Tektronix 2465B Service Manual

Maintenance—2465B/2467B Service
Table 6-8
Front-Panel LED Device Codes
READY
LED
(bit 2)
OFF
OFF
OFF
OFF
ON
ON
ON
ON
Device Code
+
LED
(bit 1)
OFF
OFF
ON
ON
OFF
OFF
ON
ON
LED
(bit 0)
OFF
ON
OFF
ON
OFF
ON
OFF
ON
Device
Number
0
1
2
3
4
5
6
7
Even if a Kernel test fails, the operator may try to go to
normal oscilloscope operation by pressing the A/B TRIG
select push button. Depending on the exact nature of the
failure, the instrument may or may not be functional.
Kernel tests are automatically executed at power-up.
The Kernel tests are divided into RAM tests and ROM
tests as follows:
RAM TEST. This test is done with a complementary
data pattern starting at the highest RAM address available
and continuing to the lowest. The process reads and
saves the original data, and then writes a pattern of
01010101's (55 Hex) at the highest RAM memory address.
The data is then read back to see if it is still 55 (Hex).
Next a complementary pattern of 10101010 (AA Hex) is
written to the same address. Then the address content is
read back and tested to see if it is still AA (Hex). After the
memory is checked, the original data is written back into
the memory address. RAM TEST then checks the next
lower address. The testing continues until all of RAM is
checked.
Test checks: RAM address decoding, RAM address
lines, RAM data lines, RAM memory, and Data Bus
Buffers.
ROM TEST. The ROM test performs three checks on
each of the system read-only memories.
Data Bus Drive—Two locations containing
complementary data patterns are read.
6-14
Test checks: Data bus lines and the Data Bus Driver.
Correct Part—A byte in the ROM being checked is
compared to the most-significant byte of the addressed
ROM block (starting address of where the ROM should be
installed).
Test checks: ROM address decoding and proper
installation of ROM components.
Checksum—A sixteen bit, spiral-add checksum is
calculated and compared to a two-byte value stored in
ROM being checked.
Test checks: ROM contents, ROM addressing, ROM
data lines, and the Data Bus Driver.
Confidence Tests
The Confidence tests provide checks for much of the
remaining circuitry to ensure that instrument operation is
correct. Confidence tests are performed automatically at
power-up after the Kernel is determined to be functional or
initiated by the operator from the Diagnostic Monitor.
A failure of any Confidence test during power-up will
pass control to the Diagnostic Monitor; this permits the
test results to be examined. Descriptions of the
Confidence tests follow.
KERNEL TEST (Test 00). This test is not user
selectable, but runs automatically when cycle mode is
entered at power up. During cycle mode the
microprocessor forces a self-reset by setting the PWR
DOWN bit (bit #5) of U2310. If this does not force a reset
condition, an error is recorded. Any kernel failures
detected during cycle mode are also recorded.
INTERRUPT REQUEST (Test 01). Ten consecutive
interrupt cycles are checked to ensure that succeeding
interrupts occur not more than 4.5 ms apart (5600 "E"
cycles).
Test checks: Interrupt Timer circuitry.
SWITCH STUCK (Test 02). The front-panel,
momentary-contact switches are scanned, checking for a
closed switch. At power-up, the test runs immediately.

Tektronix 2465B Specifications

General

Bandwidth	400 MHz
Channels	4
Vertical Sensitivity	2 mV/div to 5 V/div
Maximum Input Voltage	400 V (DC + peak AC)
Display	CRT
Trigger Modes	Auto, Normal, Single
Time Base Range	500 ps/div to 0.5 s/div
Rise Time	875 ps
Power Supply	48 to 440 Hz
Dimensions	495 mm

Summary

Service Manual

WARRANTY

Tektronix warranty for product defects in materials and workmanship for a period of three years.

OPERATORS SAFETY SUMMARY

SERVICING SAFETY SUMMARY

Do Not Service Alone

Prohibits servicing or adjustment unless another person capable of first aid is present.

Use Care When Servicing With Power On

Warns about dangerous voltages and touching exposed components.

