Tektronix 556 User manual

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IVIAIMUAL
Serial Number
TYPE
556
OSCILLOSCOPE
Tektronix, Inc.
S.W. Millikan Way • P. O. Box 500 • Beaverton, Oregon 97005 • Phone [phone] • Cables: Tektronix
070-0757-00 1167

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,
therefore all requests for repairs and re
placement parts should be directed to
the Tektronix Field Office or representative
in your area. This procedure will assure
you the fastest possible service. Please
include the instrument Type and Serial or
Model Number with all requests for parts
or service.
Specifications and price change privi
leges reserved.
Copyright ® 1966, new material 1967
by Tektronix, Inc., Beaverton, Oregon.
Printed in the United States of America.
All rights reserved. Contents of this pub
lication may not be reproduced in any
form without permission of the copyright
owner.
Type 556

Section 7
Section 8
Section 9
Parts Ordering Information
Electrical Parts List
Mechanical Parts List Information
Mechanical Parts List
Mechanical Parts List Illustrations
Accessories
Abbreviations and symbols used in this manual
are based on or taken directly from IEEE Stand
ard 260 “ Standard Symbols for Units” , MIL-STD-
1 2B and other standards of the electronics indus
try. Change information, if any, is located at the
rear of this manual.
Type 556

Serial numbor 2000 and up.
Serial number 1999 and below.
Fig. 1-1. Type 556 Oscilloscopes.
Type 556

SECTION I
CHARACTERISTICS
Type 556
Change information, if any, affecting this section is found at the rear of the manual.
Introduction
The Type 556 Oscilloscope—is a versatile dual-beam labor
atory type instrument providing accurate voltage and time
measurements in the DC to 50 M z frequency range. Two
complete horizontal and vertical deflection systems permit
completely indepentent operation of the two beams.
The Upper Beam can display the signal from either the
left or right vertical plug-in unit and may be controlled by
either the A or B time base or an external signal. The Lower
Beam displays the signal from the right plug-in and the sweep
is controlled by the B time base or an external signal. The
left and right plug-in compartments accept all letter series
and 1-series plug-ins.
Special circuits within the oscilloscope provide selection
of an accurate, continuously-variable delay when using the
B sweep. The B sweep may be delayed by the A sweep from
0.1 [is to 50 s (calibrated) after application of a trigger pulse.
This feature permits the delayed B sweep to expand a
selected portion of the undelayed A sweep, thereby pro
viding precise time measurements and detailed observation
of the signal. Both the delayed and undelayed sweeps can
be presented simultaneously on the oscilloscope screen. The
Upper Beam trace has an intensified zone indicating the por
tion of the signal being displayed by the B sweep and Lower
Beam.
The instrument is designed to operate over an ambient
temperature range of 0° C to +50° C. Performance speci
fications that are given in the center column apply over this
temperature range after a warmup time of 20 minutes. Sup
plemental information describing a characteristic or a feature
is also included in this portion of the manual.
VERTICAL AMPLIFIERS
Characteristics Performance Specification Supplemental Information
Frequency Response DC to >50 M z at 3dB down with a 1-series
plug-in unit having a risetime of 3.12 ns or less.
Risetime <6.25 ns. Indicated risetime of 6.93 ns
with a Test Load Plug-In Unit (Tektronix
Part No. 067-0521-00) having a risetime
of 3 ns.
Transient Response on Screen <2.25% peak overshoot, rounding, ringing or
tilt. Applies to all three vertical modes with
Test Load Plug-In Units.
Gain Change v/ith Line Voltage
Change <1% from 147 VAC peak to 178 VAC peak.
Trace Drift with Line Voltage
Change ± 2 mm from 147 VAC peak to 178 VAC peak.
A & B S EEP GENERATORS
Calibration Accuracy
5 s/cm to 0.1 [is/cm ±3% of displayed time between two points
displayed within the middle 8 cm.
X10 Magnified Display ±5% of displayed time between any two
points >1 cm apart displayed within the
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 Length 10.5 cm ±0.5 cm At 1 ms/cm.
VARIABLE TIME DELAY
Delay Time Accuracy
5 s/cm to 1 jus/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 the DELAY-TIME
MULTIPLIER dial.
0.5 [i.s/cm to 0.1 jus/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 the Operation Instructions.
1-1

