Service Manual
1503C
Metallic Time-Domain Reflectometer
070-7170-05
This document applies to firmware version 5.04
and above.
Warning
The servicing instructions are for use by qualified
personnel only. To avoid personal injury, do not
perform any servicing unless you are qualified to
do so. Refer to all safety summaries prior to
performing service.
www.tektronix.com
Copyright © T ektronix, Inc. All rights reserved. T ektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes
that in all previously published material. Specifications and price change privileges reserved.
T ektronix, Inc., P.O. Box 500, Beaverton, OR 97077
TEKTRONIX and TEK are registered trademarks of T ektronix, Inc.
WARRANTY
T ektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship
for a period of one (1) year from the date of shipment. If a product proves defective during this warranty period, T ektronix,
at its option, either will repair the defective product without charge for parts and labor, or will provide a replacement in
exchange for the defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customer shall be responsible for
packaging and shipping the defective product to the service center designated by T ektronix, with shipping charges prepaid.
T ektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
T ektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any
other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. T ektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than T ektronix representatives to install, repair or service the product; b) to repair
damage resulting from improper use or connection to incompatible equipment; c) to repair any damage or malfunction
caused by the use of non-T ektronix supplies; or d) to service a product that has been modified or integrated with other
products when the effect of such modification or integration increases the time or difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX IN LIEU OF ANY OTHER WARRANTIES, EXPRESS OR
IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TEKTRONIX’ RESPONSIBILITY TO
REP AIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO
THE CUSTOMER FOR BREACH OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS WILL NOT BE
LIABLE FOR ANY INDIRECT , SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES IRRESPECTIVE
OF WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH
DAMAGES.
Table of Contents
General Safety Summary xiii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Safety Summary xv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Information xvii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Installation and Repacking xviii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Contacting T ektronix xiv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Instructions
Operating Instructions 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overview 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preparing to Use the 1503C 1–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Display 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front-Panel Controls 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Menu Selections 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
T est Preparations 1–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cable T est Procedure 1–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additional Features (Menu Selected) 1–25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operator Performance Checks
Operator Performance Checks 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications
Specifications 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Characteristics 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Environmental Characteristics 3–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Physical Characteristics 3–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Options and Accessories
Options and Accessories 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 04: YT–1 Chart Recorder 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 05: Metric Default 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 06: EthernetR 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 07: YT–1S Chart Recorder 4–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 08: T oken Ring Adapter 4–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 09: Universal Service Ordering Code 4–17. . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 10: T oken Ring Interface 4–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Cord Options 4–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accessories 4–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1503C MTDR Service Manual
i
Table of Contents
Circuit Descriptions
Circuit Descriptions 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply 5–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Processor System 5–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option Port Interface 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Video Processor 5–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Timebase 5–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse Generator/Sampler 5–23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Panel 5–25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Display Module 5–29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 06 (EthernetR) 5–41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibration and Adjustments
Calibration 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibration Performance Check 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Display Module Check 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Panel Check 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Horizontal Scale (Timebase) Check 6–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vertical Position (Offset) Check 6–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Noise Check 6–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Impedance Check 6–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Offset/Gain Check 6–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RAM/ROM Check 6–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse Balance Check 6–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse Width Check 6–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Auto Pulse Select Check 6–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jitter Check 6–21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aberrations Check 6–23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse Amplitude Check 6–27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 04/07: YT-1/YT-1S Chart Recorder Check 6–30. . . . . . . . . . . . . . . . . . . . . . .
Option 05: Metric Default Check 6–31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 06: EthernetR Adapter Checks 6–31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adjustment Procedures 6–37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Visual Inspection 6–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply Checks and Adjustments 6–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Main Board "12 VDC Check and Adjust 6–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LCD Check and Adjustment 6–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulser/Sampler Voltage Check 6–49. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sampling Efficiency Adjustment 6–51. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1st Blow-By Compensation Adjustment 6–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Impedance Check 6–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 06: EthernetR Adapter Adjustments 6–58. . . . . . . . . . . . . . . . . . . . . . . . . . . .
After Adjustments are Completed 6–59. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1503C MTDR Service Manual
Maintenance
Maintenance 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preventive Maintenance 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Part Removal and Replacement 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting 7–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Panel Installation 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Installing the Case Cover Over the Chassis 7–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replaceable Electrical Parts
Replaceable Electrical Parts 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagrams
Diagrams 9–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table of Contents
Replaceable Mechanical Parts
Replaceable Mechanical Parts 10–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Glossary
Index
1503C MTDR Service Manual
iii
Table of Contents
List of Figures
Figure 1–1: Rear Panel Voltage Selector, Fuse, AC Receptacle 1–1. . . . .
Figure 1–2: Display Showing Low Battery Indication 1–4. . . . . . . . . . . .
Figure 1–3: 1503C Front-Panel Controls 1–5. . . . . . . . . . . . . . . . . . . . . .
Figure 1–4: Display and Indicators 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–5: Vp Set at .30, Cursor Beyond Reflected Pulse
(Setting Too Low) 1–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–6: Vp Set at .99, Cursor Less Than Reflected Pulse
(Setting Too High) 1–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–7: Vp Set at .66, Cursor on Rising Edge of Reflected Pulse
(Set Correctly) 1–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–8: 20-ft Cable at 5 ft/div 1–14. . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–9: Short in the Cable 1–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–10: Open in the Cable 1–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–11: 455-ft Cable 1–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–12: 455-ft Cable with 20 ft/div, Cursor Off Screen 1–16. . . . . . . .
Figure 1–13: Return Loss 1–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–14: Reflection Adjusted to One Division in Height 1–17. . . . . . .
Figure 1–15: Display with VIEW INPUT Turned Off 1–18. . . . . . . . . . . . .
Figure 1–16: Display of a Stored Waveform 1–19. . . . . . . . . . . . . . . . . . . .
Figure 1–17: Display of a Stored Waveform and Current Waveform 1–19.
Figure 1–18: Display of a Stored Waveform, Current Waveform,
and Difference Waveform 1–20. . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–19: Waveform Moved to Top Half of Display 1–20. . . . . . . . . . . .
Figure 1–20: Current Waveform Centered, Stored Waveform
Above 1–21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–21: Current Waveform Center, Stored Waveform Above,
Difference Below 1–21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–22: Waveform of Three-Foot Lead-in Cable 1–22. . . . . . . . . . . . .
Figure 1–23: Cursor Moved to End of Three-Foot Lead-in Cable 1–23. . . .
Figure 1–24: Cursor Moved to End of Three-Foot Lead-in Cable 1–23. . . .
Figure 1–25: Cursor Moved to 0.00 ft 1–24. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–26: Incident Pulse at Four Divisions, FILTER at
Desired Setting 1–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1–27: Waveform Viewed in Normal Operation 1–25. . . . . . . . . . . . .
Figure 1–28: Waveform Showing Intermittent Short 1–26. . . . . . . . . . . . . .
Figure 1–29: Waveform Display with No Outgoing Pulses 1–26. . . . . . . . .
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1503C MTDR Service Manual
Table of Contents
Figure 1–30: A Captured Single Sweep 1–27. . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–1: Start-up Measurement Display 2–2. . . . . . . . . . . . . . . . . . . .
Figure 2–2: Measurement Display with 10-foot Cable 2–2. . . . . . . . . . .
Figure 2–3: Cursor at End of 10-foot Cable 2–3. . . . . . . . . . . . . . . . . . . .
Figure 2–4: Cursor at End of 10-foot Cable, Vp Set to .30 2–3. . . . . . . .
Figure 2–5: Flatline Display Out to 50,000+ Feet 2–4. . . . . . . . . . . . . . .
Figure 2–6: Waveform Off the Top of the Display 2–4. . . . . . . . . . . . . . .
Figure 2–7: Waveform at the Bottom of the Display 2–5. . . . . . . . . . . . .
Figure 2–8: Waveform with Gain at 57 dB 2–5. . . . . . . . . . . . . . . . . . . . .
Figure 2–9: Distance at –2.00 ft 2–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–10: Pulse Adjusted to Four Major Divisions in Height 2–7. . . . .
Figure 2–11: Waveform Centered, Cursor at 10.00 ft 2–8. . . . . . . . . . . . .
Figure 2–12: Pulse Adjusted to Four Major Divisions in Height 2–8. . . . .
Figure 2–13: Aberrations Less Than Four Divisions Out to
30.00 ft 2–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–14: Pulse Adjusted to Four Major Divisions in Height 2–9. . . . .
Figure 2–15: Aberrations Less Than Four Divisions Out to
300.00 ft 2–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–16: Pulse Adjusted to Four Major Divisions in Height 2–10. . . . .
Figure 2–17: Aberrations Less Than Four Divisions Out to
3000.00 ft 2–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–1: A Typical Ethernet System 4–2. . . . . . . . . . . . . . . . . . . . . . .
Figure 4–2: N-Type Male T-Connector 4–5. . . . . . . . . . . . . . . . . . . . . . .
Figure 4–3: N-Type Female T-Connector 4–5. . . . . . . . . . . . . . . . . . . . . .
Figure 4–4: System 1 – Tap Hidden by Traffic
(1 avg, 50 ft/div. 35 dB) 4–10. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–5: System 1 – Traffic and Tap Nearly Identical
(4 avg, 50 ft/div, 35 dB) 4–10. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–6: System 1 – Tap Becoming Visible
(16 avg, 50 ft/div, 35 dB) 4–11. . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–7: System 1 – Tap Quite Visible
(128 avg, 50 ft/div, 35 dB) 4–11. . . . . . . . . . . . . . . . . . . . . . .
Figure 4–8: System 1 – No Traffic
(1 avg, 50 ft/div, 35 dB) 4–11. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–9: System 1 – Tap Expanded, No Traffic
(1 avg, 2 ft/div, 35 dB) 4–12. . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–10: System 2 – Cable w/ Revision One Repeater
(1 avg, 200ft/div, 2.25dB) 4–12. . . . . . . . . . . . . . . . . . . . . . . .
1503C MTDR Service Manual
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Table of Contents
Figure 4–11: System 2 – First Tap, No Traffic
(1 avg, 1 ft/div, 44.5 dB) 4–12. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–12: System 2 – Same Tap with 5% Traffic
(1 avg, 1 ft/div, 44.5 dB) 4–13. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–13: System 2 – Same Tap, Increased Averaging
(16 avg, 1 ft/div, 44.5 dB) 4–13. . . . . . . . . . . . . . . . . . . . . . . .
Figure 4–14: System 2 – Farther Out, More Gain
(128 avg, 10 ft/div, 53.5 dB) 4–13. . . . . . . . . . . . . . . . . . . . . .
Figure 4–15: System 2 – 1000-ft Cable at 10 ns
(128 avg, 100 ft/div, 43.75 dB) 4–14. . . . . . . . . . . . . . . . . . . .
Figure 4–16: System 2 – Previous Waveform Expanded
(128 avg, 20 ft/div, 54.75 dB) 4–14. . . . . . . . . . . . . . . . . . . . .
Figure 4–17: System 2 – Next Group of Taps
(128 avg, 20 ft/div, 54.75 dB) 4–14. . . . . . . . . . . . . . . . . . . . .
Figure 4–18: System 2 – Group of Taps Expanded
(128 avg, 10 ft/div, 54.75 dB) 4–15. . . . . . . . . . . . . . . . . . . . .
Figure 4–19: System 2 – Another Group of Taps
(128 avg, 10 ft/div, 54.75 dB) 4–15. . . . . . . . . . . . . . . . . . . . .
Figure 4–20: System 2 – End of Cable
(128 avg, 20 ft/div, 61.25 dB) 4–15. . . . . . . . . . . . . . . . . . . . .
Figure 4–21: Typical Frequency Response Curve with
EthernetR Option 06 4–16. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–1: System Block Diagram 5–2. . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–2: Waveform Accumulation Diagram 5–3. . . . . . . . . . . . . . . . .
Figure 5–3: Power Supply Block Diagram 5–4. . . . . . . . . . . . . . . . . . . . .
Figure 5–4: Processor Block Diagram 5–8. . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–5: Option Port Interface Block Diagram 5–11. . . . . . . . . . . . . . .
Figure 5–6: Video Processor Block Diagram 5–13. . . . . . . . . . . . . . . . . . .
Figure 5–7: Video Processor Output 5–15. . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–8: Timebase Block Diagram 5–16. . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–9: Timebase Control 5–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–10: Combined Effects of Time Delay 5–18. . . . . . . . . . . . . . . . . .
Figure 5–11: Calibration of Delay Zero and 50-ns Analog Delay 5–19. . . .
Figure 5–12: Pulse Generator/Sampler Block Diagram 5–23. . . . . . . . . . . .
Figure 5–13: Front Panel Block Diagram 5–26. . . . . . . . . . . . . . . . . . . . . . .
Figure 5–14: Display Module Block Diagram 5–29. . . . . . . . . . . . . . . . . . .
Figure 5–15: SBE Cell 5–31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–16: Row Driver Block Diagram 5–31. . . . . . . . . . . . . . . . . . . . . .
Figure 5–17: Column Driver Block Diagram 5–32. . . . . . . . . . . . . . . . . . . .
Figure 5–18: Row Timing Diagram 5–33. . . . . . . . . . . . . . . . . . . . . . . . . . .
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1503C MTDR Service Manual
Table of Contents
Figure 5–19: Column Timing Diagram 5–35. . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–20: Shift Register 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 5–21: CPU and Display Memory Interface 5–39. . . . . . . . . . . . . . . .
Figure 5–22: Option 06 (EthernetR) Block Diagram 5–41. . . . . . . . . . . . .
Figure 6–1: Typical Start-Up Display 6–2. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–2: Waveform on the Display 6–2. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–3: Setup Menu 6–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–4: Main Menu 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–5: Diagnostics Menu 6–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–6: Front Panel Diagnostic Display 6–5. . . . . . . . . . . . . . . . . . . .
Figure 6–7: Front Panel Diagnostic Display 6–6. . . . . . . . . . . . . . . . . . . .
Figure 6–8: Front Panel Diagnostic Display 6–7. . . . . . . . . . . . . . . . . . . .
Figure 6–9: Front Panel Diagnostic Display 6–7. . . . . . . . . . . . . . . . . . . .
Figure 6–10: Waveform on the Display with No Cable Attached 6–8. . . .
Figure 6–11: Waveform on the Display with 10-ft Cable Attached 6–8. . .
Figure 6–12: Cursor on Rising Edge of Reflected Pulse at 5 ft/div 6–9. . .
Figure 6–13: Cursor on Rising Edge of Reflected Pulse at 1 ft/div 6–9. . .
Figure 6–14: Cursor on Rising Edge of Reflected Pulse with
Vp at .84 6–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–15: Flatline Display to >50,000 ft 6–10. . . . . . . . . . . . . . . . . . . . .
Figure 6–16: Waveform at Top of the Display 6–11. . . . . . . . . . . . . . . . . .
Figure 6–17: Waveform at Bottom of the Display 6–11. . . . . . . . . . . . . . . .
Figure 6–18: Waveform at Center of the Display 6–11. . . . . . . . . . . . . . . . .
Figure 6–19: Distance Moved Beyond Trailing Edge of Pulse 6–12. . . . . .
Figure 6–20: Noise with Gain at 57 dB 6–13. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–21: Noise Diagnostic Display 6–13. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–22: Service Diagnostic Menu 6–14. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–23: Service Diagnostic Menu 6–14. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–24: Service Diagnostic Menu 6–15. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–25: Pulse Appx. Five Divisions High 6–16. . . . . . . . . . . . . . . . . .
Figure 6–26: Current Waveform Shifted from Stored Waveform 6–17. . . .
Figure 6–27: Initial Pulse 6–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–28: Pulse Adjusted to Six Divisions High 6–18. . . . . . . . . . . . . . .
Figure 6–29: Cursor on Leading Edge at Center Graticule 6–19. . . . . . . . .
Figure 6–30: Cursor on Trailing Edge at Center Graticule 6–19. . . . . . . . .
Figure 6–31: Initial Pulse with Cursor at 0.00 ft 6–20. . . . . . . . . . . . . . . . .
Figure 6–32: Waveform on Auto Pulse Select 6–21. . . . . . . . . . . . . . . . . . .
Figure 6–33: Initial Pulse Centered on Horizontal Graticule 6–21. . . . . . . .
1503C MTDR Service Manual
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Table of Contents
Figure 6–34: Gain Increased to 30.00 dB 6–22. . . . . . . . . . . . . . . . . . . . . . .
Figure 6–35: Jitter Apparent Using Max Hold 6–22. . . . . . . . . . . . . . . . . . .
Figure 6–36: Cursor at –2.00 ft 6–23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–37: Pulse Height at Four Divisions at 1 ft/div 6–24. . . . . . . . . . . .
Figure 6–38: Gain Increased to 25.00 dB 6–24. . . . . . . . . . . . . . . . . . . . . . .
Figure 6–39: Pulse Height at Four Divisions at 2 ft/div 6–25. . . . . . . . . . . .
Figure 6–40: Gain Increased to 30.00 dB 6–25. . . . . . . . . . . . . . . . . . . . . . .
Figure 6–41: Pulse Height at Four Divisions at 50 ft/div 6–26. . . . . . . . . . .
Figure 6–42: Gain Increased to 30.00 dB 6–26. . . . . . . . . . . . . . . . . . . . . . .
Figure 6–43: Pulse Height at Four Divisions at 500 ft/div 6–27. . . . . . . . . .
Figure 6–44: Gain Increased to 30.00 dB 6–27. . . . . . . . . . . . . . . . . . . . . . .
Figure 6–45: Oscilloscope Waveform 6–28. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–46: 1503C Waveform of 1000-ns Pulse 6–29. . . . . . . . . . . . . . . .
Figure 6–47: 1503C Waveform of 100-ns Pulse 6–29. . . . . . . . . . . . . . . . .
Figure 6–48: 1503C Waveform of 2-ns Pulse 6–30. . . . . . . . . . . . . . . . . . .
Figure 6–49: Head Alignment Chart Print 6–30. . . . . . . . . . . . . . . . . . . . . .
Figure 6–50: Equipment Setup 6–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–51: Main Menu 6–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–52: Ethernet Menu 6–33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–53: Ethernet Menu 6–33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–54: Ethernet Menu 6–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–55: Ethernet Menu 6–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–56: Ethernet Menu 6–35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–57: Circuit Board Locations in the Instrument 6–37. . . . . . . . . . .
Figure 6–58: Power Supply Board 6–39. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–59: Power Supply Test Points TP1020 and TP1010 6–39. . . . . .
Figure 6–60: Power Supply Test Point TP2030 6–40. . . . . . . . . . . . . . . . .
Figure 6–61: Connector Plug P5040 and Pins J5040 on Bottom of
Main Board 6–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–62: Power Supply Test Point TP1020 6–41. . . . . . . . . . . . . . . . .
Figure 6–63: Power Supply Test Point TP2030 6–41. . . . . . . . . . . . . . . . .
Figure 6–64: Location of Main Board in Instrument 6–42. . . . . . . . . . . . . .
Figure 6–65: Main Board Probe Points 6–42. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–66: Waveform on Display 6–43. . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–67: Battery Connections to Power Supply Board 6–44. . . . . . . . .
Figure 6–68: CR2012 on Power Supply Board 6–44. . . . . . . . . . . . . . . . . .
Figure 6–69: Display Showing Power is Battery 6–45. . . . . . . . . . . . . . . . .
Figure 6–70: Display Showing Battery Voltage is Low 6–45. . . . . . . . . . . .
Figure 6–71: R2012 on Power Supply Board 6–46. . . . . . . . . . . . . . . . . . . .
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1503C MTDR Service Manual
Table of Contents
Figure 6–72: R1018 on Front Panel Board 6–47. . . . . . . . . . . . . . . . . . . . . .
Figure 6–73: LCD Pattern with Contrast Too Light 6–47. . . . . . . . . . . . . . .
Figure 6–74: LCD Pattern with Contrast Too Dark 6–47. . . . . . . . . . . . . . .
Figure 6–75: LCD Pattern Adjusted for Sharpness 6–48. . . . . . . . . . . . . . .
Figure 6–76: Waveform with Contrast Too Light 6–48. . . . . . . . . . . . . . . . .
Figure 6–77: Waveform with Contrast Adjusted Correctly 6–49. . . . . . . . .
Figure 6–78: Location of Pulser/Sampler Board in Instrument 6–50. . . . . .
Figure 6–79: TP1081 and TP1082 on Pulser/Sampler Board 6–50. . . . . . .
Figure 6–80: VR3020 and VR30212 on Pulser/Sampler Board 6–50. . . . . .
Figure 6–81: Service Diagnostic Menu 6–52. . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–82: Location of Pulser/Sampler Board in Instrument 6–52. . . . . .
Figure 6–83: Location of R1080 on Pulser/Sampler Board 6–53. . . . . . . . .
Figure 6–84: Service Diagnostic Efficiency Readout 6–53. . . . . . . . . . . . . .
Figure 6–85: Location of Pulser/Sampler Board in Instrument 6–54. . . . . .
Figure 6–86: Location of R2097 on Pulser/Sampler Board 6–55. . . . . . . . .
Figure 6–87: Over-Compensated 6–55. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–88: Under-Compensated 6–55. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–89: Correctly Compensated 6–56. . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–90: Location of Pulser/Sampler Board in Instrument 6–56. . . . . .
Figure 6–91: Location of C3010, TP3020, and TP3030 on
Pulser/Sampler Board 6–57. . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–92: Main Menu 6–57. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 6–93: L2010, R1011, and R1013 on Option 06 Board 6–58. . . . . . .
1503C MTDR Service Manual
Figure 7–1: Location of Voltage Selector, Fuse Holder on Rear Panel 7–2
Figure 7–2: Power Supply Module and P/O Rear Panel 7–4. . . . . . . . . .
Figure 7–3: Main Board 7–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 7–4: EPROM on Main Board 7–7. . . . . . . . . . . . . . . . . . . . . . . . .
Figure 7–5: Lithium Battery on Main Board 7–8. . . . . . . . . . . . . . . . . . .
Figure 7–6: Display Module/Front Panel Board Screw Locations 7–10. . .
Figure 7–7: Display Module/Front Panel Board Showing Hex Nuts 7–11.
Figure 7–8: Location of Default Jumper on Front Panel Board 7–12. . . . .
Figure 7–9: Default Jumper Positions 7–12. . . . . . . . . . . . . . . . . . . . . . . .
Figure 7–10: Main Board TP1041 7–13. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 7–11: Main Board TP3040 and Main Board TP3041 7–17. . . . . . . .
Figure 7–12: Main Board TP4040 and Main Board TP6010 7–17. . . . . . . .
Figure 7–13: Main Board TP7010 and Main Board TP9011 7–17. . . . . . . .
Figure 7–14: Main Board TP9041 and Front Panel CABLE
Connector 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Table of Contents
Figure 7–15: Installing the Case Cover Over the Chassis 7–20. . . . . . . . . .
Figure 9–1: Special Schematic Symbols 9–3. . . . . . . . . . . . . . . . . . . . . .
Figure 9–2: Component Locator – Main Board 9–15. . . . . . . . . . . . . . . . .
Schematics – Main Board 9–16. . . . . . . . . . . . . . . . . . . . . .
Figure 9–3: Component Locator – Front Panel Board 9–25. . . . . . . . . . . .
Schematics – Front Panel 9–26. . . . . . . . . . . . . . . . . . . . . .
Figure 9–4: Component Locator – Power Supply Board 9–28. . . . . . . . . .
Schematics – Power Supply 9–29. . . . . . . . . . . . . . . . . . . . . .
Figure 9–5: Component Locator – Pulser/Sampler Board 9–31. . . . . . . . .
Schematics – Pulser/Sampler 9–32. . . . . . . . . . . . . . . . . . .
Figure 9–6: Component Locator – EthernetBoard 9–34. . . . . . . . . . . . . . .
Schematics – Ethernet Board 9–35. . . . . . . . . . . . . . . . . . . . .
Figure 10–1: Cabinet 10–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 10–2: Frame, Assemblies and Front Panel Controls 10–15. . . . . . . . .
Figure 10–3: Option 06 EthernetR 10–17. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 10–4: Power Supply 10–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
x
1503C MTDR Service Manual
List of Tables
Table of Contents
Shipping Carton Test Strength xvii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse / Voltage Ratings 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vp of Various Dielectric Types 1–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Impedance of Various Cable Types 1–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cable Length / Suggested Pulse / Suggested ft/div 1–14. . . . . . . . . . . . . . . . . .
Operator Performance Checks – Equipment Required 2–1. . . . . . . . . . . . . . .
Specifications: Electrical Characteristics 3–1. . . . . . . . . . . . . . . . . . . . . . . . .
Specifications: Environmental Characteristics 3–3. . . . . . . . . . . . . . . . . . . . .
Specifications: Physical Characteristics 3–4. . . . . . . . . . . . . . . . . . . . . . . . . .
Option 06 Ethernet: Electrical Characteristics 4–16. . . . . . . . . . . . . . . . . . . . .
Option Port Wiring Configuration 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Row Driver Latch Bits 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Column Driver Latch Bits 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Controller Periods 5–37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Option 06 Ethernet Control Lines 5–41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Calibration Performance Check – Equipment Required 6–1. . . . . . . . . . . . . .
Pulse Widths with Allowable Tolerances 6–19. . . . . . . . . . . . . . . . . . . . . . . . .
Auto Pulse: Distance per Division and Pulse Width 6–20. . . . . . . . . . . . . . . . .
Option 06 EthernetR Checks – Equipment Required 6–31. . . . . . . . . . . . . . . .
Adjustment Procedures – Equipment Required 6–37. . . . . . . . . . . . . . . . . . . .
Main Board Voltages, Tolerances, Test Point Locations 6–40. . . . . . . . . . . . . .
Pulser/Sampler Voltages and Test Point Locations 6–51. . . . . . . . . . . . . . . . . .
Impedance Range and Specification 6–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maintenance – Equipment Required 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Cord Conductor Color Code 7–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sealing Materials 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1503C MTDR Service Manual
xi
Table of Contents
xii
1503C MTDR Service Manual
General Safety Summary
Review the following safety precautions to avoid injury and prevent damage to
this product or any products connected to it. To avoid potential hazards, use this
product only as specified.
Only qualified personnel should perform service procedures.
To Avoid Fire or Personal Injury
Power Source
Use Proper Power Cord. Use only the power cord specified for this product and
certified for the country of use.
Use Proper Voltage Setting. Before applying power, ensure that the line selector is
in the proper position for the power source being used.
This product is intended to operate from a power source that will not apply more than
250 volts RMS between the supply conductors or between the supply conductor and
ground. A protective ground connection, by way of the grounding conductor in the
power cord, is essential for safe operation.
Ground the Product. This product is grounded through the grounding conductor
of the power cord. To avoid electric shock, the grounding conductor must be
connected to earth ground. Before making connections to the input or output
terminals of the product, ensure that the product is properly grounded.
The standard power cord (161-0288-00) is rated for outdoor use. All other optional
power cords are rated for indoor use only.
Observe All Terminal Ratings. To avoid fire or shock hazard, observe all ratings
and markings on the product. Consult the product manual for further ratings
information before making connections to the product.
Do not apply a potential to any terminal, including the common terminal, that
exceeds the maximum rating of that terminal.
1503C MTDR Service Manual
Replace Batteries Properly. Replace batteries only with the proper type and rating
specified.
Recharge Batteries Properly. Recharge batteries for the recommended charge
cycle only.
Use Proper AC Adapter. Use only the AC adapter specified for this product.
Do Not Operate Without Covers. Do not operate this product with covers or panels
removed.
Use Proper Fuse. Use only the fuse type and rating specified for this product.
Avoid Exposed Circuitry. Do not touch exposed connections and components
when power is present.
xiii
General Safety Summary
Do Not Operate With Suspected Failures. If you suspect there is damage to this
product, have it inspected by qualified service personnel.
Do Not Operate in an Explosive Atmosphere.
Symbols and Terms
Terms in this Manual. These terms may appear in this manual:
WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.
CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.
Terms on the Product. These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read the
marking.
WARNING indicates an injury hazard not immediately accessible as you read the
marking.
CAUTION indicates a hazard to property including the product.
Symbols on the Product. The following symbols may appear on the product:
xiv
CAUTION
Refer to Manual
WARNING
High Voltage
Double
Insulated
Protective Ground
(Earth) Terminal
1503C MTDR Service Manual
Service Safety Summary
Only qualified personnel should perform service procedures. Read this Service
Safety Summary and the General Safety Summary before performing any service
procedures.
Do Not Service Alone
Disconnect Power
Use Care When Servicing
With Power On
Disposal of Batteries
Do not perform internal service or adjustments of this product unless another person
capable of rendering first aid and resuscitation is present.
T o avoid electric shock, disconnect the main power by means of the power cord or
the power switch.
Dangerous voltages or currents may exist in this product. Disconnect power, remove
battery, and disconnect test leads before removing protective panels, soldering, or
replacing components.
To avoid electric shock, do not touch exposed connections.
This instrument contains a lead-acid battery . Some states and/or local jurisdictions
might require special disposition/recycling of this type of material in accordance
with Hazardous Waste guidelines. Check your local and state regulations prior to
disposing of an old battery.
T ektronix Factory Service will accept 1503C batteries for recycling. If you choose
to return the battery to us for recycling, the battery cases must be intact, the battery
should be packed with the battery terminals insulated against possible short-circuits,
and should be packed in shock-absorbant material.
1503C MTDR Service Manual
Tektronix, Inc.
Attn: Service Department
P.O. Box 500
Beaverton, Oregon 97077 U.S.A.
For more information, call 1-800-833-9200.
xv
Service Safety Summary
xvi
1503C MTDR Service Manual
General Information
Product Description
Battery Operation
Options
The Tektronix 1503C Metallic-cable Time-Domain Reflectometer (MTDR) is a
cable test instrument that uses radar principles to determine the electrical
characteristics of metallic cables.
The 1503C generates a half-sine wave signal, applies it to the cable under test, and
detects and processes the reflected voltage waveform. These reflections are
displayed in the 1503C liquid crystal display (LCD), where distance measurements
may be made using a cursor technique. Impedance information may be obtained
through interpreting waveform amplitude.
The waveform may be temporarily stored within the 1503C and recalled or may be
printed using the optional dot matrix strip chart recorder, which installs into the
front-panel Option Port.
The 1503C may be operated from an AC power source or an internal lead-gel
battery, which supplies a minimum of eight hours operating time (see the
Specifications chapter for specifics).
Options available for the 1503C are explained in the Options and Accessories
chapter of this manual.
Standards, Documents,
and References Used
Changes and History
Information
1503C MTDR Service Manual
Terminology used in this manual is in accordance with industry practice.
Abbreviations are in accordance with ANSI Y1.1–19722, with exceptions and
additions explained in parentheses in the text. Graphic symbology is based on ANSI
Y32.2–1975. Logic symbology is based on ANSI Y32.14–1973 and manufacturer’s
data books or sheets. A copy of ANSI standards may be obtained from the Institute
of Electrical and Electronic Engineers, 345 47th Street, New York, NY 10017.
Changes that involve manual corrections and/or additional data will be incorporated
into the text and that page will show a revision date on the inside bottom edge.
History information is included in any diagrams in gray.
xvii
General Information
Installation and Repacking
Unpacking and InItial
Inspection
Power Source and Power
Requirements
Before unpacking the 1503C from its shipping container or carton, inspect for signs
of external damage. If the carton is damaged, notify the carrier. The shipping carton
contains the basic instrument and its standard accessories. Refer to the replaceable
parts list in the Service Manual for a complete listing.
If the contents of the shipping container are incomplete, if there is mechanical
damage or defect, or if the instrument does not meet operational check requirements,
contact your local T ektronix Field Office or representative. If the shipping container
is damaged, notify the carrier as well as Tektronix.
The instrument was inspected both mechanically and electrically before shipment.
It should be free if mechanical damage and meet or exceed all electrical
specifications. Procedures to check operational performance are in the Performance
Checks appendix. These checks should satisfy the requirements for most receiving
or incoming inspections.
The 1503C is intended to be operated from a power source that will not apply more
than 250 volts RMS between the supply conductors or between either supply
conductor and ground. A protective ground connection, by way of the grounding
conductor in the power cord, is essential for safe operation.
The AC power connector is a three-way polarized plug with the ground (earth) lead
connected directly to the instrument frame to provide electrical shock protection. If
the unit is connected to any other power source, the unit frame must be connected
to earth ground.
Repacking for Shipment
xviii
Power and voltage requirements are printed on the back panel. The 1503C can be
operated from either 115 VAC or 230 VAC nominal line voltage at 45 Hz to 440 Hz,
or a 12 VDC supply, or an internal battery.
Further information on the 1503C power requirements can be found in the Safety
Summary in this section and in the Operating Instructions chapter.
When the 1503C is to be shipped to a T ektronix Service Center for service or repair,
attach a tag showing the name and address of the owner, name of the individual at
your firm who may be contacted, the complete serial number of the instrument, and
a description of the service required. If the original packaging is unfit for use or is
not available, repackage the instrument as follows:
1. Obtain a carton of corrugated cardboard having inside dimensions that are at
least six inches greater than the equipment dimensions to allow for cushioning.
The test strength of the shipping carton should be 275 pounds (102.5 kg). Refer
to the following table for test strength requirements:
1503C MTDR Service Manual
General Information
SHIPPING CARTON TEST STRENGTH
Gross Weight (lb)
0 – 10 200
11 – 30 275
31 – 120 375
121 – 140 500
141 – 160 600
CAUTION. The battery should be removed fr om the instrument befor e shipping. If it
is necessary to ship the battery, it should be wrapped and secur ed separately befor e
being packed with the instrument.
2. Install the front cover on the 1503C and surround the instrument with
polyethylene sheeting to protect the finish.
Carton Test Strength (lb)
3. Cushion the instrument on all sides with packing material or urethane foam
between the carton and the sides of the instrument.
4. Seal with shipping tape or an industrial stapler.
If you have any questions, contact your local Tektronix Field Office or
representative.
1503C MTDR Service Manual
xix
General Information
Contacting Tektronix
Product
Support
Service
support
Toll-free
Number
Postal
Address
For questions about using Tektronix measurement products, call
toll free in North America:
1-800-833-9200
6:00 a.m. – 5:00 p.m. Pacific time
Or contact us by e-mail:
tm_app_supp@tek.com
For product support outside of North America, contact your local
Tektronix distributor or sales office.
T ektronix offers a range of services, including Extended Warranty
Repair and Calibration services. Contact your local Tektronix
distributor or sales office for details.
For a listing of worldwide service centers, visit our web site.
In North America:
1-800-833-9200
An operator can direct your call.
Tektronix, Inc.
Department or name (if known)
P.O. Box 500
Beaverton, OR 97077
USA
Web site www.tektronix.com
xx
1503C MTDR Service Manual
Operating Instructions
Overview
Handling
Powering the 1503C
The 1503C front panel is protected by a watertight cover, in which the standard
accessories are stored. Secure the front cover by snapping the side latches outward.
If the instrument is inadvertently left on, installing the front cover will turn off the
POWER switch automatically.
The carrying handle rotates 325° and serves as a stand when positioned beneath the
instrument.
The 1503C can be stored in temperatures ranging from –62° C to +85° C if a battery
is not installed. If a battery is installed and the storage temperature is below –35°
C or above +65° C, the battery pack should be removed and stored separately (see
1503C Service Manual for instructions on removing the battery). Battery storage
temperature should be between –35° C to +65° C.
In the field, the 1503C can be powered using the internal battery . For AC operation,
check the rear panel for proper voltage setting. The voltage selector can be seen
through the window of the protective cap. If the setting differs from the voltage
available, it can be easily changed. Simply remove the protective cap and select the
proper voltage using a screwdriver.
REMOVE
CAP TO
REPLACE
FUSE
Voltage
Selector
REMOVE
CAP TO
SELECT
VOLTAGE
1503C MTDR Service Manual
Line Fuse
AC Power
Cord Receptacle
Figure 1–1: Rear Panel Voltage Selector, Fuse, AC Receptacle
The 1503C is intended to be operated from a power source that will not apply more
than 250 V RMS between the supply conductors or between either supply conductor
1–1
Operating Instructions
and ground. A protective ground connection by way of the grounding conductor in
the power cord is essential for safe operation.
The AC power connector is a three-way polarized plug with the ground (earth) lead
connected to the instrument frame to provide electrical shock protection. If the unit
is connected to any other power source, the unit frame must be connected to an earth
ground. See Safety and Installation section.
CAUTION. If you change the voltage selector, you must change the line fuse to the
appropriate value as listed near the fuse holder and in the table below.
FUSE RATING VOLTAGE RATING
250 V NOMINAL RANGE
0.3 A T 115 VAC (90 – 132 VAC)
0.15 A T 230 VAC (180 – 250 VAC)
Care of the Battery Pack
Battery Charging
CAUTION. Read these instructions concerning the care of the battery pack. They
contain instructions that reflect on your safety and the performance of the
instrument.
The 1503C can be powered by a rechargeable lead-gel battery pack that is accessible
only by removing the case from the instrument. When AC power is applied, the
battery pack is charged at a rate that is dependent on the battery charge state.
The battery pack will operate the 1503C for a minimum of eight continuous hours
(including making 30 chart recordings) if the LCD backlight is turned off.
The battery pack will charge fully in 16 hours when the instrument is connected, via
the power cord, to an AC power source with the instrument turned off. The
instrument may be turned on and operated while the batteries are charging, but this
will increase the charging time. For longest battery life, a full charge is preferred
over a partial charge.
For maximum capacity , the batteries should be charged within a temperature range
of +20° C to +25° C. However, the batteries can be charged within a temperature
range of 0° C to +40° C and operated in temperatures ranging from –10° C to +55° C.
1–2
1503C MTDR Service Manual
Battery Removal
Operating Instructions
CAUTION. Do not charge battery pack below 0° C or above +40° C. Do not
discharge battery pack below –10° C or above +55° C. If r emoving the battery pack
during or after exposure to these extreme conditions, turn the instrument off and
remove the AC power cord.
The battery pack should be stored within a temperature range of –35° C to +65° C.
However, the self-discharge rate will increase as the temperature increases.
If the instrument is stored with the battery pack installed, the battery pack should
be charged every 90 days. A fully charged battery pack will lose about 12% of its
capacity in three to four months if stored between +20° C and +25° C.
NOTE. The battery pack in the 1503C is inside the instrument case with no external
access. Refer removal and replacement to qualified service personnel.
1. Ensure that the instrument power is off.
2. If the instrument is connected to an AC power source, remove the AC power
cable from the source and from the instrument.
3. If installed, remove the chart recorder, or other device, from the option port.
4. Loosen the four screws on the back of the case and set the instrument face-up
on a flat surface.
5. Swing the handle out of the way of the front panel.
6. Break the chassis seal by pushing downward with both hands on the handle
pivots on each side of the case.
7. Grasp the case with one hand and tilt the chassis out with the other. Lift by
grasping the outside perimeter of the front panel.
CAUTION. Do not lift the instrument by the front-panel controls. The controls will
be damaged if you do so.
8. Remove the top shield from the instrument by gently lifting the rear edge near
the sides of the instrument.
9. Unplug the battery cable positive lead at the battery.
1503C MTDR Service Manual
10. Unplug the battery cable negative lead at the battery.
11. Unplug the battery cable at the power supply.
1–3
Operating Instructions
12. Remove the cable.
13. Remove the two screws mounting the battery clamp to the chassis.
14. Carefully remove the clamp without touching the battery terminals.
15. Lift the battery out.
To re-install or replace the battery, repeat the above steps in reverse order.
Low Battery
If the battery is low, it will be indicated on the LCD (bat/low). If this is the case,
protective circuitry will shut down the 1503C within minutes. Either switch to AC
power or work very fast. If the instrument is equipped with a chart recorder, using
the recorder will further reduce the battery level, or the added load might shut down
the instrument.
bat/low 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
50 W 2 ns
1 avg
0.00 dB 5000 ft
Low Battery
Indicator
Figure 1–2: Display Showing Low Battery Indication
Protection circuits in the charger prevent deep discharge of the batteries during
instrument operation. The circuits automatically shut down the instrument
whenever battery voltage falls below approximately 10 V. If shutdown occurs, the
batteries should be fully recharged before further use.
1–4
Low Temperature
Operation
NOTE. Turn the POWER switch off after instrument shutdown to prevent continued
discharge of the batteries.
When the instrument is stored at temperatures below –10° C, voids might develop
in the liquid crystal display (LCD). These voids should disappear if the instrument
is placed in an ambient temperature w +5° C for 24 hours.
When operating the 1503C in an environment below +10° C, a heater will activate.
The element is built into the LCD module and will heat the display to permit normal
operation. Depending on the surrounding temperature, it might take up to 15
minutes to completely warm the crystals in the LCD. Once warmed, the display will
operate normally.
1503C MTDR Service Manual
Preparing to Use the 1503C
Check the power requirements, remove the front cover, and you are ready to test
cables. The following pages explain the front-panel controls.
Operating Instructions
11
12
13
14
15
Tektronix
MENU
VIEW
INPUT
VIEW
STORE
VIEW
DIFF
STORE
INPUT PROTECTED
400 V PEAK MAX
CABLE
1 3 4 5 6 7
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
50 Ω
IMPEDANCE
1 avg
NOISE FILTER VERT SCALE DIST/DIV
HORZ
SET REF
VERT
2
1503C
0.00 db
METALLIC TDR
CABLE TESTER
1 ft
2 ns
.3
.4
POSITION
POSITION
PULSE WIDTH
Vp
.5
.6
.03
.7
.02
.8
.01
.9
.04
.05
.06
.07
.08
.09
.00
POWER
(PULL ON)
910
8
Figure 1–3: 1503C Front-Panel Controls
CAUTION. Do not connect to circuits or cables with live voltages gr eater than 400 V
peak. Voltages exceeding 400 V might damage the 1503C front-end circuits.
1503C MTDR Service Manual
1–5
Operating Instructions
Display
Power
Type Cursor Waveform
Front-Panel to Cursor
Distance Window
Front-Panel Controls
IMPEDANCE
View Input
Indicator
View Store
Indicator
View Difference
Indicator
Store
Indicator
ac
O
N
O
F
F
O
F
F
O
F
F
50 W 2 ns
Selected
Impedance
1 avg
Selected
Noise Filter
0.00 dB 5000 ft
Selected Selected Selected
Vertical Scale Distance per
Division
0.00 ft
Pulse Width
Figure 1–4: Display and Indicators
1. CABLE: A female BNC connector for attaching a cable to the 1503C for
testing.
2. IMPEDANCE: A four-position rotary switch that selects the output impedance
of the cable test signal. Available settings are 50, 75, 93, and 125 Ohms. The
selected value is displayed above the control on the LCD.
Grid
1–6
NOISE FILTER
VERT SCALE
DIST/DIV
3. NOISE FILTER: If the displayed waveform is noisy, the apparent noise can
be reduced by using noise averaging. A veraging settings are between 1 and 128.
The time for averaging is directly proportional to the averaging setting chosen.
A setting of 128 might take the instrument up to 35 seconds to acquire and
display a waveform. The first two positions on the NOISE FILTER control are
used for setting the vertical and horizontal reference points. The selected value
or function is displayed above the control on the LCD.
4. VERT SCALE: This control sets the vertical gain, displayed in dB, or the
vertical sensitivity, displayed in mr per division. Although the instrument
defaults to dB, you may choose the preferred mode from the Setup Menu. The
selected value is displayed above the control on the LCD.
5. DIST/DIV: Determines the number of feet (or meters) per division across the
display . The minimum setting is 1 ft/div (0.25 meters) and the maximum setting
is 5000 ft/div (1000 meters). The selected value is displayed above the control
on the LCD.
1503C MTDR Service Manual
Operating Instructions
A standard instrument defaults to ft/div. A metric instrument (Option 05)
defaults to m/div, but either may be changed temporarily from the menu. The
default can be changed by changing an internal jumper (see Chapter 7).
.3
.4 .5
POWER
(PULL ON)
Vp
.03
.6
.7
.02
.8
.01
.9 .00
PULSE WIDTH
n
POSITION
o
n
o
POSITION
.04 .05
6. Vp: The two Velocity of Propagation controls are set according to the
.06
.07
.08
.09
propagation velocity factor of the cable being tested. For example, solid
polyethylene commonly has a Vp of 0.66. Solid polytetraflourethylene
(Teflon ) is approximately 0.70. Air is 0.99. The controls are decaded: the left
control is the first digit and the right control is the second digit. For example,
with a Vp of 0.30, the first knob would be set to .3 and the second knob to .00.
7. POWER: Pull for power ON and push in for power OFF . When the front cover
is installed, this switch is automatically pushed OFF.
8. PULSE WIDTH: This is a five-position rotary switch that selects the pulse
width of the cable test signal. The available settings are: 2, 10, 100, 1000
nanoseconds, and AUTO. The selected value is displayed on the LCD adjacent
to the control. The AUTO setting sets the pulse width according to the distance
registered at the right side of the LCD. The selected value is displayed to the left
of this control on the LCD.
n
9.
POSITION: This is a continuously rotating control that positions the
o
displayed waveform vertically, up or down the LCD.
n
o
10.
POSITION: This is a continuously rotating control that moves a vertical
cursor completely across the LCD graticule. In addition, the waveform is also
moved when the cursor reaches the extreme right or left side of the display. A
readout (seven digits maximum) is displayed in the upper right corner of the
LCD, showing the distance from the front panel BNC to the current cursor
location.
MENU
VIEW
INPUT
VIEW
STORE
VIEW
DIFF
STORE
1503C MTDR Service Manual
11. MENU: This pushbutton provides access to the menus and selects items chosen
from the menus.
12. VIEW INPUT: When pushed momentarily, this button toggles the display of
the waveform acquired at the CABLE connector. This function is useful to stop
displaying a current waveform to avoid confusion when looking at a stored
waveform. This function defaults to ON when the instrument is powered up.
13. VIEW STORE: When pushed momentarily, this button toggles the display of
the stored waveform.
14. VIEW DIFF: When pushed momentarily , this button toggles the display of the
current waveform minus the stored waveform and shows the difference between
them.
15. STORE: When pushed momentarily, the waveform currently displayed will be
stored in the instrument memory . If a waveform is already stored, pushing this
button will erase it. The settings of the stored waveform are available from the
first level menu under View Stored Waveform Settings.
1–7
Operating Instructions
Menu Selections
There are several layers of menu, as explained below.
Main Menu
The Main Menu is entered by pushing the MENU button on the front panel.
1. Return to Normal Operations puts the instrument into normal operation
mode.
2. Help with Instrument Controls explains the operation of each control. When
a control or switch is adjusted or pushed, a brief explanation appears on the
LCD.
3. Cable Information has these choices:
a. Help with Cables gives a brief explanation of cable parameters.
b. Velocity of Propagation V alues displays a table of common dielectrics and
their Vp values. These are nominal values. The manufacturer’s listed
specifications should be used whenever possible.
c. Impedance Values displays impedances of common cables. In some cases,
these values have been rounded off. Manufacturer’s specifications should
be checked for precise values.
d. Finding Unknown Vp Values describes a procedure for finding an
unknown Vp.
4. Setup Menu controls the manner in which the instrument obtains and displays
its test results.
1–8
a. Acquisition Control Menu has these choices:
i. Max Hold Is: On/Off. Turn Max Hold on by pushing MENU then
STORE. In this mode, waveforms are accumulated on the display . Max
Hold can be deactivated by pushing STORE or the mode exited by
using the Setup Menu.
ii. Pulse Is: On/Off. T urns the pulse generator of f so the 1503C does not
send out pulses.
iii. Single Sweep Is: On/Off. This function is much like a still camera; it
will acquire one waveform and hold it.
b. Vertical Scale Is: dB/mr. This offers you a choice as to how the vertical
gain of the instrument is displayed. You may choose decibels or millirho.
When powered down, the instrument will default to decibels when powered
back up.
c. Distance/Div Is: ft/m. Offers you a choice of how the horizontal scale is
displayed. You may choose from feet per division or meters per division.
1503C MTDR Service Manual
Operating Instructions
When powered up, the instrument will default to feet unless the internal
jumper has been moved to the meters position. Instructions on changing this
default are contained in Chapter 7.
d. Light Is: On/Off. This control turns the electroluminescent backlight
behind the LCD on or off.
5. Diagnostics Menu lists an extensive selection of diagnostics to test the
operation of the instrument.
a. Service Diagnostics Menu has these choices:
i. Sampling Efficiency Diagnostic displays a continuous efficiency
diagnostic of the sampling circuits.
ii. Noise Diagnostic measures the internal RMS noise levels of the
instrument.
iii. Impedance Diagnostic tests the output impedance circuits in the
instrument.
iv. Offset/Gain Diagnostic reports out-of–tolerance steps in the program-
mable gain stage. This can help a service technician to quickly isolate
the cause of waveform distortion problems.
v. RAM/ROM Diagnostics Menu performs tests on the RAM (Random
Access Memory) and the ROM (Read Only Memory).
vi. Timebase Is: Normal - Auto Correction / Diagnostic - No
Correction. When in Normal - Auto Correction, the instrument
compensates for variations in temperature and voltage. This condition
might not be desirable while calibrating the instrument. While in
Diagnostic - No Correction, the circuits will not correct for these
variations.
b. Front Panel Diagnostics aids in testing the front panel.
c. LCD Diagnostics Menu has these choices:
i. LCD Alignment Diagnostic generates a dot pattern of every other
pixel on the LCD. These pixels can be alternated to test the LCD.
ii. Response Time Diagnostic generates alternate squares of dark and
light, reversing their order. This tests the response time of the LCD and
can give an indication of the effectiveness of the LCD heater in a cold
environment.
1503C MTDR Service Manual
iii. LCD Drive Test Diagnostic generates a moving vertical bar pattern
across the LCD.
iv. Contrast Adjust allows you to adjust the contrast of the LCD. It
generates an alternating four-pixel pattern. The nominal contrast is set
1–9
Operating Instructions
internally . When in Contrast Adjust mode, VERT SCALE is used as the
contrast adjustment control. This value ranges from 0 to 255 units and
is used by the processor to evaluate and correct circuit variations caused
by temperature changes in the environment.
d. Chart Diagnostics Menu offers various tests for the optional chart
recorder.
i. LCD Chart allows adjusting the number of dots per segment and the
number of prints (strikes) per segment.
ii. Head Alignment Chart generates a pattern to allow mechanical
alignment of the optional chart recorder.
6. View Stored W aveform Settings displays the instrument settings for the stored
waveform.
7. Option Port Menu contains three items. T wo items allow configuration of the
option port for communicating with devices other than the optional chart
recorder and one item test the option port.
a. Option Port Diagnostic creates a repeating pattern of signals at the option
port to allow service technicians to verify that all signals are present and
working correctly.
b. Set Option Port Timing allows adjustment of the data rate used to
communicate with external devices. The timing rate between bytes can be
set from about 0.05 to 12.8 milliseconds.
c. Option Port Debugging Is Off/On. Off is quiet, On is verbose. This
chooses how detailed the error message reporting will be when communicating with an external device.
It is possible to connect the instrument to a computer through a parallel interface
with a unique software driver. Because different computers vary widely in
processing speed, the instrument must be able to adapt to differing data rates
while communicating with those computers. With user-developed software
drivers, the ability to obtain detailed error messages during the development can
be very useful. For more information, contact your T ektronix Customer Service
representatives. They have information describing the option port hardware and
software protocol and custom development methods available.
The SP-232, a serial interface product, also allows for connection of the 1503C
to other instrumentation, including computers, via the option port. SP-232 is an
RS-232C-compatible interface. For more information, contact your Tektronix
Customer Service Representative. They can provide you with additional details
on the hardware and software protocol.
1–10
8. Display Contrast (Software Version 5.02 and above)
1503C MTDR Service Manual
Test Preparations
Operating Instructions
a. Press the MENU button firmly once. If the display is very light or very dark,
you might not be able to see a change in the contrast.
b. T urn the VER TICAL SCALE knob slowly clockwise to darken the display
or counterclockwise to lighten the display . If you turn the knob far enough,
the contrast will wrap from the darkest to lightest value.
c. When the screen is clearly readable, press the MENU button again to return
to normal measurement operation. The new contrast value will remain in
effect until the instrument is turned off.
The Importance of Vp
(Velocity of Propagation)
Vp of Various Dielectric
Types
Vp is the speed of a signal down the cable given as a percentage of the speed of light
in free space. It is sometimes expressed as a whole number (e.g., 66) or a percentage
(e.g., 66%). On the 1503C, it is the percentage expressed as a decimal number (e.g.,
66% = .66). If you do not know the velocity of propagation, you can get a general
idea from the following table, or use the Help with Cables section of the Cable
Information menu. You can also find the Vp with the procedure that follows using
a cable sample.
NOTE. If you do not know the Vp of your cable, it will not prevent you fr om finding
a fault in your cable. However, if the Vp is set wrong, the distance readings will be
affected.
All Vp settings should be set for the cable under test, not the supplied jumper cable.
Dielectric Probable Vp
Jelly Filled .64
Polyethylene (PIC, PE, or SPE) .66
PTFE (Teflon R) or TFE .70
Pulp Insulation .72
Foam or Cellular PE (FPE) .78
Semi-solid PE (SSPE) .84
Air (helical spacers) .98
1503C MTDR Service Manual
1–11
Operating Instructions
n
o
Impedance of Various
Cable Types
Finding an Unknown Vp
50 W75 W93 W 125 W
RG–4 RG–6/U RG–7/U RG–23/U
RG–8/U RG–11/U RG–22/U RG–63/U
RG–9/U RG–12/U RG–62/U RG–79/U
RG–58/U RG–13/U RG–71/U RG–89/U
RG–62/U RG–59/U RG–111/U Flat Lead
RG–81 RG–124/U Twisted Pair Twisted Pair
RG–93 RG–140/U
RG–142B/U RG–179/U
RG–225/U 75 Video
RG–303B/U
RG–316/U
RG–393/U
Vertebrae Helix
1. Obtain a known length of cable of the exact type you wish to test. Attach the
cable to the CABLE connector on the front panel.
2. Pull POWER on.
3. Turn the DIST/DIV to an appropriate setting (e.g., if trying to find the Vp of a
three-foot cable, turn the DIST/DIV to 1 ft/div).
4. Turn the
POSITION control until the distance reading is the same as the
known length of this cable.
5. Turn the Vp controls until the cursor is resting on the rising portion of the
reflected pulse. The Vp controls of the instrument are now set to the Vp of the
cable.
The following three illustrations show settings too low, too high, and correct for a
sample three-foot cable.
ac 3.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–5: Vp Set at .30, Cursor Beyond Reflected Pulse (Setting Too Low)
1–12
1503C MTDR Service Manual
Operating Instructions
ac 3.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–6: Vp Set at .99, Cursor Less Than Reflected Pulse (Setting Too High)
ac 3.00 ft
O
N
O
F
F
Cable Test Procedure
Distance to the Fault
O
F
F
O
F
F
Figure 1–7: Vp Set at .66, Cursor on Rising Edge of Reflected Pulse (Set Correctly)
Be sure to read the previous paragraphs on Vp.
1. Set the 1503C controls:
POWER On
CABLE Cable to BNC
IMPEDANCE 50
NOISE FILTER 1 avg
DIST/DIV (see below)
Vp (per cable)
PULSE WIDTH (per cable)
2. If you know approximately how long the cable is, set the DIST/DIV
appropriately (e.g., 20-ft cable would occupy four divisions on the LCD if 5
ft/div was used). The entire cable should be displayed.
1503C MTDR Service Manual
1–13
Operating Instructions
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–8: 20-ft Cable at 5 ft/div
If the cable length is unknown, set DIST/DIV to 5000 ft/div and continue to decrease
the setting until the reflected pulse is visible. Depending on the cable length and the
amount of pulse energy absorbed by the cable, it might be necessary to increase the
VERT SCALE to provide more gain to see the reflected pulse.
The best pulse width is dependent on the cable length. A short pulse can be
completely dissipated in a long cable. Increasing the pulse width will allow the
reflected pulse to be more visible when testing long cables. AUTO will select the
pulse width for you, depending on the distance on the right side of the LCD.
CABLE LENGTH SUGGESTED PULSE
SUGGESTED ft/div
0 to 100 ft 2 ns 10 ft/div
51 to 500 ft 10 ns 50 ft/div
501 to 5000 ft 100 ns 500 ft/div
5001 to 50,000 ft 1000 ns 5000 ft/div
When the entire cable is displayed, you can tell if there is an open or a short.
Essentially, a drop in the pulse is a short and a rise in the pulse is an open. Less
catastrophic faults can be seen as hills and valleys in the waveform. Bends and
kinks, frays, water, and interweaving all have distinctive signatures.
ac 0.00 ft
O
N
O
F
F
Short
O
F
F
O
F
F
Figure 1–9: Short in the Cable
1–14
1503C MTDR Service Manual
ac 20.00 ft
n
o
n
o
O
N
Operating Instructions
O
F
F
O
F
F
O
F
F
Open
Figure 1–10: Open in the Cable
3. To find the distance to the fault or end of the cable, turn the
POSITION
control until the cursor rests on the leading edge of the rising or falling reflected
pulse (see Figure 1–10). Read the distance in the distance window in the upper
right corner of the display.
A more thorough inspection might be required. This example uses a longer cable:
4. When inspecting a 455-foot cable, a setting of 100 ft/div allows a relatively fast
inspection. If needed, turn VERT SCALE to increase the gain. The higher the
gain, the smaller the faults that can be detected. If noise increases, increase the
NOISE FILTER setting.
ac 455.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–11: 455-ft Cable
5. Change DIST/DIV to 20 ft/div . The entire cable can now be inspected in detail
on the LCD. Turn the
POSITION control so the cursor travels to the far right
side of the LCD. Keep turning and the cable will be “dragged” across the
display.
1503C MTDR Service Manual
1–15
Operating Instructions
ac 299.80 ft
O
N
O
F
F
O
F
F
O
F
F
Cursor
Figure 1–12: 455-ft Cable with 20 ft/div, Cursor Off Screen
A “rise” or “fall” is a signature of an impedance mismatch (fault). A dramatic rise
in the pulse indicates and open. A dramatic lowering of the pulse indicates a short.
Variations, such as inductive and capacitive effects on the cable, will appears as
bumps and dips in the waveform. Capacitive faults appear as a lowering of the pulse
(e.g., water in the cable). Inductive faults appear as a rising of the pulse (e.g., kinks
in the cable). Whenever an abnormality is found, set the cursor at the beginning of
the fault and read the distance to the fault on the distance window of the LCD.
Return Loss
Measurements
Return loss is another was of measuring impedance changes in a cable.
Mathematically, return loss is related to rho by the formula:
Return Loss (in dB) = –20 * log (base ten) of Absolute Value of Rho (V
ref/Vinc)
To measure return loss with the 1503C, note the height of the incident pulse, then
adjust the reflected pulse to be the same height that the incident pulse was and read
the dB on the LCD display. The amount of vertical scale change that was needed
is the return loss in dB.
ac
O
N
O
F
F
O
F
F
O
F
F
455.00 ft
Loss
Figure 1–13: Return Loss
A large return loss means that most of the pulse energy was lost instead of being
returned as a reflection. The lost energy might have been sent down the cable or
absorbed by a terminator or load on the cable. A terminator matched to the cable
1–16
1503C MTDR Service Manual
Operating Instructions
would absorb most of the pulse, so its return loss would be large. An open or short
would reflect all the energy, so its return loss would be zero.
Reflection Coefficient
Measurements
The 1503C can be made to display in m/div instead of dB through MENU.
1. Press MENU.
2. Select Setup Menu.
3. Press MENU.
4. Select Vertical Scale is: Decibels.
5. Press MENU. This changes the selection to Vertical Scale is: Millirho.
6. Press MENU again to exit from the Setup Menu.
7. Press MENU again to return to normal operation.
The reflection coefficient is a measure of the impedance change at a point in the
cable. It is the ratio of the signal reflected back from a point divided by the signal
going into that point. It is designated by the Greek letter , and is written in this
manual as Rho. The 1503C measures reflection coefficient in millirho (thousandths
of a rho).
To measure a reflection, adjust VERT SCALE to make the reflection one division
high. Read the reflection coefficient directly off the display above the VERT
SCALE control. For reflections that are greater than 500 m/div, adjust VERT
SCALE for a reflection that is two divisions high and multiply the VERT SCALE
reading by two.
1503C MTDR Service Manual
ac 455.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–14: Reflection Adjusted to One Division in Height
In an ideal transmission system with no changes in impedance, there will be no
reflections, so rho is equal to zero. A good cable that is terminated in its
characteristic impedance is close to ideal and will appear as a flat line on the 1503C
display .
1–17
Operating Instructions
Small impedance changes, like those from a connector, might have reflections from
10 to 100 m. If rho is positive, it indicates an impedance higher than that of the
cable before the reflection. It will show as an upward shift or bump on the waveform.
If rho is negative, it indicates an impedance lower than that of the cable prior to the
reflection. It will show as a downward shift or dip on the waveform.
If the cable has an open or short, all the energy sent out by the 1503C will be
reflected. This is a reflection coefficient of rho = 1, or +1000 m for the open and
–1000 m for the short.
Effect of Cable
Attenuation on Return
Loss and Reflection
Coefficient Measurements
Using VIEW INPUT
Cable attenuation influences the return loss and reflection coefficient measurements
made with the 1503C. If you desire to measure the return loss of only an impedance
mismatch, the cable attenuation, as measured with an open or short circuit on the
cable, must be subtracted from the directly measured value.
For reflection coefficient, the directly measured value of rho must be divided by the
value measured with an open or short circuit on the cable. These calculations can
be done manually, or the instrument can perform them by proper use of the VERT
SET REF function.
It is is not possible to measure the cable under test with an open or short, sometimes
another cable of similar type is available to use as a reference. Note that cable
attenuation is strongly influenced by signal frequency and, therefore, will be
different from one pulse width to another on the 1503C.
When pushed, the VIEW INPUT button displays the input at the front panel CABLE
connector. When VIEW INPUT is turned off and no other buttons are pushed, the
display will not have a waveform on it (see Figure 1–15). The default condition
when the instrument is powered up is to have VIEW INPUT on.
ac 0.00 ft
1–18
O
N
O
F
F
O
F
F
O
F
F
Figure 1–15: Display with VIEW INPUT Turned Off
1503C MTDR Service Manual
Operating Instructions
How to Store the
Waveform
Using VIEW STORE
When pushed, the STORE button puts the current waveform being displayed into
memory. If already stored, pushing STORE again will erase the stored waveform.
ac 3.00 ft
O
N
O
F
F
O
F
F
O
N
Figure 1–16: Display of a Stored Waveform
The front panel control settings and the menu-accessed settings are also stored. They
are accessed under View Stored Waveform Settings in the first level of the menu.
The VIEW STORE button, when pushed on, displays the waveform stored in the
memory as a dotted line. If there is no waveform in memory , a message appears on
the LCD informing you of this.
Using VIEW DIFF
ac 3.00 ft
O
N
Stored
Waveform
O
N
O
F
F
O
N
Figure 1–17: Display of a Stored Waveform and Current Waveform
When pushed on, the VIEW DIFF button displays the difference between the current
waveform and the stored waveform as a dotted line. If no waveform has been stored,
a message will appear. The difference waveform is made by subtracting each point
in the stored waveform from each point in the current waveform.
NOTE. If the two waveforms are identical (e.g., if ST ORE is pushed and VIEW DIFF
is immediately pushed) the difference would be zero. Therefore you would see the
difference waveform as a straight line.
1503C MTDR Service Manual
1–19
Operating Instructions
ac 3.00 ft
O
N
O
N
O
N
O
N
Figure 1–18: Display of a Stored Waveform, Current Waveform,
and Difference Waveform
Difference
Waveform
The VIEW DIFF waveform will move up and down with the current input as you
move the
n
POSITION control. Any of the waveforms may be turned on or off
o
independently . You might want to turn off some waveforms if the display becomes
too busy or confusing.
NOTE. Because the stored waveform is not affected by changes in the instrument
controls, care should be taken with current waveform settings or the results could
be misleading.
One method to minimize the overlapping of the waveforms in VIEW DIFF is:
1. Move the waveform to be stored into the top half of the display.
ac 3.00 ft
O
N
O
F
F
O
F
F
O
N
1–20
Figure 1–19: Waveform Moved to Top Half of Display
2. Push STORE to capture the waveform. Remember, once it is stored, this
waveform cannot be moved on the display.
3. Move the current waveform (the one you want to compare against the stored
waveform) to the center of the display.
1503C MTDR Service Manual
Operating Instructions
4. Push VIEW STORE and the stored waveform will appear above the current
waveform.
ac 3.00 ft
O
N
O
N
O
F
F
O
N
Figure 1–20: Current Waveform Centered, Stored Waveform Above
5. Push VIEW DIFF and the difference waveform will appear below the current
waveform.
ac 3.00 ft
O
N
O
N
O
N
O
N
Figure 1–21: Current Waveform Center, Stored Waveform Above, Difference Below
Notice the VIEW INPUT waveform is solid, VIEW DIFF is dotted, and VIEW
STORE is dot-dash.
There are many situations where the VIEW DIFF function can be useful. One
common situation is to store the waveform of a suspect cable, repair the cable, then
compare the two waveforms after the repair. During repairs, the VIEW INPUT,
VIEW DIFF , and VIEW ST ORE waveforms can be used to judge the effectiveness
of the repairs. The optional chart recorder can be used to make a chart of the three
waveforms to document the repair.
Another valuable use for the VIEW DIFF function is for verifying cable integrity
before and after servicing or periodic maintenance that requires moving or
disconnecting the cable.
1503C MTDR Service Manual
The VIEW DIFF function is useful when you want to see any changes in the cable.
In some systems, there might be several reflections coming back from each branch
of the network. It might become necessary to disconnect branch lines from the cable
1–21
Operating Instructions
n
o
n
o
under test to determine whether a waveform represents a physical fault or is simply
an echo from one of the branches. The STORE and VIEW DIFF functions allow you
to see and compare the network with and without branches.
Two important things to be observed when using the VIEW DIFF function:
H If you change either the VERT SCALE or DIST/DIV, you will no longer be
comparing features that are the same distance apart or of the same magnitude
on the display. It is possible to save a feature (e.g., a connector or tap) at one
distance down the cable and compare it to a similar feature at a different distance
by moving the
POSITION and
n
POSITION controls.
o
H When this is done, great care should be taken to make sure the vertical and
horizontal scales are identical for the two waveforms being compared. If either
the stored or current waveform is clipped at the top or bottom of the display , the
difference waveform will be affected.
Using Horizontal Set
Reference
HORZ SET REF ( mode) allows you to offset the distance reading. For example,
a lead-in cable to a switching network is three feet long and you desire to start the
measurement after the end of the lead-in cable. HORZ SET REF makes it simple.
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
End of
3-ft cable
Figure 1–22: Waveform of Three-Foot Lead-in Cable
1. Turn the NOISE FILTER control to HORZ SET REF. The noise readout on the
LCD will show: set .
2. Turn the
POSITION control to set the cursor where you want to start the
distance reading. This will be the new zero reference point. For a three-foot
lead-in cable, the cursor should be set at 3.00 ft.
1–22
1503C MTDR Service Manual
Operating Instructions
n
o
ac 3.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–23: Cursor Moved to End of Three-Foot Lead-in Cable
3. Push STORE.
4. Turn the NOISE FIL TER control to 1 avg. The instrument is now in HORZ SET
REF , or delta mode. The distance window should now read 0.00 ft. As the cursor
is scrolled down the cable, the distance reading will now be from the new zero
reference point.
ac
O
N
O
F
F
O
F
F
O
F
F
0.00 ft
D
Figure 1–24: Cursor Moved to End of Three-Foot Lead-in Cable
NOTE. Vp changes will affect where the r eference is set on the cable. Be sure to set
the Vp first, then set the delta to the desired location.
5. To exit HORZ SET REF, use the following procedure:
a. Turn the NOISE FILTER control to HORZ SET REF.
b. Turn DIST/DIV to 1 ft/div. If the distance reading is extremely high, you
might want to use a higher setting initially , then turn to 1 ft/div for the next
adjustment.
c. Turn the
1503C MTDR Service Manual
POSITION control until the distance window reads 0.00 ft.
1–23
Operating Instructions
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
move cursor to reference and Press STORE
Figure 1–25: Cursor Moved to 0.00 ft
d. Push STORE.
e. Turn NOISE FILTER to desired setting.
Using Vertical Set
Reference
VERT SET REF works similar to HORZ SET REF except that it sets a reference
for gain (pulse height) instead of distance. This feature allows zeroing the dB scale
at whatever pulse height is desired.
1. Turn NOISE FIL TER fully counterclockwise. “Set Ref” will appear in the noise
averaging area of the LCD.
2. Adjust the incident pulse to the desired height (e.g., four divisions). It might be
necessary to adjust
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
return FILTER to desired setting ...
n
POSITION.
o
Figure 1–26: Incident Pulse at Four Divisions, FILTER at Desired Setting
3. Push STORE.
1–24
4. Return NOISE FILTER to the desired setting. Notice that the dB scale is now
set to 0.00 dB.
5. To exit VERT SET REF, use the following procedure:
a. Make sure the vertical scale is in dB mode (access the Setup Menu if change
is needed).
1503C MTDR Service Manual
b. Turn NOISE FILTER to VERT SET REF.
c. Adjust VERT SCALE to obtain 0.00 dB.
d. Push STORE.
e. Turn NOISE FILTER to desire filter setting.
Because dB is actually a ratio between the energy sent out and the energy reflected
back, using VERT SET REF does not affect the dB difference measured.
NOTE. Do not use Auto Pulse Width when making measur ements in VERT SET REF.
Auto Pulse Width changes the pulse width at 100, 500, and 5000 feet. If the pulse
width changes while in VERT SET REF, it could result in an erroneous reading.
Manually controlling the pulse width assur es the pulse width remains the same for
both the incident and reflective pulses.
Additional Features (Menu Selected)
Operating Instructions
Max Hold
The 1503C will capture and store waveforms on an ongoing basis. This is useful
when the cable or wire is subjected to intermittent or periodic conditions. The 1503C
will monitor the line and display any fluctuations on the LCD.
1. Attach the cable to the 1503C front-panel CABLE connector.
2. Push MENU to access the main menu.
3. Scroll to Setup Menu and push MENU again.
4. Scroll to Acquisition Control Menu and push MENU again.
5. Scroll to Max Hold is: Off and push MENU again. This line will change to Max
Hold is: On. The monitoring function is now ready to activate.
6. Repeatedly push MENU until the instrument returns to normal operation.
ac 0.00 ft
O
N
1503C MTDR Service Manual
O
N
Figure 1–27: Waveform Viewed in Normal Operation
1–25
Operating Instructions
7. When you are ready to monitor this cable for intermittents, push STORE. The
1503C will now capture any changes in the cable.
ac 0.12 ft
O
N
Captured
changes
O
N
Figure 1–28: Waveform Showing Intermittent Short
8. To exit monitor mode, push STORE again.
9. To exit Max Hold, access the Acquisition Control Menu again, turn off Max
Hold, and push MENU repeatedly until the instrument returns to normal
operation.
Pulse On/Off
This feature puts the 1503C in a “listening mode” by turning off the pulse generator .
1. Attach a cable to the 1503C front-panel CABLE connector.
2. Push MENU to access the Main Menu.
3. Scroll to Setup Menu and push MENU again.
4. Scroll to Acquisition Control Menu and push MENU again.
5. Scroll to Pulse is: On and push MENU again. This will change to Pulse is: Off.
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 1–29: Waveform Display with No Outgoing Pulses
1–26
6. Repeatedly press MENU until the instrument returns to normal operation.
This feature allows the 1503C to act much like a non-triggered oscilloscope. In this
mode, the 1503C is acting as a detector only . Any pulses detected will not originate
1503C MTDR Service Manual
Operating Instructions
from the instrument, so any distance readings will be invalid. If you are listening
to a local area network, for example, it is possible to detect traffic, but not possible
to measure the distance to its origin.
Pulse is: Off can be used in conjunction with Max Hold is: On.
7. T o exit Pulse is: Off, access the Acquisition Contr ol Menu again, turn the pulse
back on, then repeatedly push MENU until the instrument returns to normal
operation.
Single Sweep
The single sweep function will acquire one waveform only and display it.
1. Attach a cable to the 1503C front-panel CABLE connector.
2. Push MENU to access the Main Menu.
3. Scroll to Setup Menu and push MENU again.
4. Scroll to Acquisition Control Menu and push MENU again.
5. Scroll to Single Sweep is: Off and push MENU again. This will change to Single
Sweep is: On.
6. Repeatedly press MENU until the instrument returns to normal operation.
7. When you are ready to begin a sweep, push VIEW INPUT. A sweep will also
be initiated when you change any of the front-panel controls. This allows you
to observe front panel changes without exiting the Single Sweep mode.
As in normal operation, averaged waveforms will take longer to acquire.
ac 0.00 ft
O
F
F
1503C MTDR Service Manual
O
F
F
O
F
F
O
F
F
Figure 1–30: A Captured Single Sweep
8. To exit Single Sweep is: On, access the Acquisition Control Menu again, turn
the Single Sweep back off, then repeatedly push MENU until the instrument
returns to normal operation.
1–27
Operating Instructions
1–28
1503C MTDR Service Manual
Operator Performance Checks
This chapter contains performance checks for many of the functions of the 1503C.
They are recommended for incoming inspections to verify that the instrument is
functioning properly . Procedures to verify the actual performance requirements are
provided in the Chapter 6.
Performing these checks will assure you that your instrument is in good working
condition. These checks should be performed upon receipt of a new instrument or
one that has been serviced or repaired. It does not test all portions of the instrument
to Calibration specifications.
The purpose of these checks is not to familiarize a new operator with the instrument.
If you are not experienced with the instrument, you should read the Operating
Instructions chapter of this manual before going on with these checks.
If the instrument fails any of these checks, it should be serviced. Many failure modes
affect only some of the instrument functions.
Equipment Required
Item Tektronix Part Number
50 precision terminator 011–0123–00
93 10-foot coaxial cable 012–1351–00
Getting Ready
Power On
Metric Instruments
1503C MTDR Service Manual
Disconnect any cables from the front-panel CABLE connector. Connect the
instrument to a suitable power source (a fully charged optional battery pack or AC
line source). If you are using AC power, make sure the fuse and power switch are
correct for the voltage you are using (115 VAC requires a different fuse than
230 VAC).
Pull the POWER switch on the front panel. If a message does not appear on the
display within a second or two, turn the instrument off. There are some failure modes
that could permanently damage or ruin the LCD if the power is left on for more than
a minute or so. Refer to the Troubleshooting section of the Maintenance chapter in
this manual.
Option 05 instruments default to metric; however, you can change the metric scale
to ft/div in the Setup Menu or use the metric numbers provided. To change the
readings, press the MENU button. Using the
Setup Menu and press MENU again. Scroll down to Distance/Div is: m/div and press
MENU again. This will change to ft/div. Press the MENU button repeatedly to
n
POSITION control, scroll down to
o
2–1
Operator Performance Checks
return to normal operation mode. If the instrument power is turned off, these checks
must be repeated again when the instrument is powered on again.
Set Up
1. Horizontal Scale
(Timebase) Check
Set the 1503C front-panel controls:
IMPEDANCE 93
NOISE FILTER 1 avg
VERT SCALE 10.00 dB
DIST/DIV 2 ft/div (0.25 m)
Vp .84
PULSE WIDTH 2 ns
If the instrument fails this check, it must be repaired before any distance
measurements can be made with it.
1. Turn the 1503C power on. The display should look very similar to Figure 2–1.
bat 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
2–2
Figure 2–1: Start-up Measurement Display
2. Connect the 10-foot cable to the front-panel CABLE connector. The display
should now look like Figure 2–2.
bat 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–2: Measurement Display with 10-foot Cable
1503C MTDR Service Manual
Operator Performance Checks
n
3. Using the
o
POSITION control, measure the distance to the rising edge of the
waveform at the open end of the cable. The distance shown on the display
distance window (upper right corner of the LCD) should be from 9.7 to 10.3 feet
(2.95 to 3.14 m).
bat 10.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–3: Cursor at End of 10-foot Cable
n
o
4. Change the Vp to .30. Using the
POSITION control, measure the distance
to the rising edge of the waveform at the open end of the cable. The distance
shown on the display distance window (upper right corner of the LCD) should
be from 3.50 to 3.70 feet (1.05 to 1.11 m).
bat 3.60 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–4: Cursor at End of 10-foot Cable, Vp Set to .30
5. Remove the 10-foot cable and connect the 50 terminator. Change the 1503C
front-panel controls to:
VERT SCALE 0.00 dB
DIST/DIV 5000 ft/div (1000 m/div)
PULSE WIDTH 1000 ns
n
o
6. Turn the
POSITION control clockwise until the display distance window
reads a distance greater the 50,000 feet (15,259 m). The waveform should
1503C MTDR Service Manual
2–3
Operator Performance Checks
remain a flat line from zero to this distance.
bat 50600.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–5: Flatline Display Out to 50,000+ Feet
2. Vertical Position
(Offset) Check
If the instrument fails this test, it can be used, but should be serviced when possible.
Not all of the waveforms will be viewable at all gain settings.
n
1. Using the
POSITION control, verify that the entire waveform can be moved
o
to the very top of the display (off the graticule area).
bat 50600.00 ft
Waveform
O
N
O
F
F
O
F
F
O
F
F
off display
Figure 2–6: Waveform Off the Top of the Display
n
2. Using the
POSITION control, verify that the entire waveform can be moved
o
to the very bottom of the display (to the bottom graticule line).
2–4
1503C MTDR Service Manual
bat 50600.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–7: Waveform at the Bottom of the Display
Operator Performance Checks
Waveform
3. Noise Check
If the instrument fails this check, it may still be usable for measurements of large
faults that do not require a lot of gain. A great deal of noise reduction can be made
using the NOISE FILTER control. Send your instrument to be serviced when
possible.
1. Set the PULSE WIDTH to 2 ns. Using the
n
POSITION control and VERT
o
SCALE control, set the gain to 57 dB with the waveform centered vertically in
the display.
bat 50600.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–8: Waveform with Gain at 57 dB
2. Press MENU.
1503C MTDR Service Manual
3. Using the
n
POSITION control, select Diagnostics Menu.
o
4. Press MENU again.
n
5. Using the
POSITION control, select Service Diagnostic Menu.
o
6. Press MENU again.
n
7. Using the
POSITION control, select Noise Diagnostics.
o
8. Press MENU again and follow the instructions on the display.
2–5
Operator Performance Checks
9. Exit from Noise Diagnostics, but do not exit from the Service Diagnostic Menu
yet.
4. Offset/Gain Check
5. Impedance Check
If the instrument fails this check, it should not be used for loss or impedance
measurements. Send it to be serviced when possible.
1. In the Service Diagnostic Menu, select the Offset/Gain Diagnostic and follow
the directions on the display.
There are three screens of data presented in this diagnostic. The Pass/Fail level is
3% for any single gain setting tested.
2. Exit from Offset/Gain Diagnostic, but do not leave the Service Diagnostic
Menu yet.
If the instrument fails this check, it should not be used for loss or impedance
measurements.
1. In the Service Diagnostic Menu, select the Impedance Diagnostic and follow
the directions on the screen. Passable tolerances are:
50 W 47.0 to 50.0 W
75 W 71.0 to 75.0 W
93 W 88 to 93 W
125 W 118 to 125 W
6. Sampling Efficiency
Check
7. Aberrations Check
2. Exit from the Impedance Diagnostic, but do not leave the Service Diagnostic
Menu yet.
If the instrument fails this check, the waveforms might not look normal. If the
efficiency is more than 100%, the waveforms will appear noisy . If the efficiency is
below the lower limit, the waveform will take longer (more pixels) to move from
the bottom to the top of the reflected pulse. This smoothing effect might completely
hide some faults that would normally only be one or two pixels wide on the display .
1. In the Service Diagnostic Menu, select Sampling Efficiency and follow the
directions on the screen.
2. When done with the test, press the MENU button repeatedly until the instrument
returns to normal operation.
If the aberrations are too large, they can be confused with minor faults in the cable
near the instrument.
n
1. Turn the
o
POSITION control counterclockwise until the display distance
window reads less than 20.00 ft (6.10 m).
2–6
1503C MTDR Service Manual
Operator Performance Checks
2. Set the DIST/DIV control to 1 ft/div (0.25 m/div).
ac –2.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–9: Distance at –2.00 ft
n
o
3. Turn the
POSITION control counterclockwise until the display distance
window reads –2.00 ft (–0.62 m).
4. Set the 1503C front-panel controls:
IMPEDANCE 50 W
NOISE FILTER 1 avg
VERT SCALE 0.00 dB
PULSE WIDTH 2 ns
Vp .99
5. Connect the 50 W precision terminator to the front panel.
6. Turn the NOISE FILTER control completely counterclockwise to the VERT
SET REF position.
7. Use VERT SCALE to increase the height of the pulse to four major divisions.
ac –2.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 2–10: Pulse Adjusted to Four Major Divisions in Height
1503C MTDR Service Manual
8. Press STORE.
9. Turn the NOISE FILTER control back to 1 avg.
2–7
Operator Performance Checks
10. Place the baseline of the waveform on the center graticule using the
n
POSITION control.
o
11. Increase VERT SCALE to 25.00 dB
n
o
12. Using the
POSITION control, verify that the aberrations are less than four
divisions high out to 10 feet (3.05 m).
ac
O
N
O
F
F
O
F
F
O
F
F
10.00 ft
Figure 2–11: Waveform Centered, Cursor at 10.00 ft
13. Return the cursor to –2.00 ft (–0.61 m).
14. Turn NOISE FILTER back to VERT SET REF.
15. Set the DIST/DIV to 2 ft/div (0.5 m/div).
16. Turn PULSE WIDTH to 10 ns.
17. Adjust the pulse height to four major divisions.
ac –2.00 ft
2–8
O
N
O
F
F
O
F
F
O
F
F
Figure 2–12: Pulse Adjusted to Four Major Divisions in Height
18. Press STORE.
19. Return the NOISE FILTER control to 1 avg.
1503C MTDR Service Manual
Operator Performance Checks
20. Place the baseline of the waveform on the center graticule using the
n
POSITION control.
o
21. Increase VERT SCALE to 30.00 dB.
n
o
22. Using the
POSITION control, verify that the aberrations are less than four
divisions high out to 30 feet (9.15 m)
ac
O
N
O
F
F
O
F
F
O
F
F
30.00 ft
Figure 2–13: Aberrations Less Than Four Divisions Out to 30.00 ft
23. Return the cursor to –2.00 ft (–0.61 m).
24. Turn NOISE FILTER back to VERT SET REF.
25. Set the DIST/DIV to 50 ft/div (10 m/div).
26. Turn PULSE WIDTH to 100 ns.
27. Adjust the pulse height to four major divisions.
1503C MTDR Service Manual
ac
O
N
O
F
F
O
F
F
O
F
F
–2.00 ft
Figure 2–14: Pulse Adjusted to Four Major Divisions in Height
28. Press STORE.
29. Return the NOISE FILTER control to 1 avg.
2–9
Operator Performance Checks
30. Place the baseline of the waveform on the center graticule using the
n
POSITION control.
o
31. Increase VERT SCALE to 30.00 dB.
n
o
32. Using the
POSITION control, verify that the aberrations are less than four
divisions high out to 300 feet (91.50 m).
ac
O
N
O
F
F
O
F
F
O
F
F
300.00 ft
Figure 2–15: Aberrations Less Than Four Divisions Out to 300.00 ft
33. Return the cursor to –2.00 ft (–0.61 m).
34. Turn NOISE FILTER back to VERT SET REF.
35. Set the DIST/DIV to 500 ft/div (10 m/div).
36. Turn PULSE WIDTH to 1000 ns.
37. Adjust the pulse height to four major divisions.
ac
–2.00 ft
2–10
O
N
O
F
F
O
F
F
O
F
F
Figure 2–16: Pulse Adjusted to Four Major Divisions in Height
38. Press STORE.
39. Return the NOISE FILTER control to 1 avg.
40. Place the baseline of the waveform on the center graticule using the
n
POSITION control.
o
1503C MTDR Service Manual
41. Increase VERT SCALE to 30.00 dB.
n
o
42. Using the
POSITION control, verify that the aberrations are less than four
divisions high out to 3000 feet (915.00 m)
Operator Performance Checks
Conclusions
ac
O
N
O
F
F
O
F
F
O
F
F
3000.00 ft
Figure 2–17: Aberrations Less Than Four Divisions Out to
3000.00 ft
If the instrument failed Aberrations or Sampling Efficiency checks, it is probably
still adequate for all but extremely minor fault measurements. If it failed the
Horizontal Scale check, you should not use the instrument until the cause of the
failure has been identified and corrected.
All of the previous checks only test the major functional blocks of the instrument
that could prevent you from being able to make measurements. It is possible for the
front-panel controls or the LCD to have problems that would interfere with
controlling or displaying measurements. Most problems of this type would become
evident as you perform the checks. If you suspect a problem of this nature, you
should have the instrument checked by a qualified service technician.
1503C MTDR Service Manual
If the instrument passed all of the previous checks, it is ready for use.
If your instrument is equipped with Option 06 (Ethernet), refer to Calibration,
Chapter 6.
2–11
Operator Performance Checks
2–12
1503C MTDR Service Manual
Specifications
The tables in this chapter list the characteristics and features that apply to this
instrument after it has had a warm-up period of at least five minutes.
The Performance Requirement column describes the limits of the Characteristic.
Supplemental Information describes features and typical values or other helpful
information.
Electrical Characteristics
Characteristic Performance Requirement Supplemental Information
Test Pulse
Width
Accuracy
Pulse Amplitude
T erminated
Selected: 2 ns, 10 ns, 100 ns, 1000 ns
2 ns "1 ns; 10 ns, 100 ns, 1000 ns "10%
–2.5 VDC "10% for 10 ns, 100 ns, 1000 ns;
2 ns "20%
Measured at half sine amplitude point with
matching termination.
Unterminated
Pulse Shape 1/2 sine
Pulse Output Impedance
Accuracy
Pulse Repetition Time 350 s nominal
Vertical
Scale
Accuracy
Set Adjustment
Vertical Position
Displayed Noise
Random
Aberrations
–5.0 VDC "10% for 10 ns, 100 ns, 1000 ns Internal cable length prevents 2 ns pulse from
Selected: 50 , 75 , 93 , 125
1%
0 dB to 63.75 dB gain
"3%
Set incident pulse within "3%
Any waveform point moveable to center screen.
v"1.0 division peak with 57 dB gain,
filter set to 1
v"1.0 division peak with 63 dB gain,
filter set to 8
v–30 dB p–p for 10 ns, 100 ns, 1000 ns test
pulse
v–25 dB p–p for 2 ns test pulse
reaching full unterminated voltage
256 values at 0.25 dB increments
Combined with vertical scale control.
With matching terminator at panel. Beyond
three test pulse widths after test pulse.
Within three test pulse widths after test pulse.
dB is relative to test pulse.
(continued next page)
1503C MTDR Service Manual
3–1
Specifications
Characteristic Performance Requirement Supplemental Information
Cable Connection
Coupling
Capacitively coupled
Max Input Susceptibility
Distance Cursor Resolution 1/25 of 1 major division
Cursor Readout
Range
Resolution
Accuracy
Horizontal
Scale
Range
Horizontal Position Any distance to full scale can be moved on
Vp
Range
Resolution
Accuracy
Custom Option Port Tek chart recorder is designed to operate with
Line Voltage 115 VAC (90 to 132 V AC) 45 to 440 Hz
Battery Pack
Operation
Full Charge Time
"400 V (DC + peak, AC at maximum frequency of 440 Hz). No damage with application for
up to 30 seconds (might affect measurement
capability).
–2 ft to w50,000 ft (–0.61 m to 15,230 m)
0.04 ft
Within 2% "0.02 ft at 1 ft/div
1 ft/div to 5000 ft/div (0.25 m/div to 1000 m/div)
12 values: 1, 2, 5 sequence
0 to 50,000 ft (0 to 10,000 m)
screen
0.30 to 0.99
0.01
within "1%
230 VAC (180 to 250 VAC) 45 to 440 Hz
8 hours minimum, 30 chart recordings maximum
20 hours maximum
5 digit readout
Vp must be set within "0.5% of cable
Propagation velocity relative to air
the 1503C. Produces a high resolution thermal
dot matrix recording and waveform and control
values.
Fused at 0.3 A
Fused at 0.15 A
+15° C to +25° C charge and discharge temperature, LCD backlight off. Operation of instrument with backlight on or at temperatures below
+10° C will degrade battery operation specification
Overcharge Protection
Discharge Protection
Charge Capacity
Charge Indicator
3–2
Charging discontinues once full charge is
attained
Operation terminates prior to battery damage
3.4 Amp-hours typical
Bat/low will be indicated on LCD when capacity
reaches approximately 10%
1503C MTDR Service Manual
Environmental Characteristics
Characteristic Performance Requirement Supplemental Information
T emperature
Operating
–10° C to +55° C
Specifications
Battery capacity reduced at other than +15°C to
+25°C
Non-operating
Humidity to 100%
Altitude
Operating
Non-operating
Vibration 5 to 15 Hz, 0.06 inch p–p
Shock, Mechanical
Pulse
Bench Handling
Operating
Non-operating
Loose Cargo Bounce 1 inch double-amplitude orbital path at 5 Hz,
Water Resistance
Operating
–62° C to +85° C
to 10,000 ft
to 40,000 ft
15 to 25 Hz, 0.04 inch p–p
25 to 55 Hz, 0.013 inch p–p
30 g, 11 ms 1/2 sine wave, total of 18 shocks
4 drops each face at 4 inches or 45 degrees
with opposite edge as pivot
4 drops each face at 4 inches or 45 degrees
with opposite edge as pivot. Satisfactory operation after drops.
6 faces
Splash-proof and drip-proof
With battery removed. Storage temp with battery in is –20° C to +55° C. Contents on nonvolatile memory (stored waveform) might be lost
at temps below –40° C.
MIL–T–28800C, Class 3
MIL–T–28800C, Class 3
MIL–T–28800C, Class 3
MIL–STD–810, Method 516, Procedure V
Cabinet on, front cover off
Cabinet off, front cover off
MIL–STD–810, Method 514, Procedure XI,
Part 2
MIL–T–28800C, Style A
Front cover off
Non-operating
Salt Atmosphere Withstand 48 hours, 20% solution without
Sand and Dust Operates after test with cover on, non-operating MIL–STD–810, Method 510, Procedure I
Washability Capable of being washed
Fungus Inert Materials are fungus inert
Watertight with 3 feet of water above top of case
corrosion
Front cover on
(continued next page)
1503C MTDR Service Manual
3–3
Specifications
Certifications and Compliances
Category Standard or description
EC Declaration of Conformity –
EMC
Australia/New Zealand
Declaration of Conformity – EMC
EMC Compliance Meets the intent of Directive 89/336/EEC for Electromagnetic Compatibility when it is used with the
FCC Compliance Emissions comply with FCC Code of Federal Regulations 47, Part 15, Subpart B, Class A Limits.
Safety Standards
U.S. Nationally Recognized
Testing Laboratory Listing
Canadian Certification CAN/CSA C22.2 No. 231 CSA safety requirements for electrical and electronic measuring and
European Union Compliance Low Voltage Directive 73/23/EEC, amended by 93/68/EEC
Meets intent of Directive 89/336/EEC for Electromagnetic Compatibility . Compliance was demonstrated
to the following specifications as listed in the Official Journal of the European Union:
EN 50081-1 Emissions:
EN 55022 Class B Radiated and Conducted Emissions
EN 60555-2 AC Power Line Harmonic Emissions
EN 50082-1 Immunity:
IEC 801-2 Electrostatic Discharge Immunity
IEC 801-3 RF Electromagnetic Field Immunity
IEC 801-4 Electrical Fast T ransient/Burst Immunity
IEC 801-5 Power Line Surge Immunity
Complies with EMC provision of Radiocommunications Act per the following standard(s):
AS/NZS 2064.1/2 Industrial, Scientific, and Medical Equipment: 1992
product(s) stated in the specifications table. Refer to the EMC specification published for the stated
products. May not meet the intent of the directive if used with other products.
UL1244 Standard for electrical and electronic measuring and test equipment.
test equipment.
EN 61010-1/A2 Safety requirements for electrical equipment for measurement,
control, and laboratory use.
Additional Compliance IEC61010-1/A2 Safety requirements for electrical equipment for measurement,
control, and laboratory use.
Safety Certification Compliance
Equipment Type Test and measuring
Safety Class Class 1 (as defined in IEC 61010-1, Annex H) – grounded product
Overvoltage Category Overvoltage Category II (as defined in IEC 61010-1, Annex J)
Pollution Degree Pollution Degree 3 (as defined in IEC 61010-1).
Installation (Overvoltage)
Category
Terminals on this product may have different installation (overvoltage) category designations. The
installation categories are:
CA T III Distribution-level mains (usually permanently connected). Equipment at this level is
typically in a fixed industrial location.
CA T II Local-level mains (wall sockets). Equipment at this level includes appliances, portable
tools, and similar products. Equipment is usually cord-connected.
CA T I Secondary (signal level) or battery operated circuits of electronic equipment.
(continued next page)
3–4
1503C MTDR Service Manual
Specifications
Category Standard or description
Pollution Degree A measure of the contaminates that could occur in the environment around and within a product.
Typically the internal environment inside a product is considered to be the same as the external. Products
should be used only in the environment for which they are rated.
Pollution Degree 1 No pollution or only dry, nonconductive pollution occurs. Products in this
category are generally encapsulated, hermetically sealed, or located in
clean rooms.
Pollution Degree 2 Normally only dry, nonconductive pollution occurs. Occasionally a
temporary conductivity that is caused by condensation must be
expected. This location is a typical office/home environment. Temporary
condensation occurs only when the product is out of service.
Pollution Degree 3 Conductive pollution, or dry, nonconductive pollution that becomes
conductive due to condensation. These are sheltered locations where
neither temperature nor humidity is controlled. The area is protected from
direct sunshine, rain, or direct wind.
Pollution Degree 4 Pollution that generates persistent conductivity through conductive dust,
rain, or snow. Typical outdoor locations.
Physical Characteristics
Characteristic Description
Weight
without cover
with cover
with cover, chart recorder, and battery pack
Shipping Weight
domestic
export
Height 5.0 inches (127 mm)
Width
with handle
without handle
Depth
with cover on
with handle extended to front
14.5 lbs (6.57 kg)
16 lbs (7.25 kg)
20 lbs (9.07 kg)
25.5 lbs (11.57 kg)
25.5 lbs (11.57 kg)
12.4 inches (315 mm)
11.8 inches (300 mm)
16.5 inches (436 mm)
18.7 inches (490 mm)
1503C MTDR Service Manual
3–5
Specifications
3–6
1503C MTDR Service Manual
Options and Accessories
The following options are available for the 1503C MTDR:
Option 04: YT–1 Chart Recorder
Option 04 instruments come equipped with a chart printer. Refer to the YT–1/ YT–1S
Chart Recorder Instruction Manual that comes with this option for instructions on
operation, paper replacement, and maintenance.
Option 05: Metric Default
Option 05 instruments will power up in the metric measurements mode. Standard
measurements may be selected from the menu, but metric will be the default.
Option 06: Ethernet
Option 06 instruments include circuitry that allows the 1503C to test an Ethernet
bus using time-domain reflectometry with minimum disruption to the IEEE 802.3
protocol.
What is Ethernet?
Ethernet was invented by the Xerox Corporation in 1973 to allow various data
devices to use a common communications bus. In an Ethernet system, signals flow
in all directions and the transceivers attached to the Ethernet receive all
transmissions.
Ethernet cable is typically 50
reflections. Reflections can interfere with transmissions sent out by the system.
ThinWire, Cheapernet, and Thin Ethernet are variations of Ethernet. These are
usually used as a branch of the main network with a limited number of stations. They
use a more flexible cable and are usually connected to each Media Access Unit
(MAU) with a T-connector instead of a tap.
Segments are the smaller sub-networks in an Ethernet system. Each segment can
be up to 500 meters long and have up to 100 transceiver taps. Each tap must have
at least 2.5 meters of cable between itself and the next tap.
with 50 terminators at each end to prevent signal
1503C MTDR Service Manual
4–1
Options and Accessories
Main
Frame
Term
Server
Main
Frame
Server
Host
PrinterPrinter
Server
Host
Server
Term
Main
Frame
Main
Frame
Host
Foreign
Host
Fiber
Optic
Link
Bridge
Gateway
Main
Frame
Main
Frame
PC PC
Figure 4–1: A Typical Ethernet System
T ransceivers transmit data to and from the stations on the Ethernet bus. The typical
Ethernet data rate is 10 million bits per second. At each tap is a transceiver (MAU)
sending and receiving this data. They also provide electrical isolation between the
coaxial cable and the station as well as housing the electronics that detect carrier
signals and recognize the collision of two signals.
MicroĆ
Computer
Network
PC
MicroĆ
Computer
4–2
1503C MTDR Service Manual
Options and Accessories
Taps are what the transceivers are attached to.
A bridge connects several network segments. Depending on the hardware used
(e.g., fiber optics), a network might extend up to 22,000 meters.
Repeaters are used to increase the effective length of a cable to allow more
transceivers. Due to distance limitations, two transceivers can have a maximum of
two repeaters between them.
Servers let a network share resources, such as terminals, disks, printers, etc.
The 1503C with Option 06 allows testing of an Ethernet bus while the network is
active. This is important because some installations might be interactive with other
installations that are dependent on the Ethernet. Physically, Option 06 is a
piggyback circuit board attached to the Sampler/Pulser board in the 1503C. A
special EPROM replaces the standard EPROM on the main board, allowing Option
06 to be transparent to the standard instrument, but accessible through the Ethernet
Menu and the Setup/Acquisition Menu.
Option 06 performs three functions:
Test Procedures for a
Working Network
H A 50 terminator for the network
H Generates a DC signal that emulates the –1.05 VDC carrier signal
H Generates a DC signal that emulates the –1.7 VDC collision signal.
Before Starting, here are some things you should know to make Ethernet tests easier:
H You need Option 06 for testing an active network.
H Make measurements from the end of a segment.
H If possible, isolate the segment you plan to test.
H Use the shortest pulse width possible.
H Do not use Auto pulse width mode. If it selects the 100 ns or 1000 ns pulse, it
might disrupt traffic on working networks.
H Use the simplest possible test first.
H Operate the 1503C on AC power when using the option chart printer.
H Changes made in the menus do not take effect until the instrument is returned
to normal operation. This prevents erroneous menu selections from creating
disruptions.
1503C MTDR Service Manual
H Have the network documentation ready. If available, have prior TDR profiles
of the network that you will be comparing.
4–3
Options and Accessories
H If possible, turn off repeaters and bridges to other networks to minimize the
extent of a possible disruption the 1503C might cause.
H If you use a jumper cable, make sure that it matches the network cable
impedance. The three-foot jumper furnished with the instrument is 50 .
Introduction
The IEEE 802.3 standard recommends only one earth ground per segment. When
connected to AC power, the 1503C provides an earth ground to the coaxial shield.
There is no connection to ground when the 1503C is used with the optional battery
pack and the AC power cord is disconnected.
The first test usually run on an active network is the normal sweep with the 2 ns or
10 ns pulse and the DC 50 W termination is: On from the Ethernet Menu. This test
provides basic TDR tests with a 50 W termination for the net. If the network traffic
is low (3 to 4%), this test is very effective. The 2 ns and 10 ns pulses are narrower
than the time occupied by a single bit and usually will not cause any collisions. All
other tests in the Ethernet Menu have potentially destructive effects on working
networks.
CAUTION. The test just described should find most problems. Before going any
further, know what you are doing. Carrier and collision tests have the potential of
causing problems on an active network. Read the warnings and instructions
carefully. Try to limit tests to one segment during times of low traffic.
The second test is the Single Sweep with Carrier is: Off/On. This test asserts the
carrier signal of –1.05 V, then single-sweeps the network and drops the carrier
signal. The test occupies the network for one to 20 seconds, depending on the
NOISE FILTER setting.
Basic Test Procedure
4–4
The third test, Carrier Test is: Off/On, helps track down transceivers suspected if
ignoring the carrier sense signal. This test holds the carrier signal of –1.05 V, turns
off the pulse, and turns on MAX HOLD. The 1503C then acts as a traffic monitor.
If spikes appear on the display, it is likely a transceiver is not responding to the
carrier signal and is “babbling.”
The following procedure describes the fundamental tests with 50 W DC termination
is: On. When performing other Ethernet tests, use essentially the same procedure.
A full description of individual tests, including custom tests, follows:
If you wish to disconnect and reconnect the 1503C to the cable segment, use a BNC
T-connector between the instrument and a 50 W jumper cable (e.g., RG-58U). To
one side of the T-connector, connect a 50 W terminator (the double termination is
about a 25 W mismatch – much less likely to cause problems than an open circuit).
The terminator can be removed during testing, allowing the 1503C to become the
50 W load. When removing the 1503C (or there is a power failure), the terminator
1503C MTDR Service Manual
Options and Accessories
should be reconnected, restoring the normal 50 W load for the network. The BNC
T-connector also allows another point of access for an oscilloscope if you need to
look for signal quality or noise levels.
Once the 1503C 50 W termination has been turned on, tests are similar to standard
measurements on an coaxial 50 W cable. Remember to use only the 2 ns or 10 ns
pulse widths. However, the waveforms might be a little different, due to traffic on
the network.
Following are suggestions on how to set up test fixtures that will provide flexibility
and provide network safety in case of power interruptions to the 1503C.
Ethernet Ethernet
50 terminator
To 1503C
Front Panel
Before Testing During T esting
Male type N
To 1503C
Front Panel
50 terminator
To 1503C
Front Panel
Figure 4–2: N-Type Male T-Connector
Before Testing During Testing
To 1503C
Front Panel
Female to Female
BNC to BNC
Female to Female
BNC to BNC
Male type N
50 terminator
1503C MTDR Service Manual
Female type N
50 terminator
Ethernet
Female type N
Ethernet
Figure 4–3: N-Type Female T-Connector
1. Before removing the Ethernet cable terminator, make sure you have the correct
adapters and cables ready.
4–5
Options and Accessories
2. Set the 1503C front-panel controls:
CABLE see below
IMPEDANCE 50 W
NOISE FILTER 1 avg
VERT SCALE see below
DIST/DIV appropriate setting for cable length
PULSE WIDTH 2 ns or 10 ns *
Vp to cable specifications
POWER ON (see below)
CAUTION. * DO NOT use the Auto pulse width mode. The longer pulses will cause
problems on working networks.
3. Request the system administrator to notify network users of possible
disruptions.
4. Using the POSITION control, access the Ethernet Menu.
5. Scroll to 50 W DC Termination is: Off and turn it On.
6. Return to normal operation.
7. As previously described, connect one end of a 50 W jumper cable to the front-
panel CABLE connector, then connect the other end to one side of the BNC
T-connector (see Figures 4–2 and 4–3).
8. Connect the Ethernet cable to the BNC T-connector.
9. Remove the 50 terminator.
At this point, you are testing on an active network.
CAUTION. The 50 W termination of the 1503C is not maintained with the power off.
In case of power failure, immediately replace the 50 W terminator on the BNC
T-connector.
10. With the NOISE FILTER set at 1 avg, traffic will appear as large random noise
spikes. If the traffic is severe enough to make measurements difficult, increase
the NOISE FILTER setting.
NOTE. The traffic on the display has no relationship to where it came from on the
cable. In fact, traffic can appear on the display beyond the end of the cable.
4–6
11. A VERT SCALE setting of 30 dB will normally allow you to see normal taps
at the near end of a network. Greater distances might require more gain,
depending on the loss of the cable and the pulse width.
1503C MTDR Service Manual
Options and Accessories
Descriptions of Test in the
Ethernet Menu
The following tests are composed of several functions found in the Acquisition
Control Menu. These combinations are displayed in the Ethernet Menu as a user
convenience. Most of the tests in the Ethernet Menu can be recreated or modified.
That is explained at the end of this section.
Changes made in the Ethernet Menu will affect some of the Setup Menu and
Acquisition Control Menu functions. For example, if Carrier Test is: Off/On is
turned on, the 50 W termination will also be turned on because it is necessary for
the carrier test to work.
50 W DC Termination is: Off/On
CAUTION. This must be on when testing on a working network or reflections will
cause collisions on the network.
This entry is a duplicate of the entry in the Setup Menu/Acquisition Control Menu.
Its function is to allow direct control of the termination inside the 1503C. With the
50 W DC termination on, the 1503C will function normally as a cable tester. This
is usually the only test needed to check a network cable.
CAUTION. The 100 ns and 1000 ns pulses might cause collisions.
Longer pulses are more likely to generate collisions than shorter pulses. On
networks with traffic less than 3 to 4%, a 2 ns pulse causes no measurable change
in network statistics. Even on heavily tapped cables, the 2 ns pulse can usually be
used for distances to 700 feet. The 10 ns pulse should be suitable for those longer
segments that still fall within the 802.3 specifications (under 500 meters).
Single Sweep with Carrier is: Off/On
CAUTION. This can interrupt prior traffic and cause late collisions. It can also
disrupt devices or applications that require periodic network traffic.
When this test is selected, the 1503C will assert a –1.05 VDC signal on the net long
enough to take a single waveform at the NOISE FILTER level selected. This is the
equivalent to the average voltage level of a normal transmission and should cause
the transceivers to assert Carrier Detect. This has the effect of causing most devices
on the net to defer transmission until the 1503C is finished. This takes from about
one to 20 seconds, depending on noise averaging, and reduces the traffic displayed
on the waveform.
1503C MTDR Service Manual
4–7
Options and Accessories
NOTE. Movement of any control that would change or move the waveform will start
a new sweep and assert the –1.05 VDC. For example, if you use the vertical position
control continuously for 20 seconds, you would be asserting the false traffic for that
duration and you are likely to disrupt the network.
Carrier Test is: Off/On
CAUTION. This carrier signal will stop traffic on the network. This might abort many
application programs and might cause communications problems.
This test asserts the –1.05 VDC signal on the network, turns off the normal 1503C
pulse, and sets up the MAX HOLD mode. This is intended to help find transceivers
that have a faulty Carrier Detect.
T o use this test, have the network prepared for disruption and turn the test on via the
Ethernet Menu. Any traffic observed is being transmitted in spite of a signal
simulating a carrier. This might be due to a transceiver not asserting its carrier detect
line, a host not reading its carrier detect line, or some other reason. This is not
unusual with some equipment. One way to isolate which units are doing this is to
disconnect them one at a time until it stops.
Descriptions of Tests in
the Setup Menu/
Acquisition Control Menu
Collision Test is: Off/On
CAUTION. The collision signal will stop traffic on the network. This might abort
many application programs and might cause communications problems.
This test is similar to the carrier test except that it asserts a –1.7 VDC signal to
simulate a collision on the network.
The entries in this menu allow you to set up custom tests on networks in addition
to the preset ones in the Ethernet Menu. This is intended for users who are familiar
enough with Ethernet to anticipate the results. Changes in this menu can affect the
state of other entries that are mutually exclusive or necessary for the chosen entry .
For example, turning on the Collision Output Signal is: Off/On will also turn off the
carrier output signal because only one voltage can be sent out.
Only the function of the entries unique to Option 06 will be explained. For the
others, refer to the Operating Instructions chapter of this manual.
4–8
1503C MTDR Service Manual
Options and Accessories
50 W DC Termination is: Off/On
CAUTION. This must be on for use on a working network or reflections will cause
collisions on the network.
This entry is a duplicate of the entry in the Ethernet Menu. Its function is to allow
direct control of the low frequency termination inside the 1503C. With the 50 W DC
termination is: On, the 1503C will functions normally to test the cable. This is
usually the only test needed to check a network cable.
Carrier (–1.05V) Output Signal is: Off/On
CAUTION. The carrier signal will stop most traffic on the network. This might abort
many application programs and might cause communications problems.
When this test is on, the 1503C will assert a –1.05 VDC level on a 50 W load (–2.1
VDC open circuit). This signal is intended to be equivalent to the average of a
standard Ethernet transmission and should trigger the carrier detect circuit on all the
transceivers. Because most applications will defer transmission when this signal is
present, it can be used to test transceivers and systems, or to reduce traffic for 1503C
testing.
Collision (–1.7V) Output Signal is: Off/On
CAUTION. The collision signal will stop most traffic on the network. This might
abort many application programs and might cause communications problems.
When this test is on, the 1503C will assert a –1.7 VDC level on a 50 W load (–3.4
VDC open circuit). This signal is intended to be equivalent to the average of two
colliding Ethernet transmissions and should trigger the collision detect circuit on all
the transceivers. This should cause applications to back off and retry , then eventually
abort, as defined in the 802.3 standard. Therefore, it can be used to test units that
do not respond to this signal or to stop traffic for TDR testing.
Customizing Your Own Tests
1503C MTDR Service Manual
Access the Acquisition Control Menu located under the Setup Menu. The various
tests listed can be used in any combination. Remember that the tests will not be
activated until you return the 1503C to normal operation, so any combination can
be chosen, then activated.
4–9
Options and Accessories
Waveform Signatures
By now you probably have a good idea what traffic looks like on the display and how
you can use the NOISE FIL TER to reduce it. Other signatures might also appear on
the display.
Terminators are small reflections seen as stationary bumps and dips. A perfect
terminator would not reflect any energy , and theoretically would be invisible on the
1503C display . Because of small impedance dif ferences between the cable and the
terminator, a small amount of energy will be reflected. The signature of a terminator
tends to go either up or down. Because a terminator absorbs nearly all the energy
of a pulse, the normal ripples in the waveform (minor changes in impedance) will
not be present after a terminator. The point where the waveform becomes flat is a
clue to the location of a terminator.
Taps commonly have a characteristic down-then-up reflection. The TDR pulse will
continue to travel past a tap because only part of the pulse’s ener gy is reflected. This
allows the 1503C to read signatures well beyond taps.
Following are examples of tests made on two Ethernet systems:
ac 173.36 ft
O
N
O
F
F
O
F
F
O
N
Figure 4–4: System 1 – Tap Hidden by Traffic
(1 avg, 50 ft/div, 35 dB)
ac 173.36 ft
O
N
O
F
F
O
F
F
4–10
O
N
Figure 4–5: System 1 – Traffic and Tap Nearly Identical
(4 avg, 50 ft/div, 35 dB)
1503C MTDR Service Manual
ac 173.36 ft
O
N
O
F
F
O
F
F
O
N
Figure 4–6: System 1 – Tap Becoming Visible
(16 avg, 50 ft/div, 35 dB)
ac 173.36 ft
O
N
O
F
F
Options and Accessories
O
F
F
O
N
Figure 4–7: System 1 – Tap Quite Visible
(128 avg, 50 ft/div, 35 dB)
ac 173.36 ft
O
N
O
F
F
O
F
F
O
N
Figure 4–8: System 1 – No Traffic
(1 avg, 50 ft/div, 35 dB)
1503C MTDR Service Manual
4–11
Options and Accessories
19
ac 167.56 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–9: System 1 – Tap Expanded, No Traffic
(1 avg, 2 ft/div, 35 dB)
ac 0.00 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–10: System 2 – Cable w/ Revision One Repeater *
(1 avg, 200ft/div, 2.25dB)
* Revision One repeaters must sense collisions and place a jam signal on both segments. When using the
carrier sense voltage level while sending out pulses (e.g., Single Sweep with Carrier is: On) the pulses
might exceed the collision or traffic thresholds of the repeater, causing it to send back jamming packets
that are synchronized with the 1503C. This creates an unusual waveform that looks similar to data. As
a rule, repeaters should be shut down prior to testing a segment to prevent such occurrences.
ac 484.56 ft
O
N
O
F
F
O
F
F
O
F
F
4–12
Figure 4–11: System 2 – First Tap, No Traffic
(1 avg, 1 ft/div, 44.5 dB)
1503C MTDR Service Manual
ac 484.56 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–12: System 2 – Same Tap with 5% Traffic
(1 avg, 1 ft/div, 44.5 dB)
ac 484.56 ft
O
N
Options and Accessories
O
F
F
O
F
F
O
F
F
Figure 4–13: System 2 – Same Tap, Increased Averaging
(16 avg, 1 ft/div, 44.5 dB)
ac 742.52 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–14: System 2 – Farther Out, More Gain
(128 avg, 10 ft/div, 53.5 dB)
1503C MTDR Service Manual
4–13
Options and Accessories
ac 714.12 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–15: System 2 – 1000-ft Cable at 10 ns
(128 avg, 100 ft/div, 43.75 dB)
ac 755.24 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–16: System 2 – Previous Waveform Expanded
(128 avg, 20 ft/div, 54.75 dB)
ac 1 116.84 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–17: System 2 – Next Group of Taps
(128 avg, 20 ft/div, 54.75 dB)
4–14
1503C MTDR Service Manual
ac 1034.44 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–18: System 2 – Group of Taps Expanded
(128 avg, 10 ft/div, 54.75 dB)
ac 1314.84 ft
O
N
Options and Accessories
O
F
F
O
F
F
O
F
F
Figure 4–19: System 2 – Another Group of Taps
(128 avg, 10 ft/div, 54.75 dB)
ac 1438.04 ft
O
N
O
F
F
O
F
F
O
F
F
Figure 4–20: System 2 – End of Cable
(128 avg, 20 ft/div, 61.25 dB)
1503C MTDR Service Manual
4–15
Options and Accessories
Electrical Characteristics
Following are the specifications for the Ethernet board:
Characteristic Performance Requirement Supplemental Information
DC Termination 50 , "1 See typical frequency response curve
below this table to estimate at other frequencies. Once the termination is
turned on, it will remain on until specifically turned off by the operator, at which
time a warning to remove the 1503C
from the network will be shown on the
display . Leaving the TDR on the network with the termination turned off will
cause traffic disruption and errors.
DC Voltage Offsets 0.0 V "0.02 V
–1.05 VDC and –1.7 VDC
"0.15 V into 50
Overvoltage
Protection
Floating Ground Only when used with battery pack. IEEE
AC pulse voltage is present on top of
DC offsets while measuring. Voltages
only asserted when 50 termination is
on.
Circuit cuts out leaving standard 1503C
protection for voltages greater than
"11 V.
802.3 specifies a single ground on the
bus.
70
Option 06
60
Board
1503C
50
Ohms
1503C with
Option 06
40
30
23
45678
1010101010101010
Frequency
Figure 4–21: Typical Frequency Response Curve with Ethernet Option 06
4–16
1503C MTDR Service Manual
Option 07: YT–1S Chart Recorder
Option 07 instruments come equipped with a splashproof chart printer. Refer to the
YT–1/ YT–1S Chart Recorder Instruction Manual that comes with this option for
instructions on operation, paper replacement, and maintenance.
Option 08: Token Ring Adapter
Option 08 instruments come with an adapter that allows you to connect the 1503C
to networks containing ECL connectors. The adapter isolates the receive pair from
the transmit pair at the ECL connector and allows you to select one or the other to
be routed to the input BNC connector on the 1503C.
Option 09: Universal Service Ordering Code
Option 09 instruments come with an adapter that allows you to connect the 1503C
to LANs using type RJ-45 connectors using the Universal Service Ordering Code.
The adapter allows selection of each of the four twisted pairs.
Options and Accessories
CAUTION. The RJ–45 USOC adapter (Option 09) is the same connector used for
many telephone installations. Active telephone wires will have 40 to 60 VDC on one
pair and this will destroy the 1502-series instrument. Do not use Option 09 with
1502, 1502B or 1502C instruments.
Option 10: Token Ring Interface
Option 10 instruments come with an adapter that allows you to connect the 1503C
to Token Ring networks via the MAU.
1503C MTDR Service Manual
4–17
Options and Accessories
Power Cord Options
The following power cord options are available for the 1503C TDR (for part
numbers, refer to the end of the Replaceable Mechanical Parts list). Note that these
options require inserting a 0.15 A fuse in the rear panel fuse holder.
NOTE. The only power cord rated for outdoor use is the standar d cord included with
the instrument (unless otherwise specified). All other optional power cords are
rated for indoor use only.
Option A1: 220 VAC, 16 A, Universal Europe
Option A2: 240 VAC, 13 A, United Kingdom
Option A3: 240 VAC, 10 A, Australia
Option A4: 240 VAC, 15A, North America
Option A5: 240 VAC, 6 A, Switzerland
4–18
1503C MTDR Service Manual
Accessories
Standard Accessories
Options and Accessories
The Standard and Optional accessory part numbers are provided at the end of the
Replaceable Mechanical Parts list.
Internal lead–gel Battery Assembly
Replacement Fuse (AC line fuse, 115 VAC)
Replacement Fuse (AC line fuse, 230 VAC)
Power Cord (outdoor rated)
Option Port Cover Assembly
50 W BNC Terminator
BNC Connector, female-to-female
93 W 10-foot Test Cable (S/N wB010625)
Optional Accessories
Connector, BNC female to Alligator Clips
BNC Connector male to N female (w/ Option 06 only)
50W 3-foot Test Cable (w/ Option 06 only)
Operator Manual
Slide Rule Calculator
Accessory Pouch
Service Manual (B01 instrument)
Service Manual (B02 instrument)
Battery
Chart Recorder, YT–1S
Chart Paper, single roll
Chart Paper, 25-roll pack
Chart Paper, 100-roll pack
(S/N wB010625)
1503C MTDR Service Manual
Cable, Interconnect, 360 inches
Connector, BNC male to BNC male
4–19
Options and Accessories
Connector, BNC female to Alligator Clip (S/N wB010625)
Connector, BNC female to Hook-tip Leads
Connector, BNC female to Dual Banana Plug
Connector, BNC male to Dual Binding Post
Connector, BNC male to N female
Connector, BNC female to N male
Connector, BNC female to UHF male
Connector, BNC female to UHF female
Connector, BNC female to Type F male
Connector, BNC male to Type F female
Connector, BNC female to GR
Connector, BNC male to GR
Precision 50 W Cable (S/N wB010625)
Terminator, 75 W BNC
Adapter, Direct Current
Isolation Network
Pulse Inverter
Token Ring Network Adapter
Twisted Pair Adapter – USOC Adapter
Star LAN Adapter
Token Ring Interface
4–20
1503C MTDR Service Manual
Circuit Descriptions
Introduction
This chapter describes how the instrument works. First is a circuit overview and how
it relates to the block diagram (Figure 5–1, next page). Following that are the
separate sections of the instrument, discussed in detail.
The 1503C uses time-domain reflectometry techniques to detect and display the
impedance characteristics of a metallic cable from one end of the cable. This is
accomplished by applying a narrow pulse to the cable and monitoring the resulting
voltage over a period of time. If the cable has a known propagation velocity , the time
delay to a particular reflection can be interpreted in cable distance. Amplitude of the
reflected voltage is a function of the cable impedance and the applied pulse and,
therefore, can be interpreted in dB or in rho.
The 1503C instrument is comprised of several subsections, as shown in the block
diagram (Figure 5–1). These are organized as a processor system, which controls
several peripheral circuits to achieve overall instrument performance.
The processor system reads the front-panel control settings to determine the cable
information that you selected for viewing. Distance settings are converted to
equivalent time values and loaded into the timebase circuits.
The timebase generates repetitive strobe signals to trigger the pulser/sampler
circuits. Pulse strobes cause a single pulse to be applied to the cable under test. Each
sampler strobe causes a single sample of the cable voltage to be taken during a very
short interval. The timebase precisely controls the time delay of the sample strobe
relative to the pulse strobe. When many sequential samples are recombined, a
replica of the cable voltage is formed. This sampling technique allows extremely
rapid repetitive waveforms to be viewed in detail.
1503C MTDR Service Manual
5–1
Circuit Descriptions
Cable
Front Panel Board
Drivers LCD
Controls, LCD Bias
and temp. compensation
Digital Bus
Main Board
CPU
Z80
RAM
ROM
Front End
Pulser Sampler
Timebase
Digital
Analog
Signal Processing
Decoding
Option Port
Power Supply
AC to DC
Converter
Figure 5–1: System Block Diagram
Offset Gain
A/D converter
Power Bus
Control
DC to DC
Converter
Battery
5–2
1503C MTDR Service Manual
Circuit Descriptions
Referring to the waveforms in Figure 5–2, cable voltage waveforms are shown at
the top. Each pulse is the result of a test pulse from the pulse generator and all pulses
are identical. At time delays (t
, t
, t
n
n+1
, etc.) after the pulses begin, a sample of
n+2
the pulse amplitude is taken. Each of these samples is digitized and stored in the
processor until sufficient points are accumulated to define the entire period of
interest. The samples are then processed and displayed at a much slower rate,
forming the recombined waveform as shown. This process allows the presentation
of waveforms too rapidly to be viewed directly.
Cable
voltage
tn tn+1 tn+2
Voltage
samples
Recombined
samples
Figure 5–2: Waveform Accumulation Diagram
Voltage samples from the pulser/sampler are combined with a vertical position
voltage derived from the front-panel control, then amplified. The amplifier gain is
programmed by the processor to give the selected vertical sensitivity. Each
amplified sample voltage is then digitized by an analog-to-digital converter and
stored in the processor memory.
When the processor has accumulated sufficient samples (251) to form the desired
waveform, the samples are formatted. This formatted data is then transferred to the
display memory . The display logic routes the data to each pixel of the LCD, where
each digital data bit determines whether or not a particular pixel is turned on or off.
Between each waveform, samples are taken at the leading edge of the 2 s pulse for
the timebase correction.
Cursor and readout display data is determined by the processor and combined with
the formatted sample waveform before it is sent to the display.
1503C MTDR Service Manual
5–3
Circuit Descriptions
Power Supply
Introduction
115/230 volt
AC line
EMI
Line
Filter
The power supply consists of the following:
H Primary Circuit
H Pre-regulator
H Battery Charger
H Deep Discharge Protection
H Port-regulator
H DC-to-DC Converters
The power supply converts either 115/230 VAC line power, or takes power from a
lead-gel battery, and provides the instrument with regulated DC voltages. A block
diagram of the power supply is shown in Figure 5–3.
Instr.
Pwr.
Fuse and
Line Select
Switch
Battery
+ 12 VDC
Step down
XFMR
Rectifier
&
Filter Cap.
+ 30 VDC + 15.8 VDC
Switcher
&
Prereq.
Battery
Charger
Switch
+ 10 to 15.5 VDC
Transistor Power Switch + 16.2 VDC
Deep
Discharge
Protection
Switcher and
Post–regulator
DC to DC
Converter
+ 16 VDC
5 VDC
±
15 VDC
±
Figure 5–3: Power Supply Block Diagram
Single-phase AC line voltage is applied to the power supply module through a
power plug with internal EMI filter. The filtered line voltage is immediately fused,
routed through a line selector switch and applied to a stepdown transformer. The
transformer secondary voltage is rectified and power switched to power the post
regulator.
DC Power
to Instrument
Power
Status
5–4
1503C MTDR Service Manual
Circuit Descriptions
A switching pre-regulator reduces this voltage to +15.8 VDC and is used to power
the battery charger. This voltage is also processed through a rectifier and power
switch to power the post-regulator.
If a battery is installed, the battery charger operates as a current source to provide
a constant charging current. Voltage limiting circuits in the charger prevent battery
overcharge by reducing the charge current as the battery voltages approaches +12.5
VDC.
The battery is lead-gel, providing a terminal voltage of 10 to 12.5 VDC, with a
nominal capacity of up to 2.0 Amp-Hours. It also is connected through a rectifier
to the instrument’s power switch and post-regulator.
When the power switch is closed, an FET power transistor is momentarily turned
on by the deep discharge protection circuit. If the voltage to the post-regulator rises
to +9.7 VDC or greater, the transistor switch remains on. If at any time, the voltage
drops below +9.7 VDC, the transistor turns off and the power switch must be
recycled to restart the instrument. This operation prevents discharge of the battery
below +10 VDC. Such a discharge could cause a reverse charge in a weak cell,
resulting in permanent cell damage.
Primary Circuit
The post-regulator is a boost switching regulator that increases its input voltage to
a constant +16.2 VDC output. This voltage is supplied directly to the processor for
large loads, such as the display heater, electroluminescent backlight, and options
port. The post-regulator also supplies a DC-to-DC converter that generates
"5 VDC and "15 VDC for use in the instrument.
Status signals indicating whether the instrument is running on AC line voltage or
the battery, and if the battery is approaching turn-off level, are supplied to the
instrument by the deep-discharge protection circuits.
The AC line power is received by the connector in the EMI filter (FL1). This filter
prevents high frequency signals generated in the instrument from being conducted
back to the AC power line. The line voltage is fused (F101) and switched (S201)
to the primary step-down transformer (T201). Both the switch and the fuse can be
accessed from the outside of the instrument via covers on the rear of the cabinet.
The primary of T201 is wound in two identical sections. These sections are
connected by S201 (in parallel for 110 VAC operation or in series for 220 VAC
operation). The secondary of T201 is connected by a short two-wire cable to the
Power Supply Board. The MOV (R101), across one of T201’s primaries, protects
the power supply if 220 VAC is applied while S2011 is in the 110 VAC position.
Fuse F101 will open in this event.
Pre-Regulator
1503C MTDR Service Manual
The secondary voltage is full-wave rectified by CR1010 and filtered by capacitor
C1010. The large value of this capacitor allows it to supply energy to the instrument
between half cycles of the line voltage.
5–5
Circuit Descriptions
Integrated circuit U1010 is a pulse-width modulator switching regulator controller.
It oscillates at approximately 70 kHz and provides drive pulses to switching
transistors Q1010 and Q1011. The output pulses from these transistors are filtered
to DC by flyback rectifier CR2010, choke L1010, and capacitors C2010 and C2012.
The resulting +16.6 VDC is fed back to the regulator U1010 by voltage divider
R1016 and R1015. It is then compared to a +2.5 VDC reference voltage from,
U1011. T o increase the output voltage, U1010 increases the pulse width of the drive
to Q1010 and Q1011. T o reduce the output voltage, U1010 decreases the pulse width
to Q1010 and Q1011. This assures that a constant +16.6 VDC is maintained.
Resistor R1010 acts as a current sensing shunt in the pre-regulator return line. In the
event that a circuit fault draws excess current, the voltage developed across R1010
(and filtered by R1011, R1012, and C1011) will cause U1010 to reduce the pulse
width of the pre-regulator. This protects the pre-regulator from damage due to
overload.
Battery Charger
Deep Discharge
Protection
The battery charger consists of a linear regulator integrated circuit, U2010, and
associated components. U2010 is connected as a current source, drawing current
from the +15.8 VDC and supplying it to the battery through T2012. The voltage
drop across T2012 is fed back to U2010 through diode CR2014 to control charging
current at a nominal 150 mA. Diode CR2013 and voltage divider R2010 and R2011
provide a voltage clamp to U2010’s feedback terminal to limit the maximum voltage
that can be applied to the battery through CR2015. As the voltage R2012 and
CR2015 approaches the clamp voltage, battery charging current is gradually
reduced to trickle charge.
Rectifier CR2015 prevents battery discharge through the charger when AC line
voltage is not present. Rectifier CR2012 allows the battery to power the instrument
when AC power is not present.
Pre-regulator or battery voltage is applied to Q2011 and Q2012 when the instrument
power switch is pulled on. The rising voltage causes Q2011 and Q2012 to turn on
due to the momentary low gate voltage while C2011 is charging. During this time,
voltage comparator U1020A compares the switched voltage to a +2.5 VDC
reference from U1022. If the voltage is greater than +9.7 VDC, U1020A turns on,
drawing current through Q2010 and R2015 to keep the gates of Q2011 and Q2012
near ground and the transistors turned on. If the voltage is less than +9.7 VDC (or
drops to that value later), U1020A and Q2010 turn off, allowing C2011 to charge
to the input voltage and turn off Q2011 and Q2012. When turned off, the deep
discharge protection circuit limits current drawn from the battery to only a few
microamperes.
5–6
Post-Regulator
The post-regulator receives from +9.7 to +15.5 VDC and boosts it to +16.2 VDC
by switching Q2022 on and off with a pulse-width modulated signal. When Q2022
is turned on, input voltage is applied across choke L2020, causing the current in
L2020 to increase. When Q2022 is turned off, the stored energy in L2020 will cause
1503C MTDR Service Manual
Circuit Descriptions
the current to continue flowing through CR2021 to filter capacitor C2025. Due to
its stored energy, the voltage developed across L2020 adds to the input voltage,
allowing C2025 to be charged to a voltage greater than the input.
The switching of Q2022 is controlled by pulse-width modulator U1023. The
post-regulator output voltage is fed back to U1023 through R1025 and R1024 and
compared to the +2.5 VDC reference from U1022. Low output voltage causes wider
pulses to be supplied to Q2022, storing more energy in L2020 during each pulse.
This results in a higher output voltage. High output voltage, however, reduces pulse
width and reverses the preceding process.
U1023 oscillates at approximately 80 kHz and supplies a synchronizing signal to
the pre-regulator at that frequency when the instrument is operating on AC power.
This raises the pre-regulator frequency to the same 80 kHz. This synchronization
eliminates beat frequency interference between the two regulators.
The synchronizing signal from U1023 is also supplied to Q2021, where it is
amplified to CMOS levels and buffered by gate U2030A. The signal is then used
to clock flip-flop U1024B to produce a 40 kHz square wave output at Q and Q
square waves are buffered by other U2030 inverters and used to drive DC-to-DC
transistors Q2030 and Q2031.
. These
DC-to-DC Converter
Processor System
Introduction
Transistors Q2030 and Q2031 apply push-pull power to the primary of T1030 at
40 kHz by switching the +16.2 VDC alternately between the primary windings. The
resulting transformer secondary voltages are rectified and filtered by CR1034,
C1032, C1033, and C1034 to produce +15 VDC and –15 VDC. Other secondary
voltages are rectified and filtered by CR1030, CR1031, CR1032, CR1033, C1030,
C1031, and C1037 to produce +5 VDC and –5 VDC.
Diodes CR2031 and CR2030 rectify the primary voltage and clamp it to the voltage
level that is across C2031. This prevents voltage transients caused by the rapid
switching of Q2030 and Q2031 and prevents the leakage inductance of T1030’s
primary from creating excessive voltage stress. R2030 provides a discharge path
from C2031. T1031 and C1036 provide additional filtering of the +16 VDC supply .
The processor system consists of the following:
H Microprocessor
H Address Decoding and Memory
H Interrupt Logic
The processor system provides control and calculation functions for the instrument.
A block diagram of the processor system is shown in Figure 5–4 (next page).
1503C MTDR Service Manual
5–7
Circuit Descriptions
An eight-bit microprocessor, clocked at 5 MHz, provides the processing capability
in a bus-organized system. Instructions are read from the program memory EPROM
and executed by the microprocessor to accomplish essentially all instrument
functions. Random access memory is connected to the microprocessor through its
data and address busses, allowing it to store and retrieve control, video, and display
data, as required.
5 MHz
CLOCK
MICROPROCESSOR
ADDRESS
PROGRAM
MEMORY
EPROM
RANDOM
ACCESS
MEMORY
ADDRESS
DECODING
DATA
SELECT
INTERRUPT
LOGIC
INTERRUPT AND
STATUS INPUTS
DATA SELECT AND
ADDRESS SIGNALS
TO CIRCUITS AND
OPTIONS PORT
Figure 5–4: Processor Block Diagram
The processor communicates with all other instrument circuits via the address, data,
and select signals, and receives requests for service from those circuits via the
interrupt and status signals. Select signals are generated in address decoding circuits
under control of the processor and used to read or write data from a circuit, or to
trigger a circuit function. Interrupts from those circuits are combined in the interrupt
logic to generate an interrupt request to the microprocessor. The processor responds
by reading a data word from this logic to determine the source of the interrupt, or
status data, and then performs the required service routine.
5–8
Microprocessor
The microprocessor, U1023, is a single chip processor using Z80 architecture
constructed in high-speed CMOS logic. Each data word, or byte, is eight bits wide
and the microprocessor has a 16-bit address capability , allowing it to address up to
65,536 memory locations. The processor’s 5 MHz clock is derived from a crystal
oscillator in the timebase circuits.
When +5 VDC power is applied to C1030 and R1032, the rising voltage
momentarily applies a positive signal to the input of gate U1031B. The resulting
1503C MTDR Service Manual
Circuit Descriptions
negative pulse at the gate output is supplied to U1023’s reset input, causing the
microprocessor to start at the beginning of its programmed routine each time power
is applied.
Address Decoding and
Memory
Program Memory
(EPROM)
RAM
The 16-bit address space of Z80 processor U1023 is divided into five primary areas.
They are:
H Program Memory (EPROM) space H RAM space H Non-volatile RAM space H Display RAM space H Enable and Select Signal space
The program memory is stored in 64 kilobyte (kb) EPROM U2020, which is
divided into two 32–kb bank-switched halves. Both halves occupy locations
OOOOH to 7FFFH in the processor’s address space. The most significant address
bit on the EPROM, which determines which bank is addressed, is set by flip-flop
U2030A. This bank-switching flip-flop can be toggled by the processor with two
select lines, decoded in the enable and select signal address space. The select signal
for the EPROM is generated by combined address line A15 with the MREQ signal
in U1045A. Whenever the processor addresses a location where A15 is not set, the
program memory will be selected to place data on the bus.
The first RAM is eight-kilobyte memory U1021, selected by a signal generated by
a 1-of-8 decoder, U1022. This decoder operates on the three most significant address
bits (A
selection of a particular
, A14, A13) in combination with MREQ. Each of its decodes represents a
15
1
/8 th of addressable locations. The first four decode signals
are not used because they are located in the program memory space. The fifth decode
is the select signal for the first RAM, occupying locations 8OOOH to 9FFFH.
Non-Volatile RAM Space
Display RAM Space
Enable and Select Signal
Space
1503C MTDR Service Manual
The second RAM is also an 8-kb memory, U1020, made non-volatile by lithium
battery BT1010 and non-volatile memory controller U1010. The select signal for
this RAM is generated similarly to that for the first RAM with the sixth
1
/8 th decode
of U1022. This decode occupies AOOOH to BFFFH.
The display RAM is also an 8-kb memory, U1040, located in the display module.
It is selected by the seventh decode of U1022. It occupies locations COOOH to
DFFFH.
The remaining addressable space is used to generate enable, select, or trigger
signals, which read, write, and control other circuits of the instrument. The eighth
1
/8 th decode signal of U1022 is used to enable four other 1-of-8 decoders: U2021,
U2022, U2024, and U2026. These four decoders are further selected by the four
5–9
Circuit Descriptions
Additional Decoding
Interrupt Logic
combinations of A
select, and trigger signals CS00 through CS31. These occupy the remaining address
space, locations EOOOH to FFFFH.
An automatic wait state is inserted for all circuits selected by U2022. The wait state
is used by the processor to compensate for the slow access times of U2041, U2046,
and U4020 on the Main Board; U2023 on the Front Panel Board; and U2040 on the
display module. The wait request is generated by U1041.
The select signals from U2024 are also modified through U1043B by a 200-ns pulse.
This pulse is created from gates U1042B, U1031C, U2040C, and J-K flip-flop
U2033A. This circuit creates a write pulse that ends prior to the completion of the
processor bus cycle, thus meeting data hold time requirements for some selected
ICs.
The most significant address bit on the EPROM is set or reset by bank-switching
flip-flop U2023A. Another control signal, heat disable, is generated by a similar
flip-flop, U2023B. This is also toggled by two select lines.
The interrupt logic consists of an eight-bit tri-state buffer, U1032, and gates U1030
and U1031D. Six interrupt requests signals are logically OR’d by U1030, then
inverted by U1031D and applied to the microprocessor interrupt request input. Five
of the interrupts are received from the video ADC, the digital timebase, a real-time
counter, the front panel control ADC, and from the Option Port connector . The sixth
interrupt input is unused.
and A11 and operate on A10, A9, and A8 to generate the enable,
12
Option Port Interface
Introduction
The six interrupt requests and two power status signals are connected to pull-up
resistors R1033 and the inputs of buffer U1032. When the microprocessor responds
to an interrupt request, it selects U1032, allowing the eight inputs to that device to
be placed on the data bus for reading.
The processor system outputs six control signals to the Driver/Sampler module.
These signals are loaded from the data bus into latch U3010 by a select signal from
the address decoder. These signals are used by the 1503C Driver/Sampler and the
Option 06 adapter (if equipped).
The option port interface consists of the following:
H Supply Controller
H Buffers
H Output Latch
5–10
1503C MTDR Service Manual
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