Tektronix 502A User manual

INSTRUCTION
MANUAL
Serial Number __________
Tektronix, Inc.
S.W. Millikan Way • P. O. Box 500 • Beaverton, Ore on • Phone Ml 4-0161 • Cables: Tektronix
463
070-382

WARRANTY
All Tektronix instruments are warranted
against defective materials and workman 
ship for one year. Tektronix transformers,
manufactured in our own plant, are war 
ranted for the life of the instrument.
Any questions with respect to the war 
ranty mentioned above should be taken up
with your Tektronix Field Engineer.
Tektronix repair and replacement part
service is geared directly to the field, there 
fore all requests for repairs and replace 
ment parts should be directed to the Tek 
tronix Field Office or Representative in your
area. This procedure will assure you the
fastest possible service. Please include the
instrument Type and Serial number with all
requests for parts or service.
Specifications and price change priv 
ileges reserved.
Copyright © 1963 by Tektronix, Inc.,
Beaverton, Oregon. Printed in the United
States of America. All rights reserved.
Contents of this publication may not be re 
produced in any form without permission
of the copyright owner.

CONTENTS
Section 1 Characteristics
Section 2 Operating Instructions
Section 3 Circuit Description
Section 4 Maintenance
Section 5 Calibration Procedure
Section 6 Parts List and Schematic
Diagrams

SECTION 1
CHARACTERISTICS
General
The Tektronix Type 502A Oscilloscope provides linear
dual beam displays with a wide range of sweep rates com 
bined with high input sensitivity. In addition, the Type
502A may be used to provide dual beam X Y displays at
medium sensitivities, and single beam X Y displays at high
sensitivities. Vertical amplifiers for both beams may be
operated with single ended inputs for conventional operation,
or with differential inputs for cancellation of common mode
signals. The wide range of operational modes available
makes the Type 502A adaptable to a great many industrial
and scientific applications.
VERTICAL-DEFLECTION SYSTEM
Characteristics at each input terminal
Direct connection — 1 megohm paralleled by 47 pf.
With P6006 Probe — 10 megohms paralleled by approx.
9 pf.
Deflection factors
Seventeen calibrated deflection factors from 0.1 mv/cm to
20 v/cm accurate within 3%.
Continuously variable deflection factors are available from
0.1 mv/cm to approximately 50 v/cm. However, when the
variable is used the frequency response in each range of the
SENSITIVITY control will be slightly reduced.
Frequency response
Frequency response characteristics of the Type 502A vary
with settings of the SENSITIVITY controls. Typical readings
are as follows:
.1 mv/cm 50 kc
.2 mv/cm
100 kc
1 mv/cm
200 kc
50 mv/cm
400 kc
.2 v/cm
1 m c
Differential input rejection ratio
The rejection ratios specified below apply if the signal
voltage at the Input connector does not exceed specified
limits. The signal limits for d c coupling are, + or — 2 volts
with respect to ground for settings of the SENSITIVITY con 
trol from 0.1 mv/cm to .2 v/cm, + or — 20 volts with respect
to ground for settings from .5 v/cm to 2 v/cm, and + or —
200 volts with respect to ground for settings from 5 v/cm to
20 v/cm. For ac coupling, the signal limits are 2 volts
peak to peak from 0.1 mv/cm, to .2 v/cm, 20 volts peak to
peak from .5 v/cm to 2 v/cm, and 200 volts peak to peak
from 5 v/cm to 20 v/cm.
The DC common mode rejection ratios are measured
with a common sine wave signal which is applied to both
inputs of one vertical amplifier simultaneously. The sine 
wave signal has a constant amplitude of 2 volts and a
frequency as stated in the table below.
DC Common Mode Rejection Ratio
† A rejection ratio of 40,000:1 can only be obtained if the DC
BAL control has been properly adjusted.
Sensitivity Setting
(Sine wave output
Ratio
held at a constant
Frequency
amplitude of 2 volts)
.2 VOLTS PER CM 1 kc 1 00:1
.2 mVOLTS PER CM 1 kc 20,000:1
† .1 mVOLTS PER CM 1 kc
40,000:1
.2 VOLTS PER CM 400 kc
50:1
.2 mVOLTS PER CM 100 kc
1000:1
.1 mVOLTS PER CM 50 kc
2000:1
HORIZONTAL-DEFLECTION SYSTEM
Sweep rates
Twenty one calibrated sweep rates from 1  sec/cm to
5 sec/cm.
Accuracy typically within 1 % of full scale; in all cases,
within 3% of full scale.
Continuously variable sweep rates are available from
1  sec/cm to approximately 2.5 sec/cm.
Ma nifier
Expands sweep 2, 5, 10, or 20 times. Calibration of
magnified sweep rates accurate within 3% for sweep rates
which do not exceed the maximum calibrated rate of
1  isec/cm.
Unblankin
DC coupled.
Tri erin si nal requirements
Internal — a signal producing 2 mm vertical deflection
on either the UPPER or LOWER BEAM.
External — 0.2 volts to 10 volts on either polarity.
Tri erin si nal sources
UPPER BEAM, LOWER BEAM, external, or line.
@2
1-1

