Tektronix 507 User manual

MODIFICATION NOTICE FOR
TYPE 507
EFFECTIVE SERIAL-NUMBER 128
CHANGE R50 FROM 47K 1/2W FIXED COMP 10% 302-473
TO 10K 1/2W FIXED COMP 10% 302-103
C57 FROM
TO
ADD C54 PBT 5 JJ FD 1000V 285-538
R54 I OK 1/2W FIXED COMP 10% 302-103
MO DIFICATION NO 2092
SWEEP TRIGGER & TR IP PULSE
JUNES, 1959
MODI FI CATI ON NOT! CE FOR
TYPE 507
EFFECTIVE SERIAL NUMBER 128
CHANGE C267 FROM 1 5 TO 4„ 7
C260 FROM 01 TO 47 PF
MODIFICATION NO 2092
TIM E MARK GENERATOR
JUNE 5, 1959
CORRECTION FOR TYPE 507
R667 SHOULD BE LABELED R674
HEATER WI RING DI AG
POWER S PPLY CHASSI S
J NE 5, 1959

MODIFICATION NOTICE FOR
TYPE 507
EFFECTIVE SERIAL NO 142
781-501
’ 81-579
MODIFICATION NO 7.171
TIME MARK GENERATOR
J NE 5, 1959
CHANGE C 7 6 7 FROM 4.7 PF 500V
TO 1 . 5 PF 500V
MODI FI CAT1 ON NOT IC E FOR
TYPE 507
EFFE C TIVE SERIAL N MBER 142
CHANGE R635 FROM 39K 1/2W FIX E D COMP 10% 302-393
TO 36K 1/2W FIXED COMP 10% 302-563
R636 FROM 18K 1/2W FIXE D COMP 10% 302-183
TO 27K 1/W FIXED COMP 10% 302-273
R637 FROM 180K 1/2W FIX E D COMP 10% 302-184
TO 270K 1/2W FIXED COMP 10% 302-274
R655 FROM 100K 1/2W FIXED COMP 10% 302-104
TO 300K 1/2W FIXED COMP 10% 302-334
R656 FROM27K 1/2W FIXED COMP 10% 302-273
TO 82K 1/2W FIXED COMP 10% 302-823
R657 FROM 270K 1/2W FIXED COMP 10% 302-274
TO 820K I/2 W FIXED COMP 10% 302-824
MODI FI CATI ON NO 2174
POWER S PPLY
J NE 5. 1959 •
MODIFICATION NOTICE FOR
TYPE 507
EFFECTIVE SERIAL NO 14’
REMOVE L 3 2 4 2. 5 JJH COIL 108-055
MODIFICATION NO 2191
HORIZONTAL AMPLIFIER
J NE 5, 1959
MODI FI CATI ON NOTI CE FOR
TYPE 507
EFFE C TIVE SERIAL N MBER 170
ADD R445 150 1/2W FIXED COMP 10% 202-151
TO R443
R446 150 1/2W FIX E D COMP 10% 302-151
R445
150
■'VW- CRT VERT DEFL PLATES
TO R444- -Wv—
R446
150
1 ,
JMODI FI CATI ON NO 2229
VERTI CAL AMPLI FI ER
J NE 5, 1959

CATHODE-RAY OSCILLOSCOPE
TYPE 507
INSTRUCTION
MAN AL
TEKTRONIX, INC
MANUFACTURERS OF CATHODE-RAY AND VIDEO TEST INSTRUMENTS
Sunset H ighw ay and Barnes Road • P O Box 831 • Portland 7, Oregon, U S A
Phone: CYpress 2-2611 • Cables: T ektronix
TYPE 507 SERIAL NUMBER _ ____
1M-507-1

Copyright © 1959 by Tektronix, Inc ,
Portland, Oregon Printed in the
United States of America All rights
reserved Contents of this publica
tion may not be reproduced in any
form without permission of the copy
right owner

