Tektronix 556 User manual

INSTRUCTION
MANUAL
Serial Number ___________
TYPE
556
OSCILLOSCOPE
Tektronix, Inc.
S.W. Millikan Way • P. O. Box 500 • Beaverton, Oregon 97005 • P one 644-0161 • Cables: Tektronix
070-0757-00 1167

or service.
Specifications and price c ange privi
leges reserved.
Copyrig t © 1966, new material 1967
by Tektronix, Inc., Beaverton, Oregon.
Printed in t e United States of America.
All rig ts reserved. Contents of t is pub 
lication may not be reproduced in any
form wit out permission of t e copyrig t
owner.
Type 556
WARRANTY
All Tektronix instruments are warranted
against defective materials and workman 
s ip for one year. Tektronix transformers,
manufactured in our own plant, are war 
ranted for t e life of t e instrument.
Any questions wit respect to t e war 
ranty mentioned above s ould be taken
up wit your Tektronix Field Engineer.
Tektronix repair and replacement-part
service is geared directly to t e field,
t erefore all requests for repairs and re 
placement parts s ould be directed to
t e Tektronix Field Office or representative
in your area. T is procedure will assure
you t e fastest possible service. Please
include t e instrument Type and Serial or
Model Number wit all requests for parts

CONTENTS
C aracteristics
Operating Instructions
Circuit Description
Maintenance
Performance C eck
Calibration
Abbreviations and Symbols
Parts Ordering Information
Electrical Parts List
Mec anical Parts List Information
Mec anical Parts List
Diagrams
Mec anical Parts List Illustrations
Accessories
Abbreviations and symbols used in t is manual
are based on or taken directly from IEEE Stand 
ard 260 "Standard Symbols for Units", MIL-STD-
1 2B and ot er standards of t e electronics indus 
try. C ange information, if any, is located at t e
rear of t is manual.
Type 556
Section 1
Section 2
Section 3
Section 4
Section 5
Section 6
Section 7
Section 8
Section 9

Sorial number 2000 and up.
Serial number 999 and below.
Fig. - . Type 556 Oscilloscopes.
Type 556

Type 556
SECTION 1
CHARACTERISTICS
C ange information, if any, affecting t is section is found at t e rear of t e manual.
Introduction
T e Type 556 Oscilloscope — is a versatile dual-beam labor 
atory type instrument providing accurate voltage and time
measurements in t e DC to 50 MHz frequency range. Two
complete orizontal and vertical deflection systems permit
completely indepentent operation of t e two beams.
T e Upper Beam can display t e signal from eit er t e
left or rig t vertical plug-in unit and may be controlled by
eit er t e A or B time base or an external signal. T e Lower
Beam displays t e signal from t e rig t plug-in and t e sweep
is controlled by t e B time base or an external signal. T e
left and rig t plug-in compartments accept all letter series
and 1 -series plug-ins.
Special circuits wit in t e oscilloscope provide selection
of an accurate, continuously-variable delay w en using t e
B sweep. T e B sweep may be delayed by t e A sweep from
0.1 µs to 50 s (calibrated) after application of a trigger pulse.
T is feature permits t e delayed B sweep to expand a
selected portion of t e undelayed A sweep, t ereby pro 
viding precise time measurements and detailed observation
of t e signal. Bot t e delayed and undelayed sweeps can
be presented simultaneously on t e oscilloscope screen. T e
Upper Beam trace as an intensified zone indicating t e por 
tion of t e signal being displayed by t e B sweep and Lower
Beam.
T e instrument is designed to operate over an ambient
temperature range of 0° C to +50° C. Performance speci 
fications t at are given in t e center column apply over t is
temperature range after a warmup time of 20 minutes. Sup 
plemental information describing a c aracteristic or a feature
is also included in t is portion of t e manual.
VERTICAL AMPLIFIERS
C aracteristics
Performance Specification Supplemental Information
Frequency Response
DC to >50 MHz at 3 dB down wit a 1 -series
plug-in unit aving a risetime of 3.12 ns or less.
Risetime
<6.25 ns. Indicated risetime of 6.93 ns
wit a Test Load Plug-In Unit (Tektronix
Part No. 067-0521-00) aving a risetime
of 3 ns.
Transient Response on Screen
<2.25% peak overs oot, rounding, ringing or
tilt.
Applies to all t ree vertical modes wit
Test Load Plug-In Units.
Gain C ange wit Line Voltage
C ange
<1% from 147 VAC peak to 178 VAC peak.
Trace Drift wit Line Voltage
C ange
±2 mm from 147 VAC peak to 178 VAC peak.
A & B SWEEP GENERATORS
Calibration Accuracy
5 s/cm to 0.1 µs/cm
±3% of displayed time between two points
displayed wit in t e middle 8 cm.
X10 Magnified Display
±5% of displayed time between any two
points >1 cm apart displayed wit in t e
middle 8 cm.
Calibrated from 4 cm to 70 cm from
sweep start. Extends fastest sweep rate
to 10 ns/cm.
Variable Time/Cm Range
>2.5:1.
Extends slowest sweep to approximately
12.5 s/cm.
Sweep Lengt
10.5 cm ±0.5 cm
At 1 ms/cm.
VARIABLE TIME DELAY
Delay Time Accuracy
5 s/cm to 1 µs/cm
±1% of indicated delay time ±2% of A
TIME/CM setting + fixed delay of <150 ns
in system.
1% of A TIME/CM setting corresponds
to 1 minor division on t e DELAY-TIME
MULTIPLIER dial.
0.5 µs/cm to 0.1 µs/cm
±1 % of indicated delay time ±5% of A
TIME/CM setting + fixed delay of <150 ns
in system.
For additional information refer to Fig.
2-10 in t e Operation Instructions.
-