Characteristics— Type 556
Characteristics Performance Specification Supplemental Information
Incremental Delay Time Accuracy
5 s/cm to 1 /i,s/cm ±1 % of indicated incremental
time ± 4% of A TIME/CM setting. delay Incremental Delay Time is the difference
between two delay time readings.
0.5/xs/cm to 0.1 /xs/cm ± 1% of indicated incremental
time ± 7% of A TIME/CM setting. delay For additional information refer to Page
2-24 in the Operating Instructions.
Short Term Jitter <1 part in 20,000 of the available delay time.
EXTERNAL HORIZONTAL AMPLIFIERS
Ext. orizontal Deflection Factor <0.1 V/cm with DISPLAY MAG in X10 posi
tion.
Transient Response ±3 % peak overshoot, rounding, ringing or tilt.
Variable Range >10:1
Frequency Response DC to >400 k z at 3 dB down. VARIABLE
control set fully cw.
Maximum Input Voltage 50 V combined DC + peak AC. With DISPLAY MAG in X10 position.
Input C Approximately 65 pF.
A & B TRIGGERING FEATURES
Characteristic Feature
Source Internal Normal (from left or right trigger pick-off circuit within the vertical amplifier),
Internal Plug-In (from one of the channels in the left or right Type 1A1 or 1A2 Plug-In
Unit), Line and External.
Coupling Capacitive (AC), low-frequency reject (AC LF REJ), high-frequency reject (AC F 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 z.
Triggered Triggered at an adjustable level.
Jitter < 2 ns.
LEVEL Control Range:
Normal > ± 2 V.
X10 Increase > ±2 0 V.
External Trigger Input:
R & C Approximately 1 megohm paralleled by approximately 35 pF.
Volts 50 V maximum (DC plus peak AC).
A & B TRIGGERING SENSITIVITY
Trigger Coupling/Source To 10 M z To 50 M z
AC:INT NORM < 2 mm display amplitude
above 60 z. < 1 cm display amplitude.
EXT < 0.2 V above 60 z. < 0.4 V.
AC LF REJ:
INT NORM > 3 cm display amplitude
at 30 z. < 2 mm display amplitude
above 2.5 k z. < 1 cm display amplitude.
EXT > 3 V at 30 z. < 0.2 V above 2.5 k z. < 0.4 V.
AC F REJ:
INT NORM < 2 mm display amplitude
from 60 z to 60 k z, >1 cm
at 6 M z.
EXT <0.2 V from 60 z to 60 k z,
>1 V at 6 M z.
DC INT NORM < 3.5 mm display amplitude. < 2 cm display amplitude.
EXT < 0.2 V. < 0.4 V.
INT PLUG IN Characteristics that apply for the EXT trigger input also apply to the Int Plug-In interconnection
(pin 5 of plug-in connectors Jll and J12).
1-2 D

AMPLITUDE CALIBRATOR
Characteristics— Type 556
Characteristic Performance Specification Supplemental Information
Voltage Accuracy
i ;
vO
o'-
CN
+1
5 mA Current Loop Accuracy ±2% .
Repetition Rate 1 k z ±25%
Duty Cycle 45% to 55%.
Risetime < 1.5 jus. 70 pF load.
Terminated Voltage Accuracy One-half indicated voltage ± 2% when termi
nated into 50 ohms ±0.1% . Applies to AMPLITUDE CALIBRATOR switch positions from 0.2 mV to 0.2 V
only.
Z AXIS INPUTS
Sensitivity 10 V P to P causes noticeable modula
tion intensity.
Input R at DC 1 megohm ±10% .
FRONT-PANEL OUTPUT SIGNALS
A GATE > 8 V positive-going pulse. With baseline at zero volts. Time coin
cident with the A sweep. Maximum
current is 10 mA. Recommended load
resistance >1 kO.
B GATE > 8 V positive-going pulse. With baseline at zero volts. Time coin
cident with the B sweep. Maximum
current is 10 mA. Recommended load
resistance >1 kQ.
DLY'D TRIG > 7 V positive-going pulse into a >1 kft load. Pulse occurs at the end of the A sweep
delay period.
A SAWTOOT > 9 V/cm. as the same time duration as the A
sweep. Recommended load resistance
>30 kn.
B SAWTOOT > 9 V/cm. as the same time duration as the B
sweep. Recommended load resistance
>30 kn.
Line Frequency 50 z to 60 z 400 z with special fan modification.
Power Consumption ±840 W maximum. ±1 kVA maximum.
Thermal Protection An automatic resetting thermal cutout
interrupts instrument power if internal
temperature exceeds safe operating
level.
PO ER SOURCE REQUIREMENTS
For serial numbers 2000 and up
Regulating Range Selection: AC RMS Operating
Range (<2% harmon
ic distortion of the in-
AC Peak Operating
Range (>2% harmon-
is distortion1)
put power waveform)
115 Volts
LO 90 to n oV 127 to 156V A Line Voltage Selector assembly facilit-
M104 to 126 V 147 to 178 V ies selection of a regulating range com-
patible with the actual line voltage.
I 112 to 136 V 158 to 192 V
230 Volts
LO 180 to 220 V 254 to 311 V
M208 to 252 V 294 to 356 V
I 224 to 272 V 316 to 384 V
1Crest Factor =
1-3
Peak V , . , ._ .
-------- “ between 1.30 and 1.414.
RMS V

