Fluke 5790A User manual

®
5790A
AC Measurement Standard
Service Manual
PN 893292
January 1992 Rev.5, 1/07
© 1992-2007 Fluke Corporation, All rights reserved. Printed in USA
All product names are trademarks of their respective companies.

LIMITED WARRANTY AND LIMITATION OF LIABILITY
Each Fluke product is warranted to be free from defects in material and workmanship under normal use and
service. The warranty period is one year and begins on the date of shipment. Parts, product repairs, and
services are warranted for 90 days. This warranty extends only to the original buyer or end-user customer of
a Fluke authorized reseller, and does not apply to fuses, disposable batteries, or to any product which, in
Fluke's opinion, has been misused, altered, neglected, contaminated, or damaged by accident or abnormal
conditions of operation or handling. Fluke warrants that software will operate substantially in accordance
with its functional specifications for 90 days and that it has been properly recorded on non-defective media.
Fluke does not warrant that software will be error free or operate without interruption.
Fluke authorized resellers shall extend this warranty on new and unused products to end-user customers
only but have no authority to extend a greater or different warranty on behalf of Fluke. Warranty support is
available only if product is purchased through a Fluke authorized sales outlet or Buyer has paid the
applicable international price. Fluke reserves the right to invoice Buyer for importation costs of
repair/replacement parts when product purchased in one country is submitted for repair in another country.
Fluke's warranty obligation is limited, at Fluke's option, to refund of the purchase price, free of charge repair,
or replacement of a defective product which is returned to a Fluke authorized service center within the
warranty period.
To obtain warranty service, contact your nearest Fluke authorized service center to obtain return
authorization information, then send the product to that service center, with a description of the difficulty,
postage and insurance prepaid (FOB Destination). Fluke assumes no risk for damage in transit. Following
warranty repair, the product will be returned to Buyer, transportation prepaid (FOB Destination). If Fluke
determines that failure was caused by neglect, misuse, contamination, alteration, accident, or abnormal
condition of operation or handling, including overvoltage failures caused by use outside the product’s
specified rating, or normal wear and tear of mechanical components, Fluke will provide an estimate of repair
costs and obtain authorization before commencing the work. Following repair, the product will be returned to
the Buyer transportation prepaid and the Buyer will be billed for the repair and return transportation charges
(FOB Shipping Point).
THIS WARRANTY IS BUYER'S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF ALL OTHER
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. FLUKE SHALL NOT BE LIABLE
FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR LOSSES,
INCLUDING LOSS OF DATA, ARISING FROM ANY CAUSE OR THEORY.
Since some countries or states do not allow limitation of the term of an implied warranty, or exclusion or
limitation of incidental or consequential damages, the limitations and exclusions of this warranty may not
apply to every buyer. If any provision of this Warranty is held invalid or unenforceable by a court or other
decision-maker of competent jurisdiction, such holding will not affect the validity or enforceability of any other
provision.
Fluke Corporation
P.O. Box 9090
Everett, WA 98206-9090
U.S.A.
Fluke Europe B.V.
P.O. Box 1186
5602 BD Eindhoven
The Netherlands
11/99
To register your product online, visit register.fluke.com

i
Table of Contents
Chapter Title Page
1 Introduction and Specifications......................................................... 1-1
1-1. Introduction........................................................................................... 1-3
1-2. Service Information .............................................................................. 1-3
1-3. Symbols ................................................................................................ 1-3
1-4. Safety Instructions ................................................................................ 1-4
1-5. Input Source Limits .......................................................................... 1-4
1-6. Power Source.................................................................................... 1-4
1-7. Proper Fuse Usage............................................................................ 1-4
1-8. Grounding of the 5790A................................................................... 1-4
1-9. Proper Power Cord Usage ................................................................ 1-4
1-10. Do Not Operate in Explosive Atmosphere....................................... 1-4
1-11. Do Not Attempt to Operate if Protection may be Impaired.............. 1-4
1-12. Do Not Remove the Cover unless Qualified .................................... 1-5
1-13. Do Not Service Alone ...................................................................... 1-5
1-14. Use Care when Servicing with Power On ........................................ 1-5
1-15. Specifications........................................................................................ 1-5
2 Theory of Operation ............................................................................ 2-1
2-1. Introduction........................................................................................... 2-5
2-2. 5790A Overview................................................................................... 2-5
2-3. Functional Block Diagram Discussion ................................................. 2-5
2-4. Digital Section Overview...................................................................... 2-6
2-5. Analog Section Overview..................................................................... 2-6
2-6. System Interconnect Detailed Circuit Description ............................... 2-9
2-7. Digital Motherboard Assembly (A4)................................................ 2-9
2-8. Transformer Assembly (A22)........................................................... 2-9
2-9. Analog Motherboard Assembly (A3)............................................... 2-9
2-10. Rear Panel I/O Assembly (A21)....................................................... 2-10
2-11. Rear Panel Power Supplies .......................................................... 2-10
2-12. Rear Panel Digital Control ........................................................... 2-10
2-13. Clock Regeneration Circuit.......................................................... 2-10
2-14. IEEE-488 (GPIB) Interface.......................................................... 2-10
2-15. RS-232-C Interface ...................................................................... 2-11
2-16. Rear Panel CPU Interface ............................................................ 2-12

