Tektronix 515 User manual

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S. W. Millikan Way • P.O. Box 500 • Beaverton, Oregon • Phone MI 4-0161 • Ca les: Tektronix
070-247

WARRANTY
All Tektronix instruments are warranted
against defective materials and workman 
ship for one ear. Tektronix transformers,
manufactured in our own plant, are war 
ranted for the life of the instrument.
An questions with respect to the war 
rant mentioned above should be taken up
with our Tektronix Field Engineer.
Tektronix repair and replacement-part
service is geared directl to the field, there 
fore all requests for repairs and replace 
ment parts should be directed to the Tek 
tronix Field Office or Representative in our
area. This procedure will assure ou the
fastest possible service. Please include the
instrument T pe and Serial number with all
requests for parts or service.
Specifications and price change priv 
ileges reserved.
Cop right © 1960 b Tektronix, Inc.,
Beaverton, Oregon. Printed in the United
States of America. All rights reserved. Con 
tents of this publication ma not be repro 
duced in an form without permission of
the cop right owner.
Type 515/515A
AA

CONTENTS
Section 1
Section 2
Section 3
Section 4
Section 5
Warranty
Specifications
Operating Instructions
Circuit Description
Maintenance
Recali ration Procedure
Section 6 Parts List and Schematic Diagrams
Section 7
Accessories
AA
Type 515/515A
http://manoman.sqhill.com

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Type 515/5 ISA
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ON 1
IFICATIONS
The Type 515/515A Oscilloscope is a compact, porta le,
general purpose oscilloscope. The dc-coupled amplifier and
wide range of sweep rates, com ined with reduced size, make
the Type 515/515A a versatile field or la oratory instrument.
ertical-Deflection System
Deflection Factor-. 05 volt/cm ac or de. (.1
volt/cm ac or de S/N 101-1000)
Frequency Response-dc to 15 me, 2 cycles
to 15 me ac. (Down not more than 3 d
at a ove limits.)
Rise Time-. 023 microseconds.
Linear Deflection-6 cm.
Step Attenuator-Nine positions, cali rated,
from .05 v/cm (.1 v/cm S/N 101-1000)
to 20 v/cm, (50 v/cm S/N 101-1000) accurate
within 3% when set on any one step.
Maximum Allowa le Com ined DC and Peak
AC Voltage Input -600 v.
Input Impedance- 1 megohm, 30 ggf; with
P410 pro e-10 megohm, 10.5 ggf. With
P6000 pro e, 10 megohm, 11.5 ggf.
Horizontal-Deflection System
Time Base Range
Twenty-two cali rated time ases from .2
gsec/cm to 2 sec/cm.
Accuracy-3 per cent.
Continuously varia le, uncali rated etween
ranges and to 6 sec/cm.
Magnifier
Expands sweep 5 times to right and left
of screen center. Extends fastest sweep
rate to .04 gsec/cm.
Accuracy-5 per cent.
Un lanking-DC coupled.
Trigger Requirements
Internal-2 mm of deflection.
External-. 2 volts to 20 volts.
Frequency Range-dc to 15 me.
Horizontal Input
Deflection Factor-1.4 v/cm.
Frequency Response-DC to 500 kc , 3 d down.
Other Characteristics
Cathode-Ray Tu e
Type T55P2.
Pl, P7, and Pll phosphors optional.
Accelerating Potential-4, 000 volts.
Deflection Factor at Plates
Vertical-5 v/cm.
Horizontal-20 v/cm.
Voltage Cali rator
Eleven fixed voltages from .05 volts to
100 volts, peak to peak.
Accuracy-3 per cent.
Waveform-square wave at a out 1 kc.
Output Waveforms Availa le
Positive gate of same duration as sweep,
approx. 20 volts. Positive going sweep saw 
tooth, 150 volts.
Power Supply
Electronic Regulation.
Power Requirements- 105 to 125, or 210
to 250 v, 50-60 cycles, 275 watts.
A A
Specifications - Type 515/515A
1-1

Accessories Included
Mechanical Specifications
Ventilation-Filtered, forced-air ventilation. 1-P6017 pro e.
Finish - Photo-etched, anodized panel, lue
wrinkle, perforated ca inet.
1-A510 Binding Post Adapter.
1-F510-5 green filter.
Dimensions-9 3/4" wide, 13 1/2" high, 211/2"
deep.
1 -Instruction manual.
Weight -40 pounds.
1-2
Specifications - Type 515/515A

EXPORT POWER TRANSFORMER
Transformer Primary
The instrument fur which this manual was prepared is equipped with a special transformer.
The transformer has eight primary terminals making possi le six different input connections.
The six primary connections are shown in Fig. 1.
POWER TRANSFORMER HAS TWO
NOMINAL PRIMARY OLTAGES OF
50 OR 60 a , OPERATION.
A
EXTRA WINDINGS PERMITTING
110, 117,
124, 220, 234, OR 248 ,
z 5 z 5
c
110 *
D
2
I
1
t
3
u
4
117 f
D
D A
/ /
2 3
B
1
* 124
B
1
t
1
t
o
c
4
t
A
4
t
4
220 t
B C
1
t 248
D
i >
D
A
4
A
B
A
2 3
BC
1
4
t 234 t
Fig.l. The power transformer has two extra windings permitting nominal primary voltages of 110,
117, 124, 220, 234, 248 volts, 50 or 60 cycle operation.
Fig. 2. When connecting the power transformer for operation with a supply voltage of 200 volts or
more, e sure that the fan is connected etween pins 1 and 3 of the primary. This is to insure that
the fan is supplied with no more than 125 volts. Fig. 2 shows a typical high-voltage fan connection,
using as an example the wiring for a 248 volt supply.

