)................................................83

A2 Hot-Wire Ionizer Diagnostic Tree ..............................................................................84

A2 Thermistor Diagnostic Tree........................................................................................86

A2-Mass-Spectrometer Diagnostic Tree...........................................................................88

A2 Cesium-Oven Diagnostic Tree....................................................................................90

A5 Diagnostic Tree (A/M Subsection 2) ..........................................................................92

A8 Diagnostic Tree (A/M Subsection 3) ..........................................................................95

A9 Diagnostic Tree (A/M Subsection 4) ..........................................................................99

A10 Diagnostic Tree (A/M Subsection 5) ......................................................................101

A15 Diagnostic Tree (A/M Subsection 6) ......................................................................107

A16 Diagnostic Tree (A/M Section 7)............................................................................111

A18 Diagnostic Tree (A/M Subsection 8) ......................................................................116

A19 Diagnostic Tree (A/M Subsection 9) ......................................................................120

3. Theory of Operation........................................................................................................125

Introduction .......................................................................................................................125

Basic Operating Principles..............................................................................................125

Simplified Functional Description..................................................................................126

Functional Block Descriptions........................................................................................126

A1 Motherboard Circuit Description..............................................................................126

Simplified Functional Description..................................................................................... 127

Instrument Control Block ...............................................................................................128

Reference Oscillator/RF chain Block .............................................................................128

Cesium Beam Tube Block..............................................................................................128

Analog Signal Chain Block ............................................................................................129

Input/Output Block.........................................................................................................129

Power Supply Block .......................................................................................................129

Contents

Functional Block Descriptions ..........................................................................................130

Instrument Control Block ...............................................................................................133

Reference Oscillator/RF chain Block .............................................................................137

Cesium Beam Tube Block..............................................................................................139

Analog Signal Chain Block ............................................................................................141

Input/Output Block.........................................................................................................143

Power Supply Block .......................................................................................................144

A1 Motherboard Circuit Description..............................................................................146

A11 Power Steering Logic Assembly.............................................................................147

Figure 3-8. Opt. 048, Power Supply Block Diagram......................................................156

A12 Dc-Dc Power Converter Module ............................................................................158

LF1 AC-Line Filter/Cable Assembly..............................................................................158

T1 Toroidal Power Transformer.....................................................................................158

B1 Internal-Standby Battery...........................................................................................158

4. Replacing Assemblies - Disassembly and Reassembly .................................................160

Introduction .......................................................................................................................160

Tools Required ..................................................................................................................160

Do This First...................................................................................................................... 161

To Remove the Covers ...................................................................................................... 161

To remove the A2 CBT Control Assembly....................................................................... 162

To Remove Any Other PC Boards ....................................................................................162

To Remove A1 Motherboard Assembly............................................................................162

To Remove A10 Output Frequency Distribution Amplifier Module................................ 163

To Remove A12 Dc-Dc Power Converter Module ...........................................................164

To Remove A13 Front Panel Module................................................................................ 165

To Remove A14 Signal Amplifier Module....................................................................... 166

To Remove A15 9.2 GHz Microwave Generator Module................................................. 167

To Remove A16 High Voltage Supply Module................................................................ 167

To Remove A17 CBT Assembly....................................................................................... 168

Preparation......................................................................................................................168

10890A or 10891A CBT Removal.................................................................................168

CBT Installation..............................................................................................................169

Operation Verification....................................................................................................171

Disposal Procedure for Symmetricom Cesium Beam Tubes..........................................172

To Remove A19 Reference Oscillator Module ................................................................. 173

Contents

5. Replaceable Parts ............................................................................................................174

Introduction .......................................................................................................................174

Replaceable Parts Table..................................................................................................... 174

How To Order A Part ........................................................................................................174

Parts Identification..........................................................................................................174

Contacting Symmetricom ...............................................................................................175

6. Specifications....................................................................................................................179

Introduction .......................................................................................................................179

7. Service and Support........................................................................................................ 180

Index ..................................................................................................................................... 182

xii

Preface

This manual provides assembly-level service information for the Symmetricom 5071A Primary Frequency Standard.

Repair Strategy

The Symmetricom 5071A Primary Frequency Standard can be returned to Symmetricom for all service work, including troubleshooting, and verifying specifications. Contact Symmetricom for more details.

If you decide to service the instrument yourself, use the operational verification procedure in Chapter 1, “Performance Tests,” in this manual to define the type of problem. For more complete tests, use the full performance tests in Chapter 1. After a repair, re-check the Standard's operation with the verification or full-performance test procedures.

This service manual is designed to isolate failures to the assembly or module level only. If a failure occurs, you can isolate the faulty assembly or module by using the procedures in Chapter 2 “Service.” The procedures in Chapter 4 “Replacing Assemblies” enable you to remove and replace defective assemblies or modules.

Text Conventions used in this manual

Throughout this manual there are symbols used to denote special meanings. These are explained below:

< > These separators mark where information may be any value or text (otherwise

known as “wild cards”). The actual value in these cases is not critical to the process.

Instrument Identification

Instrument identification is made from the serial number located on the rear panel of the 5071A. Symmetricom uses a two-part serial number with the first part (prefix) identifying a series of instruments and the second part (suffix) identifying a particular instrument within a non-repeating series. A Symmetricom assigned alpha character within the serial number identifies the country in which the instrument was manufactured. The letters “A” or “US” denote manufacture in the United States of America.

xiii

Preface

Instruments Covered by This manual

This manual applies directly to Symmetricom 5071A Primary Frequency Standards that have the same serial number prefix(es) shown on the title page. If the serial number prefix of your Standard differs from that listed on the title page of this manual, then there may be differences between this manual and your instrument. Instruments having a higher serial prefix are covered when required by one or more manual-change sheets included with this manual. If a required change sheet is missing, contact Symmetricom by phone or email using the information provided at the back of this manual.

Manual Organization

This assembly-level service manual consists of a table of contents, preface, Six chapters and an index. The page running headers identify the chapters and sections of this manual. The chapter contents are summarized as follows:

Chapter 1, Performance Tests, provides test procedures to ensure

that the Standard meets all warranted specifications.

Chapter 2, Service, is divided into five sections. Section 1 contains

instructions for returning the Standard to Symmetricom for service. Section 2 contains pre-troubleshooting information and Sections 3, 4, and 5 provide the diagnostic troubleshooting-tree procedures (diagnostic trees) to isolate faulty assemblies and/or modules.

Chapter 3, Theory of Operation, provides two levels of hardware

functional description based on a signal-flow block-diagram perspective.

Chapter 4, Replacing Assemblies, contains procedures for replacing

defective assemblies and/or modules in the instrument.

Chapter 5, Replaceable Parts, lists the replaceable parts inside the

Standard and explains how to order them from Symmetricom.

Chapter 6, Specifications, This information is duplicated in the 5071A

Operating and Programming manual P/N 05071-90041, and is therefore not printed in this manual.

How to Order Manuals

A copy of this manual (part number 05071-90040) can be downloaded from the following website:

http://www.symmttm.com/products_pfr_5071A.asp

The Symmetricom 5071A Operating and Programming manual (part number 05071-90041) can be obtained from the same site as well.

xiv

1. Performance Tests – Verifying Specifications

Introduction

NOTE

In the interest of PRESERVING its usability the information in this chapter has been retained in its original form without changes. No attempt has been made to update the equipment, accessories, or parts to current availability. It is therefore necessary for the user of this manual to consider the recommendations of test equipment and accessories as suggestions. Some or all of these items may no longer be available from Symmetricom or any other vendors. An updated list of available replacement parts from Symmetricom is provided in Chapter 5.

This chapter provides procedures to test the electrical performance of the 5071A Primary Frequency Standard, using the specifications listed in Chapter 6, “Specifications.” Three types of tests are provided:

 Operational Verification  Complete Performance Tests  RS-232 Verification

Operational Verification

The Operational Verification test is an abbreviated series of checks that may be performed to give a high degree of confidence that the instrument is operating properly without performing the complete Performance Tests. An operational verification is useful for incoming inspection, routine maintenance, and after instrument repair.

Complete Performance Tests

The complete Performance Tests verify the specifications listed in Chapter 6 of this manual. All tests can be performed without access to the inside of the instrument.

RS-232 Verification

The RS-232 Serial Port verification checks the serial port for successful data communication with a terminal or PC.

1. Performance Tests – Verifying Specifications

Test Record

The results of the Operational Verification, complete Performance Tests, and RS-232 Verification can be recorded on a copy of the Performance Test Record, located at the end of this chapter.

Equipment Required

Equipment required for the performance tests in this chapter is listed in the following table. Any equipment that satisfies the critical specification listed in the table may be substituted for the recommended model(s). (The performance test and diagnostic procedures assume the use of the listed equipment.)

If operational verification or full-performance tests are being performed, use the test equipment called out on this page and the appropriate test cables/adapters listed on page 6.

If diagnostic troubleshooting is required, use the test equipment called out on this page, page 5, and the appropriate test cables/adapters listed on page 6.

Table 1-1. Recommended Test Equipment

Instrument Required Characteristics Use Model

General-Purpose Oscilloscope

Spectrum Analyzer Frequency Range Span: 0 to 40 MHz

Linear Phase Comparator

Strip Chart Recorder Paper Movement: 1 inch/hour

At least 100 MHz bandwidth Input: 1 M

Measurement Resolution 1 kHz/Div. Center Frequency Accuracy: 1 PPM

Input Frequency Range: 5 to 10 MHz Input Level (50): 1 Vrms Output: 0 to +1 Vdc Output Linearity: Proportional from 0 to 360 degrees phase

Input Range: 0 to +1 Vdc Full Scale Range: +1 Vdc Full Scale Resolution: 50 minor divisions

OV, T HP/Agilent

54600A

P, T HP/Agilent

3585A/B

P HP/Agilent

K34-59991A

P No

Recommendation

1. Performance Tests – Verifying Specifications

Equipment Required

Table 1-1. Recommended Test Equipment (Continued)

Digital Multimeter

40kV ac/dc High Voltage Probe

Clip-on Current Probe Range: >= 1 Amp dc

Universal Counter Range: >= 500 MHz

CW Microwave Counter

Spectrum Analyzer Frequency Range: >= 9.5 GHz

Input Probe 10:1 Divider (included with

Input Probe RF Signal Generator Frequency Range: > 80 MHz

Input Resistance: 10 M Accuracy: 0.04% at 1 Vdc

Range: >= 5KV dc, input Z= 1 G, Accuracy: 2%, 10 M load

Output: 1 Vdc at 10 Amp dc

Accuracy: 0.1 PPM Range: >= 10 GHz

Accuracy: >= 0.1 ppm

Resolution: 100 kHz / Division Center Frequency Accuracy: 1 PPM Input: Up to 1 watt input capability Dynamic Range: 100 dB

54600A oscilloscope) 1:1 1 M (for 50  measurements)

Power: >= +7 dBm

T HP/Agilent 34401A

T HP/Agilent 34300A

T HP/Agilent 34302A

T HP/Agilent 53131A,

Opt 010, 030

T HP/Agilent 5350B,

Option 010

T HP/Agilent 8566A/B

T HP/Agilent 10071A

T HP/Agilent 10070A T HP/Agilent 8656B

Pulse Generator Repetition Rate: 10 Hz

Pulse Width: <= 10 usec Output Voltage: >= +3V

General-purpose DC Power Supply, Adjustable

IBM-Compatible PC

Service Accessories Kit

Profiling Software For Online CBT Performance Testing

0 - 10V, >= 25 ma

MS-DOS 3.3 or later, 640 kB RAM, 1 serial (COM: ) Port

Special Test Tools, Devices, and Fixtures

(See Title Page for download instructions)

T HP/Agilent 8111A

T HP/Agilent E3610A

T Any Vendor

T 05071-67003

T 05071-13501

1. Performance Tests – Verifying Specifications

Equipment Required

Table 1-1. Recommended Test Equipment (Continued)

BNC, and Datacommunication cables

Adapters

Microwave Test Cable SMA (male) at both ends, <10dB loss

Special Tools Narrow bladed non-conducting

BNC Cables, 50 , 1 M long, quantity 4 RS-232 Cable, 9-pin (jack) to 9-pin (jack)

50  BNC In-line Feed through 2-Way 3dB Power Splitter BNC (jack) to BNC (jack), quantity 4 BNC (jack) to SMC (plug), quantity 2 BNC (plug) to SMC (jack) BNC (jack) to SMB (plug) BNC (plug) to SMB (jack) N (plug) to BNC (jack) N (plug) to SMA (jack) SMA (jack) to SMA (plug) Right-Angle SMA (plug) to SMA (plug) SMA (jack) to SMA (jack) SMB (jack) to SMB (jack) SMB (plug) to SMB (plug) SMC (jack) to SMC (jack) SMC (plug) to SMC (plug)

at 10 GHz

screwdriver TORX T-8 Driver TORX T-10 Driver TORX T-15 Driver TORX T-25 Driver

T HP/Agilent 10503A

24542U

T HP/Agilent 10100C

0960-0496 1250-0080 1250-0832 1250-0831 1250-1236 1250-1857 1250-0780 1250-1250 1250-1249 1250-1159 1250-1158 1250-0672 1250-0669 1250-0827 1250-1113

T GoreTex

32R01R01048.0

T Jacobsen #8777

8710-1614 8710-1623 8710-1622 8710-1617

OV = Operational Verification P = Complete Performance Tests T = Troubleshooting

1. Performance Tests – Verifying Specifications

5071A Operational Verification

Power-On Self-Tests and Servo Lock

1 Inspect the 5071A for any damage (see the section titled “Initial

Inspection” in Chapter 7 of the 5071A Operating and Programming Manual for detailed inspection information).

2 Ensure that the ac-power setting, ac-line fuse (rear panel), and

supplied power cord are appropriate for your ac-power source. (Refer to Chapter 7, “Installation,” for detailed information.)

3 Now, apply power to the instrument by connecting ac-power

source to the instrument via the ac power cord. The amber Attention light is lit indicating normal power-up sequence and the following messages are displayed on the LCD in sequence:

a. The message “waiting for ion pump start” may appear. If so it could

stay on for up to 20 minutes before the following messages appear. b. Warming up (this indicates self-test passed successfully) c. Lowering E_mult voltage d. Setting Osc. Control e. Setting RF amplitude f. Setting E_mult voltage g. Logging signal levels h. Setting C-field i. Locking servo loops j. Operating normally

4 After about 15 minutes (typically), the Attention (amber) light

goes out and the Continuous Operation (green) light flashes. This indicates that all servo loops have locked and the instrument is operating normally.

5 Press Shift, then 5 (Utilities).

LCD display shows RESET.

6 Press Enter.

This resets the continuous operation circuit, causing the light to be on steadily. Any subsequent fault will cause the Continuous Operation light to go out or flash.

7 Mark Pass or Fail on the Performance Test Record, line 1.

NOTE

1. Performance Tests – Verifying Specifications

5071A Operational Verification

The 5071A powers up at shipment receipt with the following configuration:

Output Ports:

Port 1 5 MHz output Port 2 10 MHz output

RS-232C:

Baud rate 2400 Data bits 8 Parity none Stop bits 1

System Logs:

Printer log disabled Error log lock

completed

These first-time power-up configurations can be changed by using the front panel controls. See the section titled “Setting the Output Port Frequency” in the 5071A Operating and Programming Manual for instructions on how to do this.