Characteristics — Type 502A
Input characteristics at TRIGGER INPUT connector
AC coupled — 1 megohm in series with 0.01  f.
DC coupled — 1 megohm.
Horizontal input
With UPPER BEAM amplifier connected to crt horizontal
deflection plates:
Deflection factors of 0.1 mv/cm to 20 v/cm in 17 steps.
With external input connected to horizontal amplifier:
Deflection factors of 0.1 v/cm to 2 v/cm in 5 steps which
are within ±5%.
Input characteristics at EXTERNAL connector
1 megohm shunted by approximately 70 pf.
OTHER CHARACTERISTICS
Cathode-ray tube
Type T5021P2 — P 1 , P7, and P11 phosphors optional.
Each vertical beam covers a minimum of 8 cm of vertical
scan.
Volta e calibrator
Square wave output at approximately 1 kc.
Six calibrated voltage steps from 0.5 mv to
50 volts peak to peak. Accuracy — within 3%.
Graticule
Edge lighted — marked in 10 vertical and 10 horizontal
1 cm divisions with 2 mm markings on the baselines.
Power requirements
Line voltage — 105 to 125 volts, or 210 to 250 volts, 50 60
cycles.
Power — Approximately 300 watts.
Mechanical characteristics
Ventilation — filtered, forced air.
Construction — aluminum alloy chassis and three piece
cabinet.
Dimensions — 23 ½ " long, 11¼" wide, 15" high.
Weight — 52 pounds.
Accessories included
2 — Type P6006 attenuator probes, 010 125.
2 — Binding post adapters, 013 004.
1 — Light filter.
2 — Instruction manuals.
1 — Test lead, 012 031.
1 — 3 to 2 wire adapter, 103 013.
1 — 3 conductor power cord, 161 010.
1-2

Shippin Blocks
It is very important to remove the shipping blocks from
the vertical amplifier prior to using the oscilloscope. The
shipping blocks are narrow inserts, which are used to hold
the vertical amplifiers firmly in place during shipment. A
small tug with a pair of plier towards the outside of the
instrument will remove each of the two shipping blocks used
on each vertical amplifier. See figure 2 1 for the shipping
block positions.
The shipping blocks should be kept for future use.
Coolin
A fan maintains safe operating temperature in the Type
502A Oscilloscope by circulating air through a filter and
over the components. Therefore, the instrument must be
placed so that the air intake is not blocked. The air filter
must be kept clean to permit adequate air circulation. If
the interior temperature should rise too high for some reason,
SECTION 2
OPERATING
INSTRUCTIONS
a thermal cutout switch will disconnect the power and keep
it disconnected until the temperature drops to a sofe value.
For proper air circulation, the bottom and side panels
must be in ploce. Be sure the bottom panel is installed ac 
cording to directions.
Power Requirements
The regulated power supplies in the Type 502A will
operate with line voltages from 105 to 125 volts, at 117
nominal line volts, or from 210 to 250 volts at 234 nominal
line volts. Proportionate line voltage variations apply
when other nominal line voltage primary connections are
made. For maximum dependability and long life the voltage
should be near the center of this range. Fig. 2 2 shows
the connections for the various line voltages.
Voltages outside of these limits, or poor line voltage
waveforms, may cause hum or jitter on the trace and may
cause unstable operation. Be sure to check for proper line
voltage if indications such as these are present.
Fi . 2-1. The position of the shippin blocks for each vertical amplifier.
2-1