General Information
The Type 515/515A Oscilloscopes are
extremely versatile instruments, adapta le to
a great num er of applications. However, to
make use of the full potentialities of the instru 
ment, it is necessary that you understand com 
pletely the operation of each control. This
portion of the Operators Manual is intended
to provide you with the asic information that
you require. If you are familiar with other
Tektronix oscilloscopes, you should have very
little difficulty in understanding the operation
of the 515/515A, since the function of many
of the controls is the same as the function
of corresponding controls in other Tektronix
instruments.
Cooling
Unless tagged otherwise, this oscilloscope
is connected at the factory for 117 -volt operation.
For 234- volt operation, refer to the Maintenance
section of this manual for proper transformer
connections.
FIRST-TIME OPERATION
Control Settings
The following procedure will help you get
a trace on the screen and ecome familiar
with some of the controls.
Connect the line cord to a sorce of 117-
volt 50 to 60 cycle power, and set the front 
panel controls as follows:
A fan maintains safe operating temperature
in the Type 515/515A Oscilloscope y circulat 
ing air through a filter and over the rectifiers
and other components. The instrument must
therefore e placed so the air intake is not
locked. The air filter must e kept clean
to permit adequate air circulation. If the
interior temperature does rise too high lor
some reason, a thermal cutout switch will
disconnect the power and keep it disconnected
until the temperature drops to a safe value.
Power Requirements
The regulated power supplies in the Type
515/515A will operate with line voltages from
105 to 125 volts or from 210 to 250 volts.
For maximum dependa ility and long tu e life
the voltage should e near the center of this
range.
Voltages outside of these limits may cause
hum or jitter on the trace. Be sure the line
voltage is correct if indications such as these
are present.
FOCUS
Centered
INTENSITY
ASTIGMATISM
POWER
INPUT SELECTOR
VOLTS/CM
( lack kno )
Counterclockwise
(CCW)
Centered
ON
INPUT 1, DC
5
TRIGGER SELECTOR
lack kno + INT
red kno AUTO
TRIGGERING
LEVEL
STABILITY
(red kno )
HOR1Z. DISPLAY
Counterclockwise
PRESET (CCW S/N
101-1000)
NORM.
AA
Operating Instiuctions - Type 515/515A
2-1

.5 MILLISEC
TIME/CM
VERTICAL
POSITIONING
Center
HORIZONTAL
POSITIONING
Center
CALIBRATOR
10
Connect a lead from the CAL. OUT con
nector to the INPUT 1 connector. If the tu es
have had time to warm up, turn the INTENSITY
control clockwise until a trace is visi le on
the screen. Adjust the FOCUS, ASTIGMATISM
and INTENSITY controls to produce a sharp
trace of comforta le rightness.
The two POSITIONING controls will move
the trace vertically and horizontally as nec 
essary to position the display where you want
it on the crt screen.
Triggering Modes
If you have not had previous experience
with the type of trigger controls used on
this oscilloscope, the cali rator waveform is
a good one to practice with. A few minutes
spent on trying the triggering modes descri ed
elow will e time well spent in terms of
future operating convenience.
Auto
The triggering method used in the preceeding
example is the AUTO, (automatic) mode of
operation. It is the simplest mode of triggering.
There are no front-panel controls to e adjusted
when using this mode. If the signal is removed
from the input connector, the sweep will con 
tinue, ut at a reduced repetition rate. This
provides a visual indication that the signal
has een removed and the sweep and triggering
circuits are operating.
AC
Now try the AC mode of triggering. Turn
the red TRIGGER SELECTOR kno to AC.
Advance the TRIGGERING LEVEL control
clockwise until you get a sta le trace. There
may e a considera le range over which you
get a sta le trace. The start of the trace
will move up and down the edge of the square
wave over this range. Notice that the trace
starts on the up-going part of the cali rator
square wave.
Now turn the lack TRIGGER SELECTOR
switch to the -INT position and readjust the
TRIGGERING LEVEL control to get a sta le
trace again. Notice now that the trace starts
on the down-going portion of the square wave
and that the position of the start can again
e changed somewhat with the level control.
DC
Turn the red TRIGGER SELECTOR kno to
DC. If necessary adjust the TRIGGERING
LEVEL control for sta le triggering. Move
the trace vertically on the screen with the
VERTICAL POSITIONING control and note that
triggering occurs at a vertical level on the
screen selected y the LEVEL control, and
that the triggering point changes relative to
the waveform as the waveform is positioned
vertically. This effect will e more noticea le
if you look at a low-frequency sine wave.
H F Sync
The H F SYNC position of the TRIGGERING
SELECTOR switch is primarily for signals
having a repetition rate in excess of five
megacycles. In this position the time ase
will trigger poorly, if at all, on the cali rator
waveform. To sta ilize the display of a high-
frequency signal , simply advance the STABILITY
control clockwise until a sta le trace is o tained.
The LEVEL control is not used in the H F
SYNC mode.
FUNCTIONS OF CONTROLS AND CONNECTORS
CRT Controls
FOCUS
INTENSITY
Control to adjust the eam for maximum sharpness of the trace.
Control to vary the rightness of the trace.
2-2
Operating Instructions - Type 515/515A
AA

