Tektronix 531 User manual

CATHODE RAY OSCILLOSCOPE
TYPE 531/541
INSTRUCTION
MANUAL
TEKTRONIX, INC.
MANUFACTURERS OF CATHODE-RAY AND VIDEO TEST INSTRUMENTS
Sunset Highway and Barnes Road ¢ P.O.Box 831 © Portland 7, Oregon, U. S.A.
Phone: CYpress 2-2611 ¢ Cables: Tektronix
070-203

NOTE
This instruction manual has been prepared to
cover TEKTRONIX Type 531/541 Oscilloscopes of
all serial number ranges. Text, diagrams, and
parts lists have been expanded to incorporate all
circuit modifications adopted during the course of
manufacture. The serial ranges of instruments to
which various modifications were applied before
shipping from the factory have been noted wher-
ever necessary.
However, because many instruments have been
modified in the field and out of serial sequence,
component values and circuitry of a given instru-
ment may differ considerably from those indicated
in this manual for its serial number. Theuser is
urged, therefore, to enter whatever changes may
be necessary to bring this manual intoagreement
with the present circuitry of his oscilloscope.
When ordering parts, always include the fol-
lowing information:
Instrument Type (531/541).
Instrument Serial Number (as, S/N 9999).
Part Circuit Number (as, R999).
Part Description (value, type, rating,
tolerance, etc.).
5. The 6-digit TEKTRONIX part number (as,
999-999),
kone
SAFETY NOTICE
This oscilloscope employs dangerously high voltages, Since
some maintenance must of necessity be performed with the
case removed, great care should be taken. Use only insulated
tools, stand on a dry floor and if possible keep one hand in
your pocket. Care should also be used in making any con-
nections to the deflection plates of the cathode-ray tube through
the access panel. It is advised that the access panel never be
removed until the power has first been turned off. The instru-
ment should not be operated with this protective cover removed,

CONTENTS
GENERAL DESCRIPTION SECTION 1
Characteristics. Functions of Front-Panel Controls and Connectors.
OPERATING INSTRUCTIONS SECTION 2
Preliminary Instructions. First-Time Operation. Triggering Modes.
‘Triggering Instructions. Sweep Operation. Auxiliary Functions. Sim-
plified Sweep Diagrams.
CIRCUIT
DESCRIPTION
SECTION
3
Block Diagram. Vertical-Deflection System. Horizontal-Deflection
System. Power Supply. CRT Circuit.
MAINTENANCE SECTION 4
General Information. Trouble Shooting. Recalibration Procedure.
PARTS
LIST
SECTION
5

SECTION 1
GENERAL DESCRIPTION
NOTE
The
Types
531
and
541
are
high-speed
laboratory
oscilloscopes,
designed
for
general
laboratory
use.
Their
extremely
fast
rise-
time,
wide
sweep-speed
range
and
10-kilovolt
accelerating
volt-
age
permit
accurate
analysis
of
many
types
of
waveforms.
Addi-
tional
adaptability
is
provided
by
plug-in
preamplifiers
which
extend
the
use
of
these
oscilloscopes
to
practically
all
laboratory-
oscilloscope
applications.
Accurately
calibrated
sweep
speeds
and
vertical-deflection
sensitivity
permit
quantitative
time
and
amplitude
measurements
to
be
made.
CHARACTERISTICS
Cathode-Ray Tube
A Tektronix 5-inch post-deflection accelera-
tion cathode-ray tube is furnished with the in-
strument.
With
10-kv
acceleration
potential
the
trace is bright enough that a single sweep can be
photographed
with
a
Pll
screen
even
at
the
fast-
est sweep speeds. A P2 phosphor is furnished
unless other phosphors are specially requested.
Vertical-Deflection System
A dc-coupled vertical amplifier in the main
unit
is
adjusted
for
optimum
transient
response
and
wide
passband.
A
plug-inchannel-switching
unit
provides
a
dual-trace
presentation
for
re-
petitive
signals.
Input
to
the
vertical-deflection
system
must
be
made
through
one
of
the
avail-
able types of plug-in units.
Horizontal-Deflection System
Sweep Circuit
The linear sweep generator is a Miller runup
generator
with
excellent
linearity,
and
the
ex-
tremely
wide
speed range
of
.02
microseconds
per centimeter to 12 seconds per centimeter.