Characteristics— Type 556
Characteristic Performance Specification Supplemental Infromation
For serial numbers 100-1999
Normal Line: AC RMS Operating AC Peak Operating
Range (<2% harmon- Range (>2% harmon
ic distortion of the in- ic distortion1)
put power waveform)
115 VAC Nominal 100 to 130 V 142 to 183 V Normally wired at the factory for this
voltage unless directed otherwise.
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
Characteristic Information
Tube Type T5560-31-1. Dual-Beam, round, glass envelope. Tektronix Part No. 154-0500-00.
Phosphor P31 standard. Others available on special order.
Accelerating Potential Approximately 10kV; gun potential is 2 kV.
Scan Area > 6 cm vertical by 10 cm horizontal per beam. Beams can be overlapped in a 4 cm area.
Graticule Type Internal. 8 cm vertical by 10 cm horizontal. Each major division is 1 cm; four corners are
omitted.
Graticule Illumination Variable edge lighting.
Internal Unblanking DC-coupled to CRT control grids from the Sweep Generators.
Orthogonality Within ±1 % .
Trace Rotation Range Sufficient to align traces with their respective graticule lines.
Beam Finder Limits traces within graticule area.
ELECTROMAGNETIC INTERFERENCE
Electromagnetic Interference Meets interference specifications of MIL-I-6181D over the following frequency ranges:
Radiated (with CRT mesh filter, cabinet covers and BNC connector covers installed)— 150
k z to 1 G z; conducted (power line)—150 k z to 25 M z.
MECHANICAL CHARACTERISTICS
Construction Aluminum alloy chassis, panel and cabinet. Glass laminate etched circuit boards.
Finish Anodized front panel. Blue vinyl-finished cabinet and rear panel.
Overall Dimensions: Measured at maximum points; 15 inches high, 16-7/8 inches wide, 24 inches deep.
peak V
2Crest Factor = ------------- = between 1.30 and 1.414.
RMS V
ENVIRONMENTAL CHARACTERISTICS
The Type 556 has been designed to operate over a temper
ature range of 0° C to +50° C, altitude up to 15,000 feet.
The non-operating storage temperature range is —40° C to
+65° C, altitude up to 50,000 feet. After storage at either
extreme, the instrument must be allowed at least 4 hours time
for all components to return to the ambient temperature range
0° C to +50° C before operating.
Further information on environmental test procedures may
be obtained by contacting your local Tektronix Field Office
or representative.
ACCESSORIES
Standard accessories supplied with the Type 556 can be
found on the last pullo-ut page of the Mechanical Parts List
Illustrations. For optional accessories see the Tektronix, Inc.
catalog.
1-4

SECTION 2
OPERATING INSTRUCTIONS
Type 556
Change information, if any, affecting this section will be found at the rear of the manual.
General
This section of the manual provides for the effective use of
the instrument by describing the function and operation of
the front panel controls and connectors, listing the first time
and general operating instructions and presenting some basic
applications.
Nomenclature and Terminology
For reference and guidance, these terms are defined as they
are used in this manual.
Alternate Mode— A time-sharing method of displaying
the output signals of two or more channels with a single
cathode ray tube beam. Channel switching is sequential and
occurs at the end of the sweep.
Chopped Mode— A time-sharing method of displaying
output signals of two or more channels with a single cathode
ray tube beam, in sequence, at a rate not referenced to the
sweep.
Chopping Rate— The rate at which channel switching
occurs in Chopped Mode.
Chopping Transient Blanking— The process of blanking
the indicating spot during the switching periods in Chopped
Mode.
Dual-Beam Oscilloscope— An oscilloscope in which the
cathode ray tube produces two separate electron beams
that may be individually or jointly controlled.
Dual-Trace— A mode of operation in which a single beam
in a cathode ray tube is shared by two signal channels.
Multi-Trace— A mode of operation in which a single beam
in a cathode ray tube is shared by two or more signal chan
nels.
Signal Channel— A signal amplifying circuit in a plug-in
unit. With dual and multi-channel plug-ins, the channels are
generally designated Channel 1 (or A) Channel 2 (B), etc.
Power Requirements
This instrument may be operated with power from either
a 115-volt or a 230-volt (nominal) power source. With proper
positioning of the Line Voltage Selector connectors, the power
supply circuit will provide correct DC voltages with adequate
regulations with any line voltage within voltage limits of
90 to 136 volts RMS and 180 to 272 volts RMS and frequency
limits of 50 to 60 z. The adjustable turns ratio design of
the power transformer provides the means of making the
instrument compatible with this wide range of power source
voltages.
SN 2000-up
A Line Voltage selector assembly is provided to facilitate
changing the power transformer turns ratio (see Fig. 2-1).
The assembly contains two line fuses and two movable pins
and socket type connectors. The two-position connector is
termed the Voltage Selector and the three-position connector
is termed the Range Selector.
Table 2-1 lists the six Voltages and Range selector com
binations and the line voltage ranges they should be used
with. Before connecting the instrument to a power source,
measure the power source line voltage and position the Volt
age and Range selectors accordingly.
TABLE 2-1
Voltage Range W ill provide optimum
Selector Selector regulation for line
position position voltages from
115V LO 90 to 110 volts
115 V M104 to 126 volts
115 V I 112 to 136 volts
230 V LO 180 to 220 volts
230 V M208 to 252 volts
230 V I 224 to 272 volts
To change the power transformer from one regulating
range configuration to another use the following procedure:
1. Disconnect the instrument from the power source.
2. Loosen the two captive screws and remove the cover.
Since the line fuses are attached to the cover, they will be
pulled from their holders with the cover.
3. To change nominal line selections, pull the Voltage
Selector until its pins are.free of the sockets, invert the selec
tor and reseat the pins in the desired sockets.
NOTE
115-volt to 230-volt plug adapters are not sup
plied with this instrument. If a suitable adapter
is not available, it may be necessary to change
the line-cord plug.
4. To change regulating range selections, pull the Range
selector until its pins are free of the sockets, move it to the
desired range position and seat the pin in the sockets.
5. Replace the assembly cover and the two line fuses. Press
the cover firmly onto the assembly to seat the two fuses in
their holders, then tighten the captive screws.
6. The indicating tabs on the selectors will be protruding
through the covers to indicate the selected regulating range.
Always check the position of these tabs before applying
power to the instrument.
<D 2-1

