Tektronix 315D Series User manual

CATHODE-RAY OSCILLOSCOPE
TYPE 315D
SERIAL N U M B E R _______________
INSTRUCTION
MANUAL
MANUFACTURERS OF CATHODE-RAY AND VIDEO TEST INSTRUMENTS
Sunset Highway an Barnes Roa • P. O. Box 831 • Portlan 7, Oregon, U. S. A.
Phone: CYpress 2-2611 • Cables: Tektronix

SECTION I Time Base Magnifier
General Descr pt on
The TEKTRONIX Type 315D catho e-ray oscil
loscope is a small compact an portable high-perform
ance laboratory instrument particularly esigne to
occupy minimum space. The vertical ban wi th ex
ten s to five megacycles from c. Time-base ranges
exten ing from one microsecon per sweep to fifty
cycles per sweep are provi e . An amplitu e cali
brator an a time-base magnifier are also inclu e .
Sensitivity
Twelve calibrate fixe sensitivities: ac only, 0.01,
0.02 an 0.0& volts per ivision, 5 cycles to 5 mega
cycles : c an ac 0.1, 0.2, 0.5,1, 2, 5,10, 20, an 50 volts
per ivision. These sensitivities fit graticule ivisions
for irect rea ing of voltages. Continuously variable
10 to 1 sensitivity multiplier control also available.
Calibrator
Square wave at approximately one kilocycle avail
able at front-panel UHF connector at four fixe peak-
to-peak voltages of 0.1, 1, 10, an 100 volts with accu
racy within 3 per cent.
Signal Delay
Quarter-microsecon signal elay line permits all
of the triggering waveform to be viewe .
Trigger Amplitude Discriminator
Permits time base to be triggere at any esire
amulitu e point on the triggering waveform.
Time Base
Twenty-four fixe times per ivision between
0.1 microsecon an 5 secon s per ivision fit grati
cule ivisions for irect rea ing of time. Continuously
variable 10 to 1 sweep-time control also available.
Magnifies time base to right an left of center by
factor of five times. Portion of trace appearing at cen
ter is ma e five times as wi e.
Direct-Coupled Unblan ing
Accommo ates slowest sweeps.
Cathode-Ray Tube
Flat-face high efinition three-inch tube.
Graticule
Quarter-inch ivisions, 8 lines vertically, 10 lines
horizontally. Variable-intensity e ge lighting.
Power Supply
Four electronically regulate plate-voltage supplies.
Power transformer will operate on either 117 or 234
volts, 50 to 800 cycles. (Special ventilating fan re
quire for other than 50- to 60-cycle operation.)
Crt Accelerating Voltage
1630 volts from electronically regulate rf oscillator
high-voltage supply.
Ventilating Fan
The Type 315D is normally supplie with a
50- to 60-cycle in uction-motor fan. For frequencies
much above 60 cycles a c commutator motor an
selenium rectifier are available at extra cost to exten
the range to 800 cycles.
Dimensions
12^s" high, 8$4" wi e an I8V4" long.
Weight
36 lbs.
Construction
Wel e aluminum alloy.
Finish
Ano ize photo-etche aluminum panel, grey
crackle enamel case.
SECTION I, PAGE 1 TYPE 315D

Funct ons of Front-Panel Term nals
and Controls 5X MAGNIFIER
(Re label,
re knob)
Vertical Amplifier
MULTIPLIER Four-position switch to multiply
VOLTS/DIVISION by factors
of 1, 2, or 5. Fourth position
marke 10-1 in re permits re
coaxial knob to a just multiplier
continuously over 10 to 1 range.
INPUT Coaxial UHF connector for con
necting signal to vertical- eflec
tion system.
AMPLITUDE Seven - position control provi es
four fixe ac sensitivities an three
fixe c sensitivities.
FOCUS A justs voltage of focusing ano e
to provi e focusing.
INTENSITY A justs control-gri voltage to
control brightness of trace.
SCALE ILLUM A justable series resistor in grati
cule lighting circuit to control
amount of scale illumination.
POSITION
HORIZ. A justs average voltage of hori
zontal eflection plates to position
trace horizontally.
VERT. A justs average voltage of verti
cal eflection plates to position
trace vertically.