Fig. 2-2. Sweep controls in typical position for AC mode of triggering.
This mode is useful for general-purpose triggering over the range
from 60 cps to 5 me.
F ig. 2-1. Sweep controls in typical position for AUTO mode of trigger 
ing. This mode is the most convenient triggering method over the
frequency range from 60 cps to 2 me.
C TIME BASE A I
INPUT
TRIGGER
SELECTOR
( TIME BASE moote >
INPUT
AA
STABILITY
OK HOIIZ INFUT ATTIN
TRIGGERING LE EL
Fig. 2-3. Sweep controls in typical position for DC mode of triggering.
This mode is particularly useful for the frequency range elow 60 cps.
STABILITY
0* HOtll *rut ATTfN.
TRIGGERING LE EL
Fig. 2-4. Sweep controls in typical position for HF SYNC mode of
sweep synchronization. This mode is most effective a out 5 me.
Operating Instructions - Type 515/515A
2-3
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Time-Base Generator
ASTIGMATISM
Control used in conjunction with the FOCUS control to adjust the
eam for maximum sharpness of the trace.
SCALE ILLUM.
Control to vary the rightness of the graticule illumination.
VERTICAL
POSITIONING Control to position the trace vertically.
HORIZONTAL
POSITIONING
Control to position the trace horizontally.
TRIGGER SELECTOR
(red kno )
Four-position switch to select four kinds of triggering: H F SYNC,
AUTO, AC and DC.
TRIGGER SELECTOR
( lack kno )
Six-position switch to select the source and polarity of the triggering
signal.
TRIGGER INPUT
Coax connector to triggering circuits.
STABILITY
Control to adjust time- ase circuits for triggered or recurrent
operation. This control has a PRESET position suita le for most
triggering applications (S/N 1001 -up). This control also functions
as an attenuator for external signals connected to the EXT. HORIZ.
INPUT inding post.
TRIGGERING LEVEL
Control to select the point on the triggering waveform where the time
ase egins.
HORIZ. DISPLAY
Three-position switch to increase the sweep rate five times in the
MAG. position and to connect the horizontal amplifier to the EXT.
HORIZ. INPUT inding post in the EXT. position. When this control
is in the MAG. position, the MAG. light indicates that the sweep
rate has een increased five times.
EXT. HORIZ. INPUT
Binding post to apply an external signal to the horizontal amplifier.
T1ME/CM Twenty-two-position switch to select cali rated sweep rates from
2 sec/cm to .2 gsec/cm.
VARIABLE
(red kno )
Continuously varia le control to vary the sweep rate etween ranges
and to 5 sec/cm. When this control is away from the clockwise
stop the UNCALIBRATED light indicates that the time ase is not
cali rated.
ertical Amplifier
INPUT 1
INPUT 2
Separate signal inputs to the vertical amplifier y way of the INPUT
SELECTOR switch.
INPUT SELECTOR Four-position switch to select either input connector and insert or
remove a de locking capacitor from the input circuits.
DC BAL. Screwdriver control to alance the amplifier circuits so that there
is no shift in the trace position as the VARIABLE control is rotated.
2-4
Operating Instructions - Type 515/515A AA

Auxiliary Functions
VOLTS/CM Nine-position switch to select the desired deflection sensitivity.
VARIABLE Continuously varia le control to vary the sensitivity etween ranges
and to 50 volts/cm. When this control is away from the clockwise
stop the UNCALIBRATED light indicates that the amplifier is not
cali rated.
Rear Panel
+ GATE Binding post to supply a positive pulse for the duration of the time ase.
SAWTOOTH OUT
Binding post to supply a positive-going sawtooth, synchronized with
the internal time ase.
SQUARE-WAVE
CALIBRATOR
Twelve-position switch to select one of eleven taps on a precision
voltage divider in the cali rator circuit and to turn the cali rator off.
CAL. OUT
Coax connector from the cali rator.
POWER
On-off switch in the lead to the power transformer and fan.
TRIGGERING INSTRUCTIONS
CRT CATHODE
Binding post to the ert cathode for the application of intensity modulation.
General
The function of the trigger circuit is to
derive from the incoming waveform a sharp
pulse of suita le amplitude to trigger the
time- ase generator. One such pulse occurs
for each cycle of the incoming waveform. This
pulse is independent of the incoming waveform
in shape and amplitude.
The time- ase generator develops the saw 
tooth waveform necessary to provide a linear
time ase. If the STABILITY control is set
for triggered operation, the time ase circuits
wait until a trigger pulse is received, at which
time one sawtooth waveform is produced. After
the sawtooth waveform is completed the time
ase circuits wait for the next trigger pulse
and the process is repeated.
The following paragraphs descri e the function
of the controls which affect this operation.
Later paragraphs descri e specific triggering
procedures.
Triggering Controls
Triggering Level
In the Type 515/515A the TRIGGERING LEVEL
control determines the point on the triggering
waveform at which triggering will occur. The
TRIGGERING LEVEL control is not a trigger
amplitude or gain control if you are accustomed
to this type of circuit. Instead, it is an amplitude
or voltage discriminator. If the waveform
you are o serving is centered on the screen and
the TRIGGERING LEVEL control is set near
0 the sweep will start as the waveform passes
through the center line on the screen. As
the LEVEL control is turned clockwise, the
triggering point will move a ove the center
line on the screen, and, as it is turned counter 
clockwise the triggering point will move elow
the center line. If the LEVEL control is
set for a voltage greater than that of the
waveform eing o served the sweep will stop.
Thus, if the waveform is of low amplitude
the LEVEL control should e set near 0
(or near the de level with DC triggering).
The LEVEL control is used only in the AC
and DC positions of the TRIGGER SELECTOR
switch.
AA
Operating Instructions - Type 515/515A
2-5