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2-17. Digital Section Detailed Circuit Description ........................................ 2-12
2-18. Digital Power Supply Assembly (A19)............................................ 2-12
2-19. +5 V Power Supply ...................................................................... 2-12
2-20. ±12 V Power Supplies.................................................................. 2-12
2-21. +35 V Power Supply .................................................................... 2-13
2-22. +75 V Power Supply .................................................................... 2-13
2-23. +35 V and +75 V Shut-Down Circuit .......................................... 2-13
2-24. CPU Assembly (A20)....................................................................... 2-14
2-25. Power-Up and Reset Circuit......................................................... 2-14
2-26. Clock Generation ......................................................................... 2-17
2-27. Watchdog Timer .......................................................................... 2-17
2-28. Address Decoding and DTACK (Data Acknowledge) ................ 2-18
2-29. Interrupt Controller ...................................................................... 2-19
2-30. Glue Logic.................................................................................... 2-19
2-31. RAM (Random-Access Memory) ................................................ 2-19
2-32. ROM (Read-Only Memory)......................................................... 2-19
2-33. Electrically-Erasable Programmable Read-Only Memory
(EEPROM)................................................................................... 2-20
2-34. DUART (Dual Universal Asynchronous Receiver/Transmitter)
Circuit........................................................................................... 2-20
2-35. Clock/Calendar Circuit................................................................. 2-20
2-36. Clock Filter Circuit ...................................................................... 2-20
2-37. CPU to Rear Panel Interface ........................................................ 2-20
2-38. CPU to Front Panel Interface ....................................................... 2-21
2-39. Front Panel Assembly (A2) .............................................................. 2-21
2-40. Clock Regeneration Circuitry ...................................................... 2-21
2-41. Refresh Failure Deject Circuitry .................................................. 2-21
2-42. Decoding and Timing Circuitry ................................................... 2-22
2-43. Control Display Circuitry............................................................. 2-22
2-44. Measurement Display Circuitry ................................................... 2-23
2-45. Keyboard Scanner Circuitry......................................................... 2-24
2-46. LED Circuitry .............................................................................. 2-24
2-47. Keyboard Assembly (A1)................................................................. 2-25
2-48. Analog Section Detailed Circuit Description ....................................... 2-26
2-49. Filter Assembly (A18)...................................................................... 2-26
2-50. Unregulated CH Supplies............................................................. 2-27
2-51. Unregulated LH Supplies............................................................. 2-27
2-52. Unregulated ±17 SR Supplies ...................................................... 2-27
2-53. Triac Circuit ................................................................................. 2-27
2-54. FR1 Supplies ................................................................................ 2-27
2-55. Unregulated FR1 Supply.............................................................. 2-28
2-56. FR2 Supplies ................................................................................ 2-28
2-57. Regulator/Guard Crossing Assembly (A17)..................................... 2-28
2-58. Voltage Regulator Circuitry......................................................... 2-28
2-59. Regulated LH Supplies ................................................................ 2-29
2-60. Regulated ±17 S Supplies ............................................................ 2-29
2-61. Regulated ±15 CH Supplies ......................................................... 2-29
2-62. FR1 Supply .................................................................................. 2-29
2-63. FR2 Supply .................................................................................. 2-30
2-64. Guarded Digital Control Circuitry ............................................... 2-30
2-74. Transfer Assembly (A10) ................................................................. 2-33
2-75. Input Signal Paths ........................................................................ 2-33
2-80. Precision Amplifiers..................................................................... 2-35
2-81. Thermal Sensor Circuit ................................................................ 2-36
2-82. Digital Interface and Control ....................................................... 2-36