1. Performance Tests – Verifying Specifications

5071A Operational Verification

Rear-Panel Output Signal Checks

Check the rear-panel outputs for appropriate signal waveform, frequency and voltage.

Required Equipment

 BNC-to-BNC 1-meter cable (male connectors),

model number HP/Agilent 10503A

 Type N (male)-to-BNC (female) adapter,

HP/Agilent part number 1250-0780

 50- feedthrough BNC (male) and (female) adapter,

model number HP/Agilent 10100C

 HP/Agilent 54600A General-Purpose 100 MHz Oscilloscope

(or equivalent)

To check the rear-panel output connectors quickly for the presence of valid output signals, perform the following steps:

NOTE

The LCD display backplane light will turn off after approximately 4 minutes to conserve energy if no front-panel key is pressed. Press any key to turn the backplane light back on.

1 Connect one of the 5071A outputs to an input channel of the

HP/Agilent 54600A with a 50- feed through termination and BNC cable as shown in Figure 1-1.

Figure 1-1. Rear-Panel Outputs Verification Setup

1. Performance Tests – Verifying Specifications

5071A Operational Verification

2 On the HP/Agilent 54600A Oscilloscope, press “Autoscale.”

(Use manual settings if needed to check the 1pps Outputs.)

3 Verify that the output signal waveform, frequency, and nominal

voltage correspond to the values listed in Chapter 6,

“Specifications,” for the signal under test. 4 Repeat steps 1 through 4 for all outputs. 5 Mark Pass or Fail on the Performance Test Record, line 2.

RS-232 Serial Port Verification

1 Ensure that the correct hardware connections exist between the

5071A and your terminal, personal computer, or workstation for

your remote operation needs as shown in Figure 1-2. 2 Ensure that the 5071A and your data communications equipment

(terminal) are powered-up and have passed their own self-tests. 3 On your terminal, press the “Enter” or “Return” key several times. 4 Observe the returned scpi> or E-xxx> prompt on the terminal

screen. if the above prompt appears, the RS-232 Verification check passed. If the prompt does not appear:

 Check and verify all serial port parameters: baud rate, data bits,

stop bits, and parity.

 Check and verify the hardware connections and cabling for correct

DTE-DCE signal paths. (Serial-port pin assignments are shown on

page 4-2 of the Operating and Programming manual.)

 Check and verify all cables and connections for open or shorted

lines. 5 Mark Pass or Fail on the Performance Test Record, line 3.

1. Performance Tests – Verifying Specifications

5071A Operational Verification

Figure 1-2. RS-232C Cabling Setups

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Before performing the following tests, the 5071A under test must have been in operation for at least 30 minutes. If you are initially starting the

5071A, follow the instructions in the “Power-On Self Tests” procedure under the Operational Verification Test on page 7.

Test 1 — Output Signals: Harmonic Distortion and Spurious Signals Check

A. Harmonic Distortion Check for the 5 and 10 MHz Outputs

Harmonics on the 10 MHz and 5 MHz output signals must be more than 40 dBc below the fundamental. To perform this check, a spectrum analyzer is tuned to the fundamental frequency and an amplitude reference is established. The output frequency spectrum is then examined to determine fundamental-to-sideband amplitude relationship at harmonic points of the fundamental.

Equipment

HP/Agilent 3585B Spectrum Analyzer

Setup

Figure 1-3. Harmonic Distortion Test Setup

Specifications

Verify all harmonics are < 40 dBc with respect to the fundamental frequency.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Procedure

If you are using the HP/Agilent 3585B Spectrum Analyzer, follow the steps below to test for harmonic signals on the 5 and 10 MHz outputs. If you are using a different spectrum analyzer, use these steps as a guide for operation of that analyzer.

1 Connect the 5071A Port 1 to the HP/Agilent 3585B analyzer as shown in

2 On the 5071A, set output ports 1 and 2 to 10 MHz using the front panel

3 On the HP/Agilent 3585B, perform the following steps:

Figure 1-3. Set the 3585B for 50 input impedance.

controls. See the section titled “Setting the Output Port Frequency” in the

5071A Operating and Programming Manual for instructions on how to do

this.

a) Press the green “INSTR PRESET” button and allow the analyzer

to go through its auto range algorithm (this takes about 5 seconds).

b) Press the “DISP LINE” (display line) button in the marker menu

and adjust the line to 40.0 dBc.

NOTE

c) Press the “PEAK SEARCH” button and then the “MKR->REF LVL”

button (both are in the marker menu area).

d) Set both the resolution bandwidth (RES BW) and the video

bandwidth (VIDEO BW) to 1 kHz. Enter the 1 kHz values using the numeric and unit keys. The RES BW and VIDEO BW values are displayed at the bottom of the screen.

The sweep time is 125 seconds. DO NOT adjust the sweep time manually.

e) Press the “CONT” button in the sweep menu area to begin a new

sweep.

f) When the new sweep has passed through the fundamental

frequency, press the “PEAK SEARCH” button again. Then press the “OFFSET” and the “ENTER OFFSET” buttons in the marker menu area. Verify that both the offset frequency (Hz) and the offset level (dB) go to zero (0 Hz and 0 dB should be displayed at the top of the screen). If necessary, press and hold the “ENTER OFFSET” button to zero-out the marker offsets.

g) When at least one sweep has completed, verify that there are no

harmonic signals on or above the 40dBc display line. Use the knob in the marker area to move the offset marker to any harmonic signal that you want to measure or record. The marker shows the offset frequency and level in dBc from the output signal at 5 or 10 MHz. Verify that there are no harmonically related signals on or above  40dBc within 5 harmonics of the fundamental.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

4 On the 5071A, set output ports 1 and 2 to 5 MHz using the front

panel controls. 5 Repeat step 3. 6 Connect 5071A Port 2 to the HP/Agilent 3585B Spectrum

Analyzer and repeat steps 2 through 5 to test Port 2. 7 Record the actual reading in the appropriate place in the

Performance Test Record.

B. Non-Harmonic (Spurious) Signal Check for the 5 and 10 MHz Outputs

Non-harmonically related (spurious) signals on the 5 and 10 MHz outputs must be more than 80 dBc below the output signal levels. To perform this test, a spectrum analyzer is tuned to the 5 or 10 MHz signal and an amplitude reference is established. The output frequency spectrum is then examined at 1 MHz on either side of the center frequency to determine the fundamentalto-sideband amplitude relationship for any signals occurring within this range.

Equipment

Setup

HP/Agilent 3585B Spectrum Analyzer

Figure 1-4. Non-Harmonic Distortion Test Setup

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Specifications

All spurious nonharmonic signals must be < 80 dBc with respect to the fundamental frequency.

Procedure

If you are using the HP/Agilent 3585B Spectrum Analyzer, follow the steps below to test for spurious signals on the 5 and 10 MHz outputs. If you are using a different spectrum analyzer, use these steps as a guide for operation of that analyzer.

1 Connect the 5071A Port 1 to the 3585B analyzer as shown in

Figure 1-4. Set the 3585B for 50 input impedance. 2 On the 5071A, set output ports 1 and 2 to 10 MHz using the front

panel controls. See the section titled “Setting the Output Port

Frequency” in the 5071A Operating and Programming Manual for

instructions on how to do this. 3 On the 3585B, perform the following steps:

a) Press the green “INSTR PRESET” button and allow the analyzer

to go through its auto range algorithm (this will take about 5 seconds).

NOTE

b) Press the “DISP LINE” (display line) button in the marker menu

and adjust the line to 80.0 dBc.

c) Press the “PEAK SEARCH” button and then the “MKR->REF LVL”

button (both are in the marker menu area).

d) Set both the resolution bandwidth (RES BW) and the video

bandwidth (VIDEO BW) to 1 kHz. Enter the 1 kHz values using the numeric and unit keys. The RES BW and VIDEO BW values are displayed at the bottom of the screen.

The sweep time is 125 seconds. DO NOT adjust the sweep time manually.

e) Press the “CONT” button in the sweep menu area to begin a new

sweep.

f) When the new sweep has passed through the fundamental

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

g) When at least one sweep has completed, verify that there are no

spurious signals on or above the 80 dBc display line. Use the knob in the marker area to move the offset marker to any spurious signal that you want to measure or record. The marker shows the offset frequency and level in dBc from the output signal at 5 or 10 MHz.

h) Verify that one of the following conditions is true:

No spurious signals are on or above the 80 dBc display line

between 4 MHz and 6 MHz for the 5 MHz output, or

No spurious signals are on or above the 80 dBc display line

between 9 MHz and 11 MHz for the 10 MHz output. 4 On the 5071A, set output ports 1 and 2 to 5 MHz using the front

panel controls. 5 Repeat step 3. 6 Connect 5071A Port 2 to the 3585B Spectrum Analyzer and

repeat steps 2 through 5 to test Port 2. 7 Record the actual reading in the appropriate place in the

Performance Test Record.

C. Harmonic Distortion Check for the 1 MHz Output

Harmonics on the 1 MHz output signal must be more than 40 dBc below the fundamental. To perform this check, a spectrum analyzer is tuned to the fundamental frequency and an amplitude reference is established. The output frequency spectrum is then examined to determine the fundamental-tosideband amplitude relationship at harmonic points of the fundamental.

Equipment

HP/Agilent 3585B Spectrum Analyzer

Setup

Figure 1-5. 1MHz Output Harmonic Distortion Test Setup

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Specifications

All harmonics must be < 40 dBc with respect to the fundamental frequency.

Procedure

If you are using the HP/Agilent 3585B Spectrum Analyzer, follow the steps below to test for harmonic signals on the 1 MHz output. If you are using a different spectrum analyzer, use these steps as a guide for operation of that analyzer.

1. Connect the 5071A 1 MHz output to the 3585B Spectrum Analyzer as shown in Figure 1-5. Set the 3585B for 50 input impedance.

2. On the 3585B, perform the following steps:

a. Press the green “INSTR PRESET” button and allow the analyzerto go

through its auto range algorithm (this will take about 5 seconds).

b. Press the “STOP FREQ” button. Then set the stop frequency to 20 MHz

using the numeric and unit keys in the entry menu. c. Press the “DSP LINE” button and move the display line to40.0 dBc. d. Press the “PEAK SEARCH” button, then the “MKR->REF LVL” button. e. When the new sweep has passed through the fundamental frequency,

press the “OFFSET” and the “ENTER OFFSET” buttons in the marker

menu area. Verify that both the offsetfrequency (Hz) and the offset level

(dB) go to zero (0 Hz and 0 dBshould be displayed at the top of the

screen). If necessary, pressand hold the “ENTER OFFSET” button to

zero-out the markeroffsets. f. When at least one sweep has completed, verify that there are no

signals on or above the 40 dBc display line at multiples of 1 MHz up to

4 MHz. Use the knob in the marker area to move the offsetmarker to

any signals within this range if you want to measure or record these

signals. The marker shows the offset frequency and level in dBc from

the 1 MHz signal.

3. Record the actual reading in the appropriate place in the Performance Test Record.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

D. Harmonic Distortion Check for the 100 kHz Output

Harmonics on the 100 kHz output signal must be more than 40 dBc below the fundamental. To perform this check, a spectrum analyzer is tuned to the fundamental frequency and an amplitude reference is established. The output frequency spectrum is then examined to determine fundamental-to-sideband amplitude relationship at harmonic points of the fundamental.

Equipment

HP/Agilent 3585B Spectrum Analyzer

Setup

Figure 1-6. 100 kHz Harmonic Distortion Test Setup

Specifications

All harmonics must be < 40 dBc with respect to the fundamental frequency.

Procedure

If you are using the HP/Agilent 3585B Spectrum Analyzer, follow the steps below to test for harmonic signals on the 100 kHz output. If you are using a different spectrum analyzer, use these steps as a guide for operation of that analyzer.

1 Connect the 5071A 100 kHz output to the 3585B Spectrum Analyzer as

shown in Figure 1-6. Set the 3585B for 50 input impedance.

2 On the 3585B, perform the following steps:

a. Press the green “INSTR PRESET” button and allow the analyzer to go

through its auto range algorithm (this will take about 5 seconds).

b. Press the “STOP FREQ” button. Then set the stop frequency to 3 MHz

using the numeric and unit keys in the entry menu.

c. Press the “DSP LINE” button and move the display line to 40.0 dBc.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

d. Press the “PEAK SEARCH” button, then the “MKR->REF LVL” button. e. Set the resolution bandwidth (RES BW) to 300 Hz and the video

bandwidth (VIDEO BW) to 1 kHz.

NOTE The sweep time is 66.8 seconds. DO NOT adjust the sweep

time manually.

f. Press the “CONT” button in the sweep menu area to begin a new

sweep.

g. When the new sweep has passed through the fundamental frequency,

press the “OFFSET” and the “ENTER OFFSET” buttons in the marker menu area. Verify that both the offset frequency (Hz) and the offset level (dB) go to zero (0 Hz and 0 dB should be displayed at the top of the screen). If necessary, press and hold the “ENTER OFFSET” button to zero-out the marker offsets.

h. When at least one sweep has completed, look for any signals that

appear on or above the 40 dBc display line at multiples of 100 kHz up to 500 kHz. Use the knob in the marker area to move the offset marker to any signals within this range if you want to measure or record these signals. The marker shows the offset frequency and level in dBc from the 100 kHz signal.

3 Record the actual reading in the appropriate place in the Performance Test

Record.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Test 2 — Frequency Accuracy

The following accuracy check measures the changing phase relationship between the 5071A 10 MHz output and another primary frequency standard (5071A Primary Frequency Standard or better). An HP/Agilent K34-59991A Linear Phase Comparator is used to measure the phase between the 5071A under test and the reference standard.

NOTE

In this test, the reference standard must be of known accuracy. The measurement time must be of sufficient length so the accuracy of the measurement is not impaired by the stability of either the reference standard or the unit under test. If the reference standard is a 5071A with the High-Performance CBT, the accuracy measurement must be made for 24 hours if the unit under test is a Long-Life (Standard) CBT. The test can be made in 2 1/2 hours if the unit under test has the High-Performance CBT.

Equipment

HP/Agilent K34-59991A Linear Phase Comparator Strip Chart Recorder

Setup

Figure 1-7. Frequency Accuracy Test Setup

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Specifications

NOTE

Long-Life (Standard):  1x10 High-Performance:  2x10

The accuracy of the 5071A is better than 2x10 1x10 known with sufficient precision to make this measurement accurately.

Procedure

1 The 5071A must be on for at least 30 minutes and the green

2 Connect the HP/Agilent K34-59991A Phase Comparator OUTPUT

3 Turn on the K34-59991A power. 4 Connect the 10 MHz reference to INPUT A and the 5071A (unit

5 Set K34-59991A “ZERO-OPER-FULL” front panel mounted toggle

12

13

-13

-12

(Long-Life). Be sure the accuracy of the reference standard is

(High-Performance)

continuous operation LED must be on.

terminals to the strip chart recorder as shown in Figure 1-7. Set the recorder for 1V full scale and 1 inch/hour. Turn on the recorder.

under test) 10 MHz to INPUT B as shown in Figure 1-7.

switch to “ZERO.” Adjust the “ZERO SCALE” control for a zero reading on the meter. Then adjust the recorder for a zero indication.

6 Set K34-59991A switch to “FULL” and adjust “FULL SCALE”

control for a full scale reading on the recorder.