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Fig. 2-6. Photograph showing the phase-shifting effect of the TRIGGER 
ING LEVEL control. All waveforms were o tained with the TRIGGER
SELECTOR set at + INT.
Fig. 2-5. Photograph showing the effect of the + and - positions of
the lack TRIGGER SELECTOR kno .
iiii
A
1^ 1
till 1 i 1111
ih i i
1 ’ ' T I 1 i
r B
1
Ft T *
ill!
r •
Fig. 2-8. Photograph showing an application of the level selection
a ility of the TRIGGERING LEVEL control. By setting the LEVEL
control to the + side of the 0 mark, the trigger circuits can e made
to reject all of the waveform except the highest peaks.
Fig. 2-7. To trigger along slope A set the lack TRIGGER SELECTOR
kno to +. Use the positions marked - to trigger along slope B.
For maximum trace sta ility, trigger on the fastest rising or falling
portion of a waveform.
t i Ji
i Ai i
/ill
L 1 1 1 1111
1 11L
iili
4 M 4 ,
T tit t
flit
T T • t
1
1 itr
■ *♦
w
X
X
j
a a i i
T f T
Fig. 2-9. Photograph showing a waveform where external triggering
may e needed to examine a small discontinuity in a larger waveform.
Usually a triggering waveform can e o tained which is synchronized
with the discontinuity.
F ig. 2-10. A triple-exposure photograph of a waveform showing the
effect of positioning on the triggering point when using the DC triggering
mode. The TRIGGER SELECTOR controls are set at 4- INT, DC and
the TRIGGERING LEVEL control is at 0.
2-6
Operating Instructions - Type 515/515A
AA

Trigger Slope
The lack TRIGGER SELECTOR kno selects
the trigger source and determines whether the
sweep will start as the waveform is going
positive or negative. The + positions of this
switch cause triggering to occur during the
rising portion of the waveform. The - positions
cause triggering to occur during the falling
portion of the waveform. The trigger slope
feature is not used in the H F SYNC mode.
Triggering Mode
The red TRIGGER SELECTOR kno selects
the kind, or mode, of triggering used. The
DC position will permit triggering on all signals
from de to a out five megacycles. It is
especially useful for signals elow 60 cycles
where the sensitivity of AC triggering egins
to fall off.
In the AC position, the switch inserts a
capacitor in the trigger circuits to make the
trigger settings independent of the vertical
position of the trace. This mode is slightly
more sensitive than the DC mode.
The AUTO position arranges the circuits
for an automatic synchronizing action rather
than a strict triggering action. In this position
the trigger-shaper multivi rator free-runs at
a repetition rate of a out 50 cycles. The
multivi rator will lock in and run synchronously
with trigger signals from 60 cycles to a out
2 megacycles. If the trigger signal is lost
the sweep will not stop ut will continue at
a reduced repetion rate without synchronization.
In the H F SYNC position the trigger-shaper
circuits are ypassed and the triggering wave 
form is used to synchronize the time ase
circuits directly. The time- ase generator
must e free-running for this type of operation.
It free-runs at advanced settings of the
STABILITY control. This mode of operation
is primarily useful for signals in excess of
two megacycles.
Stability
The STABILITY control adjusts the ias
level on a multivi rator in the time- ase
generator near the level at which the sweep
will free-run. Three principal settings of the
STABILITY control are used; the first setting
is with the control advanced to the right, past
the point where thegenerator free-runs; second,
retarded to the left just past the point where
free-running ceases; and third, retarded all
the way left to make the generator inoperative.
The second setting is duplicated y an internal
circuit when the STABILITY control is rotated
to the PRESET position.
When the time- ase generator free-runs,
the sawtooth waveforms are produced at a
repetition rate determined y the generator
circuit itself. The STABILITY control varies
this repetition rate slightly. In the second,
or triggered, position of the STABILITY con 
trol the time- as j generator does not run
until a trigger pulse is received at which time
one sawtooth waveform is produced and the
generator waits for the next trigger pulse.
This is also the case when the STABILITY control
is set at PRESET.
For synchronized operation of the time- ase
generator, as used in the H F SYNC position,
set the STABILITY control to the advanced
position so that the generator just free-runs,
and keep it to the right of this point while
adjusting its point to synchronize the time
ase.
For all triggered operation except AUTO. ,
the STABILITY control should e retarded
to the left of the free run point or set to the
PRESET position (S/N 1001 -up).
General-Purpose Triggering
For most average triggering applications
the AUTO, mode of triggering is the easiest
to use. Only one control need e adjusted
and after it is once set the sweep will trigger
satisfactorily on a wide variety of waveforms
and over a wide range of sweep speeds without
resetting. When the STABILITY control is
set properly there will always e a trace
on the screen, whether a signal is present or
not, unless the trace is positioned off the
screen vertically. This feature is especially
valua le, if the pro e is eing moved from
one point to another in a circuit under test.
To use the AUTO, mode, set the red TRIGGER
SELECTOR kno to AUTO. A horizontal trace
should appear immediately. A sta le display
should e o tained on most signals within
the range of 60 cycles to 2 megacycles when
using this mode.
AA
Operating Instructions - Type 515/515A
2-7