Contents (continued)
iii
2-83. A/D Amplifier Assembly (A15)....................................................... 2-37
2-84. Chopper Circuit............................................................................ 2-37
2-90. A/D Amplifier Circuits ................................................................ 2-39
2-96. Digital Control and Power Supply ............................................... 2-41
2-97. DAC Assembly (A16) ...................................................................... 2-41
2-98. DAC Assembly Reference Circuitry............................................ 2-42
2-99. Duty-Cycle Control Circuit.......................................................... 2-43
2-100. DAC Filter Circuit ....................................................................... 2-44
2-101. DAC Output Stage ....................................................................... 2-44
2-102. Sense Current Cancellation Circuit.............................................. 2-44
2-103. Linearity Control Circuit.............................................................. 2-44
2-104. Negative Offset Circuit ................................................................ 2-45
2-105. Wideband Module (A6, Option -03) ................................................ 2-45
2-106. Input Signal Path for the Upper Four Ranges .............................. 2-47
2-107. Input Signal Path for the Lower Four Ranges.............................. 2-47
2-108. DC Offset Feedback for Amplifier U3 (Lower Ranges).............. 2-48
2-109. RMS Sensor Circuit ..................................................................... 2-48
2-110. Transfer Methodology.................................................................. 2-48
2-111. DC Offset Feedback for the RMS Sensor Amplifier ................... 2-48
2-112. Range Comparator ....................................................................... 2-49
2-113. Wideband Frequency Counter...................................................... 2-49
2-114. Digital Control ............................................................................. 2-50
2-115. A6A2 Input Protection Module.................................................... 2-50
3 Calibration and Verification................................................................ 3-1
3-1. Introduction........................................................................................... 3-3
3-2. Calibration Cycle.............................................................................. 3-3
3-3. Periodic and Service Calibration ...................................................... 3-3
3-4. Full or Range Calibration ................................................................. 3-3
3-5. Automating Calibration and Verification ......................................... 3-3
3-6. How Calibration Memory is Organized ........................................... 3-4
3-7. How to Use the Calibration Menus .................................................. 3-5
3-8. The Cal Menu............................................................................... 3-5
3-9. Zero Cal Softkey .......................................................................... 3-6
3-10. See Cal Dates Softkey.................................................................. 3-6
3-11. Cal Reports Softkey ..................................................................... 3-6
3-12. Update Cal Dates Menu ............................................................... 3-6
3-13. Periodic Calibration .............................................................................. 3-7
3-14. Calibrating the Main Input ............................................................... 3-7
3-15. Characterizing the DC Source...................................................... 3-7
3-16. DC Calibration ............................................................................. 3-13
3-17. AC Calibration ............................................................................. 3-19
3-18. Calibrating the Wideband AC Option .............................................. 3-27
3-19. Characterizing the AC Source...................................................... 3-29
3-20. Calibrating Wideband Input Gain at 1 kHz.................................. 3-31
3-21. Calibrating Wideband Input Flatness........................................... 3-33
3-22. Service Calibration ............................................................................... 3-35
3-23. Xfer Offset Adjustment .................................................................... 3-39
3-24. Wideband Amplifier Rolloff Adjustment......................................... 3-40
3-25. Verification ........................................................................................... 3-43
3-26. Verifying the Main Input (INPUT 1 or 2) ........................................ 3-43
3-27. Verifying AC-DC Difference for Regions I and III
(220 mV through 1000 V Range)................................................. 3-48