7 Check both “ZERO” and “FULL SCALE” settings on the recorder

and readjust if necessary. 8 Set K34-59991A switch to “OPER” for normal operation. 9 The recorder now provides a continuous record of the phase

difference between the reference standard and the 5071A unit

under test. When its output reaches full scale (360 degrees), the

K34-59991A will automatically reset to 0 (0 degrees). 10 With the recorder set as described, the phase record is 100 ns full

scale (with 10 MHz inputs). The figure below shows an example of

a frequency difference measurement under these conditions. 11 The frequency difference between the unit under test and the

reference is given by the following equation:

f/F = t/T

Where: f/F is the desired frequency difference, and t is the phase change (in seconds) over the measurement time, T.

The Figure 1-8 shows a typical plot using the strip chart recorder.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

NOTE

Figure 1-8. Error Measurement

In the example, the frequency difference, f/F, is computed as follows:

f/F = t/T

t

= (7 minor divisions × 2x10 = 14x10

= 8 hours or 2.88 × 10

f/F

= t/T = 14 × 10 = 4.9 × 10

-13

9

seconds

-9

/2.88 × 10

or 4.9 parts in 1013

-9

seconds/minor divisions)

seconds

This shows that frequency difference between the unit under test and the reference is 4.9 parts in ten to the 13th. This is only an example. The

measured frequency accuracy of a 5071A should be 1 x 10

13

Long-Life (Standard), or 2 x 10

or better for a high performance unit

12

or better for a

The final computation should include the accuracy of the reference source.

12 Record the actual reading in the appropriate place in the

Performance Test Record.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Test 3 — Stability

NOTE

High accuracy precision measurements of time stability are available through the National Institute of Standards and Technology (NIST) in the USA. NIST can completely characterize and verify all major specifications of the 5071A. For information regarding the various tests available, contact:

M.C. 847.4 National Institute of Standards and Technology 325 Broadway Boulder CO 80303-3328 USA Telephone: (303) 497-3753

A. Time Domain

This is an engineering-level measurement requiring a special test setup. The test setup must be carefully designed to eliminate all sources of noise. For more information on how to make this measurement, see NIST Technical Note 1337 (available from US Government Printing Office, Washington DC., USA). This is an excellent theoretical as well as technical reference for this measurement.

Record the actual reading in the appropriate place in the Performance Test Record. This completes the performance test.

B. Frequency Domain

This measurement requires the HP/Agilent 3048A or equivalent Phase Noise Measurement System, a highly specialized test system. In order to perform properly, this system must contain a reference oscillator with phase noise characteristics that are equal to or better than the 5071A. Instructions for performing frequency domain stability tests can be found in the HP/Agilent 3048A system documentation.

Record the actual reading in the appropriate place in the Performance Test Record.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Performance Test Record

Model 5071A Primary Frequency Standard Serial Number:

Test Performed By: Temperature: Date: Relative Humidity: Notes:

Repair/Work Order No.

Test

Number Operational Verification

1 2 3

Test

Number Description

Power-On Self-Tests/Servo Lock Rear-Panel Output Signal Checks RS-232 Serial Port Verification

Complete Performance Tests

Output Signals: Harmonic Distortion and Spurious Signals Check

A. Harmonic Distortion Check for the 5 and 10 MHz Outputs

B. Non-harmonic (Spurious) Signal Check for the 5 and 10 MHz Outputs

C. Harmonic Distortion Check for the 1 MHz Output

D. Harmonic Distortion Check for the 100 kHz Output

Pass Fail

_______ ______ _______ _______ _______ _______

Actual

Reading

____________

Test Results

Limits

Greater than 40 dBc

Greater than 80 dBc

Greater than 40 dBc

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

Number

Test

Description

Frequency Accuracy

Stability

A. Time Domain B. Frequency Domain

Actual

Reading

____________

____________ ____________

Limits

Long-Life:

 1x10 High-Performance:

 2x10

See Specifications table in Chapter 6 of this manual.

1. Performance Tests – Verifying Specifications

5071A Complete Performance Tests

2. Service

Introduction

NOTE

In the interest of PRESERVING its usability most of the information in this chapter has been retained in its original form. No attempt has been made to update the equipment, accessories, or parts to reflect current availability. It is therefore necessary for the user of this manual to consider the recommendations of test equipment and accessories as suggestions. Some or all of these items may no longer be available from Symmetricom or any other vendors. An updated list of available replacement parts from Symmetricom is provided in Chapter 5.

This chapter provides service information for your 5071A and is divided into three major sections:

 Returning the Instrument to Symmetricom for Service. This section

provides you with step-by-step instructions on how to return the

instrument for service.

 Pre-Troubleshooting Information. This section provides you with pertinent

information such as safety considerations, recommended test equipment,

repair and after service considerations, service accessories, and

assembly identification and location.

 Diagnostic Trees and Procedures. This section provides you with

diagnostic trees and procedures to isolate faulty assemblies or modules.

(Once you find a faulty assembly or module, use Chapter 4, “Replacing

Assemblies,” to remove the defective assembly and replace it with a

functioning unit.) If the instrument is under warranty, return the instrument to Symmetricom for

service. Refer to the first section of this chapter titled “Returning the Instrument to Symmetricom.” If you decide to troubleshoot the instrument yourself, refer to the section titled “Diagnostic Trees and Procedures.”

2. Service Returning the Instrument to Symmetricom for Service

Returning the Instrument to Symmetricom for Service

To Provide Repair Information

If you are shipping the instrument to Symmetricom for service or repair, call your nearest Symmetricom sales representative or distributor to make arrangements. Alternatively you can visit our web site at http://www.symmetricom.com/support/warrantyandrepair and fill out the form to receive an RMA and return address information.

IMPORTANT NOTE

If you do not have the original shipping container for the 5071A it is STRONGLY recommended that you first order the packaging kit part number 59991-91105 from Symmetricom before returning for repair. This kit provides all the necessary packaging material to give the greatest amount of protection against shipping damage. Any 5071A received for repair in any other packaging and found damaged will not be covered under any Symmetricom warranty program. Such damage will be evaluated and you will be provided with a quotation to repair such damage before regular repair or calibration can be performed.

It is also advised that all hazardous materials regulations for labeling be followed for your local and country laws. The following web site will provide you with up-to-date instructions: http://www.symmttm.com/5071A/Shipping/

Be sure to include the RMA with the shipment.

To Pack in the Original Packaging Materials

To protect your 5071A against shipping damage repack the instrument in its original packaging for shipment. Shipping kit Part Number 59991-91105 is available through Symmetricom. In any correspondence, refer to the instrument by the model number and complete serial number.

1 Disconnect the power cord, probes, cables, or other accessories

attached to the instrument. 2 Make sure the folded corrugated spacer (which normally contains

the manuals) is in the box to ensure proper fitting. 3 Make sure the four polystyrene corner blocks are in their proper

positions in the box. 4 Place the instrument on the four polystyrene corner blocks with

the 3-ply pad at the rear panel end of the instrument.

2. Service Pre-Troubleshooting Information

5 Place four more polystyrene corner blocks on top of the

instrument to secure it. 6 Do not return the manuals with the instrument. Return an

accessory only when it is a part of the failure symptoms. 7 Seal the shipping container securely. 8 Apply the appropriate shipping labels.

Pre-Troubleshooting Information

This section contains the following pertinent troubleshooting information:

 Safety Considerations

 Recommended Test Equipment

 Repair Considerations

 After Service Considerations

 Service Accessories

 Assembly Identification and Location

WARNING

Safety Considerations

Although this instrument has been designed in accordance with international safety standards, this manual contains information, cautions, and warnings which must be followed to ensure safe operation and to retain the instrument in a safe condition. Service instructions, and adjustment procedures requiring removal of the instrument cover, are for use by service-trained personnel only. To avoid dangerous electric shock, do not perform any servicing or make any adjustments with the cover removed, unless qualified to do so.

BEFORE APPLYING AC POWER, THE INSTRUMENT AND ALL PROTECTIVE EARTH TERMINALS, EXTENSION CORDS, AUTO TRANSFORMERS, AND DEVICES CONNECTED TO THE INSTRUMENT SHOULD BE CONNECTED TO A PROTECTIVE EARTH GROUNDED SOCKET.

ANY INTERRUPTION OF THE PROTECTIVE GROUNDING CONDUCTOR INSIDE OR OUTSIDE THE INSTRUMENT OR DISCONNECTION OF THE PROTECTIVE EARTH TERMINAL WILL CAUSE A POTENTIAL SHOCK HAZARD THAT COULD RESULT IN PERSONAL INJURY. INTENTIONAL INTERRUPTION IS PROHIBITED.

Any adjustment, maintenance, and repair of the opened instrument under voltage should be avoided as much as possible and, if necessary, should be carried out only by a skilled person who is aware of the hazards involved (for example, fire and electric shock).

2. Service

Pre-Troubleshooting Information

Recommended Test Equipment

Test equipment recommended for testing and troubleshooting the 5071A is listed in Chapter 1, “Performance Tests.” Substitute equipment

may be used if it meets or exceeds the required characteristics listed in Table 1-1.

Repair Considerations

Electrostatic Discharge

Electronic components and assemblies in the 5071A can be permanently degraded or damaged by electrostatic discharge. Use the following precautions when servicing the instrument:

1 ENSURE that static sensitive devices or assemblies are serviced

at static safe workstations providing proper grounding for service

personnel. 2 ENSURE that static sensitive devices or assemblies are stored in

static shielding bags or containers. 3 DO NOT wear clothing subject to static charge buildup, such as

wool or synthetic materials. 4 DO NOT handle components or assemblies in carpeted areas. 5 DO NOT remove an assembly or component from its static

shielding protection until you are ready to install it. 6 AVOID touching component leads. (Handle by packaging only.)

Disassembly and Reassembly Specifics

Refer to the Chapter 4, “Replacing Assemblies,” in this manual for complete disassembly and reassemble details, and Chapter 5, “Replaceable Parts” for an exploded view of the instrument parts.

After Service Considerations

Product Safety Checks

The following safety checks must be performed after any trouble-shooting and repair procedures have been completed to ensure the safe operation of the instrument.

WARNING

RESISTANCE CHECKS DESCRIBED IN THE FOLLOWING TEXT REQUIRE THAT THE POWER CORD BE CONNECTED TO THE INSTRUMENT AND THAT AC POWER BE DISCONNECTED. BE SURE THAT THE POWER CORD IS NOT CONNECTED TO POWER BEFORE PERFORMING ANY SAFETY CHECKS.

2. Service Pre-Troubleshooting Information

1 VISUAL INSPECTION. Visually inspect the interior of the

instrument for any signs of abnormal internally generated heat,

such as discolored printed circuit boards or components,

damaged insulation, or evidence of arcing. Determine and remedy

the cause of any such condition. 2 GROUND CONTINUITY TEST. Plug the power cord into the rear-

panel power receptacle. (DO NOT connect the instrument to ac

power at this time.) Using a suitable ohmmeter, check resistance

from the instrument's metallic connection (such as the rear panel

or BNC ground collar) to the ground pin on the power cord plug.

The reading must be less than 1. Flex the power cord while

making this measurement to determine whether intermittent

discontinuities exist. 3 Check any indicated front or rear panel ground terminals marked,

using the above procedure. 4 INSULATION RESISTANCE TEST. Tie the line and neutral pins of

the power cord plug together. Measure the resistance from the

instrument enclosure (chassis) to the line and neutral pins of the

power cord plug. The minimum acceptable resistance is 2 M.

Replace any component that results in a failure. 5 LINE FILTER/CABLE ASSEMBLY CHECK. Check the line fuse

and voltage selector card in the rear panel line filter/cable

assembly to verify that the instrument is properly set for the ac-

power source to be applied.

Product Performance Checks

After replacement of any assembly or module, perform the Operational Verification Test in Chapter 1, “Performance Test,” of this manual.

Service Accessories

Service accessories for troubleshooting the 5071A are available from Symmetricom. Table 2-1 lists the items in the 5071A Service Accessories Kit. The list includes the name, the part number, and a brief description and use of each item.

2. Service

Pre-Troubleshooting Information

Table 2-1. Service Accessories Kit (05071-67003) Contents

Accessory Part Number Use

Service Manual 05071-90040 Corrective maintenance Extender board for short PCAs 05071-60051 A4, 6, 7, 8 diagnosis Extender board for long PCAs 05071-60052 A2,3 diagnosis 100 nA Current Source (powered by A6) 05071-60274 A14 diagnosis SO-8 SMT Dip clip (#5250 ITT Pomona) 1400-1708 SMT signal access SO-14 SMT Dip clip (#5251) 1400-1705 SMT signal access SO-16 SMT Dip clip (#5252) 1400-1706 SMT signal access SO-20 SMT Dip clip (#5253) 1400-1707 SMT signal access

2. Service

Pre-Troubleshooting Information

Assembly Identification and Location

The assembly number, name and part number of the 5071A assemblies are listed in Table 2-2. Figures 2-1 and 5-2, illustrate the replaceable assemblies and cables in the 5071A.

Table 2-2. 5071A Assembly Identification

Assembly Name Part No.

A1 A1 A2 CBT Controller Assembly 05071-60202 A3 Microprocessor Assembly 05071-68003 A4 Digital Synthesizer Assembly 05071-68004 A5 87 MHz PLL Module 05071-60272 A6 Servo Assembly 05071-68006 A7 Interface Assembly 05071-68007 A8 1 PPS Assembly 05071-68008 A9 Frequency Multiplier Module 05071-60292 A10 Output Frequency Distribution Amplifier Module 05071-60210 A11 A11 A12 A12 A13 Front-Panel PC Assembly 05071-60213 A14 Signal Amplifier Module 05071-60214

Motherboard Assembly Motherboard Assembly, Opt.048 only

Power Steering Logic Assembly, Std Power Steering Logic Assembly, Opt. 048 only Dc-Dc Power Converter Module DC-DC Power Converter Module. Opt. 048 only

05071-68001 05071-68028

05071-68029 05071-68033 05071-60212 05071-60279

A15 9.2 GHz Microwave Generator Module 05071-60215 A16 High Voltage Supply Module 05071-60216 A17 CBT (Cesium Beam Tube) Assembly

A18 9.2 GHz PLL Module 05071-60218 A19 Reference Oscillator (Quartz) Module 05071-60294 LF1 Line Filter/Cable Assembly 05071-60259 T1 T1

or Option 001 High Performance CBT Assembly

Toroidal Power Transformer Toroidal Power Transformer, Opt. 048 only

10890A

10891A

9100-4962 9100-5134

2. Service

Pre-Troubleshooting Information

Figure 2-1. Instrument Top View

2. Service

Diagnostic Trees and Procedures

The following sections contain diagnostic-troubleshooting trees (diagnostic trees) in the form of stepwise procedures and Yes/No decision points. The intent of this process is to isolate a faulty printed circuit assembly (PCA) or module. Component-level troubleshooting is NOT supported in this manual, except for the A1 motherboard.

Troubleshooting on the 5071A requires disassembly for access. Refer to the “Disassembly and Reassembly” procedures in chapter 4 for that information. Assembly specific tests and probing frequently requires the use of either a long or short PCA extender board. The extender boards and their part numbers are listed in Table 2-1.