Characteristics — Type 556
C aracteristics
Performance Specification
Supplemental Information
Incremental Delay Time Accuracy
5 s/cm to 1 µs/cm
±1% of indicated incremental delay
time ±4% of A TIME/CM setting.
Incremental Delay Time is t e difference
between two delay time readings.
0.5/is/cm to 0.1 µs/cm
±1% of indicated incremental delay
time ±7 % of A TIME/CM setting.
For additional information refer to Page
2-24 in t e Operating Instructions.
S ort Term Jitter
<1 part in 20,000 of t e available delay time.
EXTERNAL HORIZONTAL AMPLIFIERS
Ext. Horizontal Deflection Factor
<0.1 V/cm wit DISPLAY MAG in X10 posi 
tion.
Transient Response
±3% peak overs oot, rounding, ringing or tilt.
Variable Range
>10:1
Frequency Response
DC to >400 kHz at 3 dB down. VARIABLE
control set fully cw.
Maximum Input Voltage
50 V combined DC -|- peak AC. Wit DISPLAY MAG in X10 position.
Input C
Approximately 65 pF.
A & B TRIGGERING FEATURES
C aracteristic
Feature
Source
Internal Normal (from left or rig t trigger pick-off circuit wit in t e vertical amplifier),
Internal Plug-In (from one of t e c annels in t e left or rig t Type 1A1 or 1A2 Plug-In
Unit), Line and External.
Coupling
Capacitive (AC), low-frequency reject (AC LF REJ), ig -frequency reject (AC HF REJ) or
direct (DC).
Slope
Triggering on positive-or-negative-going portion of triggering signal.
Mode:
Auto Stability
Free runs sweep in absence of a triggering signal; instrument can be triggered on signals
>30 Hz.
Triggered
Triggered at an adjustable level.
Jitter
<2 ns.
LEVEL Control Range:
Normal
> ±2V.
X10 Increase
> ±20 V.
External Trigger Input:
R & C
Approximately 1 mego m paralleled by approximately 35 pF.
Volts
50 V maximum (DC plus peak AC).
A & B TRIGGERING SENSITIVITY
INT PLUG IN C aracteristics t at apply for t e EXT trigger input also apply to t e Int Plug-In interconnection
(pin 5 of plug-in connectors JI 1 and JI 2).
Trigger Coupling/Source
To 10 MHz
To 50 MHz
AC:
INT NORM
< 2 mm display amplitude
above 60 Hz.
< 1 cm display amplitude.
EXT
< 0.2 V above 60 Hz. < 0.4 V.
AC LF REJ:
INT NORM > 3 cm display amplitude
at 30 Hz.
< 2 mm display amplitude
above 2.5 kHz.
< 1 cm display amplitude.
EXT > 3 V at 30 Hz.
< 0.2 V above 2.5 kHz.
< 0.4 V.
AC HF REJ:
INT NORM <2 mm display amplitude
from 60 Hz to 60 kHz, >1 cm
at 6 MHz.
EXT <0.2 V from 60 Hz to 60 kHz,
> 1 V at 6 MHz.
DC
INT NORM
< 3.5 mm display amplitude.
< 2 cm display amplitude.
EXT
< 0.2 V.
< 0.4 V.
1-2

Characteristics — Type 556
AMPLITUDE CALIBRATOR
C aracteristic
Performance Specification
Supplemental Information
Voltage Accuracy ±2%.
5 mA Current Loop Accuracy ±2%.
Repetition Rate
1 kHz ±25%
Duty Cycle
45% to 55%.
Risetime
< 1.5 µS. 70 pF load.
Terminated Voltage Accuracy
One- alf indicated voltage ±2% w en termi 
nated into 50 o ms ±0.1%.
Applies to AMPLITUDE CALIBRATOR
switc positions from 0.2 mV to 0.2 V
only.
Z AXIS INPUTS
Sensitivity I
10 V P to P causes noticeable modula 
tion intensity.
Input R at DC 1
1 mego m ±10%.
FRONT-PANEL OUTPUT SIGNALS
A GATE
> 8 V positive-going pulse.
Wit baseline at zero volts. Time coin 
cident wit t e A sweep. Maximum
current is 10 mA. Recommended load
resistance >1 k.
B GATE
> 8 V positive-going pulse. Wit baseline at zero volts. Time coin 
cident wit t e B sweep. Maximum
current is 10 mA. Recommended load
resistance >1 k.
DLY'D TRIG
> 7 V positive-going pulse into a >1 k load. Pulse occurs at t e end of t e A sweep
delay period.
A SAWTOOTH
> 9V/cm.
Has t e same time duration as t e A
sweep. Recommended load resistance
>30 k.
B SAWTOOTH
> 9V/cm.
Has t e same time duration as t e B
sweep. Recommended load resistance
>30 k.
Line Frequency
50 Hz to 60 Hz
400 Hz wit special fan modification.
Power Consumption
±840 W maximum. ±1 kVA maximum.
T ermal Protection
An automatic resetting t ermal cutout
interrupts instrument power if internal
temperature exceeds safe operating
level.
POWER SOURCE REQUIREMENTS
For serial numbers 2000 and up
Regulating Range Selection: AC RMS Operating
Range (<2% armon 
ic distortion of t e in-
AC Peak Operating
Range (>2% armon-
is distortion 1 )
put power waveform)
115 Volts
LO 90 to 110 V 127 to 156 V
A Line Voltage Selector assembly facilit-
M
104 to 126 V 147 to 178 V
ies selection of a regulating range com-
patible wit t e actual line voltage.
HI
112 to 136 V
158 to 192 V
230 Volts
LO
180 to 220 V
254 to 311 V
M 208 to 252 V
294 to 356 V
HI
224 to 272 V 316 to 384 V
_ Peak V
Crest Factor ~ — between .30 and .4 4.
-3