Operating Instructions— Type 556
SN 100-1999
Instruments with serial numbers 100-1999, unless tagged
otherwise, are connected at the factory for operation at 115
volts (nominal). The power transformer has eight primary
terminals which are connected to solderless pin connectors
on the Power board. These quick-change connectors make
possible operation from four different nominal AC voltages:
104, 115, 208 and 230 V, 50 to 60 z. Fig. 2-2 illustrates
the jumper and lead connections required for operation on
each of the stated lino voltages. For 208 V and 230 V opera
tion, the two unused jumpers can be stored on the unused pins
of terminals J and T. All lead connections to the board that
are not shown in Fig. 2-2 remain as they are.
No change in fan connections is required when changing
the connection on the board as directed in the illustration.
NOTE
Two metal tags (printed on each side) are pro
vided at the rear of the instrument to indicate the
four nominal line voltages. If tho primary wiring
is changed, be sure to use the proper tag to indi
cate the voltage for which the instrument is wired.
Temperature considerations
To rcduco operating temperatures, air is drawn in through
the filter at the rear and blown forward through tho instru
ment. For tho most efficient air circulation and heat dis
sipation, provido at least three inches clearance at tho rear,
two inches at the sidos and operate tho instrument with tho
side covers installed. If the fan becomos inoperative or tho
air circulation is obstructed, tho intornal tomporafuros will
exceed a safo operating levol in a relatively short period of
timo. To provont damago to tho components from oxccssivc
temperaturos, a thormal cutout switch is incorporated in the
power supply circuitry. This switch is designed to interrupt
powor to tho instrument when the ambient temporaturo ex
ceeds about 140° F.
CAUTION
Since the thermal cutout switch w ill reset when its
ambient temperature decreases to some level be
low its actuating temperature, set the POWER
switch to OFF before attempting to remedy the
causo of the high temperature condition.
CONTROLS AND CONNECTORS
Figure 2-3 shows the location of all the instrument operat
ing controls and connectors. A brief description of each type
of control and connector is given in the following table.
Controls with the same nomenclatures generally perform
identical functions for their respective beams and a descrip
tion for one is applicable to the other. Those controls with
the some nomenclature, but with differences in their func
tions, are pointed out and described as separate typo con
trols.
Some of the controls and connectors, particularly those
with 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 switches are combined under the no
menclature of SOURCE to provide this
complex switching function. The selections
of the two position selector switch are:
LEFT: From left plug-in or left vertical
amplifier.
RIG T: From right plug-in or right vertical
amplifier. The selections of the four posi
tion selector switch are:
town
(A) Cover In pla«o.
(B l Covor romoved,
Fig. 2-1. Lino Voltage Selector assembly; provided In instruments
with serial number 2000 and up.
2-2

Operating Instructions— Type 556
on
Yellow
From
• V ir»
« • *h <h f n.
<A1 104 V
ft ft t <1. V
A*r * W
A « • t X
Store extra
jumper hero
Rod on
208 V
From
FI 402
Groan on
Yellow
Store extra
jumpor hero
©ft « Y Itr
A«i »
<D> 230 V
From
F1402
From
FI 402
Green on
Yellow
Store extra
jumper here
Fig. 2-2. Positions of the movable jumpor wires (black on yellow) for the four nominal lino voltage selections. This illustration Is
applicable to 556 SN's 100 to 1999.
2-3