Section 1—2465B/2467B Service

PERFORMANCE CONDITIONS

Defines the electrical characteristics and environmental requirements for the instrument.

Specification—2465B/2467B Service

Table 1-8

Details environmental requirements, including temperature, altitude, humidity, vibration, and shock.

Section 2—2465B/2467B Service

SAFETY

Provides crucial safety information for operating and connecting the oscilloscope.

START-UP

Describes the automatic diagnostic tests performed when the instrument is turned on.

Section 3—2465B/2467B Service

INTRODUCTION

Provides detailed information on the electrical operation and circuit relationships of the instrument.

BLOCK DIAGRAM

Provides a simplified block diagram of the instrument showing basic interconnections.

BLOCK DESCRIPTION

Discusses the Low Voltage and High Voltage Power Supply circuits and DC Restorer function.

DETAILED CIRCUIT DESCRIPTION

PROCESSOR AND DIGITAL CONTROL

Explains how the microprocessor directs oscilloscope functions and interacts with controls.

Theory of Operation—2465B/2467B Service

Reset Control

Ensures Microprocessor starts execution from a known memory point and handles power-down states.

Address Decode

Generates enabling signals and strobes for Microprocessor control of various devices.

Random-Access Memory (RAM)

Provides temporary storage for data and calibration constants, retaining settings after power-off.

FRONT-PANEL SCANNING and ANALOG CONTROLS

Explains how the Analog Control circuitry reads front-panel controls and sets analog voltages.

Front-Panel Switches

Describes the front-panel switch matrix arrangement and scanning process.

Pot Scanning

Describes how the Pot Scanning circuitry derives digital values for front-panel potentiometers.

Analog Control

Explains setting and updating various analog voltages for instrument functions.

Front-Panel Pots

Details the front-panel potentiometers that control linear functions and are digitized indirectly.

ATTENUATORS AND PREAMPS

Explains how the Attenuators and Preamps circuitry allows selection of vertical deflection factors.

Auxiliary Control Register

Allows Microprocessor to control mode and range dependent functions, including attenuation factors.

Channel 1 Preamplifier

Converts single-ended input signal to differential output for Vertical Channel Switch.

DISPLAY SEQUENCER, TRIGGERS, AND SWEEPS

Controls and sequences analog-type oscilloscope functions in real time.

Display Sequencer

Holdoff Circuitry

Delays sweep start until circuits recover from previous sweep, setting charging current for integrating capacitor.

HOLDOFF BOARD (2467B ONLY)

Triggers

Selects triggering signal source for horizontal sweep and produces triggering gate signal.

A Sweep

Calibrator

VERTICAL CHANNEL SWITCH AND OUTPUT AMPLIFIERS

Selects vertical signal source and provides amplification necessary to drive CRT deflection plates.

Vertical Output Amplifier

Z-Axis Amplifier

READOUT

Responsible for displaying alphanumeric readout characters in the CRT.

Section 4—2465B/2467B Service

INTRODUCTION

Explains the procedure for verifying instrument controls and performance.

PREPARATION

VERTICAL

Details performance checks for vertical controls, input coupling, and signal display amplitude.

COUNTER/TIMER/TRIGGER CHECKS

Covers performance checks for options affecting horizontal timing modes.

Check Delay Time

Check Delta Time Accuracy

Verifies delta time accuracy by aligning cursors and checking readout.

Verify Delay-By-Events

Check Logic Trigger

Verify Trigger Delta Delay

Checks trigger delta delay by aligning reference and delta cursors.

HORIZONTAL (cont)

ADDITIONAL FUNCTIONAL VERIFICATION

Verify ALT, CHOP, and ADD Modes and TRACE SEP

Verify BEAM FIND Operation

Check Probe Encoding

WORD RECOGNIZER CHECKS

Initial Setup

Check Data Setup Time

Verifies data setup time by varying pulse duration and checking signal display.

Check Data Hold Time

Verifies data hold time by varying pulse duration and checking signal stability.