Twenty-four
calibrated
sweep
speeds
are
avail-
able
accurate
within
three
per
cent.
The
main
sweep
control
has
eight
positions,
.1,
1,
10,
and
100
microseconds
per
centimeter,
1,
10,
100
milliseconds
per
centimeter,
and
1
second
per
centimeter.
Three
multiplier-switch
positions
1, 2,
and
5
times,
provide
a
total
of
twenty-
four
speeds.
Remaining
positions
of
the
multi-
plier
switch
provide
continuously
adjustable
ie
531/54I—GENERAL. DESCRIPTION
multipliers of 1 to 2.5 times, 2 to 5 times, and
5 to 12 times so that the above range is also
covered
continuously.
The
five-times
sweep
magnifier increases the maximum sweep speed
to .02 microseconds per centimeter.
Magnifier
Sweep magnification is produced by increasing
the sweep output amplifier gain five times. The
center two centimeters of the trace is expanded
to 10 centimeters, Any one-fifth of the sweep
so magnified can be positioned to show on the
screen by means of the HORIZONTAL POSI-
TION control.
DC-Coupled Unblanking
The
unblanking
square
wave
is
dc-coupled
to
the
grid
of
the
cathode-ray
tube
to
assure
uni-
form
unblanking
bias
for
all
sweep
times
and
repetition
rates.
Triggering System
The sweep can be triggered by a wide range
of triggering voltages either derived internally
from the signal to be displayed, or through a
front-panel connector from an external source.
The circuit permits the sweep to be triggered
from any selected point along the triggering
waveform. A recurrent triggering arrangement
which runs at a fifty-cycle repetition rate will
synchronize with repetitive trigger signals from
sixty cycles to two megacycles.
PAGE 1-1

Horizontal-Deflection Amplifier
A de-coupled horizontal-deflection amplifier
provides horizontal sensitivity of 2 volts per
centimeter to approximately 15 to 20 volts per
centimeter, continuously adjustable by means
of a ten-to-one continuously adjustable control
and a 10X and 1X switched attenuator.
Because this amplifier was designed for op-
timum performance with a sweep sawtooth, its
performance with sine waves is limited. This
sine-wave limitation can best be defined by an
amplitude-frequency product, which can be ex-
ceeded only at the expense of considerable dis-
tortion. The amplitude-frequency product is
2.4 centimeter-megacycles. Thus a full 10-
centimeters of deflection can be used at 240 kc,
and a 2.4-me sine wave can be viewed if the
amplitude is one centimeter peak-to-peak or
less. The amplifier frequency response toa sine
wave is down less than 30% at 400 kc when the
amplitude is within this limitation.
Output Waveforms Available
Front-panel connectors provide a positive-
going sawtooth, a positive gate synchronized
with the sweep, and a signal derived from the
displayed vertical signal. The calibrator pro-
vides an adjustable amplitude symmetrical
square wave with a repetition rate of about one
kilocycle, The amplitude is adjustable intwenty
steps between .2 millivolts and 100 volts.
Power Supply
All de voltages are regulated to accommodate
line-voltage variations between 105 and 125 volts
or 210 volts to 250 volts, 50 to 60 cycles, ac,
and for the differences in dc loads imposed by
the different plug-in units.
Power Consumption
At 117 or 234 volts, 475 watts with plug-
in unit in place.
Cooling
Safe operating temperature is maintained with
filtered, forced-air ventilation. A thermal dis-
connect device turns off the ac power in the
event the fan fails or the air intake becomes
blocked.
Illuminated Graticule
The graticule is accurately scribed in centi-
meters and fifths of centimeters. The scribed
lines can be edge-lighted either by white or by
red light. A green filter is supplied to increase
contrast in the presence of room brightness.
At extra cost, a light shield is available con-
structed so that it will slip onover the graticule
bezel.
Mechanical Characteristics
Construction
The cabinet and chassis are madeof electric-
ally-welded aluminum alloy.
Finish
Photo-etched anodized aluminum -alloy panel,
wrinkle-enameled cabinet.
Dimensions
24 inches long, 13 inches wide, 16-3/4 inches
high.
Weight
61-1/2 pounds.