NOTE

Following the diagnostic-tree procedures is essential to isolating the faulty assembly or module. If the internal self test diagnostics are used without reference to this process, misleading results may be obtained, leading to improper and unproductive repair actions. Besides the diagnostics, other means are required to localize and isolate the problem PCA or module. These include visual checks of LEDs, and LCD display messages along with test equipment checks such as scope, multimeter, or spectrum analyzer tests.

The diagnostic self tests may be executed via SCPI commands, or from the 5071A front-panel software interface. All the information is given in the description of the diagnostic trees.

Ensure that all internal modules and assemblies are correctly installed and all interconnect cables are present and properly routed. (Refer to the functional-block interconnect tables in chapter 3, “Theory of Operation” for cable interconnect information.) Each PCA must be fully seated in its correct bus slot position on the A1 motherboard. (A9J101 if present is capped with no connection.)

2. Service

Diagnostic Trees and Procedures

5071A Diagnostic Tree Organization

 Diagnostic-Tree Section 1 - Top-level Diagnostics Trees:

provides the beginning entry point for the troubleshooting process;

organized around start-up events, front-panel operation/messages, and

rear-panel output/input signals.

 Diagnostic-Tree Section 2 - Functional-Group Diagnostic Trees:

provides diagnostic trees for any two or more assemblies or modules that

interact with each other in the normal performance of instrument

operation.

 Diagnostic-Tree Section 3 - Assembly/Module Diagnostic Trees:

provides diagnostic trees for individual assemblies and modules when

indicated by either Top-level tree pointers or Functional-Group tree

pointers.

Navigating the Diagnostic Trouble-Tree Sections

1 Go to the beginning of the Top-level diagnostic tree:

a) If you already know the symptom/operating problem - go to the

subsection in section 1 that provides its fault isolation.

b) If you do not know what's wrong with a failed instrument, start at

the beginning of the Top-level tree checking all items sequentially until you find a specific isolated fault or find a pointer to further details in sections 2 or 3.

2 If you know for certain

exists, go to the applicable Functional-Group diagnostic tree in

section 2. (If replacement of an obviously defective component

does not restore normal operation, then you must start at step 1b

above). 3 If you know for certain

fault, go to section 3, Assembly/Module diagnostic trees to locate

the applicable diagnostic tree. (If replacement of an obviously

defective component does not restore normal operation, then you

must start at step 1b above.)

the general hardware area where the fault

that a particular assembly/module is at

2. Service

Diagnostic Trees and Procedures

Top-Level Diagnostic Tree Organization

The following list of titles outlines the organization of the Top-Level Diagnostic tree and its seven subsections:

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.0.0 First Power On

1.0.1.1 Digital Supply Voltage Check

1.0.1.2 A3 Microprocessor Fault

1.0.2 Dc-Supply Test/Log-Record Examination

1.0.3 Power On Fatal Error Check

1.0.4 Instrument Self Tests

1.0.5 CBT Warm Up

1.0.6 Servo-Lock Warning State

1.0.7 User-Input/Output Checks

1.0.8 5071A Profiling

1.0.8.1 Profiling Results Interpretation

1.0.8.2 Conclusion of Diagnostic Procedure

1.0.9 Delayed Failures, Warnings, and Messages

1.0.9.1 Delayed Fatal Errors

1.0.9.2 Delayed Warnings

1.0.9.3 Delayed Advisory Messages

Power-On Fatal-Error Diagnostic Tree (Diagnostic Subsection 1)

1.1.1 Fatal Error Interpretation

1.1.2 Sequencer Error Test

1.1.2.1 1 PPS Assembly 80 MHz Input Test

1.1.3 Tube PROM Test

Self Test Diagnostic Tree (Diagnostic Subsection 2)

1.2.1 Self Test Failure Interpretation

1.2.2 Pps Interrupt Error Test

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Diagnostic Trees and Procedures

Warm-up and Operating Fatal Error Diagnostic Tree (Diagnostic Subsection 3)

1.3.1 Warm-Up/Operating Error

1.3.1.1 Operating Error-Code Interpretation

1.3.2 Interpreting Warm-Up Errors

1.3.2.1 Cs Oven Failed: Ion-Pump Over current Warm-up Error

1.3.2.2 A16/CBT Excess Ion-Pump Current Test

1.3.3 CBT Signal Fatal Errors

1.3.4 CBT Shutdown Message

1.3.5 Cs Oven Timeout Test

1.3.6 CBT Background Signal Warm-Up Errors

1.3.7 CBT Depth of Modulation Warm-Up Errors

1.3.7.1 CBT Support Circuits Test

1.3.8 RF Level Control-Current Test

Warning Message Diagnostic Tree (Diagnostic Subsection 4)

1.4.1 Warning Message Interpretation

1.4.2 Signal Gain at Range Limit/CBT Signal Low

1.4.3 5071A Profiling (CBT Performance Evaluation)

1.4.4 Power Source is Batt (Ignore this for Opt 048)

1.4.4.1 Ac Line Operation - Battery Indicator On

1.4.4.2 Instrument Ac Power Absent

1.4.4.2.1 A1C4 Voltage Test

1.4.4.3 LF1/T1 Transformer Fault Verification

I/O Diagnostic Tree (Diagnostic Subsection 5)

1.5.1 Input/Output Faults

CBT Performance Evaluation (Diagnostic Subsection 6)

1.6.0 Running the 5071A Profiling Software

1.6.1 5071A Profiling Results Evaluation

Advisory Messages (Diagnostic Subsection 7)

1.7.1 Advisory Message Interpretation

2. Service Top-Level Diagnostic Tree (Diagnostic Section 1)

Top-Level Diagnostic Tree

(Diagnostic Section 1)

This section describes the top-level diagnostic procedures for the 5071A Primary Frequency Standard and provides pointers to lower-level procedures. It is complete and must be performed sequentially. The procedures are designed to troubleshoot an instrument that has failed in normal operation, and is no longer able to lock-up correctly at power on.

When the complete procedure is performed on a functional 5071A, it will end at section 1.0.8.2 with no errors or failures. The operational verification and Performance Test procedures described in Chapter 1 of this manual must be performed successfully on a repaired instrument before it is placed back in service.

A transient error condition is evident when an instrument generates an error or warning but subsequently passes the operational verification procedure without any repair. This could for example occur when the cesium beam tube (CBT) nears the end of its life.

In case of difficulty, contact Symmetricom for assistance.

1.0.0 First Power On

1 Remove the instrument from service. 2 Remove all external power. 3 Disconnect the internal-standby battery. (See Operating and Programming

manual, pg 2-15). (For Opt. 048, ensure that the rear-panel dc-line fuse

holder has a good fuse of the correct rating). 4 Ensure that rear-panel ac-line filter/cable assembly has a good fuse. 5 Remove 5071A top/bottom covers and top inner shield (see pg 4-3). 6 Power on the 5071A by applying dc or ac power. 7 Verify that all front-panel LEDs, the LCD, beeper, and keypad work:

a. Observe the large red seven-segment and small amber LEDs

momentarily illuminate.

b. Observe the LCD illuminate its top row of pixels followed by normal two-

row-display operation.

c. Check each key by pressing it and either hear or observe a confirming

response.

NOTE a & b above should occur within first few seconds of

operation.

QUESTION: Is the front-panel functional (beeper, LEDs, keyboard operational)?

2. Service Top-Level Diagnostic Tree (Diagnostic Section 1)

If Yes: Go to, 1.0.2. If No: Disconnect power immediately and check the appropriate rear panel

power fuse. If fuse is intact, Go to, 1.0.1.1. (For Opt. 048 Go to 1.0.1.1.0.) If fuse is blown, Go to, 2.1.1.1.0 (Power supply diagnostic tree).

1.0.1.1.0 DC Input 1 and 2 Power Steering Circuit Check

1 Use the DC Input 1 and 2 Power Steering Schematic (Figure 2-1.)

located on page 32 of this chapter to troubleshoot the dc power

input steering function. QUESTION: Is the DC input power steering circuit functional? If Yes: Go to, 1.0.1.1. If No: Replace the 48V Sub-panel Assembly (P/N 05071-60277) and retest.

1.0.1.1 Digital Supply Voltage Check

1 Install the short extender board (part number 05071-60051) into

the spare slot on the A1 motherboard. 2 Use a DMM with a point-tipped probe to verify +5V supply on the

extender board test points. QUESTION: Is +5V between 5.28 to 5.50 volts? If Yes: Go to, 1.0.1.2 If No: Go to, 2.1.1.1.0 (Power-Supply diagnostic tree).

1.0.1.2 A3 Microprocessor Fault

1 Observe upper edge row of LEDs on A3 microprocessor

assembly. QUESTION: Are LED DS6 lit and LEDs DS1 - DS4 extinguished? If Yes: Remove power, replace A13 (see page 159.), and retest. If No: Remove power, replace A3, and retest.

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.0.2 DC-Supply Test/Log-Record Examination

1 If the INFO/STATUS menu selections display Warming

up, use

the CONFIG, MODE, and STANDBY menu selections to place the

5071A into STANDBY mode. (This will put the instrument into a

stable state if it has not gone to Fatal Error mode.) 2 Record all information in the log (LOG/BROWSE menu selections). 3 Clear the log (use LOG/CLEAR). 4 Install the short extender board (part number 05071-68051) into

the spare slot on the A1 motherboard. 5 Use a DMM (with point-tipped probes) set for dc volts to measure

the +5, +12, and -12 volt supplies on the extender-board test-

voltage points to chassis ground. They should all be within the

following ranges:

+5V = 5.28 to 5.50 volts

+12V = 12.08 to 12.40 volts

-12V = -12.08 to -12.40 volts

QUESTION: Are the measured voltages within the given ranges? If Yes: Go to, 1.0.3 If No: Go to, 2.1.1.1.0 (Power-supply diagnostic tree).

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.0.3 Power On Fatal Error Check

1 Cycle power to the instrument, wait fifteen seconds. 2 Go to the INFO/STATUS section of the front-panel menu.

QUESTION: What state is the 5071A in? If Warming Up, Go to, 1.0.2, perform step 1, then go to 1.0.4.,

NOTE

If in Fatal

For some test purposes it is useful to force the instrument into the fatal error state. This can be done by applying power with A2P3 disconnected from A2J2.

Error, Go to, 1.1.1 (Power-On Fatal-Error diagnostic tree).

1.0.4 Instrument Self Tests

1 Execute all Self tests from front panel in Standby mode as follows:

a) Go to the UTIL menu, select TEST option, and press Enter.

b) Press INC to initiate the Self test cycle.

c) Observe the front-panel display CYCLES = 0: when 0 changes to

1 or greater, all Self tests have passed.

d) If a Self test routine fails, record the displayed message and attempt

to continue the tests by pressing INC again.

e) Press DEC to halt Self test execution.

QUESTION: Did the 5071A pass all the Self tests?

If Yes: Go to, 1.0.5

If No: Go to, 1.2.1 (Self-test diagnostic tree).

1.0.5 CBT Warm Up

1 Change operating mode to NORMAL (press CONFIG, MODE, and

NORMAL), the instrument state changes to Warming up.

2 Wait until the green LED is flashing, or 45 minutes have passed.

QUESTION: Does the green LED continue to flash for at least

If Yes: Go to, 1.0.6.

If No: Go to, 1.3.1, Warm-up and Operating Error diagnostic tree.

60 seconds?

(For delayed error conditions, go to 1.0.9.)

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.0.6 Servo-Lock Warning State

QUESTION: Is the amber LED flashing? If Yes: Go to, 1.4.1, Warning-Message diagnostic tree. (For delayed

error/warnings go to 1.0.9.)

If No: Go to, 1.0.7.

1.0.7 User-Input/Output Checks

1 Check the performance of the following outputs/inputs:

(Refer to chapter 1, page 1-8 to verify operation and page 1-7 in

the Operating and Programming manual for checking the Sync

inputs with a pulse source.)

a) Both 5/10MHz outputs,

b) 1 MHz output,

c) 100 kHz output,

d) RS232 port,

e) All 1PPS outputs,

f) Both Sync inputs

g) Status Output

1) Use an oscilloscope to verify TTL-high state.

2) Put the instrument into Standby.

3) Verify transition to TTL-low state.

4) Return the instrument to Normal. QUESTION: Did all Input/Output checks pass? If Yes: Go to, 1.0.8. If No: Go to, 1.5.1 (I/O diagnostic tree).

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.0.8 5071A Profiling

Successful completion of the preceding tests indicate that all functional blocks of the 5071A under test are operational. This is confirmed by the instruments' ability to lock-up its servo loops successfully with no errors. These tests are however, not sufficiently detailed to predict the accuracy or stability of the instrument, which could be degraded by noise or instability in the CBT and the electronic circuits.

Because the operating accuracy and stability of the 5071A can only be confirmed by long observations, it is useful to assess the noise contribution of the CBT at the completion of the top-level test procedure. The CBT has a finite lifetime, and measurements of its operating parameters may be used to give advanced warning of required service.

1 Perform the 5071A profiling procedure provided at 1.6.0. The procedure has

no effect on the timekeeping performance of the instrument, and may be conducted on an 5071A currently in use. The procedure requires only that the instrument will run in Normal Operation mode.

2 When the profiling software has generated its report, use the following

information to evaluate the results.

1.0.8.1 Profiling Results Interpretation

Signal to Noise Ratio

The Signal to Noise Ratio is an estimate of the current overall operating condition of both the CBT and instrument electronics.

 If the result is Band 1, the instrument's stability should meet specification.

CBT problem is unlikely.

 If the result is Band 2, the test is indeterminate. High Probability that

CBT is performing to specifications.

 If the result is Band 3, instrument stability will probably not meet

specification. CBT problem is likely. Consult Chapter 1 on Performance Tests to confirm poor performance.

Depth of Modulation

The Depth of Modulation can help isolate faults to either the CBT or instrument electronics.

A Band 3 modulation depth combined with a peak-output current below 100 nA indicates deteriorating CBT performance. Be sure to thoroughly diagnose the entire instrument before considering the A17 CBT to be at fault. Contact your nearest service facility for further assistance.

2. Service Top-Level Diagnostic Tree (Diagnostic Section 1)

VCXO Control Value

The frequency of the VCXO is continually adjusted by the frequency servo to correct for noise and aging. The present state of the adjustment is provided by the VCXO control value. This value has no discernible effect on instrument operation as long as it remains within a 100% range. It is desirable to schedule readjustment of the A19 frequency if the control value reaches  90%. The adjustment procedure is provided at 3.9.1.7 and 3.9.1.8.

1.0.8.2 Conclusion of Diagnostic Procedure

If the results of the profiling procedure do not suggest CBT replacement, the instrument can be returned to service. If repairs have been made, full performance testing or operational verification must be performed as described in chapter 1.

If a 5071A has been successfully tested as described above and fails to meet specifications, you may need to return the instrument to the nearest qualified repair facility. Contact Symmetricom for further assistance.

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.0.9 Delayed Failures, Warnings, and Messages

The error messages covered in sections 1.1.1, 1.2.1, 1.3.1, and 1.4.1 describe the error conditions which can occur respectively at power-up, during self-test, during servo lock-up, and immediately following servo lockup. Error conditions can occur later than this, for example due to component failure, aging, or progressive loss of CBT performance. These will be described as delayed error conditions.

Delayed error conditions include “Fatal Errors” which result in the instrument going off-line, “Warnings” of unsatisfactory internal conditions which do not necessarily cause operation to fail completely, and “Messages” which are advisory.