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3-28. Verifying Absolute AC Error for Region IV (70 mV through
700 mV Range) ............................................................................ 3-49
3-29. Verifying Absolute AC Error for Region II (2.2 V through
1000 V Range) ............................................................................. 3-52
3-30. Verifying Absolute AC Error for Region V (2.2 mV through
22 mV) ......................................................................................... 3-53
3-31. Verifying the Wideband AC Option................................................. 3-53
3-32. Wideband 1-kHz Gain VerificatioN, 7V, 2.2V, 700 mV, and
70 mV Ranges.............................................................................. 3-65
3-33. WIDEBAND 1-kHz GAIN VERIFICATION, 22 mV RANGE . 3-65
3-34. Wideband Gain Verification, 10 Hz to 500 kHz.......................... 3-66
3-35. Wideband Flatness Verification................................................... 3-66
4 Maintenance......................................................................................... 4-1
4-1. Introduction........................................................................................... 4-3
4-2. Cleaning the Air Filter .......................................................................... 4-3
4-3. General Cleaning .................................................................................. 4-3
4-4. Cleaning PCA's..................................................................................... 4-4
4-5. Access Procedures ................................................................................ 4-5
4-6. Top and Bottom Covers.................................................................... 4-5
4-7. Digital Section Cover ....................................................................... 4-5
4-8. Analog Section Covers..................................................................... 4-5
4-9. Rear Panel Removal and Installation................................................ 4-5
4-10. Rear Panel Assembly Access ........................................................... 4-6
4-11. Front Panel Removal and Installation .............................................. 4-7
4-12. Display Assembly Removal and Installation ............................... 4-7
4-13. Keyboard Assembly Removal and Installation............................ 4-7
4-14. Analog Assembly Removal and Installation .................................... 4-8
4-15. Digital Assembly Removal and Installation..................................... 4-8
4-16. Power Transformer Removal and Installation.................................. 4-8
4-17. Hybrid Cover Removal..................................................................... 4-9
4-18. Installing a Wideband AC Module (Option -03) .................................. 4-9
4-19. Clearing Ghost Images from the Control Display ................................ 4-10
4-20. Replacing the Clock/Calendar Backup Battery .................................... 4-11
4-21. Using Remote Commands Reserved for Servicing .............................. 4-11
4-22. Using the FATALITY? and FATALCLR Commands..................... 4-11
4-23. Error Codes........................................................................................... 4-12
5 Troubleshooting .................................................................................. 5-1
5-1. Introduction........................................................................................... 5-3
5-2. Main CPU (A20) Power-Up Tests ................................................... 5-3
5-3. A17 Guard Crossing Processor Power-Up Tests.............................. 5-3
5-4. System Startup Tests ........................................................................ 5-4
5-5. Diagnostic Tests ............................................................................... 5-4
5-6. Test Step: MAMA8255 (Motherboard 8255) .............................. 5-5
5-7. Test Step: DAC8254 (DAC 8254) ............................................... 5-6
5-8. Test Step: AD8255 (A/D 8255) ................................................... 5-6
5-9. Test Step: ADSELFTEST (A/D Internal Selftest) ....................... 5-7
5-10. Test Step: ADZEROS (A/D Zeros).............................................. 5-7
5-11. Test Step: ADNULLDAC (A/D Null DAC)................................ 5-7
5-12. Test Step: ADDAC (A/D DAC Output) ...................................... 5-8
5-13. Test Step: CHOPPER (A/D Chopper) ......................................... 5-9
5-14. Test Step: PROT (Protection) ...................................................... 5-10
5-15. Test Step: OVLD (Overload) ....................................................... 5-10

Contents (continued)
v
5-16. Test Step: ZEROS........................................................................ 5-11
5-17. Test Step: DIVIDERS (Input Dividers) ....................................... 5-11
5-18. Test Steps: X2_2V through X2_2MV.......................................... 5-12
5-19. Test Step: MATCH (Sensor Match) ............................................ 5-13
5-20. Test Step: XFREQ (Frequency Measuring) ................................. 5-13
5-21. Test Step: LOOPFILT (Sensor Filter).......................................... 5-13
5-22. Test Step: WOVLD (Wideband Overload).................................. 5-14
5-23. Test Steps: W7V through W2_2MV (Wideband 2.2 mV Range) 5-14
5-24. Test Step: WFREQ (Wideband Frequency Measuring)............... 5-14
5-25. Test Step: WLOOPFILT (Wideband Sensor Filter) .................... 5-15
6 List of Replacable Parts...................................................................... 6-1
6-1. Introduction........................................................................................... 6-3
6-2. How to Obtain Parts.............................................................................. 6-3
6-3. Manual Status Information ................................................................... 6-3
6-4. Newer Instruments................................................................................ 6-3
6-5. Service Centers ..................................................................................... 6-4
6-6. Parts Lists.............................................................................................. 6-4
7 Schematic Diagrams ........................................................................... 7-1
Appendices
A Glossary of AC-DC Transfer Related Terms .............................................. A-1
B ASCII and IEEE – 488 Bus Codes.............................................................. B-1
C Calibration Constant Information................................................................ C-1