Operatin Instructions — Type 502A
Fi . 2-2. The power transformer has two extra windin s permittin nominal primary volta es of 110, 117, 124, 220, 234 or 248 volts, 50
or 60 cycle operation.
Fan Connections
The manner in which the fan is wired depends on the line
voltage. For 110 124 or 220 248 volt operation, the fan is
connected as shown in Fig. 2 3.
Fuse Requirements
Use a 4 amp., 3AG, Fast Bio fuse for 110, 117 or 124 volt
60 cycle operation; for 50 cycles use a 3.2 amp., 3AG, S l o
B l o fuse. For 220, 234 or 248 volt, 60 cycle operation, use
a 2 amp., 3AG, Fast Bio fuse; for 50 cycles use a 1.6 amp.,
3AG, S l o B l o fuse.
Input Selection
On the Type 502A oscilloscope, you can connect single
ended inputs to either the A or B input connectors of the
LOWER or UPPER BEAM amplifiers by rotating the Input
Selector switches to the corresponding position. The choice
of input connections will depend upon the display desired.
Waveforms applied to input B are displayed in an inverted
position on the face of the crt while waveforms applied to
input A are displayed in the normal upright position. If
you are not aware of this difference in the input connectors,
it is probable that you will improperly evaluate the results
obtained from an input to the B connector.
Fi . 2-3. Fan connections for the various line volta e connections.
2-2

Operatin Instructions — Type 502A
Fi . 2-4. Inputs to the vertical amplifiers. Waveforms applied to
input connector A are displayed in the upri ht position, while wave 
forms applied to input connector B are inverted.
Differential inputs must be connected to both the A and B
input connectors of one amplifier. In the A and B positions
of the input selector switch, the corresponding waveforms
are displayed on the crt. In the A B (DIFF) position, the
B input is algebraically added to the A input and the
difference is displayed. This feature permits you to elim 
inate common mode signals within specified limits.
Input Couplin
Input signals to the vertical amplifiers can be either
ac or d c coupled by placing the Input Selector switch in
the corresponding positions. DC coupling applies both the
ac and d c components of the input signal to the vertical
amplifier circuits. This permits you to measure the d c
voltage level as well as the amplitude of the ac component.
It is sometimes neither necessary nor desirable to display
the d c component. In such cases ac coupling should be used.
With ac coupling, a capacitor is placed in series with the
input connector to block the d c component while at the same
time allowing the ac component to be displayed.
Fi . 2-5. Rejection of a common mode si nal by the differential
amplifier. The waveform applied to input connector B is al ebra 
ically added to the waveform applied to input connector A and
the resultant waveform is displayed on the screen of the crt.
Input Connections
Here are some precautions you should observe in connect 
ing your oscilloscope to the signal source:
1. Avoid errors in readings due to stray electric or magne 
tic coupling between circuits, particularly in the leads
connected to the input connector. In general, unshielded
leads of appreciable length are unsuited for this use. When
shielded leads are used, the shields should be grounded to
the input connector shield and to the chassis of the equipment
being tested. Coaxial cables are recommended for many
purposes. Special care must be taken in the high sensitivity
ranges of the oscilloscope due to the low signal level and
high amplifier gain.
2. As nearly as possible, simulate actual operating condi 
tions in the equipment being tested. The equipment should
have a load on it which is approximately equal to the load
encountered in normal operation.
3. Consider the effect of loading upon the signal source due
to the input circuit of the oscilloscope. The circuit at the
input connectors can be represented by a resistance of 1
megohm shunted by a capacitance of 47 pf. With a few
feet of shielded cable, the capacitance may well be 100 pf
or more. In many cases, the effects of these resistive and
capacitive loads are not negligible, and to minimize them,
you might want to use a probe in the manner described in
the next section.
Use of Probes
An attenuator probe lessens both capacitive and resistive
loading, at the same time reducing sensitivity. When making
amplitude measurements with an attenuator probe, be sure
to multiply the observed amplitude by the attenuation of the
probe.
A Type P6006 Probe is furnished as an accessory to the
Type 502A Oscilloscope. Connected to the Input connector
of the Type 5 0 2A, the probe presents an input characteristic
of 10 megohms shunted by approximately 9 picofarads and
has an attenuation ratio of 10:1. The maximum voltage
which may be applied to the probe is 600 volts. Exceeding
this rating, either in peak ac volts or d c volts, may result
in damage to the components inside the probe body.
If the waveform being displayed contains fast changing
portions, it is generally necessary to clip the ground lead
of the probe to the chassis of the equipment being tested.
Select a ground point which is near the probe connection.
Probe Adjustment
An adjustable capacitor, which is built into the probe
body, is used to compensate for slight variations in input
capacitance from one instrument to another. To insure the
accuracy of pulse and transient measurements, this adjust 
ment should be checked frequently.
To make this adjustment, set the AMPLITUDE CALIBRATOR
and SENSITIVITY Controls on the Type 502A to display a
signal of suitable amplitude. Touch the probe tip to the
CAL OUT Connector and adjust the TIME/CM Control to
display several cycles of the waveform.
Loosen the locking sleeve several turns. (See figure 2 6.)
Now while holding onto the knurled part near the cable, turn
2-3

Operatin Instructions — Type 502A
Fi . 2-6. Location of lockin sleeve and knurled parts on the Type P6006 Probe.
the probe body until a flat top is obtained on the square 
wave waveform. The locking sleeve should now be tight 
ened. After the locking sleeve has been tightened, the probe
compensation should be checked once more to insure that
the compensation did not change when the locking sleeve
was tightened.
Tri ered Operation
In order to obtain a stable display of some recurrent
waveform, it will be necessary for you to trigger the hori 
zontal sweep at the correct instant of time. This will in 
sure that the sweep will start at the same point on the ob 
served waveform for each cycle of operation. The sweep
should be triggered either by some waveform bearing a
fixed time relationship to the observed waveform or by the
observed waveform itself. Either method will produce the
desired stable display. If the waveform which is applied to
the UPPER BEAM and the waveform which is applied to the
LOWER BEAM have a definite time relationship to each
other it is possible to trigger from either beam and obtain
simultaneously a stable display of both waveforms.
The following instructions tell you how to select the
proper triggering signal for various applications of your
oscilloscope. These instructions also provide information
about the advantages and limitations of each triggering con 
figuration. You should attempt to become thoroughly familiar
with all of the various triggering configurations in order
that you may obtain maximum use from your instrument.
A thorough knowledge of the triggering configurations will
allow you a greater selection of triggering methods when
you are confronted with a definite triggering problem.
How to select the tri erin si nal source
1. To trigger the sweep from the waveform displayed on the
UPPER BEAM, set the TRIGGER SELECTOR switch at UPPER
AC or UPPER DC.
2. To trigger the sweep from the waveform displayed on the
LOWER BEAM, set the TRIGGER SELECTOR switch at LOWER
AC or LOWER DC.
3. To trigger the sweep at the power line frequency, set
the TRIGGER SELECTOR switch at LINE. This mode of trig 
Fi . 2-7. The Type P6006 Probe is adjusted for a flat-topped square-wave display of the Calibrator waveform.
2-4