Use the following information to investigate possible malfunctions. Examine the instrument's log and record any error conditions which have occurred before beginning troubleshooting.

1.0.9.1 Delayed Fatal Errors

Operational fatal errors are usually caused by a significant malfunction of one of the instrument's functional blocks. These errors will usually prevent subsequent operation and can be diagnosed in the usual way using the top level diagnostic procedure.

1.0.9.2 Delayed Warnings

Warnings which occur in normal operation may not always require the instrument to be removed from service, especially when some loss of performance is tolerable. For example declining CBT performance will result in a “CBT signal low” warning. This warning is only issued once, as it does not cause the instrument to stop operating.

Some errors may occur due to transient conditions, or perhaps be caused by unusually strong external EMI (Electro-Magnetic Interference). Such error conditions can be cleared using the front-panel Shift , 5 , Enter sequence. When ever possible, however, the instrument should be run through Operational Verification procedure as a precaution. The procedure in section

1.4.1 can be used to investigate the cause of warnings.

1.0.9.3 Delayed Advisory Messages

Advisory messages have several degrees of importance, and may occur together with fatal errors. Messages are discussed in section 1.7.1.

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

Power-on Fatal-Error Diagnostic Tree (Subsection 1)

This subsection describes the power-on fatal-error diagnostic tree. It assumes that the internal +5, +12, and -12 dc-supply voltages are all present and within specifications.

1.1.1 Fatal-Error Interpretation

1 Observe the log contents for any of the following error messages.

QUESTION: What is the error? If Error = Sequencer interrupt error <number>, Go to, 1.1.2 If Error = Config load err <number>, page <number>, Go to, 1.1.3 If Error = Config write error <number>, Go to, 1.1.3 If Error = Bad CBT EEPROM format, Go to, 1.1.3 If Error = CBT load error <number> page <number>, Go to, 1.1.3 If Error = none of the above, Go to, 1.3.1

1.1.2 Sequencer Error Test

This error occurs when 1MHz is absent on A3. 1 Place the short extender board (part number 05071-60051) into the

available spare slot on the motherboard (XOPTP1 and XOPTP2).

2 Use an oscilloscope to verify that a 1 MHz signal is present at the test

point labeled “+1 MHz” with an amplitude of 4 volts, 50% duty cycle, and a nominal 20 ns rise time.

QUESTION: Is the 1 MHz signal present as specified? If Yes: Remove power, replace A3, and retest. If No: Go to 1.1.2.1.

1.1.2.1 1-PPS Assembly 80 MHz Input Test

1 Remove ac power and disconnect the cable from A8J3. 2 Connect free end of the cable to the 50  impedance input of an

oscilloscope. (If a 50  input is absent, use the high impedance input with a 50  feed-through terminator at the scope end of the cable.)

3 Apply ac power and verify that the signal at A8P3 is an 80 MHz sine wave

with at least 0.6 Vp-p amplitude. QUESTION: Is the 80 MHz signal as described in step 3?

If Yes: Remove power, replace A8, and retest. If No: Go to, 3.4.1.0 (A9 diagnostic tree)

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

1.1.3 Tube PROM Test

1 Remove power from the instrument. 2 Disconnect A2P3 from A2J2. 3 Apply power to the instrument. 4 Verify presence of +5 V ( 0.5) at pin 1 on A2J2 to chassis

ground.

5 Use a digital storage scope or logic analyzer (trigger set to 2.5V,

DC coupled, timebase to 50 us/div., no auto trigger) to verify the signals are toggling at A2J2 pins 2 and 3 following activation of the reset button on top of A3. The pulse levels should be approximately 4.0 Vp-p. (Refer to the A2 connector pinout diagrams at the beginning of the A2 diagnostic trees opposite procedure 3.1.1.1.0.)

QUESTION: Is there +5 V at pin 1 and a toggling signal present on

pins 2 and 3 of A2J2? If Yes: CBT ROM may be defective: contact Symmetricom for assistance. If No: Remove power, replace A2, and retest.

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Top-Level Diagnostic Tree (Diagnostic Section 1)

Self Test Diagnostic Tree (Subsection 2)

This subsection describes what to do after a Self-test fails.

1.2.1 Self-Test Failure Interpretation

QUESTION: Which test(s) failed? (If 13/14: Repair A7 and retest.) If TEST 13, Interface register test, Remove power, replace A7, and retest. If TEST 14*, Interface abus offset test,

Interface abus +5V test,

Interface abus +12V test,

Interface abus -12V test, Remove power, replace A7, and retest.

NOTE If test 13/14 fails, remove power, replace A7 and retest.

If TEST 0, CBT register test: Remove power, replace A2, and go to 1.1.3. If TEST 1, CBT window comp test (open)

CBT window comp test (short), Go to, A2 Thermistor tree beginning at 3.1.2.1.0.

If TEST 2, CBT therm zero test, CBT therm ones test, Go to, A2 Thermistor tree beginning at 3.1.2.1.0.

If TEST 3, CBT Cs oven zero test (<num.> V), CBT Cs oven ones test (<num.> V), CBT Cs oven bit test (bit <num.>), Go to, A2 Cesium-Oven tree beginning at 3.1.4.1.0.

If TEST 4, CBT hw ion zero test (<num.> V), CBT hw ion all 1's test (<num.> V), CBT hw ion bit test (bit <num.>), Go to, A2 Hot-Wire Ionizer tree beginning at 3.1.1.1.0.

If TEST 5, CBT mspec zero test (<num.> V), CBT mspec ones test (<num.> V), CBT mspec bit test (bit <num.>), Go to, A2 Mass-Spectrometer tree beginning at 3.1.3.1.0.

If TEST 6, CPU RTDS test (no interrupt), CPU RTDS test (<num.> tics),

CPU RTDS test (no 1MHz), Remove power, replace A3, and retest. If TEST 7, CPU clock locked test, Remove power, replace A3, and retest. If TEST 8, DDFS register test, Remove power, replace A4, and retest.

2. Service Top-Level Diagnostic Tree (Diagnostic Section 1)

If TEST 9, 87 MHz PLL test (<num.> kHz, <num.> V), Go to, A5 87 MHz

PLL tree (3.2.1.0). If TEST 10, 9.2 GHz PLL test (<num.> V), Go to, Rf-chain tree (2.3.1.0). If TEST 11, Servo register test, Remove power, replace A6, and retest. If TEST 12, Servo converter timeout test, Remove power, replace A6, and

retest. If TEST 15, Pps register test, Remove power, replace A8, and retest. If TEST 16, Pps interrupt test, Go to, 1.2.2. If TEST 17, Power logic signals test, Remove power, replace A11, and

retest.

*Failure of test 14 may occur with any combination of tests 2, 3,4,5,9, and 10.

1.2.2 Pps Interrupt-Error Test

1 Install the short-extender board (part number 05071-60051) into

the spare slot on the A1 motherboard.

2 Use an oscilloscope with trigger level set to +1.5 volts (no auto

trigger) and high-impedance probe to check presence of 20 s pulses with an amplitude greater than 4 V at a rate of 1 pulse per second on XOPTJ1 pin 44.

QUESTION: Is the waveform correct? If Yes: Remove power, replace A3, and retest.

(If the problem persists: remove power, replace A1, and retest; or contact Symmetricom for further assistance.)

If No: Remove power, replace A8, and retest.

2. Service

Top-Level Diagnostic Tree (Diagnostic Section 1)

Warm-up And Fatal Error Diagnostic Tree (Subsection 3)

This subsection describes the warmup- and fatal-error diagnostic tree.

1.3.1 Warm-Up/Operating Error

1 Examine the log (LOG/BROWSE).

QUESTION: Is the last item in the log an error code that appears

similar to this: If Yes: The instrument has failed after warming up: Go to, 1.3.1.1. If No: The instrument has failed to complete warm up: Go to, 1.3.2.

1.3.1.1 Operating Error-Code Interpretation

1 Convert the two 8-character hexadecimal words in the error code into its two

corresponding 32-bit binary words using the chart below.

Error code: 000000a0 20000000?

2 Divide the right-most binary word into 16 fields each containing two adjacent

bits.

3 Divide the 14 right-most bits of the second binary word into seven fields each

containing two adjacent bits.

4 Each of the 23 two-bit fields corresponds to the output of an internal test at

the moment the instrument entered Fatal-Error mode. A non-zero number in any one of the fields indicates a potential cause of the

shut-down as shown on the following page.

Hexadecimal

Binary 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111

0 1 2 3 4 5 6 7 8 9 A B C D E F

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FIRST WORD (Rightmost word):

- 0 0 0 0 0 0 0 0  Hex digit

/ \ / \ / \ / \ / \ / \ / \ / \

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  | | | | | | | | | | | | | | | \_1. Servo offset - No Message | | | | | | | | | | | | | | \_2. CBT shutdown: <#> - Fatal Error | | | | | | | | | | | | | \_3. VCXO near tuning limit - Warning | | | | | | | | | | | | \_4. VCXO at tuning limit - Fatal Error | | | | | | | | | | | \_5. C-field current at range limit - Fatal Error | | | | | | | | | | \_6. E-multiplier voltage at range limit - Message | | | | | | | | | \_7. Signal gain at range limit - Warning | | | | | | | | \_8. Internal DC supply out of range - Warning | | | | | | | \_9. Mass spec supply regulation failure - Fatal Error | | | | | | \_10. Hotwire supply regulation failure - Fatal Error | | | | | \_11. CBT oven supply regulation failure - Fatal Error | | | | \_12. CBT oven voltage at range limit - Fatal Error | | | \_13. RF amplitude at range limit - Warning | | \_14. Microprocessor PLL unlocked - Warning | \_15. 87 MHz PLL unlocked - Message \_16. Unused bit - always zero.

Binary digit

SECOND WORD:

0 0 0 0 0 0 0 0  Hex digit / \ / \ / \ / \ / \ / \ / \ / \

\-----reserved--------/

Binary digit

Example Error-Code Interpretation

- You can create a fatal error by disconnecting A5P2 from A5 after the instrument has

powered-up and is running (wait up to 35 seconds for the software to confirm this failure). When the attention LED begins flashing, you're ready to read the error code from the log.

- Typical log display: Error code: 000000a0 20000000

- By using the above error-message map, the following information may be decoded:

- 15. 87 MHz PLL unlocked - Message

- 19. CBT sign al loss - Fatal Error (This is the event that initiated the shut-down.)

- 20. CBT signal low – Warning

NOTE You must power-off, reconnect A5P2, and then power-on again

to clear this error.

NOTE

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QUESTION: What combination of errors are indicated by the code? (Assembly/module trees are listed in diagnostic-tree section 3.)

- If FATAL ERROR #2, Go to, 1.3.4.

If ONLY FATAL ERROR #9, Go to, 3.1.3.1.0, A2 Mass-spectrometer tree. If ONLY FATAL ERROR #11, Go to, 3.1.4.1.0, A2 Cesium-oven tree. If ONLY FATAL ERROR #10, Go to, 3.1.1.1.0, A2 Hot-wire ionizer tree. If ONLY FATAL ERROR #12, Go to, 1.3.5, Cs oven timeout test. If ONLY FATAL ERROR #4, Go to, 3.9.1.1, A19 Reference-oscillator tree. If FATAL ERROR #5, Go to, 2.4.3.0, C-field tree. If FATAL ERROR #19 or #22, Go to, 1.3.3.

A non-zero total in the first field of the right-most word indicates that the 5071A was being steered at the time of shutdown: it has no diagnostic significance.

Additional diagnostic information may be obtained from any warnings or messages indicated by data in the error codes. See

1.4.1 and 1.7.1 for more details.

1.3.2 Warm-Up Error Interpretation

1 Locate the most recent error (should be at the end of the log). 2 Record this error.

QUESTION: What is the error?

(All assembly/module trees are in diagnostic tree section 3.) (RF-chain and C-field trees are in diagnostic tree section 2.)

- If ERROR = Cs oven failed: ion pump overcurrent, Go to, 1.3.2.1.

If ERROR = Cs oven timeout, Go to, 1.3.5. If ERROR = Osc. oven timeout, Go to, 3.9.1.1, A19 diagnostic tree. If ERROR = Low Cs signal <#> with max Emult, Go to, 1.3.6. If ERROR = High Cs signal <#> with min Emult, Go to, 1.3.6. If ERROR = Cannot set E-mult to avoid saturation, Go to, 1.3.6. If ERROR = Signal saturated at min E-mult voltage, Go to, 1.3.6. If ERROR = Beam min/max values not 5% apart, Go to, 1.3.7. If ERROR = Failed attempts to set Osc. control, Go to, 1.3.7. If ERROR = Osc. control range error, Go to, 1.3.7. If ERROR = CBT signal loss Go to, 1.3.7. If ERROR = Line center not found, Go to, 1.3.7. If ERROR = VCXO at tuning limit, Go to, 1.3.7. If ERROR = RF Amplitude range error, Go to, 2.3.1.0. If ERROR = RF amplitude at range limit, Go to, 2.3.1.0. If ERROR = E-mult If ERROR = Failed attempts to set C-field, Go to, 1.3.7.

voltage has changed, Go to, 3.7.1.0.

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1.3.2.1 Cs Oven Failed: Ion Pump Overcurrent Warm-up Error

This error occurs when current drawn by the CBT Ion Pump fails to go below 40 A within 45 minutes after operation begins. It can be caused by either excessive current drawn by the CBT as a result of a high internal gas pressure, or by a failure in the Ion pump high-voltage supply (P/O A16), or the current-monitoring circuit (P/O A2). The following procedures check these alternatives:

1 Observe the measured Ion-Pump supply current on the LCD display

(Use the INFO/Pump menu selection.). QUESTION: Is the current more than 40 A? If Yes: Go to, 1.3.2.2. If No: The problem may have cleared itself, remove ac power,

and retest.

1.3.2.2 A16/CBT Excess Ion-Pump Current Test

1 Remove instrument power and wait at least 60 seconds for the high voltage

supplies to bleed down.

2 Disconnect the Ion Pump high-voltage (HV) connector from the CBT (see

Figure 2.1). (Ensure that the end of the high-voltage lead is clear of any conductors.)

3 Disconnect the flexible cable joining the CBT to A2J2. 4 Power up the instrument and allow a few seconds for it to enter the Fatal-

Error mode.

5 Observe the measured Ion Pump supply current on the LCD display (Use the

INFO/Pump menu selection.).

6 Remove power, wait 1 minute, and reconnect the Ion-pump HV lead.

QUESTION: Was the current more than 1 microamp? If Yes: A fault is present in the Ion Pump power supply circuitry,

Go to, 3.7.1.0, A16 diagnostic tree (This tree also checks part of A2.).

If No: CBT Ion-Pump current is high. When caused by poor vacuum (for

example, due to prolonged storage) the condition may correct itself if the unit is placed into STANDBY mode for 24 hours. If the condition persists after this time, remove power and contact Symmetricom for assistance.

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1.3.3 CBT-Signal Fatal Errors

These errors occur when the instrument completes its lock-up procedure, and the frequency servo loop cannot operate correctly. They usually indicate the CBT output signal is unstable. This can be due to a malfunction in the CBT itself, or more frequently, in the circuits associated with it. The following procedure tests these alternatives.

1 Perform the Analog-Signal Chain tests (2.2.1.0) and repair as required. 2 Perform the RF-Chain tests (2.3.1.0) and repair as required. 3 Perform the A16 Electron-Multiplier Supply tests (3.7.2.1) and repair as

required.