FUNCTIONS OF FRONT-PANEL CONTROLS
AND CONNECTORS
TRIGGERING MODE (red knob)--Five-position
switch arranges trigger circuits for five
kinds of triggering: DC, AC SLOW, AC
FAST, AUTOMATIC and HF SYNC, In Type
531 instruments, S/N 101-6010 and in Type
541, S/N 101-5414, AUTOMATIC is labeled
AC AUTO, In Type 531, S/N 101-592, there
is no HF SYNC position.
PAGE 1-2
TRIGGER SLOPE--Six-position switch selects
source of trigger signal and converts to
negative-going output, either negative-going
Or positive-going input.
TRIGGER INPUT--UHF coax connector to trig-
gering circuits through EXT positions of
TRIGGER SLOPE switch.
531/541—GENERAL DESCRIPTION

STABILITY (red knob)--Contro] for adjusting
the
stability
of
the
sweep
circuits
for
a
stable
display.
The
control
has
a
PRESET
position
suitable
for
most
triggering
ap-
plications. Type 531, S/N101-6710, and
Type 541, S/N101-5942, have no PRESET
position on the STABILITY control.
TRIGGERING
LEVEL--Potentiometer
deter-
mines
part
of triggering
waveform
where
sweep
triggers.
TIME/CM-
-Eight-position
switch
selects
timing
capacitors
to
determine
sweep
speeds,
and
determine
duration
of
trigger
holdoff
period.
MULTIPLIER-
-Six-position
switch.
Three
po-
sitions
place
precision
charging
resistors
in
series
with
timing
capacitors
to
determine
sweep
speeds
in
conjunction
with
selected
timing
capacitor.
Three
positions
, marked
in
red,
place
adjustable
charging
voltages
in
series
with
timing
capacitors
for
contin-
uous
control
of
sweep
speeds.
5X
MAGNIFIER--Two-position
switch
removes
or
inserts
feedback
in
sweep
amplifier
to
change
sweep
speeds
by
a
factor
of
five.
HORIZONTAL
DISPLAY--Three-position
switch
connects
sweep
amplifier
to
internal
sweep
generator
in
one position,
or to front
panel
connector
directly
or
through
10-1
fixed
attenuator
in second
and
third
positions.
EXTERNAL
SWEEP
ATTENUATOR,
10-1---
Continuously
adjustable gain
control on
hor-
izontal
amplifier.
Switched
out
of
circuit
for
internal sweeps.
EXTERNAL
SWEEP
IN--Front-panel
connector
to
horizontal
amplifier
through
HORIZON-
TAL
DISPLAY
switch.
Magnifier
must
be
switched
to
ON
for
undistorted
10-cm
deflection.
VERT.
SIG.
OUT--Front-panel
connector
sup-
plies
signal
from
vertical
amplifier
via
trigger
cathode
follower.
HORIZONTAL POSITION-- Positions trace along
horizontal axis.
al
531/541—-GENERAL DESCRIPTION
VERNIER (red knob)- -Fine adjustments of hori-
zontal positioning, with five times the reso-
lution of the coarse adjustment.
SQUARE-WAVE
CALIBRATOR
(red
knob)---
-
Three-position
switch turns
on
calibrator
plate
voltage
and
switches
in
or
out
1000-
to-1
voltage
divider
to
give
either
volts
or
millivolts
output.
SQUARE-WAVE
CALIBRATOR
(black
knob)---
Nine-position
switch
selects
nine
taps
on
precision
voltage
divider
in
calibrator
cir-
cuit.
Provides accurate
voltages
of .2, .5,
1,
2, 5, 10,
20,
50, and
100 volts
in VOLTS
position,
or millivolts
in the MILLIVOLTS
position
of
the
red
concentric
control
knob.
CAL OUT---UHF coax front-panel connector
from the calibrator.
+GATE
OUT---Front-panel
binding
post
sup-
plies
positive
20-volt
square
pulse,
dc-cou-
pled
through cathode
follower
,
synchronized
with
the
internal
sweep.
SAWTOOTH
OUT---Front-panel
binding
post
supplies
150-volt
positive-going
sawtooth
dc-coupled
through
cathode
follower,
syn-
chrenized
with
the
internal
sweep.
POWER---On-off
switch
in
primary
of
power
transformer
and
ventilating-fan
lead.