TYPE 507 OSCILLOSCOPE
AND ACCESSORIES

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II

CONTENTS
GENERAL DESCRIPTION SECTION 1
Vertical Deflection System. Sweep Circuit. Power Sup
plies. Miscellaneous. Functions of Controls and Con
nectors.
CIRC IT DESCRIPTION SECTION 2
Sweep. Vertical Deflection System. Cathode-Ray Tube
Circuit. High-Voltage Power Supply. Time Mark Gen
erator. External Power Supply.
MAINTENANCE SECTION 3
Preventive Maintenance. Analyzing Trouble.
ADJ STMENT PROCED RE SECTION 4
PARTS LIST SECTION 5
SCHEMATIC DIAGRAMS SECTION 6
ACCESSORIES SECTION 7
507 ®

-
H .
I
1

GENERAL DESCRIPTION
The Tektronix Type 507 Oscilloscope is a specialized instrument
designed primarily for high-voltage surge testing as applied to
power transformers, high-voltage insulators, lighting arrestors and
allied components, and their associated design and acceptance
tests
The use of a 24-kv accelerating potential on a new type cathode
ray tube permits photographic recording of single sweeps at the
maximum writing-rate permitted by the vertical deflection and
sweep circuits The vertical deflection system provides a risetime
of approximately 5 millimicroseconds and a sensitivity of approx
imately 50 v/cm An external length of delay cable can be inserted
into the vertical-input signal circuit to permit viewing of the lead
ing edge of the waveform which triggers the sweep Time markers
are available for convenient calibration of the sweep
The Type 507 consists of two units, indicator and power supply,
mounted on a Scope-Mobile, thus making a convient mobile unit
If desired, the units may be lifted off the Scope-Mobile for bench
use
VERTICAL DEFLECTION SYSTEM
Transient Response
Risetime between 10-percent and 90-percent
amplitude points is about 5 millimicroseconds
(005 microseconds) A passive damping network
inserted in the deflection leads is adjusted for
optimum transient response without overshoot
or ringing
The maximum vertical sensitivity with a Type
T507P cathode-ray tube operated at 24-kv ac
celerating is 50 v/cm
Attenuator
A step attenuator with a characteristic imped
ance of 72 ohms is provided in the vertical-input
signal circuit The attenuator is composed of
ten equal resistors of 7 2 ohms each, mounted
on a tap switch The percentage of input signal
applied to the deflection plates can be selected
by the tap switch from 10 percent to 100 per
cent in 10-percent steps
Signal Mode
A three-position switch reverses the deflection-
plate polarity; the center position of the switch
is used in conjunction with a trigger-selector
switch to apply markers for photographing time
references
Positioning Switch
The Type 507 has a seven-step vertical-posi
tion switch with 50-volt steps of —150 v, —100 v,
—50 v, 0, +50 v, +100 v and +150 v A sep
arate two-position switch selects either 50-volt
steps or continuously variable adjustment
External Voltmeter Connections
Terminals are provided for a high-impedance
(50000/v) dc voltmeter, permitting vertical cali
bration when using the variable positioning
GENERAL DESCRIPTION — TYPE 507 1-1

Signal Delay
Two standard UHF connectors are provided on
the rear of the instrument for insertion of an
external length of delay cable into the vertical-
input signal circuit Choice of the appropriate
length and type of cable is at the discretion of
the user; no delay cable is furnished with the
instrument A signal delay permits the sweep to
be triggered and under way before the signal is
applied to the vertical deflection plates
SWEEP CIRC IT
Type
Triggered, hard-tube bootstrap sweep circuit
with inverter to produce balanced deflection
Rates
An eleven-position switch selects rates of 02,
05, 1, 2, 5, 1, 2, 5, 10, 20 and 50 MICRO-
SECONDS/CM, with a maximum displacement
error of 2 percent over the center 8 cm of the
10-cm sweep length
Sweep Starting Time
The horizontal sweep starts approximately
100-m^sec after the signal or triggering pulse
arrives at the rear-panel connector An inserted
signal delay of approximately 150 m//,sec permits
the sweep to be triggered and under way before
the signal is applied to the vertical deflection
plates
Duty Cycle Limitation
A duty-cycle limiting control automatically
limits the duty cycle of the sweep circuit to about
10 percent to avoid exceeding the dissipation
limits of some of the circuit components The
limiting system serves purely a protective func
tion and does not provide a frequency dividing
operation
The following table shows the maximum per
missible repetition rate for each of the avail
able sweep times per centimeter
SWEEP TIME MAXIMUM
REPETITION RATE
50 jasec/cm 600 c/s
20 /xsec/cm 15 kc
10 jusec/cm 3 kc
5 use c/cm 6 kc
2 jasec/cm 10 kc
1 fxse c/cm 20 kc
5 jitsec/cm 50 kc
2 fxsec/cm 50 kc
1 fi sec/cm 50 kc
05 fisec/ cm 50 kc
02 fjisec/cm 50 kc
Triggering
A triggering phase-inverter amplifier in con
junction with a selector switch permits the sweep
circuit to be triggered from either positive- or
negative-going portions of the observed signal,
or from positive or negative triggers from an
external source A trigger voltage range of 100
volts to 3000 volts amplitude will be adequate
for stable triggering The MARKER position on
the selector switch must be used when time
markers are desired
Sweep Mode
A two-position switch provides for either re
petitive or single-sweep operation When the
switch is in the single-sweep position, pressing
the RESET button arms the sweep circuit The
sweep can then be triggered internally, by MAN
UAL TRIGGER, or by an external trigger The
1-2 GENERAL DESCRIPTION — TYPE 507

MANUAL TRIGGER switch is primarily for photo
graphing a zero reference line and any or all of the calibrated vertical position lines, to create,
in effect, a parallax-free graticule
POWER SUPPLIES
Cathode-Ray Tube Accelerating Voltage
An oil-sealed supply of the a-f oscillator type
provides 24 kv (+20 kv and —4 kv) for the ac
celerating potentials The —4-kv supply is reg
ulated to compensate for load changes and line-
voltage changes
Low-Voltage Supply
A separate power unit provides regulated dc
voltages for the indicator unit of +750, +475,
+225 and —250 volts The unit also provides
an unregulated voltage of +360 volts for the
oscillator in the high-voltage supply for the crt
circuit
Power Requirements
600 watts at 117 volts Voltage range 105-125
or 210-250 volts, 60-cycle, single-phase ac Two
primary circuit fuses are provided for protection
against sustained over-load conditions
MISCELLANEO S
Cathode Ray Tube
A Type T507P cahode-ray tube with PI 1 phos
phor is furnished with the Type 507 unless an
other phosphor is specified
Construction
Contained in two separate units of convenient
size, normally mounted on a Tektronix Type
500A Scope-Mobile The anodized chassis and
the blue wrinkle-finished cabinets are made of
an aluminum alloy Photo-etched anodized pan
els are employed
Dimensions
Indicator unit: 16-3/4// high, 13" wide, 23-
5/b" deep
Power unit: 10y2" high, 13" wide, 17y2"deep
Weight
Indicator u nit 50 lbs
Power U nit 39 lbs
Type 500A Scope-Mobile 35 lbs
F NCTIONS OF CONTROLS AND CONNECTORS
6 3V 1A AC
SCALE ILLUM
ASTIGMATISM
INTENSITY
FOCUS
Tip jack from heater bus
Variable resistor controlling brightness of lamps illuminating graticule over
face of cathode-ray tube
Potentiometer controlling the voltage at the astigmatism anode of the cath
ode-ray tube Proper setting of the voltage at this anode, with respect to
the deflection plates, permits the spot to be focused sharply in both dimen
sions simultaneously
Potentiometer controlling dc grid voltage of the cathode-ray tube and there
by the brightness of the trace
Potentiometer controlling the voltage applied to the focusing anode of the
cathode-ray tube for focusing the trace
®GENERAL DESCRIPTION — TYPE 507 1-3