4 Perform the RF-Level Control-Current Check, (1.3.8), and repair as required. 5 Apply power to the instrument: observe the warm up and subsequent

operation. QUESTION: Did the instrument fail in the same manner?

If Yes: The CBT is possibly defective, contact Symmetricom for further

assistance.

If No: Problem may be resolved - retest.

1.3.4 CBT Shutdown Message

1 Read the CBT shutdown message preceding the error code.

QUESTION: What is the message? If CBT shutdown:

thermistor open, Go to, A2 thermistor

(3.1.2.1.0) diagnostic tree. If CBT shutdown:

thermistor shorted, Go to, A2 thermistor

(3.1.2.1.0) diagnostic tree. If CBT shutdown:

ion pump overcurrent, Go to, Excess Ion-

pump current (1.3.2.1) test.

If CBT shutdown:

E-mult adjust failed – This indicates that although

larger e-mult movements were attempted the internal CBT parameters could not be compensated sufficiently to allow continued operation. Repair is likely necessary, however a re-start of the 5071A should first be attempted as a possible remedy. If the failure re-occurs with the same message, contact Symmetricom to arrange repair/replacement of the CBT. If the error is not repeated but another error occurs, follow the procedures for that error.

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1.3.5 Cs Oven-Timeout Test

This error occurs because the indicated cesium oven temperature has not reached the correct value within 45 minutes from power on or an error has subsequently occurred. This may be due to a failure of the cesium-oven heater or thermistor, or the associated circuits on A2.

1 Perform the A2 Thermistor and Cesium Oven diagnostic test procedures in

diagnostic section 3 (3.1.2.1.0 and 3.1.4.1.0) of this chapter.

2 Replace A2 and/or A7 as indicated. 3 Reapply power to the instrument and observe the warm up behavior.

QUESTION: Did the instrument fail in the same manner? If Yes: The CBT may be defective, contact Symmetricom for assistance. If No: Continue diagnostic testing.

1.3.6 CBT Background-Signal Warm-Up Errors

NOTE

These errors occur when the CBT background signal is not within acceptable limits after warm up. This condition can be caused by a malfunction in the CBT itself or by various circuits that control it. This procedure checks these alternatives.

The instrument self-tests must pass successfully for the following procedure to be conclusive.

1 Perform the Electron-Multiplier Supply tests with procedure 3.7.2.1. Replace

A16 if necessary, and re-connect all leads.

2 Perform the Analog-Signal Chain tests 2.2.1.0. Repair as necessary, and re-

connect all cables and assemblies.

3 Retest the instrument by cycling ac power.

QUESTION: Does the instrument fail to lock-up, then display one of

the same errors? If Yes: A CBT fault is indicated, contact Symmetricom for further assistance. If No: Continue the diagnostic procedures.

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1.3.7 CBT Depth-of-Modulation Warm-Up Errors

These errors usually indicate that modulation of CBT output signal that results from tuning the microwave-probe signal through cesium resonance, does not fall within minimal limits for correct operation. The errors can be caused by incorrect operation of the microwave multiplication process (RF chain), mis-tuning of the A19 VCXO (voltage-controlled crystal oscillator), failure of the A7 C-field control circuits or rarely, failure of the CBT. The following procedure checks these alternatives:

1 Test the RF chain by performing procedure 2.3.1.0. through 2.3.6.0. 2 Test the C-field circuit by performing procedure 2.4.1.0. through 2.4.3.0.

QUESTION: Did all diagnostic tests pass? If Yes: The microwave signal is adequate for satisfactory warm-up

completion, Go to, 1.3.7.1.

If No: Repair as required and retest.

1.3.7.1 CBT Support-Circuit Tests

1 Perform the A19 VCXO tests 3.9.1.1 through 3.9.1.8). 2 Check the RF-level control current as described at 1.3.8. 3 When all tests complete satisfactorily, cycle power to the instrument.

QUESTION: Did warm-up fail with the same error message? If Yes: CBT is probably defective, contact Symmetricom for further

assistance.

If No: Continue the diagnostic procedure.

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1.3.8 RF-Level Control-Current Test

The amplitude of the microwave probe signal is controlled by an amplitude modulator in A15 driven with current generated from a DAC on A7. If control current is absent, amplitude modulation is lost.

1 Remove power and disconnect the cable from A1J19 to A15J1. 2 Using a suitable SMA adapter, connect the DMM to the cable from A1J19

and set the DMM to measure at least 16 mA dc.

3 Disconnect the CBT from A2 at A2J2. Cycle instrument power and wait for it

to enter the Fatal Error mode.

4 Observe and record the current measured at A1J19. 5 Remove power and reconnect the CBT cable to A2J2. 6 Reapply power to the instrument and verify that LCD displays Warming up. 7 Quickly observe and record the average current at A1J19. 8 Remove power and reconnect the cable to A1J19.

QUESTION: Was the Fatal Error current 15.8  0.3 mA, and the

Warming up current 1.58  0.03 mA? If Yes: The control current circuit is operational. If No: Remove power, replace A7, and retest.

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Warning Message Diagnostic Tree (Subsection 4)

This subsection describes the warning-message diagnostic tree.

1.4.1 Warning Message Interpretation

1 Examine the log for any of the following entries (LOG/BROWSE menu

selections) (Assembly/Module trees are located in diagnostic tree section 3.) QUESTION: What is the warning message? If WARNING is: If WARNING is: If WARNING is:

VCXO near tuning limit, Go to, 3.9.1.1. Signal gain at range limit, Go to, 1.4.2. Internal DC supply out of range, Remove power,

replace A7, and retest.

If WARNING is:

Microprocessor PLL unlocked, Remove power,

replace A3, and retest. If WARNING is: If WARNING is: If WARNING is:

CBT signal low, Go to, 1.4.3. Power source is Batt, Go to, 1.4.4. RF amplitude at range limit, Go to, 1.3.7.

(Warning 21 relates to factory testing and will typically not occur during actual use.)

1.4.2 Signal Gain at Range Limit/CBT Signal Low

1 Perform A16 Electron-multiplier tests (3.7.2.1). 2 Perform analog-signal-chain tests (2.2.1.0). 3 Replace assemblies/modules as indicated.

QUESTION: Did all tests/evaluation pass? If Yes: Ignore Warning, a transient error may have occurred: Go to 1.4.3. If No: Remove power, repair as indicated, and retest: Go to 1.4.3.

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1.4.3 5071A Profiling (CBT Performance Evaluation)

The errors observed suggest deteriorating CBT performance.

1 Use the 5071A Profiling software as described at 1.6.0 to evaluate CBT

performance. QUESTION: Did the CBT pass the profiling performance evaluation.

If Yes: CBT is operational. If No: Remove instrument power, replace A17, and retest.

If the error persists contact Symmetricom for further assistance.

1.4.4 Power Source is Batt

(Note: Step 1.4.4 does not apply for Opt. 048) If ac power is applied and this message appears, you must determine

whether the instrument is operating from the ac line or from the battery.

1 Disconnect both batteries from the 5071A by:

a. opening the rear battery compartment door, then b. disconnect the two connectors to the batteries.

QUESTION: Does the instrument continue to operate or has all power

been lost? If still operating, Go to, 1.4.4.1. If power has been lost, Go to, 1.4.4.2.

1.4.4.1 AC-Line Operation - Battery Indicator On

(Fault is most likely in A11 power-steering-logic assembly).

1 Disconnect A11P102 from A11. 2 Verify that power-source indicator returns to normal with no indication of

battery operation. QUESTION: Do the indicators return to normal (no indication

of battery operation)? If Yes: A11 assembly is at fault, remove power, replace A11, and retest. If No: Fault is in one or more of the following: swap-out in this order and

retest. a. cable assembly (05071-60257), b. A1 motherboard (circuit traces or connectors), or c. A3 assembly.

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1.4.4.2 Instrument AC Power Absent

1 Reconnect the internal standby batteries and reapply ac power. (For Opt.

048 reapply ac power).

2 Measure the dc voltage between TP5 on A11 and a common test point (not

chassis ground), such as TP6,9, or 12 on A11.

3 Verify that the voltage is between 32 and 38 Vdc and record results.

QUESTION: Is the voltage 32 - 38 Vdc? If Yes: Remove power, replace A11 (probable CR14 fault), and retest. If No: Go to, 1.4.4.2.1

Opt. 048

Verify that the voltage is between 45 and 51 Vdc and record results. QUESTION: Is the voltage 45 - 51 Vdc?

If Yes: Remove power, replace A11 (probable CR14 fault), and retest. If No: Go to, 1.4.4.2.1

1.4.4.2.1 A1C4 Voltage Test Procedure

1 Measure the dc voltage across A1C4 (large-can filter capacitor).

QUESTION: Is the voltage between 32 and 38 Vdc? If Yes: Remove power, replace faulty 05071-60253 cable, and retest. If No: Go to, 1.4.4.3.

QUESTION: Is the voltage between 45 and 51 Vdc? If Yes: Remove power, replace faulty 05071-60253 cable, and retest. If No: Go to, 1.4.4.3.

1.4.4.3 LF1/T1 Transformer Fault Verification

1 Measure the 60 Hz ac voltage between CR3 pins 2 and 3 on the

A1 (motherboard) assembly.

2 Verify presence of 25-35 Vrms. (33-47 Vrms for Opt. 048)

QUESTION: Is the voltage between 25-35 Vrms?

(33-47 Vrms for Opt. 048) If Yes: Remove power, replace A1, (or A1CR3), and retest. If No: The LF1 line filter/cable assembly (05071-60259) or toroidal power transformer T1 (9100-4962, (9100-5134 for Opt. 048)), may be each or both at fault. Ensure that F1 line fuse is not open, then replace LF1/T1 and retest.

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Top-Level Diagnostic Tree (Diagnostic Section 1)

I/O Diagnostic Tree (Subsection 5)

This subsection describes the Input/Output (I/O) diagnostic tree.

1.5.1 Input/Output Faults

1 Use the following list to find a fault-isolation procedure associated with the

observed I/O problem. (Assembly/Module diagnostic trees are located in diagnostic tree section 3.)

QUESTION: Which I/O was found at fault? If 5/10 MHz: Go to, 3.5.1.0 (A10 diagnostic tree). If 1 MHz: Go to, 3.5.1.0 (A10 diagnostic tree). If 100 kHz: Go to, 3.5.1.0 (A10 diagnostic tree) If 1 PPS: Go to, 3.3.0 (A8 diagnostic tree). If 1 PPS Sync: Go to, 3.3.0 (A8 diagnostic tree). If RS-232: Confirm fault, (check datacomm config., internal cables)

remove power, replace A3, and retest.

If Status Output: Confirm fault, (check internal cables), replace A7, and

retest.

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CBT Performance Evaluation (Subsection 6)

This subsection describes how to use the 5071A Profiling software.

1.6.0 Running the 5071A Profiling Software

You can evaluate suspect CBT performance with the 5071A Profiling program running on a PC compatible computer (DOS  3.3 or higher) that has at least one RS-232 serial port. Use the instructions below to run this software (See the title page for information on how to download a copy)

1 Set up serial data communications link hardware between the 5071A and the

computer. (Refer to chapter 4 of the 5071A Operating and Programming manual to connect the 5071A to the computer's COM1 or COM2 serial port.)

2 Ensure that the 5071A's Baud rate is set to 2400 or greater. 3 Locate the folder with the ‘ck5071a.exe’ file and execute it at the DOS

prompt. The program will prompt you to enter the number of the COM port in use (1 or 2) and the Baud rate in use.

4 Enter these values into the computer.

Soft-key labels will appear at the bottom of the display when the program establishes communication with the 5071A operating system.

5 Press Terminal emulator to start a terminal emulator program that can

be used for SCPI instructions. (Exit with Alt

Q.)

6 Verify the serial link by pressing Return and observe the SCPI

prompt on the computers' display as follows: scpi >

Allow the instrument to stabilize for about 30 minutes before running the

Profile program.

7 Press 5071A

Profile to start the instrument profiling program.

The program takes about 10 minutes to evaluate the internal operating conditions of the instrument.

While the program runs, data appears on the screen and a text file is created. When the measurements are complete, leave the program by pressing the appropriate soft-key.

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NOTE

If the 5071A should return a prompt other than “scpi >“ or “E-xxx>“, it will not be possible to monitor and control the instrument with SCPI commands as documented in the manual.

This could occur in a terminal emulator after using the Profiling Software if the program was not exited properly, or suffered a system crash during execution.

1 If the prompt is “p4th A>>“ (note the double “>>“ in this prompt)

type h and press the Enter or Return key.

This should result in an error message and bring up a second prompt “p4th A>“. Proceed to step 2 below.

2 If the prompt is “p4thA >“ type (all lower case) halt and press the

Enter or Return key. This should return you to the SCPI system with either the “scpi >“ or

“E-xxx>“ prompt.

The output file is in the current directory with the name PROFILE.TXT. The file can be viewed using the usual DOS utilities, or printed.

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1.6.1 5071A Profiling Results Evaluation

A 5071A Profiling report example appears on the next page. You can use the example along with the explanations below to interpret your instrument’s profiling results.

VCXO Control Value

The present A19 VCXO adjustment state is shown by the VCXO Control

value

. This value normally changes with time as a result of aging in A19.

There is no resulting loss of performance. If the value is outside the -90% to +90% range, then the A19 VCXO Set-Point

Adjustment (3.9.1.7 and 3.9.1.8) should be performed as soon as is convenient.

The instrument will experience a Fatal Error if the value reaches 100%.

Depth of Modulation

The Depth of Modulation can help isolate faults to either the CBT or the instrument electronics.

A “Band 3” modulation depth combined with a peak-output current below 100 nA indicates deteriorating CBT performance.Be sure to thoroughly diagnose the entire instrument before considering the A17 CBT to be at fault. Contact Symmetricom for further assistance.

Signal to Noise Ratio

The Signal to Noise Ratio is an estimate of the current overall operating condition of both the CBT and instrument electronics.

 If the result is Band 1, the instrument’s stability should meet

specification. CBT problem is unlikely.

 If the result is Band 2, the test is indeterminate. High probability that CBT

is performing to specifications.

 If the result is Band 3, instrument stability will probably not meet

specification. CBT problem is likely. Consult Chapter 1 on Performance Tests to confirm poor performance.

NOTE

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=============================================== Output file from program CK5071A (rev. A.00.01) ===============================================

DOS System time: 1994-01-25 16:25:07

5071A Status: ============= Instrument time: 1994-01-25 16:25:07 (49377) CBT Serial number: 3112A00102(H) Tube Type: 10891A Instrument Status summary: Operating normally, Steered Power source: ac Log status: 101 entries Last Message in Log: "Lock completed" Fractional frequency offset: 314e-15 VCXO control value: -13.72 % Internal temperature: 42.6 C

Cesium Beam Tube measured data: =============================== Ion Pump current: 0.2 uA Peak output current: 101 nA Electron multiplier voltage: 1234 V Depth of Modulation: Band 1 (see note) Signal to noise ratio: Band 1 (see note)

Result may be "Band 1", "Band 2", or "Band 3".

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Advisory Messages (Subsection 7)

Advisory Messages are found in the log. If they are associated with fatal errors or warnings, they may be useful in fault isolation.