Operating Instructions— Type 556
COUPLING
SLOPE
MODE
LEVEL
TRIGGER
INPUT
Upper Beam
DISPLAY Selects vertical (Y-axis) and horizontal (X-
axis) mode of operation for the Upper
Beam.
INT NORM: From trigger pickoff in the
oscilloscope vertical amplifier for the
respective plug-in unit.
INT PLUG IN: From trigger pickoff in the
respective plug-in unit. Applies to multi
trace plug-in units with this capability.
LINE: Uses a line-frequency signal as a
trigger.
EXT: From signal applied to the TRIGGER
INPUT connector. Not affected by LEFT-
RIG T switch.
Determines method of coupling the trigger
ing signal to the trigger circuit.
AC: Blocks the DC component and allows
triggering to take place on the AC com
ponent. With frequencies about 30 z
and below, use the DC position.
AC LF REJ: Rejects DC and progressively
attenuates signal frequencies below
about 2.5 k z, allowing the trigger cir
cuits to respond only to the higher
frequencies.
AC F REJ: Rejects DC, passes signals be
tween 60 z and 60 k z and progres
sively attenuates signals above 60 k z.
DC: Permits triggering on both high and
low (to DC) frequency signals.
Selects portion of triggering signal which
will trigger the sweep.
LEFT PLUG-IN EXT: Left plug-in signal
provides the vertical deflection while
the signal applied to the UPPER BEAM
EXT ORIZ IN connector provides the
horizontal deflection.
LEFT PLUG-IN A: Left plug-in signal pro
vides the vertical deflection and the A
TIME/CM switch sets the sweep rate of
the Upper Beam.
LEFT PLUG-IN B: Left plug-in signal pro
vides the vertical deflection and the B
TIME/CM switch sets the sweep rate of
the Upper Beam.
RIG T PLUG-IN A: Right plug-in signal
provides the vertical deflection and the
A TIME/CM switch sets the sweep rate
of the Upper Beam.
RIG T PLUG-IN B: Right plug-in signal
provides the vertical deflection and the
B TIME/CM switch sets the sweep rate
of the Upper Beam.
RIG T PLUG-IN EXT: Right plug-in signal
provides the vertical deflection while
the signal applied to the UPPER BEAM
EXT ORIZ IN connector provides the
horizontal deflection of the Upper Beam.
+ : Sweep triggers from positive-going POSITION Controls horizontal position of Upper Beam
portion of the triggering signal.
—: Sweep triggers from negative-going
portion of the triggering signal.
trace. Single knob controls both coarse
and fine adjustment of the beam position
by means of a backlash coupling between
the two sections of the control.
Selects triggering mode.
AUTO STABILITY: Permits normal trigger
ing on signals with repetition rates
higher than about 30 z. With no
trigger signal or with a lower repetition
rate, the time-base circuit free runs and
provides a convenient reference trace.
TRIG: Permits normal triggering on all
triggering signals. No trace occurs
when the triggering signal is removed.
DISPLAY
MAG
A Sweep
Expands the Upper Beam display to left
and right of graticule center.
X I: Normal presentation of the display.
X 10: orizontal length of Upper Beam
display is magnified by 10. The X10
light indicates that the display is magni
fied.
Selects the amplitude point on the trigger
ing signal where sweep triggering occurs.
When the knob is pulled out, greater
triggering range is offered for triggering
on higher amplitude signals. The sweep
trigger circuit is most sensitive to small
signals with the LEVEL control pushed in
and set close to 0.
Connector for applying an external trig
ger signal to the Sweep Trigger circuit
when its SOURCE switch is set to EXT.
A TIME/CM Normally referred to as the A TIME/CM
OR switch in this manual. Selects the sweep
DELAY TIME rare of the A sweep generator. Also selects
the basic delay time (to be multiplied by
the DELAY-TIME MULTIPLIER dial setting)
for delaying the B sweep when the B
MODE switch is set to DLY'D BY A.
VARIABLE Provides continuously variable sweep rate
to at least 2.5 times the setting of the A
TIME/CM switch. Sweep rate is calibrated
when the control is set fully clockwise to
®
2-4