FOCUS--
Adjustable
voltage
for
the
cathode-ray
tube
focusing
grid.
INTENSITY--Bias
adjustment
to
cathode-ray
control
grid.
ASTIGMATISM-
Adjustable
voltage
for the
astig-
matism
grid
of
the
cathode-ray
tube.
SCALE
ILLUM-
-Adjustable
series
resistor
con-
trols
voltage
across
graticule
lights.
Beam-
position
indicators,
unlabeled,
marked
with
arrows.
Thé
arrow
nearest
the
illuminated
indicator
shows
which
way
the
beam
is
off
the
screen
if
it
cannot
be
seen.
Rear of Cabinet
CRT CATHODE--Binding post connects to crt
cathode through high-voltage capacitor. In-
put impedance 8 k to 15 k. Discharge
time eonstant about 15 milliseconds.
PAGE 1-3

SECTION 2
OPERATING INSTRUCTIONS
PRELIMINARY INSTRUCTIONS
Cooling
The Oscilloscope is cooled by filtered, forced-
air ventilation. The instrument must therefore
be
placed
so
the
air
intake
is
not
blocked,
and
the filter must be clean enough to permit ade-
quate air circulation. If the interior tempera-
ture does rise too high for some reason, a
thermal cutout switch will disconnect the power
and keep it disconnected until the temperature
drops to a safe value.
Time-Delay DC Power Relay
A time-delay relay delays application of the
rectified dc to the circuits long enough for all
heaters to reach operating temperature. The
time delay is approximately 25 seconds, If you
switch the ac power off, even briefly, the time-
delay relay will delay reapplication of the dc.
Cathode-Ray Tube Controls
The Tektronix cathode-ray tube inthis instru-
ment has a total accelerating voltage of 10,000
volts. The spot intensity with this amount of
acceleration can be bright enough to damage the
screen in a short time if the spot is left in one
place. Be careful not to leave a fixed bright
spot or slow sweep on the screen. Turn the
INTENSITY control counterclockwise so that
the spot is dim whenever you leave the instru-
ment unattended.
The separate FOCUS, ASTIGMATISM and IN-
TENSITY controls are somewhat interdependent,
and may require readjustment for different IN-
TENSITY control settings.
Illuminated Graticule
The adjustable graticule lighting control la-
beled SCALE ILLUM., can be adjusted to suit
the lighting conditions of the room. Thecolored
filter supplied is colored to provide the maximum
trace contrast for the P2 phosphor in the pres-
ence of room light.
The graticule is accurately scribed in centi-
meters and fifths of centimeters. These scale
markings and the calibrated fixed vertical-de-
flection sensitivities and sweep times, can be
used to convert deflections in centimeters into
volts and seconds. Vertical sensitivities are
calibrated in volts per centimeter, and hori-
zontal sweep-times are calibrated in seconds per
centimeter, which, if multiplied by centimeters
of deflection, give volts and seconds.
The graticule can be mounted in either of two
positions rotated 180 degrees from each other.
In one position, the graticule illumination is
colored red, and in the other position in white.
The white will reproduce well photographically.
FIRST-TIME OPERATION
First get atrace onthe screen by the simplest
method, and then proceed with the presentation
you want after you get an idea of the functions
of the controls To get a simple trace on the
screen,
insert
a
preamplifier,
and
proceed
as
follows:
Turn the POWER switch to OFF. Connect the
power
cord
toa
source
of
117-volt,60-cycle
pow-
er. Then set the front-panel controls as follows:
INTENSITY
Counterclockwise (CCW)
FOCUS
eo
Center
531/541-OPERATING INSTRUCTIONS
ASTIGMATISM
Center
POWER
ON
TRIGGERING LEVEL
CCW
STABILITY (red knob)
PRESET or CCW
TRIGGER SLOPE
+ INT
PAGE 2-1

TRIGGERING MODE (red)
Connect a lead between the CAL, OUT ter-
AUTOMATIC or AC AUTO minal and the INPUT terminal of the unit. Set
TIME/CM
100 MICRO SEC
MULTIPLIER
2
HORIZONTAL DISPLAY
INTERNAL SWEEP
HORIZONTAL POSITION
Center
SQUARE-WAVE CALIBRATOR
5
VOLTS, MILLIVOLTS, OFF
VOLTS
the controls of the plug-in as follows:
AC--DC AC.