1.7.1 Advisory Message Interpretation

Message: E-mult adjusted - this appears to notify that due to internal CBT parameters the E-mult voltage was adjusted by a larger amount than usually required during steady-state operation. The appearance of this message on the display will be accompanied by a visible "wink" of the green Continuous Operation LED which is normal. No action required.

Message:

E-multiplier at voltage range limit. This message may

occur with CBT aging. The condition does not by itself imply any loss of performance. No action required.

Message:

87 MHz PLL unlocked. This message indicates an RF-chain

problem leading to an erroneous voltage level in the A5 module. This message may be associated with a fatal error. Go to, 1.3.7.

Message:

DRO unlocked. This message indicates an RF-chain problem

leading to an erroneous voltage level in the A15 module. This message may be associated with a fatal error. Go to, 1.3.7.

Message:

VCXO Oven error. This message indicates a problem with the

A19 module or its monitoring circuit. A malfunction in the A19 module will usually cause degraded performance or a fatal error. Go to, 3.9.1.1.

Message:

Center peak saturated. This message indicates that the

amplified CBT output signal is unstable. If the condition persists, a CBT signal loss fatal error may result.

Check the analog signal chain (2.2.1.0), and the Electron Multiplier supply (3.7.2.1).

If no problems are found with A6, A14, or A16 with the above procedures, the CBT may be faulty. Contact Symmetricom for further assistance.

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Functional-Group-Diagnostic Trees (Diagnostic Section 2)

This section provides functional-group-level diagnostic trees for the 5071A Primary Frequency Standard.

Functional-group diagnostic trees necessarily evaluate two or more assemblies/modules when such operation is interactive. The cumulative operation of the constituent parts is analyzed as a whole.

When possible, an assembly or module is isolated to fault-status within the functional-group diagnostic tree. At other times, the functional-group tree points to individual assembly/module diagnostic trees located in section 3.

The names of the functional-groups are listed below in order with the assemblies and modules that comprise them:

1 Power-supply diagnostic tree: 2.1.1.1.0

 A1 motherboard assembly  A11 Power steering logic assembly  A12 Dc-to-Dc Converter module  LF1 Line filter module/cable assembly  T1 Toroidal power transformer  B1 24V Internal-Standby Battery. (Does not apply for Opt. 048).

2 Analog-signal chain diagnostic tree: 2.2.1.0

 A6 Servo assembly  A14 Signal amplifier module

3 RF-chain diagnostic tree: 2.3.1.0

 A4 Digital Synthesizer assembly  A5 87 MHz PLL module  A9 Frequency multiplier module  A10 Output frequency distribution amplifier module  A15 9.2 GHz microwave module  A18 9.2 GHz PLL module  A19 Reference oscillator module

4 C-field diagnostic tree: 2.4.1.0

 A7 Interface assembly  A17 Cesium-beam tube assembly

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Functional-Group-Diagnostic Trees (Diagnostic Section 2)

Power-Supply Diagnostic Tree (Functional Group Subsection 1)

This subsection describes the Power-supply diagnostic tree and provides information for fault isolation to:

 A1 Motherboard,  T1 Toroidal power transformer,  A11 Steering-logic assembly,  A12 Dc-to-Dc Converter module,  LF1 Line filter module/cable assembly, and  B1 24V Internal-Standby Battery. (Does not apply for Opt. 048).

2.1.1.1.0 AC Line-Fuse Test

QUESTION: Does the ac-line fuse blow at power-up? If Yes: Go to 2.1.1.2.0. If No: Go to 2.1.1.1.1.

2.1.1.1.1 A12 Power Input Test

1 Remove the instrument top/bottom covers and inner shield. 2 Apply ac power to the instrument. 3 Use a DMM to measure the input voltage (Vin) at the A12 module (across the

Vin and Vin return power input lugs on the module)

4 Verify that the voltage present is between 32 and 38 Vdc (45 and 51 Vdc for

Opt. 048) with no more than 1 Vrms ripple. QUESTION: Does the measured voltage meet specifications?

If Yes: Go to, 2.1.3.0.0. If No: a) Measure the dc voltage across capacitor C4 (large can

attached to A1 with screws)

b) Verify that the voltage present is between 32 and 38 Vdc

(45 and 51 Vdc for Opt. 048) with no more than 1 Vrms ripple.

QUESTION: Does the measured voltage meet specifications? If Yes: Go to, 2.1.1.1.2.

If No: Go to, 2.1.1.1.4

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Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.1.1.1.2 A11/A11 Cable Test

1 Use a DMM to measure the voltage from A11TP5 to

A11TPs 6, 9, or 12.

2 Verify that the voltage is between 32 and 38 Vdc (45 and 51 Vdc for Opt.

048) with no more than 1 Vrms ripple. QUESTION: Does the measured voltage meet specifications?

If Yes: Go to, 2.1.1.1.3. If No: The fault is at either A11 or assembly 05071-60253 or both.

Remove power, replace A11, assembly 05071-60253 or both, and retest.

2.1.1.1.3 A11/A11-A1 Cables Test

The fault here is probably within A11 (CR14), or the A11-to-A1

cable

(05071-60253), or the A12 module cable. 1 Use a DMM to measure the voltage across A1C3. 2 Verify that the voltage present is between 32 and 38 Vdc (45 and 51 Vdc for

Opt. 048) with no more than 1 Vrms ripple. QUESTION: Does the measured voltage meet specifications?

If Yes: Remove power, replace A12, and retest. If No: Remove power, replace A11 or cable 05071-60253, or both

and retest.

2.1.1.1.4 A1CR3 Bridge Rectifier Test

1 Use a DMM to measure the ac voltage across the ac input at A1CR3. 2 Verify that the voltage is at least 25 Vrms (33 Vrms for Opt. 048).

QUESTION: Does the measured voltage meet specifications? If Yes: Remove power, replace CR3 (or A1), and retest. If No: Remove power, ensure that F1 line fuse is not open

then, replace T1 or LF1, or both, and retest.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.1.1.2.0 AC-Line Fuse Fault Isolation, Rule Out A11

1 Ensure that proper line fuse and line-switch setting (for the available ac-input

voltage) are used. (See operating manual for details.) 2 Replace ac-line fuse. 3 Disconnect A11P101 to isolate the problem. 4 Apply ac-line voltage again. 5 Check the ac-line fuse immediately for possible open condition.

QUESTION: Did the line fuse blow?

If Yes: Go to 2.1.1.2.1.

If No: Go to 2.1.2.4.0.

2.1.1.2.1 AC-Line Fuse Fault Isolation: Rule Out A1

1 Replace ac-line fuse. 2 Disconnect the ac-line toroidal transformer connector going to A1J5. 3 Apply ac-line voltage again. 4 Check the ac-line fuse immediately for possible open condition.

QUESTION: Did the line fuse blow?

If Yes: Go to, 2.1.2.2.0.

If No: Go to, 2.1.2.3.0.

2.1.2.2.0 AC-Line Fuse Fault Isolation: Rule Out LF1/T1

Fault is between the ac-line connector on the back panel, the ac-line toroidal

transformer, or the cable connecting the two. 1 Disconnect LF1 (line filter/cable assembly 05071-60259) at the bulkhead by

the toroidal power transformer T1. 2 Replace the line fuse. 3 Re-apply power to the unit. 4 Check the ac-line fuse immediately for possible open condition.

QUESTION: Did the fuse blow?

If Yes: Remove power, replace LF1 (05071-60259), and retest.

If No: Remove power, replace T1 (9100-4962), (9100-5134 for Opt. 048)

and retest.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.1.2.3.0 A1 Fault

1 Remove power, ensure interconnecting cables are not shorted, then either

troubleshoot or replace A1, and retest.

The problem is on the motherboard (A1), in one or more of the following:

 CR3 full-wave bridge rectifier circuit,

 C4 and R4 filter capacitor and bleeder resistor , or

 Over voltage protection circuitry (around CR1).

You may elect to use the A1 Theory of Operation information in chapter 3 to

effect component-level repair

2.1.2.4.0 AC-Line Fuse Fault Isolation: A11/A12 Inputs

If the ac-line fuse doesn't blow after disconnecting A11P101, then the fault

can be further isolated: 1 Reconnect all connectors. (Install a new fuse if necessary.) 2 Disconnect A1P2 from A1J2 on A1 motherboard. (This breaks the circuit at

the dc-dc power converter module, A12.) 3 Apply ac-line voltage again. 4 Check the ac-line fuse immediately for possible open condition.

QUESTION: Did the ac-line fuse blow?

If Yes: Go to, 2.1.2.5.0.

If No: Go to, 2.1.3.0.0 (Fault is in the A12 power supply module or

the circuits loading the supply.

2.1.2.5.0 A11P101 Connection Test

1 Disconnect A11P101. 2 Check for a short circuit between pins 1 or 4 (positive side) and pin 2 (gnd) of

the cable using an ohmmeter or equivalent. 3 Verify that the pins are not shorted: flex the cable several times to ensure

there are no intermittent connections

QUESTION: Is the cable faulty?

If Yes: Replace A11P101 cable, and retest: go to 2.1.1.1.0.

If No: Remove power, replace A11, and retest.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.1.3.0.0 A12 Module Test

1 Power on the instrument. 2 Use a DMM to measure the A12 output voltages at the module

solder-lug connections.

3 Verify that they are within the ranges shown below:

+5V supply: at least +5.28 Vdc

+12V supply: at least +12.08 Vdc

-12V supply: at least -12.08 Vdc

QUESTION: Are all voltages approximately zero?

If Yes: Remove power, replace A12, and retest.

If No: One or two are less than specified, Go to, 2.1.3.1.0.

NOTE

A situation could occur during troubleshooting to cause similar

symptoms. If, for example, one of the output voltages were

accidentally shorted to another power supply output voltage, the

protection circuits within the A12 module will shut down all the

output voltages. In order to recover from this protection mode, the

ac power must be removed from the instrument for at least 30

seconds. Then reapply ac power and all output voltages should

return to normal. If they do not, replace A12 and retest.

2.1.3.1.0 Rule Out A1 or Module Fault

1 Remove all power from the instrument. 2 Measure the resistance (to the chassis) of each supply voltage on the A1

motherboard.

3 Verify that they conform to the following ranges:

+5V resistance:  2.0 

+12V resistance:  10.0 

-12V resistance:  10.0 

QUESTION: Do the resistances meet or exceed the values shown

above?

If Yes: Remove power, replace A12, and retest.

If No: Go to, 2.1.3.2.0.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.1.3.2.0 Rule Out Shorted Assemblies/Modules

1 Remove each printed circuit board assembly from A1 in a stepwise manner

and observe whether the resistance value for the faulty supply voltage returns

to normal. 2 Disconnect all module connectors to A1 in a stepwise manner and observe

whether the resistance value for the faulty supply voltage returns to normal. 3 Verify the Assembly/Module that causes the faulty supply voltage resistance

to return to normal.

QUESTION: Which assembly/module appears at fault?

If a specific assembly/module is isolated, replace, and retest.

If, after removing all loads from the motherboard, the resistance is still below

specification, replace A1, and retest.

2.1.4.0.0 Ext. DC Input Fuse Fault

The Ext. DC Input fuse blows when powering-on or running the

5071A. The assumption here is that ONLY the dc fuse blows, with the

instrument operating normally from the ac line or internal standby battery for

non-Opt. 048. 1 Remove all power and disconnect A11P101. 2 Replace the blown fuse. 3 Reapply dc instrument power. 4 Check the dc fuse immediately for possible open condition.

QUESTION: Did the fuse blow?

If Yes: The problem is either on A1 or in the wiring of the Ext. DC

connector which can be visually inspected for faults,

or in cable assembly 05071-60253

If No: Remove power, replace A11, and retest.

2.1.5.0.0 No Operation From Internal Standby Battery

(Note: Sections 2.1.5.0.0 through 2.1.5.2.0 do not apply for Opt. 048

instruments)

QUESTION: Does the 5071A operate at all from the

internal battery?

If Yes: Go to, 2.1.5.1.0.

If No: Go to, 2.1.5.2.0.

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Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.1.5.1.0 Internal-Battery Charger Test

If the 5071A operates for less time than specified, the fault is either the

battery or that it is not being charged properly. Verify charger operation as

follows: 1 Apply ac power and observe the instrument complete warm-up. 2 Remove ac power and do not disconnect or turn-off

internal-standby

batteries. 3 Allow the instrument to run on the internal-standby batteries for at least one

minute. 4 Reapply ac power to the instrument. (This causes the boost-charge mode

entry: the current to the batteries should be between 140 mA and 180 mA., if

the charger is operating correctly. 5 Verify that the boost-charge current is between 140 and 180 mA using a clip-

on ammeter at any battery lead.

QUESTION: Is the boost-charge current within specification?

If No: Remove power, replace A11, and retest charging current.

If Yes: Replace both battery packs and retest operating time.

2.1.5.2.0 A11 F1 Fuse Fault

If the instrument will not operate from the internal batteries at all, the fault

could be fuse F1 on the A11 board. Fuse F1 is in series with the batteries to

protect them from catastrophic discharge if a short circuit occurs. 1 Ensure that both batteries are connected in the normal configuration and all

external instrument power is removed, 2 Measure the voltage at TP1 on A11 with respect to a common point (not

chassis ground) such as TP's 6,9, and 12. 3 Verify a battery voltage of approximately 24 volts.

QUESTION: Is 24 volts present?

If Yes: The battery packs may be at fault or are not being properly

charged. Go to, 2.1.5.1.0.

If No: Disconnect the two internal-standby battery connections and

replace F1 on A11 (or A11 entirely). Reconnect the internal-

standby battery connections and retest. If only F1 is replaced

and it blows again at retest, replace A11 entirely, then retest.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

Analog-Signal Chain Diagnostic Tree

(Functional-Group Subsection 2)

This subsection describes the analog-signal chain diagnostic tree.

The tree provides information to check both A14 Signal-Amplifier

module and A6 Servo assembly.

2.2.1.0 A6 TP 5 and 6 Voltage Test 1

1 Remove instrument power. 2 Mount A6 on the short extender board (05071-60051). 3 Disconnect the CBT wiring harness from A2J2. 4 Connect the output of the resistive current source (05071-60274) to

the input connector of A14, instead of the cable from the CBT. (Do

not connect the ET-current-source input lead at this time.) 5 Ensure that the power and signal cable from A14 is seated in A6J3. 6 Reapply power and wait until the LCD displays Fatal 7 Verify that the gain value displayed via the INFO/GAIN menu

selections is 14.4%. 8 Measure the following voltages:

Gnd to A6-TP5; voltage should be between 10.3 and 11.3 volts.

Gnd to A6-TP6; voltage should be between -11.3 and -10.3 volts.

QUESTION: Are the voltages within the above specification?

If Yes: Go to, 2.2.2.0.

If No: Go to, 2.2.1.1.

Error.

2.2.1.1 A6 TP 5 and 6 Voltage Test 2

1 Disconnect the Signal Amplifier power/signal cable from A6J3. 2 Repeat the previous voltage measurements at A6-TP5 and A6-TP6 with the

same voltage limits.

QUESTION: Are the voltages within correct tolerances?

If Yes: Remove power, replace A14, and retest.

If No: Remove power, replace A6*, and retest.

*NOTE

Ensure that the jumper position of the new A6 is in the same position as the one being replaced.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.2.2.0 A6J7 Voltage Test

1 Use the DMM or oscilloscope to measure the voltage at A6J7 and record the

result.