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

Operating Instructions— Type 556
SCALE ILLUM
LO ER BEAM
EXT HORIZ
VAR
DELAY-TIME
MULTIPLIER
BEAM FINDER
AMPLITUDE
CALIBRATOR
5 mA Current
Loop
PO ER
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 the Lower
Beam horizontal deflection.
Works in conjunction with the A TIME/
CM (OR DELAY TIME) switch. Provides
variable delay of the B sweep up to 10.00
times the delay time indicated by the A
TIME/CM switch.
tion. A positive voltage deflects the beam
from left to right.
A SA TOOTH Output connector which supplies a saw
tooth voltage from the A sweep generator.
Peak amplitude is equal to or greater than
9V/cm. The sawtooth ramp is positive
going from near ground.
B SA TOOTH Same as A SAWTOOT except applies to
the B sweep generator output.
Returns the displays of both beams to the
screen when the button is pressed. Limits
the horizontal and vertical amplifier dy
namic ranges of both beams. Used to
locate trace(s) which exceeds scan of dis
play area.
Determines the peak-to-peak positive-from-
ground voltage available at the CAL OUT
connector.
LO ER BEAM Same as UPPER BEAM EXT ORIZ IN
EXT HORIZ IN except applies to the Lower Beam hori
zontal amplifier when the Lower Beam
DISPLAY switch is set to EXT.
Rear Panel (Upper and Lower Beam)
EXT CRT Input connector for intensity modulation
CATHODE (Z-axis) of the display.
NOTE
When working into an external 50-
ohm load using the .2 VOLTS to 200
mVOLTS positions, output amplitude
is one-half the indicated voltage.
Provides 5 mA square-wave current from
the calibrator circuit. The arrow shows
direction of conventional current flow (i.e.,
positive to negative).
Toggle switch: Applies line power to the
low-voltage power transformer.
Light: Indicates that the AC line voltage
is applied to the power transformer.
Output connector which supplies a sharp
positive-going trigger spike equal to or
greater than 7 V at the end of the delay
period as set by the A TIME/CM (OR
DELAY TIME) switch and the DELAY-TIME
MULTIPLIER control.
Output connector which supplies a posi
tive-going square-wave pulse equal to or
greater than 8 V coincident with the
A sweep. Pulse duration is approximately
10.5 X the setting of the A TIME/CM
switch when the (A) VARIABLE control is
set to CALIBRATED.
Same as A GATE except applies to B
TIME/CM switch and (B) VARIABLE control.
Output connector for the Amplitude Cali
brator.
Input connector for applying an external
horizontal signal to the Upper Beam hori
zontal amplifier when the Upper Beam
DISPLAY switch is set to either EXT posi-
CRT Cathode Toggle switch for the CRT cathode circuit.
Selector EXT CRT CAT ODE: Normal operation
with shorting cover connected. With
shorting cover removed, CRT cathode
can be intensity modulated with a 10 V
or more signal applied to the EXT CRT
CAT ODE connector.
UPPER BEAM (LOWER BEAM) C OPPED
BLANKING: Permits blanking the Upper
(Lower) Beam while the multi-trace plug
in unit is switching from one channel to
another during chopped mode of opera
tion.
LINE VOLTAGE Facilitates changing the power transformer
SELECTOR circuit configuration. The 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
The Type 556 Oscilloscope is designed to use Tektronix
letter-series and 1-series plug-in units as the input stages for
the two vertical deflection systems.
A plug-in unit installed in the left-hand compartment of
the oscilloscope is identified as the “ left plug-in”. This unit
provides vertical deflection for the Upper Beam only when
the Upper Beam DISPLAY switch is set to the LEFT PLUG-IN
positions. Similarly, the plug-in unit installed in the right-
hand compartment is referred to as the “right plug-in". This
unit, however, provides vertical deflection for both beams
simultaneously or for the Lower Beam only, depending on
the settings of the DISPLAY switches.
The use ot plug-in units as the vertical inputs permits
changing the vertical characteristics of the oscilloscope to
meet a wide range of application requirements. The parti
cular plug-in units to be used must be selected to satisfy the
requirements of your applications. In selecting the vertical
plug-in units, consider the bandpass, risetime, deflection
2-6 <D