VOLTS/CM 2
VARIABLE Clockwise
VERTICAL POSITION Center
When
the
POWER
switch
has
been
turned
on
for
about
one
minute,
turn
the
INTENSITY
control
clockwise
until
you
can
see
a
trace
on
the
screen.
With
the
calibrator
waveform
dis-
played,
you
can
set
the
FOCUS,
INTENSITY
,
and
ASTIGMATISM
controls
for
a
sharp
line,
and
position
the
trace
near
the
screen
center
with
the
HORIZONTAL
POSITION
and
VERTICAL
POSITION
controls.
TRIGGERING MODES
Automatic
You
are
now
displaying
the
calibrator
wave-
form,
whose
repetition
rate
is
about
one
kilo-
cycle,
and
whose
amplitude
is
five
volts,
peak-
to-peak,
with
the
AUTOMATIC
mode
of
trigger-
ing.
This
is
about
the
simplest
mode
of
trigger-
ing.
It
is
useful
for
general
purpose
viewing,
and
will
operate
satisfactorily
for
a
wide
variety
of
trigger
signals
whose
repetition
rates
are
be-
tween
sixty
cycles
and
about
two
megacycles.
AC Slow
When
you
have
a
good,
well-focused
trace
of
the
calibrating
waveform
by
the
AUTOMATIC
mode
of
triggering,
try
the
other
four
TRIG-
GERING
MODE
switch
positions.
Turn
the
switch
to
the
AC
SLOW
position.
Advance
the
TRIGGERING
LEVEL
control
clockwise
until
you
getastable
trace
again.
There
may
be
a
con-
siderable
range
of
the
LEVEL
control
over
which
you
can
get
a
stabletrace,and
the
start
of
the
trace
will
move
up
and
down
the
edge
of
the
square
wave
within
this
range.
Notice
that
the
trace
starts
on
the
upgoing
partof
the
calibrator
square
wave.
Now
turn
the
TRIGGER
SLOPE
switch
to
the
-INT
position,
and
readjust
the
TRIGGER-
ING
LEVEL
to
obtain
a
stable
trace
again.
No-
tice
now
that
the
trace
starts
on
the
down-going
portion
of
the
trace
and
that
the
position
of
the
PAGE 2-2
start
can
again
be
changed
somewhat
with
the
LEVEL
control.
DC Triggering
Now turn the TRIGGERING MODE switch to
DC,
Adjust
the
LEVEL
control
for
stable
trig-
gering,
and
then
position
the
trace
with
the
VERTICAL
positioning
control.
You
will
notice
that
triggering
occurs
at
a
vertical
level
on
the
screen
selected
by
the
LEVEL
control
and
that
the
triggering
point
changes
relative
to
the
waveform
as
the
waveform
is
positioned
verti-
cally.
This
effect
will
be
more
noticeable
if
you
look
at
a
low-frequency
sine
wave.
This
triggering
position
is
most
useful
for
low-frequency
signals.
Ir
is
not
suitable
for
applications
where
the
de
level
is
changing
such
as
when
a
Dual-Trace
Unit
is
being
used.
AC Fast
In
the
AC
FAST
position
of
the
TRIGGERING
MODE
switch,
the
circuit
is
quite
similar
to
that
in
the
AC
SLOW
position,
and
you
will
notice
no
difference
when
displaying
the
cali-
brator
waveform.
The
only
difference
is
thatan
re
filter
is
inserted
in
the
circuit,
making
it
insensitive
to
low
frequencies,
and
allowing
it
to
recover
quickly
from
de
level
changes.
This
is
the
position
to
use
when
there
is
hum
present.
This
is
also
the
best
position
to
use
with
the
mn
531/541-OPERATING INSTRUCTIONS

alternate
sweep
feature
of
the
53/54C
unit
if
you
use
INTernal
triggering
with
signals
having
fre-
quency
components
above
10
kc.
HF Sync
The HF SYNC position of the TRIGGERING
TRIGGERING
Triggering Level
The TRIGGERING LEVEL control selects the
point
on
the
triggering
waveform
at
which
trig-
gering will occur. To trigger on small signals
this
control
must
be
set
near
O,
or
near
the
dc
level with dc triggering. The levels are indi-
cated on the panel as positive to the right and
negative
to
the
left.