For any application within the frequency
range from 60 cycles to a out 5 megacycles
where the display is unsta le on AUTO., the
AC mode can e used. To use this mode of
triggering, proceed as follows:
1. Set the red TRIGGER SELECTOR kno to AC.
2. Set the STABILITY control to the PRESET
position (counterclockwise S/N 101-1000).
3. Adjust the TRIGGERING LEVEL control
for sta le triggering.
The procedure outlined a ove will provide
sta le triggering for most applications. How 
ever, with some triggering waveforms , it may
e necessary to manually set the STABILITY
control. This is done as follows:
1. Set the red TRIGGER SELECTOR kno to AC.
2. Turn the TRIGGERING LEVEL control
counterclockwise to the stop.
3. Advance the STABILITY control clockwise
until the time- ase generator free-runs then
ack it off just past the point where the sweep
s tops .
4. Turn the TRIGGERING LEVEL control
clockwise until sta le triggering occurs. With
this same control you can now select the point
or level at which triggering occurs. Triggering
should occur near the 0 mark.
Low-Frequency Triggering
For waveforms having a slow rise and a
repetition rate of less than 60 cps, the DC
triggering mode is est.
To use this mode of triggering, proceed
as follows:
1. Set the red TRIGGER SELECTOR kno
to DC.
2. Set the STABILITY control to the PRESET
position (counterclockwise S/N 101-1000).
3. Adjust the TRIGGERING LEVEL control
for sta le triggering.
The procedure outlined a ove will provide
sta le triggering for most applications. How 
ever, with some triggering waveforms , it may
e necessary to manually set the STABILITY
control. This is done as follows:
1. Set the TRIGGER SELECTOR red kno to DC.
2. Turn the TRIGGERING LEVEL control
counterclockwise to the stop.
3. Advance the STABILITY control clockwise
until the time- ase generator free-runs then
ack it off just past the point where the
sweep stops.
4. Turn the TRIGGERING LEVEL control
clockwise until sta le triggering occurs. With
this same control you can now select the
point or level at which triggering occurs.
Triggering should occur near the 0 mark
if the trace is centered.
Since the AC mode is more sensitive than
the DC mode a ove 60 cps and is not affected
y the positioning controls, it is superior
to the DC mode, a ove 60 cps. However,
the DC mode can e used up to a out 5 me.
High-Frequency Synchronization
For sta le triggering it is necessary for
the trigger circuits to have a frequency response
considera ly in excess of the frequency of the
waveform eing displayed. At a out five mega 
cycles the efficiency of the trigger circuits
is reduced and the H F SYNC mode ecomes
the est method of synchronizing the trace.
To use the H F SYNC mode simply advance
the STABILITY control until the time ' ase
free-runs and then continue to advance it
until the time ase locks in with the signal.
The polarity markings on the TRIGGER
SELECTOR switch have no significance in
this mode, and the TRIGGERING LEVEL con 
trol is not used.
Triggering on Complex Waveforms
When the waveform under o servation is
complex there may e several points on the
waveform where ordinary triggering circuits
may tend to trigger. As a result, the trace
may e unsta le. This insta ility may e
encountered occasionally with the AUTO, mode
of triggering. The AC and DC triggering modes
allow the level on a waveform, at which trigger 
ing occurs, to e selected y the TRIGGERING
2-8
Operating Instructions - Type 515/515A
AA

LEVEL control. Thus the LEVEL control can
e set so that only one point on the waveform
is of sufficient amplitude to trip the triggering
circuits. This point can e located y setting
the controls as for the AC or DC triggering
modes and then moving the TRIGGERING LEVEL
control away from the 0 mark in either direction
until the trace ecomes sta le.
Trigger-Signal Source
For most normal triggering applications the
1NT. trigger source is most convenient. In
the INT. positions of the TRIGGER SELECTOR
switch the triggering signal is o tained from
the vertical amplifier.
If an external trigger source is availa le
it is often convenient to use the EXT. positions
of the TRIGGER SELECTOR switch. An external
trigger source is particularly useful if the
amplitude of the signal under o servation is
changing or if the pro e is eing moved from
point to point in a circuit.
The LINE positions of the TRIGGER
SELECTOR switch permit sta le triggering
at the line frequency. These positions are
useful when displaying almost any function
that is synchronized with the line.
TIME-BASE OPERATION
General
The time- ase generator produces the saw 
tooth waveform which is used to move the
eam across the crt. The TIME/CM controls
vary the slope, ut not the amplitude, of this
waveform, and thus determine the sweep rate
without affecting the length greatly.
The horizontal amplifier amplifies the saw 
tooth waveform and applies it to the crt deflection
plates. The HORIZ. DISPLAY switch increases
the gain of the amplifier five times in the
MAG. position. In this position the display
is spread over the equivalent of five screen
diameters.
Sweep Rate
The TIME/CM controls determine the sweep
rate of the horizontal trace. The TIME/CM
of horizontal deflection is indicated y the
lack num ers when the HORIZ. DISPLAY
switch is in the normal position and y the
lue num ers when it is in the MAG. position.
These num ers are correct only when the
red VARIABLE control is completely clock 
wise. The UNCALIBRATED light indicates when
the time ase is not cali rated for this reason.
The VARIABLE control has a range of a out
2 1/2 to 1.
Magnifier
The HORIZ. DISPLAY switch increases the
horizontal-amplifier gain five times in the
MAG. position expanding the time ase so
that the center one-fifth of the trace fills
the graticule. The MAG. light is energized
when the HORIZ. DISPLAY switch is turned
to the MAG. position. Any portion of the
trace may e positioned on the screen with
the HORIZONTAL POSITIONING control. If
the VARIABLE control is fully clockwise the
magnified sweep rate is indicated y the lue
num ers at the TIME/CM switch.
External Horizontal Input
When the HORIZ. DISPLAY switch is in the
EXT. position, the horizontal amplifier is con 
nected to the EXT. HORIZ. INPUT inding
post. The STABILITY control serves as an
attenuator for signals applied to this inding
post.
ERTICAL-AMPLIFIER OPERATION
Probes
The P6000 pro e furnished with this instru 
ment has a 10-to-l attenuation ratio. Be sure
to check the adjustment of the pro e regularly
and efore making critical measurements. If
the compensation is incorrect the frequency
response will e affected. Touch the pro e
tip to the cali rator output connector and
display several cycles of the cali rator wave 
form. If the top and ottom of the displayed
square wave are not flat, adjust the trimmer
capacitor located inside the pro e ody to
achieve correct square-wave response.
Input Connections
Be careful that the external circuitry does
not cause deterioration of the waveform when
you make connections to the INPUT connectors.
Improper termination of ca les may cause ring 
AA Operating Instructions - Type 515/515A
2-9

ing or loss of frequency response. If you
use unshielded leads keep them as short as
possi le.
Two ca les or pro es can e connected to
the oscilloscope at once. You can then select
the signal on either ca le with the INPUT
SELECTOR switch. However, if one signal
is very much larger than the other, some
crosstalk may occur and the ca le having
the larger signal should e disconnected.
Coupling
It is sometimes unnecessary or undesira le
to display the de level of the waveform. In
the two AC positions of the INPUT SELECTOR
switch, a capacitor in series with the input
locks the de component of the waveform so
that only the ac component is displayed.
Deflection Sensitivity
The VOLTS/CM switch inserts frequency-
compensated attenuators ahead of the amplifier.
The VARIABLE control provides continuous
adjustment of the deflection sensitivity etween
the values indicated y the VOLTS/CM switch.
The VARIABLE control must e clockwise
against the stop for the sensitivity to e as
indicated y the VOLTS/CM switch. The red
UNCALIBRATED light indicates when the
VARIABLE control is not fully clockwise.
DC Balance Adjustment
After the oscilloscope has een in use for .
a period of time you will notice that the trace
will change position as the VARIABLE control
is rotated. This is caused y tu e aging and
the resultant shift in operating potentials. To
correct this condition rotate the VARIABLE
control ack and forth and adjust the DC BAL
control until the trace position is no longer
affected y rotation of the VARIABLE control.
AUXILIARY FUNCTIONS
Square-Wave Calibrator
The square-wave cali rator provides a source
of square waves of known amplitude at a out
1000 cycles. The outout impedance varies
with the voltage ut is as high as 5,000 ohms.
Be sure the load impedance you connect to
the CAL. OUT connector does not change the
output voltage.
Trace-Brightness Modulation
To couple markers or other signals into
the ert cathode for rightness information,
disconnect the ground strap at the rear of
the instrument and connect the signal to the
CRT CATH. inding post.
Graticule Illumination
The graticule lighting control, la eled SCALE
ILLUM., can e adjusted to suit the lighting
conditions of the room. The graticule can
e mounted in either of two positions rotated
180 degrees from each other. In one position
the illumination is colored red and, in the
other position, white. The white will reproduce
well photographically.
A green light filter is supplied which can
e used for increased contrast. Normally this
filter should e mounted next to the ert screen
so it does not lock the light from the graticule
lines.
Direct Connection to Deflection Plates
Connections can e made directly to the
deflection plates y removing the ca inet on
the left side. The two pins on the left-hand
side of the ert neck are the vertical deflection
plates. To avoid distortion, the average de
potential on these plates should e etween
150 and 200 volts. Unless de coupling is
required, connect coupling capacitors in series
with the leads to the deflection plates and
connect one-megohm resistors from the deflec 
tion plates to the leads from the delay line.
With this connection the plates are maintained
at the proper operating potential and positioning
control is retained y the front-panel controls.
2-10
Operating Instructions - Type 515/515A
AA