Operating Instructions— Type 556
factor, input RC characteristics and the number of inputs.
Other plug-in units to consider are special purpose types
such as differential amplifiers and comparators, operational
amplifiers, spectrum analyzers, etc. Table 2-2 lists a wide
variety of plug-in units that can be used with the instrument.
The Type 556 Oscilloscope should not be used without
plug-in units installed or connected by extensions. Operating
the instrument with a plug-in missing will not damage the
oscilloscope, but will cause the vertical amplifier and the
sweep generator on that side of the oscilloscope to be
inoperative.
TABLE 2-2
VERTICAL PLUG-IN UNITS
(Plug-ln/556 system bandwidth characteristics are at
3 dB down)
Plug-In
Unit Type Calibrated Deflection
Factor
Bandwidth Risetime
For Wide-Band, Multiple Trace Applications
1A1 Dual-
Trace
50 mV/cm to
20 V/cm DC to 50 M z 7 ns
5 mV/cm DC to 28 M z 12.5 ns
500 juV/cm 2 z to 15 M z 23 ns
1A2 Dual-
Trace 50 mV/cm to
20 V /cm DC to 50 M z 7 ns
CA Dual-
Trace 50 mV/cm to
20 V/cm DC to 24 M z 15 ns
M Four-
Trace 20 mV/cm to
10 Vcm DC to 20 M z 18 ns
igh-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 M z 18 ns
5 mV/cm to
20 mV/cm 2 z to 12 M z 30 ns
K50 mV / cm to
20 V DC to 30 M z 12 ns
L
50 mV/cm to
20 V DC to 30 M z 12 ns
5 mV / cm to
2 V/cm 3 z to 24 M z 15 ns
For igh DC Sensitivity Applications
Wide- 5 mV/cm to DC to 15 M z 23 ns
Band 20 V/cm
For Differential Input Applications
D igh-
Gain 1 mV/cm (to
50 mV/crn) DC to 300 k z 0.18 {is
E Low- 50 jiiV/cm (to 0.06 z to 20 6 {is
Level 10 mV/cm) k z (to 60 k z)
G Wide-
Band 50 mV/cm to
20 V/cm DC to 20 M z 18 ns
1A7 igh- 10 /nV/cm to DC to 500 k z
Gain 10 V/cm Selectable
bandwidth 0.7 {is
For Integration, Differentiation, Function Generation,
Linear and Non-Linear Uses
O50 mV/cm to DC to 25 M z 14 ns
Operational 20 V/cm
Amplifier
For Transducer and Strain Gage Uses
Q10 /u.strain/
div to 10,000
/xstrain/div
DC to 6 k z 60 /is
For Displaying Simultaneously Delay, Rise, Storage,
and Fall Times of Transistors
R Transistor-
Risetime 0.5 mA/cm to
100 mA/cm DC to 30 M z 12 ns
For Displaying Forward and Reverse Switching Char
acteristics of Semiconductor Diodes
S Diode
Recovery
1 mA to 20
mA forward
current, 0 mA
to 2 mA re
verse current
DC to 30 M z 12 ns
For Precise Amplitude Measurements Via Slide-Back
W1 mV/cm to DC to 8 M z at 44 ns at 1
igh-Gain 50 V/cm 1 mV/cm, increas- mV/cm, 15
Differential ing to 23 M z at ns at 50
Comparator 50 mV/cm mV/cm
For Spectrum Analysis
Plug-In Unit Type Tuning Range
1L5 10 z to 1 M z
1L10 1 M z to 36 M z
1L20 10 M z to 4200 M z
1L30 925 M z to 10.5 G z
In addition, nine narrow-band spectrum analyzers cover
ing frequencies between 10 M z and 18.2 G z are available
on special order—contact your Local Tektronix Field Engi
neer or Field Office.
FIRST TIME OPERATION
This procedure describes the basic turn-on precautions and
demonstrates the function of the essential general operating
controls.
1. Before connecting the instrument to a power source, set
the POWER switch to OFF, turn both INTENSITY controls
fully counterclockwise and inspect for a power transformer
circuit configuration compatible with the 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 the instrument to the power source and turn
the POWER switch to ON.
4. While waiting for instrument warmup, set the controls
of both beams and the plug-in units as follows-.
2-7

Operating Instructions— Type 556
GENERAL OPERATING INFORMATION
A and B Triggering
A SOURCE LEFT INT NORM
B SOURCE RIG T INT NORM
COUPLING AC
SLOPE +
MODE AUTO STABILITY
LEVEL Clockwise, knob push
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 RIG T PLUG-IN B
POSITION Centered
DISPLAY MAG X I
AMPLITUDE CALIBRATOR 50 mVOLTS
Rear Panel
CRT Cathode Selector EXT CRT CAT ODE
Vertical Plug-In Units
Position Centered
Volts/Cm .05
Input Selector AC
Front Panel Adjustments
5. Apply a 50-mV signal from the oscilloscope CAL OUT
connector to both vertical plug-in units.
6. Turn the INTENSITY controls clockwise until the displays
are of normal brightness.
7. Adjust the A and B Triggering LEVEL control to obtain
stable displays.
8. Use the plug-in Position controls to position the displays
to the center of their respective graticule viewing areas.
9. Use the Upper and Lower Beam horizontal POSITION
controls to position th displays so they start at the left edge
of the graticule.
10. Adjust the FOCUS and ASTIGMATISM conrols to ob
tain well-defined displays.
11. Set the plug-in unit Input Selector switches to Gnd or
remove the signal. Check that the traces are parallel to
their respective graticule center lines. If they are not, adjust
the TRACE ROTATION control for best alignment of the
traces with the graticule lines.
12. This completes the basic operation procedure for the
Type 556. Instrument operation not explained here, or opera
tion which needs further explanation is discussed under
General Operating Information.
Light Filters
The mesh filter supplied with the Type 556 provides shield
ing against radiated EMI (electro-magnetic interference;
formerly called RFI) from the face of the CRT. It also serves
as a light filter to make the trace more visible under high
ambient light conditions. The mesh filter and graticule cover
are one unit (Tektronix Part No. 378-0572-00). To remove the
filter, remove the four graticule nuts and then remove the
graticule cover and mesh filter as a unit.
A tinted light filter is also provided. This filter minimizes
light reflections from the face of the CRT to improve contrast
when viewing the display under high ambient light condi
tions. If a light filter is needed and EMI shielding is not
required, use the tinted filter to obtain least loss of beam
brightness.
NOTE
When using a light filter, avoid the tendency to
set the beam intensities so high that they will burn
the CRT phosphor.
A clear plastic faceplate protector is provided with the
Type 556 for use when the mesh filter or the tinted filter
are not used. The clear faceplate protector provides the
best display for waveform photographs. It is also preferable
for viewing high writing rate displays under low ambient
light conditions.
The tinted filter or the faceplate protector should be used
at all times to protect the CRT faceplate from scratches. The
faceplate protector and the tinted filter are held in place by
a graticule cover (Tektronix Part No. 200-0382-00). To remove
the light filter or faceplate protector, remove the four grati
cule nuts and the graticule cover.
Calibrated Graticule
The edge-lighted internal graticule is accurately marked
with 8 vertical and 10 horizontal 1-cm divisions. There are
2-mm sub-divisions marked on the vertical center line and
the two horizontal center lines (one for each beam). One
centimeter of each corner of the graticule is omitted so the
graticule fits within the round CRT screen. The deflection
factors of the CRT beams are calibrated to the graticule
marks. Thus the marks provide a calibrated scale for making
time and voltage measurements.
Each beam has a usable vertical scan area of 6 cm. The
beams overlap in the center 4-cm area of the graticule to
permit superimposed displays.
Beam Finder
The BEAM FINDER pushbutton provides a means of locat
ing a display which overscans the viewing area either verti
cally or horizontally. When the BEAM FINDER button is
pressed, the display is compressed within the graticule area.
To locate and reposition an overscanned display, use the
following procedure.
1. Press the BEAM FINDER button.
2-8 <8