HORIZONTAL
POSITION Twin differentially-connected potentiometer controlling average potential of
cathode-ray tube horizontal deflection plates, thereby adjusting horizontal
position of sweep
SWEEP MODE Two-position toggle switch to select either repetitive or single-sweep opera
tion
RESET Button-switch arms the sweep circuit when the SWEEP MODE switch is in the
SINGLE SWEEP position The READY light indicates that a single sweep will
be produced upon reception of a trigger pulse from the signal to be ob
served (or photographed), from an external trigger source, or from the man
ual-trigger circuit (obtained by depressing the MANUAL TRIGGER switch)
STABILITY Potentiometer controlling grid bias of negative multivibrator tube Deter
mines optimum point of triggering
MICROSECONDS/CM Gang switch controlling sweep duration and sweep rate Selects appropri
ate multivibrator pulse length, and sweep generator charging capacitor and
resistor Switch also selects TIME MARKERS for convenient calibration of the
sweep
TRIGGER SELECTOR Switch selecting source and polarity of sweep-triggering voltage
MANUAL TRIGGER Button-switch provides manually-controlled trigger for sweep generator
MANUAL TRIP PULSE Button-switch provides pulse of approximately 700 volts amplitude and 5
fisec. width at TRIP PULSE OUT connector on rear panel of instrument
ATTENUATOR
VERTICAL
Switch selects percentage of input-signal voltage applied to vertical deflec
tion plates
SIGNAL MODE Three-position switch reverses deflection-plate polarity with respect to signal
being observed The center position on the switch connects the output of the
Time-Mark Genrator to the vertical deflection plates
POSITIONING
50 VOLT STEPS Seven-position switch to control voltage at cathode-ray tube vertical deflec
tion plates in 50-volt steps Each position of the switch causes the beam to
shift approximately 1 centimeter in the vertical plane This switch is con
nected into the circuit when the toggle switch immediately below it is in the
50 VOLT STEPS position
POSITIONING
VARIABLE Potentiometer controlling average potential of cathode-ray tube vertical
deflection plates, providing continuous adjustment of vertical position of
beam This control is connected into the circuit when the toggle switch
immediately below it is in the VARIABLE position
50 VOLT STEPS
VARIABLE Toggle switch determines whether vertical positioning is continuously variable
or in 50-volt steps
VARIABLE DEFLECTION Switch connects arm of VARIABLE positioning control to EXTERNAL VOLT-
SENSITIVITY MONITOR METER connectors on front panel of instrument to monitor the variable dc
positioning voltage Polarity of voltage may be reversed
1-4 GENERAL DESCRIPTION — TYPE 507

REAR-PANEL CONNECTORS
SIGNAL IN
SIGNAL OUT TO
DELAY LINE
SIGNAL IN FROM
DELAY LINE
EXTERNAL TRIGGER
INPUT
TRIP PULSE OUT
UHF connector to TRIGGER SELECTOR switch and to SIGNAL OUT DELAY
LINE connector
UHF connector receives signal internally from SIGNAL IN connector An
external length of delay cable may be connected between this connector
and the SIGNAL IN FROM DELAY LINE connector
UHF connector to vertical ATTENUATOR switch
UHF connector to TRIGGER SELECTOR switch
UHF connector to thyratron in Trip Pulse circuit to make available external
ly a pulse of approximately 700 volts amplitude and 5 /i,sec duration
EXTERNAL POWER S PPLY
DC SUPPLIES
POWER
AC HEATERS
ON-OFF switch on power supply unit controlling ac line voltage to primary
of plate-supply transformer; pilot lamp indicates ON position
ON-OFF switch on power supply unit for controlling ac line voltage to unit;
pilot lamp indicates ON position,
GENERAL DESCRIPTION — TYPE 507 1-5