UNBLANKIMG
PULSE
V/&2A
+GATE
R.I4O
4
al
BLOCK DIAGRAM DESCRIPTION
The lock diagram shows the interconnection
of the functional parts of the oscilloscope,
except the power supplies. Functions of the
switches are shown instead of their actual
connections. This diagram, as well as the
ones which follow, is designed to fold out so
that the diagram can e studied along with
the text without turning any pages.
The vertical amplifier has a sensitivity of
.05 volt per centimeter (.1 volt per centimeter
S/N 101-1000) and provides push-pull output
to drive the deflection plates. The alanced
delay line is connected etween the output
amplifier and the deflection plates.
The trigger cathode follower applies a sample
of the vertical signal to the trigger-amplifier
stage to provide internal triggering.
The trigger amplifier and shaper provide
a sharp trigger pulse which triggers the multi 
vi rator. The multivi rator gates the time 
ase generator and is prevented from recycling
y the holdoff cathode follower until the generator
has had time to run up and return.
The time- ase generator is a Miller run-up
type and provides a 150-volt sawtooth for
the horizontal amplifier.
The horizontal amplifier converts the time 
ase sawtooth for push-pull applications to
the deflection plates.
The un lanking cathode follower applies a
positive gate to the crt grid via the high-
voltage power supply. It also supplies a gate
to the gate-out cathode follower which provides
a positive gate at a front-panel inding post.
SECTION 3
CIRCUIT
DESCRIPTION
The cali rator provides a square wave of
known amplitude for checking the gain of the
oscilloscope amplifiers and auxiliary equipment.
ERTICAL-DEFLECTION SYSTEM
General
The Type 515/515A vertical amplifier has
a maximum sensitivity of .05 volt per centimeter
(.1 volt per centimeter S/N 101-1000), ac or
de. The circuit consists of two stages of
amplification, each stage preceded y cathode
followers.
Input Connectors
There are two input connectors which can
e switched into the input circuits y SW 301,
the INPUT SELECTOR switch. This switch
is wired physically so as to reduce coupling
etween inputs to a minimum. Blocking capacitor
C301 is shorted out in the DC positions of
the selector switch.
I nput Attenuators
The VOLTS/CM switch inserts frequency-
compensated attenuators into the input circuit.
Four attenuators are used singly or in tandem
pairs to produce nine fixed sensitivities.
DC Balance
The DC BAL control, R338, provides an
adjusta le, de grid voltage for V340 so that
the cathode of V360 is at the same potential
as the cathode of V350. When this control
is properly set, no change in vertical position 
ing will result when the VARIABLE position
is rotated.
AA
Circuit Description - Type 515/515A
3-1

Input Cathod* Follower HORIZONTAL-DEFLECTION SYSTEM
The input cathode follower, V330, isolates
the input circuits from changes in capacitance
as the VARIABLE control is rotated. R330
is a current-limiting resistor to limit grid
current in the event an excess voltage is
applied to the input. The opposite cathode
follower, V340, alances the drift in V330
caused y heater-voltage changes.
I nput Amplifier
The input amplifier stage is a common 
cathode phase-splitter amplifier. Coils L351
and L361 provide high-frequency peaking. The
VARIABLE VOLTS/CM control, R356, varies
the gain y varying the degeneration in the
cathode circuit.
Vertical positioning is produced y two dual
potentiometers, R368, connected to the plates
of the amplifier so that current through one
plate load is increased as current through
the other plate load is decreased. Since the
amplifier is de coupled, the change in the
plate voltage which occurs changes the position
of the trace on the cathode-ray tu e.
The rc networks, R352, C352 and R362,
C362, provide compensation for the reduction
in gain at very-low frequencies which is a
characteristic of high-conductance amplifiers.
Output Amplifiers
Cathode followers V370A and V370B drive
the output amplifiers through series peaking
coils L390 and L400. The GAIN ADJ. control,
R396, sets the gain of the amplifier to agree
with the front-panel cali ration. Plate current
for the output amplifiers is supplied y the
delay-line termination resistors, R485 and R486.
Delay Line
The alanced delay line delays the signal
until the sweep starts and the ert is un lanked.
The trigger signal is taken from a coil which
serves as the first section of the delay line.
Each section of the line is turned for optimum
response to a square wave.
Trigger Amplifier
The TRIGGER SELECTOR switch with the
lack kno , SW20, selects the source of trigger 
ing voltage and arranges the trigger-amplifier
input circuit to produce negative-going output
for either negative-going or positive-going por 
tions of the input signal.
The trigger amplifier, V10, is a grounded-
grid cathode-coupled amplifier. A capacitor,
C4, can e switched into the grid circuit to
remove the de component of the trigger signal.
Output is always taken from the pentode plate,
ut the TRIGGER SELECTOR switch connects
either the pentode grid or the triode grid to
the input-signal source. The opposite grid is
connected to a de ias source, adjusta le y
means of the TRIGGERING LEVEL control.
This ias voltage determines the voltage on
the pentode plate. In the AC and DC positions
of the TRIGGER SELECTOR switch, the voltage
on the pentode plate is de coupled to the grid
of V30A.
Trigger Shaper
The trigger-shaper stage consists of V30
connected as a dc-coupled multivi rator. In
the normal, or quiescent, state the V30A section
is conducting and its plate is down. The grid
of the V30B section is de coupled to the V30A
plate through divider R38, R39 and R40, which
holds the " B" grid elow plate-current cutoff.
As the trigger signal drives grid of V30A
in the negative direction the cathodes of oth
tu es follow the grid down until V30B starts
to conduct. At this point the plate voltage
of V30A and the B grid rises with it. The
V30B cathode rises with its grid carrying
the " A" cathode with it and V30A cuts off.
The transition occurs very rapidly, regard 
less of how slowly the V30A grid signal falls.
The steep negative-going step at the plate
of V30B is differentiated y an rc network
including C109 shown in the sweep diagram,
and the sharpened pulse trips the sweep multi 
vi rator.
Trigger Mode Switch
The TRIGGER SELECTOR switch with the
red kno , SW5, has four positions which arrange
3-2
Circuit Description - Type 515/515A
AA