Operating Instructions— Type 556
A. Front Panel
COWER BEAM
C OPPED BLANKING
immtm/mmmtxxxmwA
—15®5)5$K8^
UPPEB BEAM
C OPPED BLANKING
B. Center portion of rear panel.
<D 2-9
Fig. 2-3. Control setup chart for Type 556 SN 2000 and up.

Operating Instructions— Type 556
B. Center portion of rear panel.
Fig. 2-4. Type 556 control setup chart for instruments with serial number 1999 and below.

Operating Instructions— Type 556
2. While the BEAM FINDER button is held in, reduce the
vertical deflection to less than 3 cm by adjusting the ampli
tude of the input signal or the deflection factor of the plug-in.
3. Adjust the POSITION controls of the plug-ins and the
Type 556 to center the display within the beam viewing area.
4. Release the BEAM FINDER button; the display should
appear within the viewing area.
Output Signals
Several low-impedance signal outputs are available at the
front panel of the Type 556 Oscilloscope. These are Delayed
trigger pulse, a gate waveform from each time base, a saw
tooth waveform from each 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-channel signal output to be used as
a reference for triggering oscilloscopes. Such units apply the
single-channel signal to the Type 556 triggering circuits
through internal wiring when the SOURCE switches are set
to the PLUG IN position.
Use of the gate and sawtooth waveforms for triggering or
driving external devices is illustrated in Fig. 2-6. In this
application, the time base is usually set for a free-running
sweep.
In addition to the sawtooth outputs on the front panel,
there is an internal sawtooth voltage that is applied to pin 6
of both plug-in interconnecting jacks. For the left plug-in
unit the sawtooth voltage originates from the A Sweep Gen
erator; for the right plug-in unit the sawtooth voltage origin
ates from the B Sweep Generator. These sawtooth voltages
provide a standardized current ramp of 20 ^A/cm (nominal)
via a standardizing resistor for use in driving plug-in spec
trum analyzers requiring this signal source.
The internal current ramps can also be used to drive low-
impedance circuits, such as the minus input of an operational
amplifier or the emitter of a transistor, with a positive-going
linear ramp of current. The internal and external sawtooths
from each sweep may not drive two circuits when both out
puts are used at the same time, nor will the internal saw
tooth successfully serve as a voltage signal source—espe
cially at the faster sweep rates.
When pin 6 is not used, the high impedance of this saw
tooth signal source prevents excessive cross-talk of the signal
into the plug-in unit.
Control Setup Chart
Fig. 2-3 and Fig. 2-4 show the front panel and a portion of
the rear panel of the Type 556. If the controls of the plug-in
unit being used are sketched in, the 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 with this oscilloscope.
Vertical Controls
The vertical plug-in unit for each beam contains ail the
front-panel vertical positioning and deflection controls for
that beam with the exception of the TRACE SEPARATION
Fig. 2-5. Output waveforms available at the front panel.
control. Refer to the instruction manuals of the particular
plug-in units for operation of the vertical controls.
CONNECTING TO THE SIGNAL SOURCE
Input signals that are to be displayed as vertical deflec
tion on the CRT screen are applied to the input connectors
on the two vertical plug-in units.
®2-11