Characteristics — Type 556
C aracteristic
Performance
Specification
Supplemental Infromation
For serial numbers 100-1999
Normal Line:
AC RMS Operating
Range (<2% armon 
ic distortion of t e in 
put power waveform)
AC Peak Operating
Range (>2% armon 
ic distortion 1 )
115 VAC Nominal
100 to 130 V
142 to 183 V Normally wired at t e factory for t is
voltage unless directed ot erwise.
230 VAC Nominal
200 to 260 V 284 to 366 V
Low Line:
104 VAC Nominal
90 to 117 V 127 to 165 V
208 VAC Nominal 180 to 234 V 254 to 330 V
CRT AND DISPLAY
2 Crest Factor = ------------- — between .30 and .4 4.
C aracteristic
Information
Tube Type
T5560-31-1. Dual-Beam, round, glass envelope. Tektronix Part No. 154-0500-00.
P osp or
P31 standard. Ot ers available on special order.
Accelerating Potential Approximately lOkV; gun potential is 2 kV.
Scan Area >6 cm vertical by 10 cm orizontal per beam. Beams can be overlapped in a 4 cm area.
Graticule Type
Internal. 8 cm vertical by 10 cm orizontal. Eac major division is 1 cm; four corners are
omitted.
Graticule Illumination
Variable edge lig ting.
Internal Unblanking DC-coupled to CRT control grids from t e Sweep Generators.
Ort ogonality Wit in ±1%.
Trace Rotation Range
Sufficient to align traces wit t eir respective graticule lines.
Beam Finder Limits traces wit in graticule area.
ELECTROMAGNETIC INTERFERENCE
Electromagnetic Interference
Meets interference specifications of MIL-I-6181D over t e following frequency ranges:
Radiated (wit CRT mes filter, cabinet covers and BNC connector covers installed) — 150
kHz to 1 GHz; conducted (power line) — 150 kHz to 25 MHz.
MECHANICAL CHARACTERISTICS
Construction Aluminum alloy c assis, panel and cabinet. Glass laminate etc ed circuit boards.
Finis
Anodized front panel. Blue vinyl-finis ed cabinet and rear panel.
Overall Dimensions: Measured at maximum points; 15 inc es ig , 16- 7 / 0 inc es wide, 24 inc es deep.
ENVIRONMENTAL CHARACTERISTICS
T e Type 556 as been designed to operate over a temper 
ature range of 0° C to +50° C, altitude up to 15,000 feet.
T e non-operating storage temperature range is — 40° C to
+65° C, altitude up to 50,000 feet. After storage at eit er
extreme, t e instrument must be allowed at least 4 ours time
for all components to return to t e ambient temperature range
0° C to +50° C before operating.
Furt er information on environmental test procedures may
be obtained by contacting your local Tektronix Field Office
or representative.
ACCESSORIES
Standard accessories supplied wit t e Type 556 can be
found on t e last pullo-ut page of t e Mec anical Parts List
Illustrations. For optional accessories see t e Tektronix, Inc.
catalog.
-4

Type 556
SECTION 2
OPERATING INSTRUCTIONS
C ange information, if any, affecting t is section will be found at t e rear of t e manual.
General
T is section of t e manual provides for t e effective use of
t e instrument by describing t e function and operation of
t e front panel controls and connectors, listing t e first time
and general operating instructions and presenting some basic
applications.
Nomenclature and Terminology
For reference and guidance, t ese terms are defined as t ey
are used in t is manual.
Alternate Mode — A time-s aring met od of displaying
t e output signals of two or more c annels wit a single
cat ode ray tube beam. C annel switc ing is sequential and
occurs at t e end of t e sweep.
Chopped Mode — A time-s aring met od of displaying
output signals of two or more c annels wit a single cat ode
ray tube beam, in sequence, at a rate not referenced to t e
sweep.
Chopping Rate — T e rate at w ic c annel switc ing
occurs in C opped Mode.
Chopping Transient Blanking — T e process of blanking
t e indicating spot during t e switc ing periods in C opped
Mode.
Dual-Beam Oscilloscope — An oscilloscope in w ic t e
cat ode ray tube produces two separate electron beams
t at may be individually or jointly controlled.
Dual-Trace — A mode of operation in w ic a single beam
in a cat ode ray tube is s ared by two signal c annels.
Multi-Trace — A mode of operation in w ic a single beam
in a cat ode ray tube is s ared by two or more signal c an 
nels.
Signal Channel — A signal amplifying circuit in a plug-in
unit. Wit dual and multi-c annel plug-ins, t e c annels are
generally designated C annel 1 (or A) C annel 2 (B), etc.
Power Requirements
T is instrument may be operated wit power from eit er
a 115-volt or a 230-volt (nominal) power source. Wit proper
positioning of t e Line Voltage Selector connectors, t e power
supply circuit will provide correct DC voltages wit adequate
regulations wit any line voltage wit in voltage limits of
90 to 136 volts RMS and 180 to 272 volts RMS and frequency
limits of 50 to 60 Hz. T e adjustable turns ratio design of
t e power transformer provides t e means of making t e
instrument compatible wit t is wide range of power source
voltages.
SN 2000-up
A Line Voltage selector assembly is provided to facilitate
c anging t e power transformer turns ratio (see Fig. 2-1).
T e assembly contains two line fuses and two movable pins
and socket type connectors. T e two-position connector is
termed t e Voltage Selector and t e t ree-position connector
is termed t e Range Selector.
Table 2-1 lists t e six Voltages and Range selector com 
binations and t e line voltage ranges t ey s ould be used
wit . Before connecting t e instrument to a power source,
measure t e power source line voltage and position t e Volt 
age and Range selectors accordingly.
TABLE 2-
Voltage
Selector
position
Range
Selector
position
Will provide optimum
regulation for line
voltages from
115 V LO
90 to 110 volts
115 V
M 104 to 126 volts
115 V
HI 112 to 136 volts
230 V LO 180 to 220 volts
230 V
M
208 to 252 volts
230 V
HI 224 to 272 volts
To c ange t e power transformer from one regulating
range configuration to anot er use t e following procedure:
1. Disconnect t e instrument from t e power source.
2. Loosen t e two captive screws and remove t e cover.
Since t e line fuses are attac ed to t e cover, t ey will be
pulled from t eir olders wit t e cover.
3. To c ange nominal line selections, pull t e Voltage
Selector until its pins are.free of t e sockets, invert t e selec 
tor and reseat t e pins in t e desired sockets.
NOTE
115-volt to 230-volt plug adapters are not sup 
plied wit t is instrument. If a suitable adapter
is not available, it may be necessary to c ange
t e line-cord plug.
4. To c ange regulating range selections, pull t e Range
selector until its pins are free of t e sockets, move it to t e
desired range position and seat t e pin in t e sockets.
5. Replace t e assembly cover and t e two line fuses. Press
t e cover firmly onto t e assembly to seat t e two fuses in
t eir olders, t en tig ten t e captive screws.
6. T e indicating tabs on t e selectors will be protruding
t roug t e covers to indicate t e selected regulating range.
Always c eck t e position of t ese tabs before applying
power to t e instrument.
2-

Operating Instructions — Type 556
SN 00- 999
Instruments wit serial numbers 100-1999, unless tagged
ot erwise, are connected at t e factory for operation at 115
volts (nominal). T e power transformer as eig t primary
terminals w ic are connected to solderless pin connectors
on t e Power board. T ese quick-c ange connectors make
possible operation from four different nominal AC voltages:
104, 115, 208 and 230 V, 50 to 60 Hz. Fig. 2-2 illustrates
t e jumper and lead connections required for operation on
eac of t e stated line voltages. For 208 V and 230 V opera 
tion, t e two unused jumpers can be stored on t e unused pins
of terminals J and T. All lead connections to t e board t at
are not s own in Fig. 2-2 remain as t ey are.
No c ange in fan connections is required w en c anging
t e connection on t e board as directed in t e illustration.
NOTE
Two metal tags (printed on eac side) are pro 
vided at t e rear of t e instrument to indicate t e
four nominal line voltages. If t e primary wiring
is c anged, be sure to use t e proper tag to indi 
cate t e voltage for w ic t e instrument is wired.
Temperature considerations
To reduce operating temperatures, air is drawn in t roug
t e filter at t e rear and blown forward t roug t e instru 
ment. For t e most efficient air circulation and eat dis 
sipation, provide at least t ree inc es clearance at t e rear,
two inc es at t e sides and operate t e instrument wit t e
side covers installed. If t e fan becomes inoperative or t e
air circulation is obstructed, t o internal temperatures will
exceed a safe operating level in a relatively s ort period of
time. To prevent damage to t o components from excessive
temperaturos, a t ermal cutout switc is incorporated in t o
power supply circuitry. T is switc is designed to interrupt
power to t o instrument w en t e ambient temperature ex 
ceeds about 140° F.
CAUTION
Since t e t ermal cutout switc will reset w en its
ambient temperature decreases to some level be 
low its actuating temperature, set t e POWER
switc to OFF before attempting to remedy t e
cause of t e ig temperature condition.
CONTROLS AND CONNECTORS
Figure 2-3 s ows t e location of all t e instrument operat 
ing controls and connectors. A brief description of eac type
of control and connector is given in t e following table.
Controls wit t e same nomenclatures generally perform
identical functions for t eir respective beams and a descrip 
tion for one is applicable to t e ot er. T ose controls wit
t e same nomenclature, but wit differences in t eir func 
tions, are pointed out and described as separate typ e con 
trols.
Some of t e controls and connectors, particularly t ose
wit complex functions or multiple applications, are de 
scribed in greater detail under General Operating Instruc 
tions.
A AND B TRIGGERING CONTROLS
Source Selects triggering signal source, Two selec 
tor switc es are combined under t e no 
menclature of SOURCE to provide t is
complex switc ing function. T e selections
of t e two position selector switc are:
LEFT: From left plug-in or left vertical
amplifier.
RIGHT: From rig t plug-in or rig t vertical
amplifier. T e selections of t e four posi 
tion selector switc are:
Fig. 2- . Line Voltage Selector assembly; provided in instruments
with serial number 2000 and up.
2-2

Operating Instructions — Type 556
Fig. 2-2. Positions of the movable jumper wires (black on yellow! for the four nominal lino voltage selections. This illustration is
applicable to 556 SN's 00 to 999.
2-3

Operating Instructions — Type 556
COUPLING
SLOPE
INT NORM: From trigger pickoff in t e
oscilloscope vertical amplifier for t e
respective plug-in unit.
INT PLUG IN: From trigger pickoff in t e
respective plug-in unit. Applies to multi 
trace plug-in units wit t is capability.
LINE: Uses a line-frequency signal as a
trigger.
EXT: From signal applied to t e TRIGGER
INPUT connector. Not affected by LEFT 
RIGHT switc .
Determines met od of coupling t e trigger 
ing signal to t e trigger circuit.
AC: Blocks t e DC component and allows
triggering to take place on t e AC com 
ponent. Wit frequencies about 30 Hz
and below, use t e DC position.
AC LF REJ: Rejects DC and progressively
attenuates signal frequencies below
about 2.5 kHz, allowing t e trigger cir 
cuits to respond only to t e ig er
frequencies.
AC HF REJ: Rejects DC, passes signals be 
tween 60 Hz and 60 kHz and progres 
sively attenuates signals above 60 kHz.
DC: Permits triggering on bot ig and
low (to DC) frequency signals.
Selects portion of triggering signal w ic
will trigger t e sweep.
+ : Sweep triggers from positive-going
portion of t e triggering signal.
— : Sweep triggers from negative-going
portion of t e triggering signal.
Upper Beam
DISPLAY Selects vertical (Y-axis) and orizontal (X-
axis) mode of operation for t e Upper
Beam.
LEFT PLUG-IN EXT: Left plug-in signal
provides t e vertical deflection w ile
t e signal applied to t e UPPER BEAM
EXT HORIZ IN connector provides t e
orizontal deflection.
LEFT PLUG-IN A: Left plug-in signal pro 
vides t e vertical deflection and t e A
TIME/CM switc sets t e sweep rate of
t e Upper Beam.
LEFT PLUG-IN B: Left plug-in signal pro 
vides t e vertical deflection and t e B
TIME/CM switc sets t e sweep rate of
t e Upper Beam.
RIGHT PLUG-IN A: Rig t plug-in signal
provides t e vertical deflection and t e
A TIME/CM switc sets t e sweep rate
of t e Upper Beam.
RIGHT PLUG-IN B: Rig t plug-in signal
provides t e vertical deflection and t e
B TIME/CM switc sets t e sweep rate
of t e Upper Beam.
RIGHT PLUG-IN EXT: Rig t plug-in signal
provides t e vertical deflection w ile
t e signal applied to t e UPPER BEAM
EXT HORIZ IN connector provides t e
orizontal deflection of t e Upper Beam.
POSITION Controls orizontal position of Upper Beam
trace. Single knob controls bot coarse
and fine adjustment of t e beam position
by means of a backlas coupling between
t e two sections of t e control.
MODE
Selects triggering mode.
AUTO STABILITY: Permits normal trigger 
ing on signals wit repetition rates
ig er t an about 30 Hz. Wit no
trigger signal or wit a lower repetition
rate, t e time-base circuit free runs and
provides a convenient reference trace.
DISPLAY
MAG
LEVEL
TRIGGER
INPUT
TRIG: Permits normal triggering on all
triggering signals. No trace occurs
w en t e triggering signal is removed.
Expands t e Upper Beam display to left
and rig t of graticule center.
X 1 : Normal presentation of t e display.
X10: Horizontal lengt of Upper Beam
display is magnified by 10. T e X10
lig t indicates t at t e display is magni 
fied.
A Sweep
Selects t e amplitude point on t e trigger 
ing signal w ere sweep triggering occurs.
W en t e knob is pulled out, greater
triggering range is offered for triggering
on ig er amplitude signals. T e sweep
trigger circuit is most sensitive to small
signals wit t e LEVEL control pus ed in
and set close to 0.
Connector for applying an external trig 
ger signal to t e Sweep Trigger circuit
w en its SOURCE switc is set to EXT.
A TIME/CM
OR
DELAY TIME
VARIABLE
Normally referred to as t e A TIME/CM
switc in t is manual. Selects t e sweep
rate of t e A sweep generator. Also selects
t e basic delay time (to be multiplied by
t e DELAY-TIME MULTIPLIER dial setting)
for delaying t e B sweep w en t e B
MODE switc is set to DLY'D BY A.
Provides continuously variable sweep rate
to at least 2.5 times t e setting of t e A
TIME/CM switc . Sweep rate is calibrated
w en t e control is set fully clockwise to
2-4

Operating Instructions — Type 556
RESET
A MODE
CALIBRATED. An UNCAL neon turns on
w en t e VARIABLE control is not in t e
CALIBRATED position.
W en t e RESET lamp is on, t e A sweep
is ready to start w en a trigger is received
(A MODE switc set to SINGLE SWEEP).
After a sweep is completed, t e RESET
button must be pressed before anot er
sweep can be presented.
Determines t e A sweep generator operat 
ing mode.
NORM: T e A sweep is triggered from an
internal or external signal as selected
by t e A TRIGGERING controls.
SINGLE SWEEP: T e A sweep generator
generates one sweep and t en s uts off
until reset.
POSITION
and DIS 
PLAY MAG
B Sweep
B TIME/CM
VARIABLE
and
RESET
B MODE
Selects t e sweep rate of t e B sweep gen 
erator. Can be used to drive t e Upper
Beam, Lower Beam, or bot beams, de 
pending on t e position of t e DISPLAY
switc es.
Performs same functions for B sweep as
corresponding control and pus button do
for A sweep.
Determines t e B sweep generator operat 
ing mode.
SINGLE SWEEP: T e B sweep generator
generates one sweep and t en s uts off
until reset.
DLY'D BY A: B sweep circuit will not pro 
duce a sweep until a trigger pulse is
received following t e delay time
selected by t e A TIME/CM (OR DELAY
TIME) switc and t e DELAY-TIME
MULTIPLIER dial.
NORM: T e B sweep is triggered from an
internal or external signal as selected
by t e B TRIGGERING controls.
ASTIGMATISM
UPPER BEAM
EXT HORIZ
VAR
Lower Beam
DISPLAY
RIGHT
PLUG-IN:
Selects orizontal (X-axis) mode of opera 
tion for t e Lower Beam.
Rig t plug-in signal provides t e vertical
deflection and t e A TIME/CM switc sets
t e sweep rate of t e lower beam (not
incorporated in instruments serial numbered
100-1999).
RIGHT PLUG-IN B: Rig t plug-in signal
provides t e vertical deflection and t e
TRACE
SEPARATION
B TIME/CM switc sets t e sweep rate
of t e Lower Beam.
RIGHT PLUG-IN EXT: Rig t plug-in signal
provides t e vertical deflection w ile
t e signal applied to t e LOWER BEAM
EXT HORIZ IN connector provides t e
orizontal deflection of t e Lower Beam.
Performs same functions for Lower Beam
as corresponding controls do for Upper
Beam.
Upper Beam and Lower Beam (for both beams
where applicable)
INTENSITY
Controls brig tness of t e display.
CAUTION
Excessive intensity can permanently
damage t e p osp or on t e CRT
screen. Use t e INTENSITY control
to keep t e beam brig tness turned
down below t e level t at causes a
alo to form around t e CRT spot
or trace.
FOCUS Provides adjustment for a well-defined
display. Used in conjunction wit t e
INTENSITY and ASTIGMATISM controls.
CONTRAST (For Ppper Beam only in instruments SN
100-1999). Controls brig tness of non-in-
tensified portion of trace or display during
delayed B sweep mode of operation.
Used in conjunction wit t e INTENSITY
and FOCUS controls for obtaining a well-
defined display.
Lower Portion of Front Panel
Controls amount of Upper Beam orizontal
deflection produced by voltage applied
to t e UPPER BEAM EXT HORIZ IN connec 
tor. Horizontal deflection factor is continu 
ously variable from about 1 to 10V/cm
wit t e Upper Beam DISPLAY switc set to
eit er of t e EXT positions and t e DIS 
PLAY MAG switc set to XI; from 0.1 to
about 1 V/cm w en DISPLAY MAG switc
is set to X10.
TRACE
ROTATION
Screwdriver adjustment to simultaneously
align t e traces of bot beams wit t eir
respective orizontal center lines.
Varies t e vertical position of t e Upper
Beam wit respect to t e Lower Beam
w en t e Upper Beam DISPLAY switc is
set to any of t e RIGHT PLUG-IN posi 
tions.
2-5

Operating Instructions — Type 556
SCALE ILLUM
LOWER BEAM
EXT HORIZ
VAR
DELAY-TIME
MULTIPLIER
BEAM FINDER
AMPLITUDE
CALIBRATOR
5 mA Current
Loop
POWER
DLY ’ D TRIG
A GATE
B GATE
CAL OUT
UPPER BEAM
EXT HORIZ IN
Controls graticule illumination.
Same function as corresponding Upper
Beam control but applied to t e Lower
Beam orizontal deflection.
Works in conjunction wit t e A TIME/
CM (OR DELAY TIME) switc . Provides
variable delay of t e B sweep up to 10.00
times t e delay time indicated by t e A
TIME/CM switc .
Returns t e displays of bot beams to t e
screen w en t e button is pressed. Limits
t e orizontal and vertical amplifier dy 
namic ranges of bot beams. Used to
locate trace(s) w ic exceeds scan of dis 
play area.
Determines t e peak-to-peak positive-from-
ground voltage available at t e CAL OUT
connector.
NOTE
W en working into an external 50-
o m load using t e .2 VOLTS to 200
mVOLTS positions, output amplitude
is one- alf t e indicated voltage.
Provides 5 mA square-wave current from
t e calibrator circuit. T e arrow s ows
direction of conventional current flow (i.e.,
positive to negative).
Toggle switc : Applies line power to t e
low-voltage power transformer.
Lig t: Indicates t at t e AC line voltage
is applied to t e power transformer.
Output connector w ic supplies a s arp
positive-going trigger spike equal to or
greater t an 7 V at t e end of t e delay
period as set by t e A TIME/CM (OR
DELAY TIME) switc and t e DELAY-TIME
MULTIPLIER control.
Output connector w ic supplies a posi 
tive-going square-wave pulse equal to or
greater t an 8 V coincident wit t e
A sweep. Pulse duration is approximately
10.5 X t e setting of t e A TIME/CM
switc w en t e (A) VARIABLE control is
set to CALIBRATED.
Same as A GATE except applies to B
TIME/CM switc and (B) VARIABLE control.
Output connector for t e Amplitude Cali 
brator.
Input connector for applying an external
orizontal signal to t e Upper Beam ori 
zontal amplifier w en t e Upper Beam
DISPLAY switc is set to eit er EXT posi 
A SAWTOOTH
B SAWTOOTH
EXT CRT
CATHODE
CRT Cathode
Selector
tion. A positive voltage deflects t e beam
from left to rig t.
Output connector w ic supplies a saw 
toot voltage from t e A sweep generator.
Peak amplitude is equal to or greater t an
9 V/cm. T e sawtoot ramp is positive 
going from near ground.
Same as A SAWTOOTH except applies to
t e B sweep generator output.
LOWER BEAM Same as UPPER BEAM EXT HORIZ IN
EXT HORIZ IN except applies to t e Lower Beam ori 
zontal amplifier w en t e Lower Beam
DISPLAY switc is set to EXT.
Rear Panel (Upper and Lower Beam)
Input connector for intensity modulation
(Z-axis) of t e display.
Toggle switc for t e CRT cat ode circuit.
EXT CRT CATHODE: Normal operation
wit s orting cover connected. Wit
s orting cover removed, CRT cat ode
can be intensity modulated wit a 10 V
or more signal applied to t e EXT CRT
CATHODE connector.
UPPER BEAM (LOWER BEAM) CHOPPED
BLANKING: Permits blanking t e Upper
(Lower) Beam w ile t e multi-trace plug 
in unit is switc ing from one c annel to
anot er during c opped mode of opera 
tion.
LINE VOLTAGE Facilitates c anging t e power transformer
SELECTOR circuit configuration. T e assembly con-
ASSEMBLY tains a Voltage Selector, a Range Selector
and two line fuses, (not incorporated in
instruments SN 100-1999).
SELECTION OF PLUG-IN UNITS
T e Type 556 Oscilloscope is designed to use Tektronix
letter-series and 1 -series plug-in units as t e input stages for
t e two vertical deflection systems.
A plug-in unit installed in t e left- and compartment of
t e oscilloscope is identified as t e "left plug-in ” . T is unit
provides vertical deflection for t e Upper Beam only w en
t e Upper Beam DISPLAY switc is set to t e LEFT PLUG-IN
positions. Similarly, t e plug-in unit installed in t e rig t 
and compartment is referred to as t e “ rig t plug-in ” . T is
unit, owever, provides vertical deflection for bot beams
simultaneously or for t e Lower Beam only, depending on
t e settings of t e DISPLAY switc es.
T e use ot plug-in units as t e vertical inputs permits
c anging t e vertical c aracteristics of t e oscilloscope to
meet a wide range of application requirements. T e parti 
cular plug-in units to be used must be selected to satisfy t e
requirements of your applications. In selecting t e vertical
plug-in units, consider t e bandpass, risetime, deflection
2-6

Operating Instructions — Type 556
factor, input RC c aracteristics and t e number of inputs.
Ot er plug-in units to consider are special purpose types
suc as differential amplifiers and comparators, operational
amplifiers, spectrum analyzers, etc. Table 2-2 lists a wide
variety of plug-in units t at can be used wit t e instrument.
T e Type 556 Oscilloscope s ould not be used wit out
plug-in units installed or connected by extensions. Operating
t e instrument wit a plug-in missing will not damage t e
oscilloscope, but will cause t e vertical amplifier and t e
sweep generator on t at side of t e oscilloscope to be
inoperative.
TABLE 2-2
VERTICAL PLUG-IN UNITS
(Plug-ln/556 system bandwidt c aracteristics are at
3 dB down )
Plug-In Calibrated
Bandwidt
Risetime
Unit Type Deflection
Factor
For Wide-Band, Multiple Trace Applications
1A1 Dual-
50 mV/cm to
20 V/cm
DC to 50 MHz 7 ns
Trace 5 mV/cm DC to 28 MHz
12.5 ns
500 µV/cm
2 Hz to 15 MHz
23 ns
1A2 Dual 
Trace
50 mV/cm to
20 V/cm
DC to 50 MHz
7 ns
CA Dual 
Trace
50 mV/cm to
20 V/cm
DC to 24 MHz 15 ns
M Four-
Trace
20 mV/cm to
10 Vcm
DC to 20 MHz
18 ns
Hig -Frequency Sampling Applications
1S1 2 mV/cm to
200 mV/cm
350 ps
1S2
5 mV/cm to
500 mV/cm
90 ps
For Wide-Band Applications
B
50 mV/cm to
20 V/cm
DC to 20 MHz 18 ns
5 mV/cm to
20 mV/cm 2 Hz to 12 MHz 30 ns
K
50 mV / cm to
20 V
DC to 30 MHz
12 ns
L
50 mV/cm to
20 V
DC to 30 MHz
12 ns
5 mV / cm to
2 V/cm
3 Hz to 24 MHz
15 ns
For Hig DC Sensitivity Applications
H Wide- 5 mV/cm to
DC to 15 MHz
23 ns
Band
20 V/cm
For Differential Input Applications
D Hig -
Gain
1 mV/cm (to
50 mV/cm)
DC to 300 kHz 0.1 8 µS
E Low-
Level
50 µV/cm (to
10 mV/cm)
0.06 Hz to 20
kHz (to 60 kHz)
6 µS
G Wide-
Band
50 mV/cm to
20 V/cm
DC to 20 MHz 18 ns
For Integration, Differentiation, Function Generation,
Linear and Non-Linear Uses
1A7 Hig -
10 «V/cm to
DC to 500 kHz
Gain
10V/cm
Selectable
0.7 µS
bandwidt
For Transducer and Strain Gage Uses
O
50 mV/cm to
DC to 25 MHz 14 ns
Operational
20 V/cm
Amplifier
For Displaying Simultaneously Delay, Rise, Storage,
and Fall Times of Transistors
10 µstrain/
DC to 6 kHz 60 µS
Q
div to 10,000
µstrain/div
For Displaying Forward and Reverse Switc ing C ar 
acteristics of Semiconductor Diodes
R Transistor- 0.5 mA/cm to
DC to 30 MHz
12 ns
Risetime
100 mA/cm
S Diode
Recovery
1 mA to 20
mA forward
current, 0 mA
to 2 mA re 
verse current
DC to 30 MHz 12 ns
For Precise Amplitude Measurements Via Slide-Back
W
1 mV/cm to
DC to 8 MHz at 44 ns at 1
Hig -Gain 50 V/cm
1 mV/cm, increas- mV/cm, 15
Differential
ing to 23 MHz at
ns at 50
Comparator
50 mV/cm mV/cm
For Spectrum Analysis
Plug-In Unit Type
Tuning Range
1L5
10 Hz to 1 MHz
1 L10
1 MHz to 36 MHz
1L20
10 MHz to 4200 MHz
1L30
925 MHz to 10.5 GHz
In addition, nine narrow-band spectrum analyzers cover 
ing frequencies between 10 MHz and 18.2 GHz are available
on special order — contact your Local Tektronix Field Engi 
neer or Field Office.
FIRST TIME OPERATION
T is procedure describes t e basic turn-on precautions and
demonstrates t e function of t e essential general operating
controls.
1. Before connecting t e instrument to a power source, set
t e POWER switc to OFF, turn bot INTENSITY controls
fully counterclockwise and inspect for a power transformer
circuit configuration compatible wit t e actual power source
voltage.
2. Install two vertical amplifier type plug-in units, or, if
available, two Tektronix Calibration Fixtures, part number
067-0521 -00.
3. Connect t e instrument to t e power source and turn
t e POWER switc to ON.
4. W ile waiting for instrument warmup, set t e controls
of bot beams and t e plug-in units as follows-.
2-7

Operating Instructions — Type 556
A and B Triggering
A SOURCE
LEFT INT NORM
B SOURCE
RIGHT INT NORM
COUPLING AC
SLOPE
+
MODE
AUTO STABILITY
LEVEL Clockwise, knob pus ed in
A and B Sweep
A TIME/CM and
B TIME/CM .5 SEC
VARIABLE
CALIBRATED
A MODE and B MODE NORM
Upper and Lower Beam
A DISPLAY
LEFT PLUG-IN A
B DISPLAY
RIGHT PLUG-IN B
POSITION
Centered
DISPLAY MAG
XI
AMPLITUDE CALIBRATOR
50 mVOLTS
Rear Panel
CRT Cat ode Selector EXT CRT CATHODE
Vertical Plug-In Units
Position Centered
Volts/Cm .05
Input Selector AC
Front Panel Adjustments
5. Apply a 50-mV signal from t e oscilloscope CAL OUT
connector to bot vertical plug-in units.
6. Turn t e INTENSITY controls clockwise until t e displays
are of normal brig tness.
7. Adjust t e A and B Triggering LEVEL control to obtain
stable displays.
8. Use t e plug-in Position controls to position t e displays
to t e center of t eir respective graticule viewing areas.
9. Use t e Upper and Lower Beam orizontal POSITION
controls to position t displays so t ey start at t e left edge
of t e graticule.
10. Adjust t e FOCUS and ASTIGMATISM conrols to ob 
tain well-defined displays.
11. Set t e plug-in unit Input Selector switc es to Gnd or
remove t e signal. C eck t at t e traces are parallel to
t eir respective graticule center lines. If t ey are not, adjust
t e TRACE ROTATION control for best alignment of t e
traces wit t e graticule lines.
12. T is completes t e basic operation procedure for t e
Type 556. Instrument operation not explained ere, or opera 
tion w ic needs furt er explanation is discussed under
General Operating Information.
GENERAL OPERATING INFORMATION
Light Filters
T e mes filter supplied wit t e Type 556 provides s ield 
ing against radiated EMI (electro-magnetic interference;
formerly called RFI) from t e face of t e CRT. It also serves
as a lig t filter to make t e trace more visible under ig
ambient lig t conditions. T e mes filter and graticule cover
are one unit (Tektronix Part No. 378-0572-00). To remove t e
filter, remove t e four graticule nuts and t en remove t e
graticule cover and mes filter as a unit.
A tinted lig t filter is also provided. T is filter minimizes
lig t reflections from t e face of t e CRT to improve contrast
w en viewing t e display under ig ambient lig t condi 
tions. If a lig t filter is needed and EMI s ielding is not
required, use t e tinted filter to obtain least loss of beam
brig tness.
NOTE
W en using a lig t filter, avoid t e tendency to
set t e beam intensities so ig t at t ey will burn
t e CRT p osp or.
A clear plastic faceplate protector is provided wit t e
Type 556 for use w en t e mes filter or t e tinted filter
are not used. T e clear faceplate protector provides t e
best display for waveform p otograp s. It is also preferable
for viewing ig writing rate displays under low ambient
lig t conditions.
T e tinted filter or t e faceplate protector s ould be used
at all times to protect t e CRT faceplate from scratc es. T e
faceplate protector and t e tinted filter are eld in place by
a graticule cover (Tektronix Part No. 200-0382-00). To remove
t e lig t filter or faceplate protector, remove t e four grati 
cule nuts and t e graticule cover.
Calibrated Graticule
T e edge-lig ted internal graticule is accurately marked
wit 8 vertical and 10 orizontal 1-cm divisions. T ere are
2-mm sub-divisions marked on t e vertical center line and
t e two orizontal center lines (one for eac beam). One
centimeter of eac corner of t e graticule is omitted so t e
graticule fits wit in t e round CRT screen. T e deflection
factors of t e CRT beams are calibrated to t e graticule
marks. T us t e marks provide a calibrated scale for making
time and voltage measurements.
Eac beam as a usable vertical scan area of 6 cm. T e
beams overlap in t e center 4-cm area of t e graticule to
permit superimposed displays.
Beam Finder
T e BEAM FINDER pus button provides a means of locat 
ing a display w ic overscans t e viewing area eit er verti 
cally or orizontally. W en t e BEAM FINDER button is
pressed, t e display is compressed wit in t e graticule area.
To locate and reposition an overscanned display, use t e
following procedure.
1. Press t e BEAM FINDER button.
2-8

Operating Instructions — Type 556
B. Center portion of rear panel.
Fig. 2-3. Control setup chart for Type 556 5N 2000 and up.
2-9

Operating Instructions — Type 556
A. Front Panel
B. Center portion of rear panel.
Fig. 2-4. Type 556 control setup chart for instruments with serial number 999 and below.
2-10

Operating Instructions — Type 556
2. W ile t e BEAM FINDER button is eld in, reduce t e
vertical deflection to less t an 3 cm by adjusting t e ampli 
tude of t e input signal or t e deflection factor of t e plug-in.
3. Adjust t e POSITION controls of t e plug-ins and t e
Type 556 to center t e display wit in t e beam viewing area.
4. Release t e BEAM FINDER button; t e display s ould
appear wit in t e viewing area.
Output Signals
Several low-impedance signal outputs are available at t e
front panel of t e Type 556 Oscilloscope. T ese are Delayed
trigger pulse, a gate waveform from eac time base, a saw 
toot waveform from eac time base, and an Amplitude Cali 
brator square wave. Typical waveforms are illustrated in
Fig. 2-5.
In addition, some multi-trace vertical plug-in units pro 
vide an amplified single-c annel signal output to be used as
a reference for triggering oscilloscopes. Suc units apply t e
single-c annel signal to t e Type 556 triggering circuits
t roug internal wiring w en t e SOURCE switc es are set
to t e PLUG IN position.
Use of t e gate and sawtoot waveforms for triggering or
driving external devices is illustrated in Fig. 2-6. In t is
application, t e time base is usually set for a free-running
sweep.
In addition to t e sawtoot outputs on t e front panel,
t ere is an internal sawtoot voltage t at is applied to pin 6
of bot plug-in interconnecting jacks. For t e left plug-in
unit t e sawtoot voltage originates from t e A Sweep Gen 
erator; for t e rig t plug-in unit t e sawtoot voltage origin 
ates from t e B Sweep Generator. T ese sawtoot voltages
provide a standardized current ramp of 20 µA/cm (nominal)
via a standardizing resistor for use in driving plug-in spec 
trum analyzers requiring t is signal source.
T e internal current ramps can also be used to drive low-
impedance circuits, suc as t e minus input of an operational
amplifier or t e emitter of a transistor, wit a positive-going
linear ramp of current. T e internal and external sawtoot s
from eac sweep may not drive two circuits w en bot out 
puts are used at t e same time, nor will t e internal saw 
toot successfully serve as a voltage signal source — espe 
cially at t e faster sweep rates.
W en pin 6 is not used, t e ig impedance of t is saw 
toot signal source prevents excessive cross-talk of t e signal
into t e plug-in unit.
Control Setup Chart
Fig. 2-3 and Fig. 2-4 s ow t e front panel and a portion of
t e rear panel of t e Type 556. If t e controls of t e plug-in
unit being used are sketc ed in, t e completed picture may
be reproduced and used as a test setup record for special
measurements, applications or procedures, or may be used
as a training aid for familiarization wit t is oscilloscope.
Vertical Controls
T e vertical plug-in unit for eac beam contains ail t e
front-panel vertical positioning and deflection controls for
t at beam wit t e exception of t e TRACE SEPARATION
control. Refer to t e instruction manuals of t e particular
plug-in units for operation of t e vertical controls.
CONNECTING TO THE SIGNAL SOURCE
Input signals t at are to be displayed as vertical deflec 
tion on t e CRT screen are applied to t e input connectors
on t e two vertical plug-in units.
2-

Operating Instructions — Type 556
\
x
Output of device
is applied to
vertical plug-in unit
Fig. 2-6. Using the A GATE or A SAWTOOTH waveform to trigger or drive an external device. Sweep is usually free running.
Use of Coaxial Cables
In general, coaxial cables s ould be used to connect t e
signal source to t e vertical input. T e use of coaxial cables
nearly eliminates pickup from stray electromagnetic fields,
and also eliminates radiation from t e connecting cables by
grounding t e outside conductors. It is sometimes possible to
use an uns ielded input lead if t e signal amplitude is ig
and if its frequency is low. W en an uns ielded lead is
used, connect anot er lead between t e oscilloscope c assis
and t e c assis of t e signal source.
In ig -frequency work it is usually necessary to terminate
signal sources and connecting cables in t eir c aracteristic
impedances. Unterminated connections result in signal reflec 
tions wit in t e cables and cause distortion of t e displayed
waveforms. T e input coaxial cable will often serve to termi 
nate t e signal source, and a termination placed at t e input
of t e plug-in unit will provide sufficient termination for sig 
nal reflections. However, if t e source impedance is consid 
erably different from t at of t e connecting cable, t e source
end of t e cable may also need to be terminated.
W en connecting an input signal, t e loading effect of t e
oscilloscope on t e signal source must be considered. T e
resistance at t e input of t e vertical plug-in unit is usually
1 mego m w ic adequately limits low-frequency loading to
a negligible value. However, at ig frequencies, t e input
capacitance of t e vertical plug-in and t e distributed capaci 
tance of t e input cable become significant. Capacitive
loading at ig frequencies may be sufficient to adversely
affect bot t e displayed waveform and t e operation of
t e signal source. Attenuator probes can be used to reduce
capacitive and resistive loading to very small values.
Use of Probes
In addition to reducing t e load on t e signal source, an
attenuator probe also decreases t e amplitude of t e dis 
played waveform by t e attenuation factor of t e probe.
T is permits observation of signals beyond t e normal ampli 
tude limits of t e oscilloscope and plug-in combination. Sig 
nal amplitudes, owever, must be limited to t e maximum
allowable value of t e probe being used.
Before a probe is used, it must be compensated to operate
properly wit t e plug-in unit. Compensation of t e probe is
adjusted according to t e procedure given in t e instruction
manual wit t e vertical plug-in unit and in t e instructions
accompanying t e probe. In general, t is adjustment is done
by connecting t e probe cable to one of t e vertical inputs
and observing several cycles of t e calibrator waveform
on t e CRT screen. T e compensating capacitor is t en
adjusted to provide minimum distortion of t e top and lead 
ing corner of t e square-wave signal (see Fig. 2-7).
Trigger Source
INT. For most applications, t e sweep can be triggered
internally. In t e INT positions of t e SOURCE switc , t e
2- 2