the circuits for four types, or modes, of
triggering.' In the DC position, the triggering
signal is de coupled as far as the trigger 
shaper stage. In the AC position, locking
capacitor C4 removes the de component of
the signal.
In the AUTO, position of SW5, the plate
of the A section of the trigger shaper, V30,
drives the grid of the B section just as it
also drives its own grid through R45 , a resistance
of several megohms. This plate-to-grid coupling
allows the trigger shaper to free-run when
no triggering signal is present. The addition
of R45 causes the trigger shaper to free run
when no trigger signal is present. For example,
when the plate of V30A rises, the grid of V30B
also rises, carrying with it the right-hand
end of R45. The left-hand end of R45 is
connected to the A grid through R22. The
time constant of the rc circuit etween the B
grid and ac ground through C20, R22 and R45
is of such length that it takes a out .01 second
for the V30A grid to rise exponentially from
its starting point elow cutoff to a point where
plate current can flow.
When V30A plate current flows, the plate
drops, forcing the V30B grid down, and thus
the right-hand end of R45 is forced down.
The left-hand end of R45 and the A grid
immediately egin to drop exponentially toward
cutoff. When the A grid reaches cutoff again
it has completed one cycle of the approximately
50-cycle triangular waveform. The range of
the V30A grid voltage etween A cutoff and
B cutoff is a out 3 volts for the circuit used
in the AUTO. mode. This is increased from
a out .5 volt for the AC and DC modes y
the addition of R45 to the circuit.
Since the V30A grid is never more than
3 volts from cutoff, a trigger signal with a
peak-to-peak voltage of three volts or more
can drive the grid to cutoff at any time and
produce a trigger output. Smaller signals can
also trigger the shaper ut only if they occur
at a time when the grid is within their peak
voltage of cutoff. The duty cycle of operation
of the time- ase generator is somewhat reduced
therefore with smaller trigger signals.
This circuit configuration is useful ecause
with it the time- ase generator can e syn 
chronized with repetitive signals over a wide
range of frequencies without readjustment. When
not triggered externally, the generator con 
tinues at a 50-cycle rate, and in the a sence
of any vertical signal, generates a ase line
that shows that the oscilloscope is adjusted
so as to display any signal that might e
connected to the vertical-deflection system.
In the H F SYNC position of SW5, the
trigger amplifier and trigger shaper stages
are ypassed and the trigger signal is applied
directly to the swep multivi rator. In this
mode the STABILITY control is set so the
sweep is superimposed on the negative-going
trigger-holdoff waveform at the grid of V110A
and will cause the multivi rator to synchronize
at a su multiple of the triggering signal
frequency. This circuit is suita le for signals
in excess of five megacycles.
Schmitt Multivibrator
The dc-coupled multivi rator, shown in the
time- ase diagram, turns on the time- ase
generator upon receipt of a negative trigger
from the trigger shaper, and holds off su 
sequent trigger signals until after the sweep
is completed. The multivi rator consists of
V110A and V120 with oth common-cathode
and plate-to-grid coupling. Plate-to-grid coupl 
ing is y means of a cathode follower.
In the quiescent state VI 10 A is conducting and
its plate is down. Cathode-follower V110B
holds the grid of V120B elow cutoff through
voltage divider R115 , R116. Cathode-follower
V110B isolates the plate of VI 10 A from the
various loads, and there y permits a faster
step.
When the negative trigger pulse from the
trigger-shaper stage reaches the grid of V110A
it is coupled to V120B and V120B starts to
conduct. The multivi rator switches quickly
to its second state with V120B conducting
and V110A cut off. The iases and plate loads
are adjusted so that when VI 10 A is conducting,
the grid of V120B is held elow cutoff, and
when V120B is conducting the cathode of VI 10 A
is held a ove cutoff.
There are thus two sta le states, in either
of which the multivi rator will remain until
a signal of the proper polarity and amplitude
to the grid of VI 10 A switches it to the other
state. To return the multivi rator ack to
the quiescent state with V110A conducting, a
AA
Circuit Description - Type 515/515A
3-3