TIME BASE Four-position switch to multiply
MULTIPLIER time-base TIME/DIVISION by
factors of 1, 2, or 5. Fourth posi
tion marke 10-1 in re permits
re coaxial knob to a just multi
plier continuously over 10 to 1
range.
RANGE Eight - position switch provi es
eight fixe time base times per i
vision in eca e ratio between
0.1 microsecon per ivision to
1 secon per ivision.
CALIBRATOR
TRIGGER
SELECTOR
STABILITY
(Re label,
re knob)
TRIGGER
AMPLITUDE
DISCRIMI
NATOR
POWER ON
CAL OUT
EXT TRIGGER
AC Bin ing
Post
DC Bin ing
Post
-(-GATE
SAWTOOTH
GND
Two-position switch turns time-
base magnifier on in clockwise po
sition, returns time base to normal
in counterclockwise position.
Five-position switch selects four
fixe peak-to-peak squarewave
voltages of 0.1, 1, 10, or 100 volts.
Turns calibrator oscillator off in
fifth position.
Ten-position switch selects trigger
source an accommo ates trigger
circuits to rising or falling trigger
waveforms. Accommo ates trig
ger circuits to fast-rising or slow-
rising triggering waveforms.
A justs voltages of gating multi
vibrator so that it can be set for
recurrent operation or at the
threshol of recurrent operation
for triggere sweeps.
Continuously variable voltage con
trol etermines point of operation
of trigger-inverter stage to select
point on triggering waveform at
which time-base circuit is trippe .
AC supply off-on toggle switch.
Coaxial UHF connector for output
of calibrator oscillator.
Connects to EXT. positions of
TRIGGER SELECTOR switch
through capacitor.
Connects irectly to EXT. posi
tions of TRIGGER SELECTOR
switch.
Bin ing post provi es 25-volt posi
tive gating pulse coinci ent with
time base.
Bin ing post provi es positive
going sawtooth voltage coinci ent
with time base.
Bin ing post connecte to frame
of instrument.
TYPE 315D SECTION I, PAGE 2

SECTION II
Operat ng Instruct ons
The TEKTRONIX Type 315 Oscilloscope may be
operate in any in oor location or in the open if it is
protecte from moisture.
Ventilation
Force -air cooling is require so that care must be
taken to avoi obstructing the air intake to the cir
culating fan.
WARNING: The Type 315D Oscilloscope
shoul not be operate unless the fan is run
ning. The interior will reach angerous tem
peratures within five to ten minutes of such
operation.
The operation of the calibrator an the trigger cir
cuits of the Type 315 oscilloscope is enough ifferent
that it is especially important for users familiar with
previous TEKTRONIX oscilloscopes to un erstan
the ifference.
The vertical amplifier is sufficiently stable that once
the gain has been stan ar ize , voltages can be rea
irectly from the graticule just as you woul rea a
voltmeter. For this reason, the calibrator in the
Type 315 is not continuously variable in amplitu e as
are the calibrators in previous TEKTRONIX oscil
loscopes. The calibrator is inten e to be use as a
source of squarewave voltage, operating in the vi
cinity of one kilocycle, available at four accurate fixe
voltage levels, 0.1, 1, 10, an 100 volts, peak to peak.
It is useful to supply a signal for aligning the vertical
amplifier, an the attenuator an probe, as well as for
stan ar izing the gain of the vertical amplifier to the
graticule calibrations.
To check the calibration of the vertical amplifier,
make a connection between the CAL OUT terminal
an the INPUT terminal. Then, for example, set the
VERTICAL AMPLIFIER MULTIPLIER selector
to 2, the AMPLITUDE selector to DC, 0.1, an the
CALIBRATOR to 1 volt, peak to peak. With these
settings, there shoul be exactly five graticule ivi
sions eflection of the trace. The amplifier gain can
be correcte for any ifference by means of a screw
river a justment in the center of the AMPLITUDE
selector switch.
To use the Type 315 for making an amplitu e
measurement, place the AMPLITUDE selector in the
approximate range of sensitivity esire , an the
MULTIPLIER selector on any one of the three steps,
1, 2, or 5. Each ivision of the graticule then cor
respon s to a voltage which can be etermine irectly
by multiplying the AMPLITUDE an the MULTI
PLIER scale rea ings.
In the most counter-clockwise position of the
MULTIPLIER selector, a continuously-variable gain
is provi e over a range of 10 to 1, marke in re . In
this selector position, varying the re knob mounte.
coaxially with the AMPLITUDE selector knob varies
the gain over the 10 to 1 range.
In a ition to the coaxial re knob on the AMPLI
TUDE selector switch, there are three other re knobs
mounte in a like manner on the TIME BASE an
TRIGGER controls. In each case, a re scale on the
panel pertains to the position or to the function of
the re knob.
In the operation of the time base of the Type 315
oscilloscope, the TRIGGER AMPLITUDE DIS
CRIMINATOR control is likely to be somewhat con
fusing to users familiar with previous TEKTRONIX
instruments. This control is not in any sense a trigger
amplitu e a justment. The triggering circuit is irect
couple to the vertical amplifier in the INT positions
of the TRIGGER SELECTOR switch, both for the
AC an DC connections of the vertical amplifier an
is irect couple to one of the EXT TRIGGER panel
connectors. The TRIGGER AMPLITUDE DIS
CRIMINATOR control etermines by amplitu e the
portion of the triggering waveform at which trigger
ing occurs. At settings of the DISCRIMINATOR
control near zero, triggering will occur at a point on
the waveform near zero. If the zero signal trace is
centere on the screen, triggering will occur at a point
on the trace above the center of the screen. Regar less
of the amplitu e of the waveform, triggering will
occur at a point on the trace the same istance above
the center of the screen, provi e that the wave
reaches that amplitu e. The negative trigger positions
of the TRIGGER SELECTOR control refer to the
irection of slope of the triggering waveform at which
triggering occurs. For example, to trigger the sweep
from a sine wave at a point beyon the peak but above
zero, the TRIGGER SELECTOR shoul be place
in one of the negative trigger positions an the TRIG
GER AMPLITUDE DISCRIMINATOR shoul be
turne to a positive position.
For slow rise signals whose rise time is longer than
SECTION II, PAGE 1 TYPE 315D

one microsecon , the TRIGGER SELECTOR shoul
be place in one of the SLOW RISE positions of the
scale. In these positions of the control, a regenera
tive trigger generator pro uces sharp triggers suitable
for initiating the sweep regar less of the rise time of
the input wave. For the FAST RISE positions, the
trigger generator is not regenerative an is capable
of pro ucing faster triggers so that for high frequency
or fast rise time signals, the TRIGGER SELECTOR
switch shoul be in one of these positions. The best
way to etermine which position is proper for a mar
ginal type of signal is to try both positions. There is
appreciable overlap.
Generally speaking, there is no ifference in trigger
sensitivity in the ifferent control positions. A change
in voltage which will pro uce a quarter of a ivision
eflection, will easily initiate a trigger at any spee
or in any part of the wave. For a small amplitu e
wave, the TRIGGER DISCRIMINATOR control will
nee to be set near zero. With settings near maximum
either clockwise or counterclockwise, a large trace will
be require to initiate a sweep an the point of initia
tion will be near the top or bottom of the waveform.
Calibrations on the DISCRIMINATOR ial are
approximately in volts for externally connecte trig
ger voltages. For internally erive triggers, approxi
mately seven ivisions on the DISCRIMINATOR
scale correspon s to about ten graticule ivisions of
eflection.
The magnifier circuit expan s to right an left the
portion of the trace that is centere on the screen.
Horizontal positioning prece es the magnifier circuits
so that this control is use for both the normal an
magnifie trace.
Placing the Type 315D Oscilloscope in Operation
for the First Time
The following proce ure is suggeste when you
put the instrument into service for the first time:
1. Set the panel controls as follows:
POWER OFF
VERTICAL AMPLIFIER MULTIPLIER. .2
VERTICAL AMPLIFIER
AMPLITUDE.DC, 0.1 VOLTS/DIVISION
FOCUS ...............................................CENTER
INTENSITY ....... COUNTERCLOCKWISE
SCALE ILLUM..................................CENTER
HORIZ. POSITION .......................... CENTER
VERT. POSITION ............................ CENTER
TIME BASE MULTIPLIER .......................... 1
TIME BASE RANGE................1 MILLISEC.
CALIBRATOR ..................................... 1 VOLT
TRIGGER SELECTOR.SLOW RISE, +INT.
STABILITY ......... COUNTERCLOCKWISE
TRIGGER AMPLITUDE
DISCRIMINATOR ................................ —50
2. Connect the power cor to a source of ac power
capable of supplying 4 amperes at 117 volts at
60 cps. (240 volts if power transformer is so con
necte , an 50 to 800 cps for the universal-fre
quency mo el.)
3. Make a connection between the CAL OUT
terminal an the INPUT terminal. Turn the
POWER switch to ON, an permit the instru
ment to warm up for about a minute.
4. A vance the INTENSITY control clockwise a
little past center.
5. A vance the STABILITY control until a trace
appears on the screen.
6. A just the FOCUS an INTENSITY controls
for a sharp trace an satisfactory brightness.
7. A just the two POSITION controls until the
trace is centere on the screen as esire .
8. Return the STABILITY control clockwise until
the trace just isappears an return the TRIG
GER AMPLITUDE DISCRIMINATOR con
trol clockwise towar O until the calibrator
waveform appears on the screen.
The stability control etermines whether the multi
vibrator retriggers itself or whether it returns to a
stable con ition after executing a single sweep for
each trigger receive .
In the SLOW RISE positions of the TRIGGER
SELECTOR switch the regenerative trigger gener
ator pro uces triggers of the same amplitu e when
trippe regar less of the amplitu e or spee of the
triggering waveform. The STABILITY control
shoul therefore be set at such a level that a trigger
output of this amplitu e will trigger the sweep an
thereafter no change in the STABILITY control set
ting will be nee e . The trigger sensitivity is the volt
age ifference nee e to trip the regenerative trigger
TYPE 315D SECTION II, PAGE 2

generator, which is etermine by the gain between
halves of this generator. There is no front-panel con
trol of this gain, but there is an internal screw river
a justment which shoul not be change , however,
except possibly after replacing the generator tube.
In the FAST RISE positions of the TRIGGER
SELECTOR switch regeneration between the halves
of the trigger-generator tube is effectively remove
by shorting out the plate-loa resistor of the input
pento e section. Since the circuit thus becomes a
catho e-couple amplifier, the amplitu e of the out
put triggers is epen ent on the ifferentiate rise 01
the triggering waveform. For slow-rising waveforms,
therefore, the output trigger will be too small to trip
the time-base generator. The point of transition at
which better triggering will result from one or the
other of the switch positions is not critical. For rise-
times near one microsecon it will be well to try both
types of operation. Triggering from the calibrator
waveform will be more satisfactory with the TRIG
GER SELECTOR switch in the SLOW RISE
positions.
®SECTION II, PAGE 3 TYPE 315D

SECTION III
C rcu t Descr pt on
Sweep Circuit
The time base of the TYPE 315 CATHODE-RAY
OSCILLOSCOPE is generate by means of a Miller
runup generator. New circuitry eliminates the usual
istortion of the early part of the sawtooth. A con
stant current charging source to the timing capacitor
improves the sawtooth linearity.
The triggering signal is selecte by means of the
TRIGGER SELECTOR switch connecte to the B
section of a catho e-couple phase inverter, V201,
with a gain of about six at each plate. The A section
gri is connecte to the arm if a potentiometer so that
its bias can be varie over a wi e range. By a justing
the bias properly you can select the portion of the trig
gering wave form that triggers the sweep.
A secon section of the trigger selector switch con
nects the output of B section plate to the trigger gen
erator, V202, for negative-going triggering waveforms
an the A section plate for positive-going triggering
waveforms.
The trigger generator consists of V202, as a bistable
multivibrator for slow-risetime trigger signals, an
as a catho e-couple amplifier for fast-risetime trig
ger signals. For signals with a risetime slower than
one microsecon , the multivibrator circuit will pro
vi e the best trigger signal. In the SLOW RISE posi
tions of the TRIGGER SELECTOR switch, SW201,
C227 connecte between the trio e-section gri an
pento e-section plate of V202 provi es the regenera
tion. For faster rising trigger signals, the FAST RISE
positions of.th'e switch effectively removes the regen
eration by shorting out plate-loa resistor R220 in the
pento e section of V202. V202 thus becomes a catho e-
couple amplifier.
Trigger output voltage is taken from the plate of
the trio e section of V202. The plate loa is in uctor-
resistor ifferentiating circuit, L221, R221, so that a
reasonably fast transition is require to evelope large
enough triggers to' operate the sweep circuit. The
multivibrator performs this fast transition for trig
gering waves otherwise too flat. It will perform a
regenerative transition in either irection for the slow
est risetime signals.
The sharp trigger signal is capacitance couple into
V203, a catho e-couple stage whose output is irect
couple through catho e follower V204A to the junc
tion of the plate of V211A an the catho e of V211B
of the casco e Eccles-Jor an multivibrator. A posi
tive signal on the B section gri of V203 is require
to trigger the multivibrator. The B section of V203
is also connecte to a bias-control potentiometer calle
STABILITY which sets the c level.
V204B, an V205 A an B surroun ing V204A com
prise a hol -off circuit. The function of the hol -off
circuit is to re uce the voltage on the gri of the trig
gering catho e follower, V204A, uring the sweep ana
for a short perio after the multivibrator has recov
ere . V205B performs this function. During the
sweep, V205B con ucts so that its plate rops. At
the termination of the sweep, V205B is cut off an
its plate rises towar 225 volts positive. A switche
capacitor between plate an groun elays this rise
towar +225 volts uring the charge perio , epen 
ing on the size of the capacitor. When the plate of
V205B reaches 100 volts positive it is clampe to this
voltage by io e-connecte V205A. The trigger am
plifier is so esigne that it will trigger the multivi
brator only when its plate is in the vicinity of 100 volts,
so that triggering is hel off uring the rise perio of
the plate of V205B.
V211 an V212 comprise the casco e Eccles-Jor an
multivibrator. The left-han si e of this multivibrator,
V211 A an B are normally con ucting. Triggering
is accomplishe with a positive trigger through V203
to catho e follower V204A causes it to ivert current
from the upper half of V211, so that the plate rises.
The positive step at V211B plate is couple through
catho e follower V210B to the gri of the opposite
lower si e of the multivibrator, V212B, an the multi
vibrator flops over with con uction on the right-han
si e. Catho e follower V210B acts as a buffer between
the plate of V21 IB an all other external loa s so that
the only a itional capacitance is that a e by the
input capacitance of the catho e follower. This per
mits the plate to execute a much more rapi rise. The
catho e follower rives the opposite si e of the multi
vibrator, the unblanking catho e follower, the hol -off
tube, V205B, an the gate output catho e follower,
V214A.
The sweep is gate by the negative-going portion
of the multivibrator, V212A an B. The plate of
V212A is connecte to the gri of the catho e-follower-
connecte pento e section of V214 through a spee -up
capacitor. The catho e of this catho e follower hol s
SECTION III, PAGE 1 TYPE 315D

the gri of V220 at about —3 volts through io e V21S
uring the quiescent state of the multivibrator. The
negative step from the multivibrator cuts off the
catho e follower an the catho e falls, isconnecting
the gri of V220 through io e V215. V220 is the
Miller tube time base generator. When the gri is
free from V214B catho e, it imme iately begins to
rop an the plate begins to rise. The plate of V220 is
couple back to the gri through catho e follower
V212A an the timing capacitor, an a Miller run up
commences. When the plate has risen to the vicinity
of 200 volts, the gri of catho e follower V213B has
risen to about 100 volts so that current begins to flow
in this tube which iverts current from the upper right
Section of the multivibrator, V212A, an the multivi
brator reverts to the initial stage with the left-han
si e con ucting. When V212A plate rises, it carries
the gri of V214B with it causing io e V215B to
con uct an the Miller gri to rise to —3 volts so
that the plate rops again to the starting position.
The a itional circuitry aroun the Miller tube an
irect-couple Eccles-Jor an multivibrator is pro
vi e to raise the maximum sweep spee an to elimi
nate the usual istortion of the sawtooth at the begin
ning of the Miller run-up action.
Since the multivibrator has no timing-circuit com
ponents, its recovery time of about 1 microsecon is
epen ent largely on tube an wiring capacitance,
an is therefore more or less constant over the entire
range of time bases. For the longer time bases, as
much as a millisecon is require to ischarge the
timing capacitor, so that circuitry is nee e to prevent
the multivibrator from being triggere before the Mil
ler tube has returne to its quiescent state. The re
quire hol -off function is pro uce by lowering the
plate return voltage of the trigger amplifier V203A
for an a equate perio after the time base termination.
Furthermore, a sharp ifferentiate pulse must be e
rive from a triggering waveform to trigger the multi
vibrator so as to prevent the multivibrator from re
triggering after the hol -off circuit has reache qui
escence, in the presence of a sustaine triggering
waveform.
The circuit complication aroun the Miller tube re
moves the step from the start of the Miller run up.
This is accomplishe by means of a c fee back net
work from the plate of the Miller tube back to its gri ,
which causes an equilibrium point to be establishe
where the plate of the Miller tube is resting at about
50 volts positive whenever the gri of the gating
catho e follower, V214B, is hel in a positive irection
by the right-han multivibrator, an the gri is at
—3 volts. This is well within the class A region of the
Miller tube, V220, where the plate voltage is irectly
proportional to the gri voltage. The relationship of
50 volts plate to —3 volts gri voltage is therefore
etermine by the gri to plate relationship of the
Miller tube itself in the class A region of its operation.
The actual gri voltage set by the voltage- ivi er
catho e follower arrangement with V214B through
isconnecting io e V215B an constant-current tube
V213A, etermines the starting voltage of the saw
tooth. When io e V215 B isconnects the Miller tube
gri from the ivi er constant-current tube V213A
attempts to sustain the current, which it oes by re
ucing its plate resistance, thereby pulling the Miller
tube gri ownwar . During the perio of the run up,
the timing-capacitor charging current is kept essen
tially constant by action of the constant-current tube.
The charging current remains constant within about
a tenth of a per cent, but the time base is not this
linear because of the variation of capacitance with
voltage of the timing capacitors.
The sawtooth voltage is fe to the output amplifier
through catho e follower V221A by means of a volt
age ivi er so that horizontal positioning can be ac
complishe . Catho e follower V221B prevents gri
current from flowing in the positioning circuit, an
catho e follower V222A prevents gri current from
flowing in the MAG-NORM fee back network. This
network re uces the net gain of the horizontal ampli
fier by a factor of five in the NORM position, an
permits the full gain to be realize when it is in the
MAG position.
The horizontal-output amplifier stage is a catho e-
couple phase inverter with a catho e-follower coup
ler to each eflection plate. Use of the catho e fol
lowers to rive the eflection plates increases the
horizontal ban wi th by a factor of about three times.
Magnifier
A egenerative network between the plate of V224B
of the output amplifier to the gri of catho e follower
V222A re uces the loop gain by a factor of five in
the NORM position of the MAG-NORM switch. In
the MAG position, the network is opene to permit
the amplifier to operate at full gain. The MAG POSI
TION screw river control permits the c level of the
catho e follower to be set at the same value for both
positions. Another screw river a justment labele
MAG GAIN ADJ on the chassis permits the magni
fie time base to be ma e exactly five times the nor
mal time base. The HORIZ POSITION control pre
ce es the magnifier circuits an therefore positions
for both the magnifie an the normal time bases.
TYPE 315D SECTION III, PAGE 2

Vertical Amplifier
VI is a twin-trio e with the two sections operate
in parallel. The signal is taken from the common
catho e connection of VI an applie to the catho e
of V2A. V2A is operate as a groun e -gri ampli
fier. V2B is a catho e-follower output coupler be
tween V2A plate an V3 gri . The preamplifier is
use only on the AC, .01 VOLTS/DIVISION posi
tion of the AMPLITUDE selector switch. In this
switch position, switch section SW1B connects the
input terminal through Cl to the gri of VIA an B,
an SW1C connects the catho e of catho e-follower
V2B to the gri of V3 through a protective network.
R1S is a screw river a justable resistor to permit the
preamplifier gain to be a juste accurately to ten
times. LI an L2 are series peaking coils to improve
high-frequency response.
V3 an V4 form a catho e-couple gain-control
stage. The signal is applie to the gri of V3 an
couple through the common unbypasse catho e con
nection to V4 which operates as a groun e -gri
amplifier. The MULTIPLIER switch, SW2, connects
any one of three resistor networks or a short circuit
between the two catho es to control the stage gain.
In the XI position, the catho es are connecte to
gether an the gain is at a maximum. In the 10-1
position, an a justable resistor is connecte between
catho es to permit continuous a justment of gain.
R51 an R53 connecte into the circuit in the other
two positions of the switch are screw river a justable
to permit the gain to be a juste to one-half or to
one-fifth accurately so as to accommo ate the gain
tp the calibrations of the graticule. R34 is a protective
resistor which limits the positive excursion of V3 gri
in case a high c voltage is connecte to the input
connector in the c position of SW1. C14 bypasses
R34 at higher frequencies.
Plate output from V4 fee s through the elay net
work to the gri of V8B, a catho e-follower output-
cupling tube. R59 terminates the elay network
through C21 to groun . (C21 is physically locate on
a bracket un erneath the elay-network assembly.)
The elay network elays the vertical- eflection sig
nal long enough to permit the portion of the wave
form that has triggere the sweep to be isplaye on
the crt screen.
The output amplifier consists of V10 an VI1 in
parallel, in a catho e-couple groun e -gri phase-
inversion circuit with V12 an V13 in parallel. The
c gri voltage of V12 an V13 is use for vertical
positioning. This voltage is controlle by V8A, a
catho e-follower voltage regulator whose gri volt
age is obtaine from potentiometer R70, labele
VERT POSITION, connecte between groun an
+100 volts. R65 an R66 limit the positioning range.
R90, a part of the coupling between catho es of
V10, Vll an V12, V13, is a screw river a justable
resistor whose shaft is mounte coaxially with the
AMPLITUDE control knob. This a justment per
mits the gain of the amplifier to be accommo ate to
the calibrations of the graticule.
L3 in the gri circuit an L4, L5, L6, an L7 in the
plate circuit provi e frequency compensation.
An internal triggering signal connection from the
plate of V3 to the trigger-selector circuits permits the
sweep circuit to be triggere by the observe signal.
In all other positions of the AMPLITUDE contro
SW1, than the previously- escribe AC, .01 VOLTS/
DIVISION position, the preamplifier is remove from
the circuit, an the INPUT connector is connecte to
the gri of V3, either through attenuators, or unatten
uate . In the AC portion of the control. Cl is con
necte in series with the INPUT connector. The gri
of V4 is groun e in these positions through switch
section SW1D, an V3 an V4 become a catho e-
couple groun e -gri amplifier.
The compensate input attenuators to the gri of
V3 are voltage ivi ers in which parallel capacitor an
resistor voltage ivi ers have the same ivision ratio.
C3 in the 10-to-l ivi er an C6 in the 100-to-l i
vi er permit a justment to be ma e of the capacitive
voltage ivision so that the high-frequency ivision
ratio is the same as the low-frequency ivision ratio.
C2, C5, an CIO are a justable so that the same
input capacitance will exist at all AMPLITUDE
switch positions. This is necessary when the probe
is use because the probe is compensate for the input
capacitance, an w'oul otherwise nee to be re
a juste for each switch setting. C15 connecte be
tween gri of V3 an screen of V4 is a neutralizing
capacitor that re uces the change in input capacitance
that occurs when the MULTIPLIER switch inserts
the various coupling resistors between catho es of
V3 an V4.
The MULTIPLIER switch, SW2, selects the
amount of coupling between catho es of V3 an V4 to
etermine the gain of the amplifier when the pre
amplifier is switche out. The VERT ATTEN ADJ
is a chassis-mounte screw river a justable potentio
meter connecting the catho es of V3 an V4 to
—150 volts. This control operates ifferentially. When
it increases the resistance to the catho e of V3 it simul
taneously ecreases the resistance to the catho e of
V4. When it is properly a juste , the c voltage at
the two catho es is the same an no change in vertical
SECTION III, PAGE 3 TYPE 315D

positioning occurs when the multiplier switch connects
larger of smaller resistors between them.
Calibrator
The calibrator provi es four squarewave voltages
of 100 volts, 10 volts, 1 volt an 0.1 volt, available
at a UHF coaxial fitting on the front panel but not
connecte internally to the vertical amplifier. The
source of squarewave voltage is a self-excite sym
metrical ac-couple multivibrator operating at a repe
tition frequency of about one kilocycle. The catho e
an gri s of this multivibrator are returne to
—150 volts.
During the con ucting perio of V601B, the gri
of V601A is below—150 volts an the A-section plate
is cut off. V602B gri is irectly connecte to V601A
gri an V602B plate is therefore also cut off uring
this perio .
During the con ucting perio of the A section of
V601, gri s of V601A an V602B are both high an
the plate of V602B is own below groun potential.
The gri of catho e-follower V602A is irectly con
necte to V602B plate, an it therefore varies between
cutoff in the negative irection an a point near
100 volts in the positive irection, etermine by volt
age ivi er R610, R611, R612.
The catho e resistor of catho e-follower V602A is
ma e up of a voltage- ivi er string, R620, R621, R622,
R623, which are of such values that voltages of
10 volts, 1 volt an 0.1 volt, peak to peak, are pro uce
at the taps when the catho e voltage is set at 100 volts,
peak to peak.
R612, a screw river a justment labele CAL ADJ
on the chassis, permits the gri of V602A to be set at
such a level that the catho e will be at 100 volts when
V602B is cut off. Since this portion of the circuit re
mains connecte to the -(-225-volt supply when the
CALIBRATOR switch is turne to the OFF position,
the voltage calibration of the calibrator circuit can be
checke with a c voltmeter.
C603 in the gri circuit an C604 in the catho e cir
cuit of the catho e follower re uce a small transient
waveform istortion.
Power Supply
The power-supply transformer, T401, is capable of
operating satisfactorily over the range of frequencies
between 50 cps an 800 cps. The primary of this trans
former is woun in two 117-volt sections, normally
parallele for 117-volt operation, but they are ar
range to be easily reconnecte in series for 234-volt
operation.
Four selenium full-wave bri ge rectifiers, each sup
plie with ac from a separate section of the trans
former secon ary, provi e c to four electronic volt
age regulators from which are obtaine the regulate
voltages of —150 volts, -(-100 volts, +225 volts an
+350 volts. In a ition to these four regulate volt
ages, two unregulate voltage sources are provi e ,
one at a nominal +330 volts from a tap taken ahea
of the +225-volt regulator, the other at a nominal
+420 volts taken from a tap ahea of the +350-volt
regulator.
The regulator will regulate satisfactorily over a
primary input-voltage range between 105 an 125
volts, or between 210 volts an 250 volts.
Five 6.3-volt secon ary win ings furnish heater
power for the various parts of the instrument, an for
the pilot light an graticule illumination.
Force -air cooling is provi e by a blower fan. Two
fan types are available. If the Type 315D oscilloscope
is to be use only on 50- to 60-cycle supply voltage,
a 60-cycle fan is recommen e , an is or inarily sup
plie with the instrument. If higher frequencies of
input voltage are to be use , however, a c fan an
rectifier are available at extra cost which will operate
over the same range of frequencies that the trans
former will.
Negative 150-Volt Regulator
The basic source of reference voltage is a type 5651
voltage-regulator gas io e, V401, in the catho e cir
cuit of V402, a voltage-comparator tube. Voltage-
ivi er string, R409, R410, R411, connecte between
regulate —150 volts an groun , is tappe at a voltage
above —150 volts approximately equal to the voltage
across the reference tube, V401, an connecte to the
gri of V402. This sets the catho e an gri of V402
at approximately the same voltage, an any change
in voltage at the —150-volt bus becomes a change in
gri -to-catho e voltage at V402. This change is
amplifie in V402 an applie irectly to the gri s of
V403 an V404, two series-regulator tubes connecte
together in parallel in the groun lea of the power
supply. If the —150-volt bus ten s to go negative
below this voltage, for example, the catho e of V402
will rop thereby increasing V402 plate current. In
crease plate current will lower V402 plate, which
will pull own the gri s of V403 an V404, thereby
increasing their plate resistance, so that they insert
a higher rop in the groun lea , an the —150-volt
bus will rise in the irection to correct the original
TYPE 315D SECTION III, PAGE 4