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vii
List of Tables
Table Title Page
1-1. Symbols.................................................................................................................. 1-3
2-1. Analog Motherboard Connectors ........................................................................... 2-10
2-2. Supplies Generated by the Digital Power Supply .................................................. 2-12
2-3. CPU Acronym Glossary......................................................................................... 2-16
2-4. CPU Memory Map................................................................................................. 2-18
2-5. CPU Interrupts, Priorities, and Vectors.................................................................. 2-19
2-6. Front Panel Memory Map ...................................................................................... 2-22
2-7. Control Lines for the Keyboard LEDs ................................................................... 2-25
2-8. Unregulated Supplies from the Filter Assembly .................................................... 2-26
2-9. Regulated Supplies from the Filter Assembly........................................................ 2-27
2-10. Regulated Outputs from the Regulator/Guard Crossing Assembly ....................... 2-28
2-11. Inguard CPU Memory Map.................................................................................... 2-30
2-12. Inguard CPU Interrupts .......................................................................................... 2-32
3-1. Equipment Required for 5790A DC Characterization ........................................... 3-7
3-2. 5700A DC Characterization Test Record, Part 1 ................................................... 3-8
3-3. 5700A DC Characterization Test Record, Part 2 ................................................... 3-8
3-4. Equipment Required for 5790A Main Input DC Calibration................................. 3-13
3-5. Calibration Steps in Periodic Calibration............................................................... 3-16
3-6. Equipment Required for 5790A Main Input AC Calibration................................. 3-20
3-7. Equipment Required for Wideband Calibration..................................................... 3-28
3-8. Wideband Calibration Worksheet .......................................................................... 3-29
3-9. Attenuators Required for Each Range.................................................................... 3-34
3-10. Calibration Steps in Service Calibration ................................................................ 3-36
3-11. Wideband Amplifier Rolloff Adjustment Worksheet ............................................ 3-42
3-12. Main Input Verification Regions............................................................................ 3-43
3-13. Test Record for Main Input Verification................................................................ 3-44
3-14. Worksheet for Wideband 22 mV, 7 mV, and 2.2 mV 1 kHz Gain ........................ 3-55
3-15. Wideband Flatness Verification Worksheet........................................................... 3-55
3-16. Wideband Verification Test Record....................................................................... 3-56
6-1. Manual Status Information..................................................................................... 6-4
6-2. Final Assembly....................................................................................................... 6-5
6-2. A62 Input Block Assembly.................................................................................... 6-13
6-4. A1 Keyboard PCA ................................................................................................. 6-17
6-5. A2 Front Panel PCA............................................................................................... 6-19
6-6. A3 Analog Motherboard PCA................................................................................ 6-22

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6-7. A4 Digiital Motherboard PCA ............................................................................... 6-24
6-8. A6 Wideband PCA (Option -03)............................................................................ 6-27
6-9. A6A1 RMS Support PCA ...................................................................................... 6-32
6-10. A6A2 WB Input Protection PCA ........................................................................... 6-35
6-11. A10 Transfer PCA.................................................................................................. 6-37
6-12. A10A1 Precision Amplifier PCA........................................................................... 6-42
6-13. A10A2 HV Protection PCA ................................................................................... 6-44
6-14. A10A3 High-Gain Precision Amplifier PCA......................................................... 6-46
6-15. A15 A/D Amplifier PCA........................................................................................ 6-48
6-16. A16 DAC PCA....................................................................................................... 6-52
6-17. A16A1 DAC Filter PCA ........................................................................................ 6-56
6-18. A17 Regulator/Guard Crossing PCA ..................................................................... 6-58
6-19. A18 Filter PCA ...................................................................................................... 6-62
6-20. A19 Digital Power Supply PCA............................................................................. 6-65
6-21. A20 CPU PCA ....................................................................................................... 6-69
6-22. A21 Rear Panel I/O PCA ....................................................................................... 6-72