QUESTION: Is the voltage between 0.00 and 0.05 volts?

If Yes: Go to, 2.2.3.0.

If No: Go to, 2.2.2.1.

2.2.2.1 A6U10 10.2 and 10.3 Voltage-Difference Test

1 Use the DMM or scope to measure the voltage difference between

A6-U10.2 and A6-U10.3 with the test clip.

QUESTION: Is the voltage difference between -0.03 and 0.03 volts.

If Yes: Remove power, replace A6*, and retest.

If No: Remove power, replace A14, and retest.

2.2.3.0 VFC Output Test 1

NOTE

1 Use the oscilloscope and the universal counter to measure the amplitude and

frequency of the logic signal at A6J2, pin 44 (This

is the twelfth pin from the right on the row of pins furthest away from the PCA

board surface.).

Use the 10:1 high-impedance probe at the measurements, with the input

impedance of the oscilloscope and counter set to 1 M. Use dc coupling

and set the trigger levels to 0.15 volts at the probe output.

The waveform should consist of TTL-level pulses with a frequency between

zero and (100+ 3.210

above.

QUESTION: Is the TTL waveform and level within tolerance?

If Yes: Go to, 2.2.4.0.

If No: Remove power, replace A6*, and retest.

2.2.4.0 Reference Voltage Test 1

1 Measure the voltage from A6, J4, pin 9 to ground with a DMM.

(Refer to 3.9.1.1.4 for pin assignment.)

QUESTION: Is the voltage between -4.995 and -5.005?

If Yes: Go to, 2.2.5.0.

If No: Remove power, replace A6*, and retest.

*See note at 2.2.1.1.

 V)Hz, where V is the voltage measured at 2.2.2.0

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.2.5.0 Analog-Signal Chain Transimpedance Test

1 Connect the 100-nA current source input lead to A6, J4, pin 9 (closest to J5

and J6). (This applies a -100 nA input signal to A14.) 2 Measure the voltage at A6J7.

QUESTION: Is the voltage difference between +6.9 and +7.5?

If Yes: Go to, 2.2.6.0.

If No: Go to, 2.2.5.1.

2.2.5.1 A6U10 10.2 and 10.3 Voltage Test

1 Use the DMM to measure the voltage difference between

A6-U10.2 and A6-U10.3 with the dip clip.

QUESTION: Is the voltage between +4.75 and +5.25?

If Yes: Remove power, replace A6*, and retest.

If No: Remove power, replace A14, and retest.

2.2.6.0 VFC Output Test 2

1 Use the high-impedance probe, frequency counter, and oscilloscope to check

frequency and amplitude of the logic signal at A6 U33-3. 2 Verify that the waveform is TTL-level pulse with a frequency between 219

and 231 kHz.

QUESTION: Does the waveform consist of TTL-level pulses between

219 and 231 kHz?

If Yes: A14 and the input section of A6 are operating correctly.

Carefully re-connect the CBT output cable to the input of

A14-J1 and resume testing.

If No: Remove power, replace A6*, and retest.

*See note at 2.2.1.1.

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Functional-Group-Diagnostic Trees (Diagnostic Section 2)

RF-Chain Diagnostic Tree

(Functional-Group Subsection 3)

This subsection describes the RF-chain diagnostic tree for the

5071A Primary Frequency Standard and provides fault isolation of, or

pointers to diagnostic trees for, constituent RF-chain assemblies or modules.

2.3.1.0 RF-Chain Test Start Up

1 Remove power by disconnecting external ac and dc power. 2 Ensure that the internal-standby battery packs are disconnected. 3 Wait at least one minute for A16 high voltage supply to bleed down. 4 Disconnect semi-rigid coax from cesium-beam tube. 5 Connect this free end to the spectrum analyzer with an SMA female-female

barrel and the Microwave Test cable for use at 9 GHz. 6 Disconnect right-hand CBT cable (viewed from front) from A2J2. 7 Go to, 2.3.2.0.

2.3.2.0 9192 MHz Signal-Spectrum Test

1 Set input attenuator on HP/Agilent 8566 microwave spectrum analyzer for a

maximum input level of +10 dBm (Must be done

before #2). 2 Reconnect external ac (or dc) power. 3 Verify that instrument powers up and goes into Fatal 4 Set spectrum analyzer for a center frequency of 9192.0 MHz and

a span of 5 MHz/division. 5 Verify presence of a single carrier signal with amplitude at least -3 dBm.

(Include the microwave test cable loss in your calculations.).

QUESTION: Is a single carrier signal present with an amplitude

of at least -3 dBm?

If Yes: Go to, 2.3.3.0.

If No: Go to, 3.6.1.0 (A15 Diagnostic tree).

Error mode.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.3.3.0 A19 Output Amplitude and Frequency Test

1 Program frequency counter to use internal timebase. (The frequency counter

timebase must be calibrated to ensure an accuracy of 110 2 Disconnect the semi-rigid cable from A9J5. 3 Use the adapter cable to connect it to the input of the oscilloscope with a 50

 terminator. 4 Verify that the amplitude of the signal, is greater than 1.0 Vp-p. 5 Disconnect semi-rigid cable from the oscilloscope. 6 Connect frequency counter input to A19 output, and measure frequency. 7 Reconnect A19 output to A9J5.

QUESTION: Is frequency 10 MHz, 5 Hz?

or better.)

If Yes: Go to, 2.3.4.0.

If No: Go to, 3.9.1.1 (A19 diagnostic tree).

2.3.4.0 A10 Port 1 and 2 Amplitude Test

1 Program the rear-panel output ports for 10 MHz. 2 Use an oscilloscope to verify that both output provide a sine wave with an

amplitude of at least 2.8 Vp-p into 50 . Record results.

QUESTION: Are both port amplitudes 2.8 Vp-p?

If Yes: Go to, 2.3.5.0.

If No: Go to, 3.5.1.0 (A10 diagnostic tree).

2.3.5.0 A10 Output Frequency Test

1 Program frequency counter to use its internal timebase. (The frequency

counter timebase must be calibrated to ensure an accuracy of 110

better.) 2 Connect the rear-panel port 1 output to the frequency counter input.

3 Measure the frequency.

QUESTION: Is frequency 10 MHz, 5 Hz?

If Yes: Go to, 2.3.6.0.

If No: Go to, 3.4.1.0 (A9 diagnostic tree).

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.3.6.0 9192 MHz Frequency Test

1 Disconnect the Microwave Test cable from the spectrum analyzer. 2 Connect to the input of a microwave-frequency counter. 3 Program the rear-panel output ports for 10 MHz. 4 Connect one output to the external reference input of the microwave

frequency counter. 5 Program the microwave frequency counter to use a 10 MHz external

reference instead of its internal timebase. 6 Measure the frequency of the microwave signal.

QUESTION: Is the indicated frequency 9192.631770 MHz 2 Hz?

If Yes: RF chain is operational.

If No: Go to, 2.3.7.0.

2.3.7.0 320 MHz Frequency and Amplitude Tolerance Test

1 Disconnect A9P1 from A9J1. 2 Connect A9J1 to the 50  input of an oscilloscope (Use a 50  feedthrough

at scope end of the cable if necessary.). 3 Verify presence of a sine-wave with at least 6.0 Vp-p amplitude. 4 Disconnect A9J1 from the oscilloscope. 5 Reprogram frequency counter to use 10 MHz external reference from 5071A

output. 6 Use the frequency counter to verify presence of a 320 MHz 0.1 Hz signal at

A9J1.

QUESTION: Did the measured signal comply with the required

characteristics?

If Yes: Go to, 2.3.8.0.

If No: Go to, 3.4.1.0 (A9 diagnostic tree).

2.3.8.0 87.36823 MHz Frequency and amplitude Test

1 Measure amplitude and frequency at A5J101 with an oscilloscope.

QUESTION: Is frequency 87.368230 MHz 0.1 Hz with an

amplitude of at least 0.4 Vp-p?

If Yes: Go to, 3.8.1.0 (A18 diagnostic tree).

If No: Go to, 2.3.8.1.

2. Service

Functional-Group-Diagnostic Trees (Diagnostic Section 2)

2.3.8.1 131.771 kHz. Frequency Test

1 Disconnect coax from A5J2. 2 Connect a spectrum analyzer (HP/Agilent 8566) to the free end of the coax

(not to A5J2). 3 Adjust the spectrum analyzer to a center frequency of 131.7 kHz and a 10

kHz span. 4 Verify the presence of a 131.770 kHz signal with amplitude of at least -13.5

dBm. 5 Reconnect coax to A5J2.

QUESTION: Did the signal meet the characteristics in step 5?

If Yes: Go to, 2.3.8.2.

If No: Go to, 3.5.3.0 (A4 diagnostic tree).

2.3.8.2 80 MHz Frequency Test

1 Disconnect coax from A5J1. 2 Connect frequency counter to the free end of the coax (not to A5J1). 3 Verify the frequency as 80 MHz 0.1 Hz. 4 Use an oscilloscope to verify that the sine-wave voltage is at least

0.6 Vp-p.

5 Reconnect coax to A5J1.

QUESTION: Did the measured signal comply with the characteristics

in steps 3 and 4?

If Yes: Go to, 3.5.3.0 (A5 diagnostic tree).

If No: Go to, 3.4.1.0 (A9 diagnostic tree).

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Functional-Group-Diagnostic Trees (Diagnostic Section 2)

C-Field Diagnostic Tree

(Functional-Group Subsection 4)

This subsection describes the C-field diagnostic tree for the 5071A Primary

Frequency Standard. (Refer to the A2 connector pinout diagram ahead of

procedure 3.1.1.1.0 for pin number and location.)

2.4.1.0 C-Field Current Test

1 Remove all power from the 5071A. 2 Remove the jumper on the right-hand side of A2J2 labeled CFC

(C-Field Current jumper.).

3 Connect the Multimeter to the pins which were occupied by the jumper using

small clip-leads. 4 Set the DMM to read dc current. 5 Reapply instrument power and wait about 15 seconds. Use the

CONFIG/MODES menu to put the instrument in STANDBY. 6 Compare the current shown on the DMM with the nominal current displayed

on the instrument LCD using the INFO/C_field Menu. (The display units are

Milliamperes. The current value is set by the instrument to match the

parameters of the CBT.) 7 Remove instrument power and replace the CFC jumper.

QUESTION: Are the measured and indicated current magnitudes in agreement to within 0.2 mA? If Yes: The C-Field system is working correctly. If No: Go to 2.4.2.0.

2.4.2.0 C-Field Current Source Test

1 Remove all power from the 5071A.

2. Disconnect CBT wiring harness from A2J2.

3. Replace the jumper on the right-hand side of A2J2 labeled CFC

(C-Field Current jumper.).

4. Connect the DMM between pins 4 and 14 of A2J2.

5. Set the DMM to measure dc current in the 10 to 100 mA range.

6. Reapply instrument power and wait about 15 seconds.

7. Measure the C-field current supplied.

8. Remove power and reconnect CBT wiring harness to A2J2.

QUESTION: Is the C-field current the same as measured in 2.4.1.0

above, within ±0.2 mA? If Yes: Re-check results before replacing A17 CBT. If No: Remove power, replace A7, and retest. Sustained failure indicates

that either A2 or traces on the A1 Motherboard are at fault.

2. Service Assembly/Module Diagnostic Trees (Diagnostic Section 3)

Assembly/Module Diagnostic Trees (Diagnostic Section 3)

This section provides diagnostic trees for individual assemblies and modules. Assembly and tree numbers in bold designate the trees that are actually present in this section. The following assemblies and modules are covered or are referenced to other sections/diagnostic trees:

A1 Motherboard (See section 2, Power-supply diagnostic tree.)

A2 CBT Controller assembly, tree 1: 3.1.1.1.0

A3 Microprocessor assembly (See section 1, Top-level diagnostic tree.) A4 Digital Synthesizer (See A5 or section 2, RF-chain diagnostic tree.)

A5 87 MHz PLL module, tree 2: 3.2.1.0

A6 Servo (See section 2, Analog signal-chain diagnostic tree.) A7 Interface assembly (See A2 diagnostic tree.)

A8 1 PPS module, tree 3: 3.3.0 A9 Frequency Multiplier module, tree 4: 3.4.1.0 A10 Output Frequency Distribution Amplifier module,

tree 5: 3.5.1.0

A11 Power-steering logic (See section 2, Power-supply diagnostic tree.) A12 Dc-Dc Converter module (See section 2, Power-supply tree.) A13 Front-panel assembly (See section 1, Top-level diagnostic tree.) A14 Signal Amplifier module (See section 2, RF-chain diagnostic tree.)

A15 9.2 GHz Microwave Generator module, tree 6: 3.6.1.0 A16 High-Voltage Supply module, tree 7: 3.7.1.0

A17 Cesium-beam tube (See section 1, Top-level tree.)

A18 9.2 GHz PLL module, tree 8: 3.8.1.0 A19 Reference Oscillator (Quartz) module, tree 9: 3.9.1.1

Assembly/Module (A/M) Procedure Numbering System

The assembly/module diagnostic tree step numbers identify the assembly or module tree under consideration (within this section, 3) by the second digit from the left of a particular procedural step, for instance: step 3.4.1.1 is the second procedure for A9.

2. Service

Assembly/Module Diagnostic Trees (Diagnostic Section 3)

A2 CBT Controller Diagnostic Tree (A/M Subsection 1)

This subsection describes the A2 Assembly diagnostic tree. The tree is divided into four functional subsections as follows:

1. A2 Hot-Wire Ionizer tree

2. A2 Thermistor tree

3. A2 Mass-Spectrometer tree

4. A2 Cesium-Oven tree

Each of the functional subsections is designed to isolate a fault to one of the following assemblies:

 A2 CBT Controller  A7 Interface  A17 Cesium-Beam Tube (CBT)

Refer to the A2 CBT Controller Assembly pinouts shown below for A2J1 and A2J2 when any A2 tests require connection to either CBT or A2 J1 or J2 pins.

For A2J1: Pin 1          Pin 9

For A2J2: Pin 1                Pin 15

2. Service

Assembly/Module Diagnostic Trees (Diagnostic Section 3)

A2 Hot-Wire Ionizer Diagnostic Tree

This functional subsection describes the A2 hot-wire ionizer 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 hotwire ionizer fault.

3.1.1.1.0 CBT Hot-Wire Resistance Test

1 Power off the 5071A. 2 Unplug cable from A2J1 and A2J2. 3 Using a 4-wire Ohm Meter, measure the resistance across pins

1 and 6 on the CBT cable. QUESTION: Is the resistance between 0.1 and 0.25 ? If Yes: Go to, 3.1.1.1.1.

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

3.1.1.1.1 CBT Hot-wire Resistance-to-Ground Test

1 Measure the resistance across pins 1 and 4 on the CBT cable.

QUESTION: Is the resistance greater than 200 k? If Yes: Go to, 3.1.1.1.2.

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

3.1.1.1.2 Hot-Wire Monitor Test (No Current)

1 Remove instrument power. 2 Remove A2 CBT Controller. 3 Install the long extender board (05071-60052) into A2 slot. 4 Turn on the 5071A. 5 Use SCPI command syst:print?.

(Terminal-to-instrument via RS-232C data communication required.) QUESTION: Is HW Ionizer: between -0.5 and +0.5 V? If Yes: Go to, 3.1.1.1.3.

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

Symmetricom 5071A Assembly And Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual