Tektronix 620-0295-00 User manual

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I Tektronix, Inc.
P.O. Box 500
Beaverton, Oregon 97077
MANUAL PART NO.
070-3732-00
COMMITTED TO EXCELLENCE
620-0295-00
LOW VOLTAGE
POWER SUPPLY
SERVICE MANUAL
First Printing FEB 1981 ·

WARNING I
THE FOLLOWING SERVICING INSTRUCTIONS ARE
FOR USE BY QUALIFIED PERSONNEL ONLY. TO
AVOID PERSONAL INJURY, DO NOT PERFORM ANY
SERVICING OTHER THAN THAT CONTAINED IN
OPERATING INSTRUCTIONS UNLESS YOU ARE
QUALIFIED TO DO SO.
Copyright
©
1981 by Tektronix, Inc., Beaverton, Oregon.
Printed in the United States of America. All rights reserved.
Contents of this publication may not be reproduced in any
form without permission of Tektronix, Inc.
This instrument, in whole or in part, may be protected by one
or more U.S. or foreign patents or patent applications.
Information provided on request by Tektronix, Inc., P.O. Box
500, Beaverton, Oregon 97077.
TEKTRONIX is a registered trademark of Tektronix, Inc.

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MANUAL REVISION STATUS
PRODUCT: 620-0295-00 Low Voltage Power Supply
This manual supports the following versions of this product: Part Numbers 620-0295-00 and up
REV. DATE DESCRIPTION
@ FEB 1981 Original Issue
620-0295-00 POWER SUPPLY @

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Section 1
Section 2
Section 3
Section 4
620-0295-00 POWER SUPPLY
CONTENTS
INTRODUCTION Page
About This Manual ..................................... 1-1
Description of the Module ............................... 1-1
General ............................................. 1-1
Physical Description ................................. 1-1
SPECIFICATIONS
Physical ............................................... 2-1
Electrical .............................................. 2-1
Environmental .......................................... 2-3
External Connections ................................... 2-4
MAINTENANCE
Safety Summary........................................ 3-1
General ................................................ 3-1
Changing the Line Voltage .............................. 3-2
Troubleshooting ........................................ 3-2
Equipment Required ................................. 3-3
Preparation .......................................... 3-4
Control Circuit ....................................... 3-4
Primary Circuit ...................................... 3-6
Logical On/Off Switch ................................ 3-7
DCSupplies ......................................... 3-8
Timing Circuit ....................................... 3-8
Assembly/Disassembly ................................. 3-9
Replacing the Line Rectifier .......................... 3-9
Replacing the Switching Transistors .................. 3-9
Removing the Inverter Board ......................... 3-1O
Removing the Regulator Board........................ 3-11
Replacing the+ 5 V Rectifier ......................... 3-12
Access to the Cavity ................................. 3-1 2
PERFORMANCE CHECK
Equipment Required ................................. 4-1
Procedures ............................................ 4-2
NOTE
Refer to the host product service manual for the
adjustment procedure.
DCVoltages ......................................... 4-2
INIT-0 and PWRFL-0................................. 4-2
Maximum and Minimum Line Voltage.................. 4-3
Current Limiting and Maximum Loads ................. 4-3
@ ii

iii
Section 5
Section 6
Section 7
Section 8
Appendix A
Table
THEORY OF OPERATION
Introduction ............................................ 5-1
DC Supplies ......................................... 5-2
System Interface Signals ............................. 5-2
Block Description ...................................... 5-3
Detailed Circuit Description ............................. 5-4
Primary Circuit ...................................... 5-4
Control Circuit ....................................... 5-6
DC Supplies ......................................... 5-8
Timing Circuit ....................................... 5-11
REPLACEABLE ELECTRICAL PARTS
DIAGRAMS AND SCHEMATICS
REPLACEABLE MECHANICAL PARTS
SIGNAL DEFINITIONS AND REFERENCES
TABLES
Description Page
2-1 Line Input................................................. 2-1
2-2 DC Supplies .............................................. 2-2
2-3 TTL Signals ............................................... 2-3
2-4 Environmental Limits ...................................... 2-3
2-5 External Connections ..................................... 2-4
4-1 Power Supply Voltage Limits ............................... 4-2
5-1 Base Drive Circuit States .................................. 5-8
@
620-0295-00 POWER SUPPLY

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Figure
1-1
1-2
2-1
3-1
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
3-10
3-11
3-12
3-13
4-1
4-2
4-3
5-1
5-2
5-3
5-4
5-5
5-6
5-7
620-0295-00 POWER SUPPLY
ILLUSTRATIONS
Description Page
The 620-0295-00 Low Voltage Power Supply ............... vi
Line Voltage Switches ..................................... 1-1
Dimensions ............................................... 2-1
Changing Line Voltage .................................... 3-2
Test Connectors .......................................... 3-3
Connection of Test Load................................... 3-4
Base Drive Test Point ..................................... 3-5
Base Drive Waveform ...................................... 3-5
Inverter Dead Time ........................................ 3-5
Connecting the Current Probe ............................. 3-6
Bypassing Triac ........................................... 3-6
Inverter Waveform ......................................... 3-7
Mounting of Switching Transistors ......................... 3-9
Removing the Inverter Board ............................... 3-1O
Removing the Regulator Board ............................. 3-11
Mounting the Diodes to the Heat Sink ...................... 3-12
Power Supply Test Points.................................. 4-2
Power-Up Waveform ...................................... 4-3
Power-Down Waveform .................................... 4-3
Simplified Inverter Circuit. ................................. 5-1
Configuration for the 115 V Line ........................... 5-4
Configuration for the 230 V Line ........................... 5-5
Logical On/Off Switch ..................................... 5-6
Pulse Width Modulator 1.C.................................. 5-7
Typical Post-Regulator Circuit ............................. 5-9
Foldback Current Limiting Characteristic ................... 5-9
@ iv

DO NOT SERVICE ALONE
SAFETY SUMMARY
POWER SOURCE
Do not perform service or adjustment of this module
unless another person capable of rendering first aid
and resuscitation is present.
USE CARE WHEN SERVICING WITH
POWER ON
Dangerous voltages exist at several points in this
module. To avoid personal injury do not touch exposed
connections or components while the power is on.
Disconnect the power before removing protective pan-
els, soldering, or replacing components.
After the power has been disconnected, the neon
flasher on the Inverter board indicates that dangerous
voltages still are present in the filter capacitors.
620-0295-00 POWERSUPPLY @
This module is intended to operate from a power
source that applies less than 250 volts rms between
the supply conductors or between either the supply
conductor and ground. A protectjve ground connection
by way of the grounding conductor in the power cord is
essential for safe operation.
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Figure 1-1. The 620-0295-00 Low Voltage Power Supply.
vi
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620-0295-00 POWER SUPPLY