Check Minimum Clock Pulse Width

Check Delay From Selected Edge to WORD RECOG OUT

Verifies delay from selected edge to WORD RECOG OUT by aligning cursors.

ADJUSTMENT PROCEDURE

IMPORTANT-PLEASE READ BEFORE USING THIS PROCEDURE

Highlights critical information and general rules before performing adjustments.

PARTIAL PROCEDURES

PREPARATION FOR ADJUSTMENT

POWER SUPPLIES AND DAC REF ADJUSTMENT

Procedure for checking and adjusting power supply DC levels, regulation, and ripple.

CRT ADJUSTMENTS

Covers adjustments for Z-AXIS DRIVE, GRID BIAS, TRACE ROTATION, FOCUS, ASTIGMATISM, and GEOMETRY.

AUTOMATIC CALIBRATION CONSTANTS, HORIZONTAL AND VERTICAL GAIN, CENTERING, AND TRANSIENT RESPONSE ADJUSTMENTS

Procedures for generating calibration constants for timing, gain, trigger level, and transient response.

CAL 01—HORIZONTAL

Checks and adjusts horizontal timing, X1 gain, X10 gain, Hrz Ctr, and Trans Resp.

CAL 02—VERTICAL

Checks and adjusts vertical preamp gain, gain (R638), and vertical centering (R639).

CAL 03—TRIGGERING

Checks and adjusts triggering parameters, including source selection and coupling.

CAL 04—CH 2 DELAY ENABLE/DISABLE

CAL 06—VERTICAL TRANSIENT RESPONSE

Checks and adjusts vertical transient response for flattest corner.

CAL 07—READOUT CENTERING AND GAIN

Checks and adjusts readout centering and gain for optimal display.

CAL 09—PARAMETRIC MEASUREMENTS

Adjusts parametric measurements, including time markers and bandwidth limit.

Section 6—2465B/2467B Service

STATIC-SENSITIVE COMPONENTS

Provides precautions for handling components susceptible to static discharge damage.

PREVENTIVE MAINTENANCE

Outlines procedures for cleaning, visual inspection, and checking instrument performance.

INSPECTION AND CLEANING

Details visual inspection and cleaning procedures for both exterior and interior of the instrument.

CLEANING

PERIODIC READJUSTMENT

TROUBLESHOOTING

Provides information for locating faults and aiding in troubleshooting the instrument.

TROUBLESHOOTING AIDS

Lists aids for troubleshooting, including diagnostic firmware, schematic diagrams, and circuit board illustrations.

Diagnostic Firmware

Explains the built-in diagnostic routines that aid in locating malfunctions via CRT readout or LED indicators.

Troubleshooting Charts

TRANSISTORS, INTEGRATED CIRCUITS, AND HYBRID CIRCUITS

Guidance on replacing semiconductor devices, emphasizing checking for actual defects.

SOLDERING TECHNIQUES

Provides general soldering techniques applicable to maintenance of precision electronic equipment.

REMOVAL AND REPLACEMENT INSTRUCTIONS

Describes special techniques and procedures required for replacing components.

Cabinet Removal

Section 8—2465B/2467B Service

Section 9—2465B/2467B Service

REPLACEABLE ELECTRICAL PARTS

Lists electrical parts available for replacement, including Tektronix and manufacturer part numbers.

Section 10—2465B/2467B Service

DIAGRAMS AND CIRCUIT BOARD ILLUSTRATIONS

Explains symbols, component values, and numbering systems used in diagrams.

Assembly Numbers and Grid Coordinates

Figure 10-3. Locating components on schematic diagrams and circuit board illustrations.

Provides a flowchart and explanation for locating components on diagrams and boards.

Figure 10-4. Instrument block diagram.

A simplified block diagram illustrating the instrument's functional blocks and interconnections.

ANALOG CONTROL (SN B050000 & ABOVE)

Section 11—2465B/2467B Service

Section 12—2465B/2467B Service

REPLACEABLE MECHANICAL PARTS

Lists mechanical parts available for replacement, including Tektronix part numbers.

PARTS ORDERING INFORMATION

Provides information on ordering replacement parts, including required details.