Negative
positions
of
the
LEVEL
control
cause
triggering
to
occur
dur-
ing
negative
levels
of
the
triggering
waveform
and
positive
positions
cause
triggering
during
positive levels. This control is not used in the
AUTOMATIC
and
HF
SYNC
positions
of
the
TRIGGERING MODE switch.
Trigger Slope
The
+
positions
of
the
TRIGGERSLOPE
switch
(black
knob)
cause
triggering
to
occur
during
the
rising
portion
of
the
triggering
waveform.
The
level
may
be
either
negative
or
positive.
The
-
positions
cause
triggering
to
occur
during
the
falling
portion
of
the
waveform.
Thus
for
slow
rising
waveforms
such
as
sine
waves,
the
triggering
point
can
be
caused
to
occur
at
almost
any
point
in
the
waveform.
An
additional
function
of
the
TRIGGERSLOPE
switch
selects
the
source
of
trigger
signals.
For
each
of
the
available
signal
sources,
the
switch
provides
a
choice
of
positive
or
negative
slope.
Triggering Mode
The
TRIGGERING
MODE
switch
arranges
the
circuits
to
provide
the
kind
of
triggering
you
need.
This
is
the
red
knob
and
the
positions
it
selects
are
labeled
in
red
on
the
panel.
Slowly
changing
waveforms
work
best
on
the
AC
SLOW
and
DC
positions.
In
the
AC
SLOW
position
a
capacitor
removes
the
dc
component
of
the
triggering
waveform
and
makes
triggering
on
the
vertical
signal
independent
of
trace
posi-
a
531/541—-OPERATING INSTRUCTIONS
MODE
switch
is
primarily
for
signals
having
a
repetition
rate
in
excess
of
ten
megacycles.
In
this
position
the
sweep
will
trigger poorly,
if
at
all,
on
the
calibrator
waveform.
To
trigger
on
a
high-frequency
signal,
simply
advance
the
STABILITY
control
until
a
stable
trace
is
ob-
tained.
The
LEVEL
control
is
not
used
in
this
position.
INSTRUCTIONS
tion.
This
position
is
suitable
for
signals
from
twenty
cycles
up to
about
five
or ten
megacycles.
The
DC
position
is the
same
except
that
it
re-
sponds
to
dc
as well.
In
the
AC
FAST
position,
the
circuit
includes
an
rc
filter,
useful
for
pre-
venting
60-cycle,
or
other
low-frequency
com-
ponents,
from
triggering
the
sweep
when
both
high-
and
low-frequency
components
are
present
in
the
triggering
waveform.
The
low-frequency
limit
is
about
two
kilocycles.
In
these three
positions,
if
the
STABILITY
control
is
properly
set,
the
sweep
will
not
run
unless
triggered
by
a
signal.
The AUTOMATIC and HF SYNC switch posi-
tions both arrange synchronizing circuits rather
than strictly triggering circuits. The AUTO-
MATIC
circuit
provides
a
free-running
multi-
vibrator with a normal repetition rate of about
50
cycles,
which
locks
in
and
runs
synchro-
nously
with
recurrent
triggering
waveforms
from
60
cycles
to
about
2
megacycles.
The
synchronized
multivibrator
then
triggers
the
sweep-gating multivibrator,
The
HF
SYNC
switch
setting
arranges
a
cir-
cuit
which
connects
the
triggering
source
di-
rectly
to
the
sweep-gating
multivibrator
so
that
it
can
synchronize
with
the
triggering
wave-
form.
The
sweep-gating
multivibrator
must
be
free-running
for
this
type
of
operation.
It
free-
runs
at
advanced
settings
of
the
STABILITY
control.
It
will
synchronize
with
signals
whose
frequencies
are
as
high
as
30
megacycles,
ata
sweep-repetiton:
rate
up
to
200
kilocycles.
Stability
The
STABILITY
control
adjusts
bias
level
on
the
sweep-gating
multivibrator
near
the
level
at
which
it
will
free-run.
Three
principal
settings
of
the
STABILITY
control
are
used,
the
first
setting
is
with
the
control
advanced
to
the
right,
just
past
the
point
where
the
sweep-gating
mul-
tivibrator
free-runs;
second,
retarded
to
the
left
PAGE 2-3