CIRC IT DESCRIPTION
SWEEP
A linear triggered sweep is available with
eleven fixed, accurately timed sweeps ranging
from 02 microseconds per centimeter to 50 mi
croseconds per centimeter The basic waveform
is generated by a pentode clamp with a cath
ode-follower bootstrap linearity corrector Push-
pull deflection is accomplished at output level by
addition of a plate-output unity-gain phase-
inverter stage, shown on the Horizontal Ampli
fier circuit diagram
Trigger Phase Changer
A trigger selector switch selects the source of
trigger signal and V4 and VI4 reverse the phase,
if necessary, to provide the trigger amplifier with
the required negative signal
Trigger Limiter Amplifier
The trigger limiter stage V24 operates with
zero bias The negative pulse from the trigger
inverter-amplifier drives this tube to plate-cur-
rent cutoff Choice of the proper value of quies
cent plate current and the use of a plate-load
resistance of low value results in a very steep
positive pulse limited in amplitude to about 10
volts This positive pulse is then used to drive
V34
Trigger Switch Tube
The resulting negative pulse at the plate of
V34, coupled through the coupling diode VI02
to the plate of the minus multivibrator VI05, trig
gers the sweep
Trigger Coupling Diode
The trigger-coupling diode VI02 serves to dis
connect the plate of the trigger-switch tube V34
from the plate of the negative multivibrator tube
VI05 when the plate voltage of VI05 drops be
low that of V34
Multivibrator
VI05 and V I15 operate as a plate-coupled
monostable multivibrator for the purpose of
m
converting a triggering pulse into a pulse of con
trollable duration suitable for operating the
sweep generator and unblanking circuits The
SWEEP STABILITY control, by varying the bias
on the grid of VI05, determines the optimum
point of triggering
Duty Cycle Limiter
The duty-cycle limiting circuit is designed as
a protective circuit to prevent the horizontal
amplifier V324 from exceeding its dissipation
rating This is accomplished by sampling the out
put of the plus multi cathode-follower VI33 and
feeding this voltage through an integrating net
work (R125-C125) to the grid of the difference
amplifier V I16 (pentode section) A rise in the
voltage at this grid forces the grid of the minus
multi VI05 toward cutoff which results in a multi
vibrator waveform shorter than normal for the
sweep speed being used Since the length of the
multivibrator waveform determines the sweep
length, as the duty cycle is increased the sweep
length is shortened
A compensated divider located at the grid of
the triode section of V I16 provides a second
means of controlling the multivibrator This cir
cuit is not duty-cycle conscious, but rather sam
ples the trigger lock-out circuitry During the
trigger locked-out configuration the grid of the
triode section is pulled down sufficiently to lock
out the multivibrator until the trigger-lockout cir
cuit is reset
Sweep-Trigger Lockout
When the SWEEP MODE switch is in the
SINGLE SWEEP position the thyraton V49 con
ducts and its plate drops This action produces
two results: (1) It pulls down the grid of the
triode section of V I16 and switches all of the
current to the pentode section This cuts off VI05
and forces the multivibrator to remain in its
quiescent state; (2) It pulls down the screen of
V34 through the cathode follower V63A and V34
cuts off With V34 cut off, the triggers are pre
vented from reaching plate of VI05 and initiat
ing a sweep
CIRC IT DESCRIPTION — TYPE 507 2-1

When the RESET button is depressed, C48 dis
charges and the resulting negative pulse at the
plate of V49 extinguishes the thyratron The re
sulting rise in voltage at the plate of the thyra
tron then pulls up the screen of V34 and permits
this tube to conduct It also pulls up the cathode
of V63B and ignites the READY light This in
dicates that the trigger circuit is now armed and
the next trigger to arrive at the grid of V34 will
produce a sweep
As the multivibrator switches to its unstable
state, and then reverts back to its stable state,
a negative pulse is produced at the plate of
VI05 This pulse is differentiated in the grid cir
cuit of V49 and the resulting positive pulse fires
the thyratron; this action locks out the trigger
circuit again and prevents the sweep from being
started from the next trigger Depressing the
RESET button will then arm the trigger circuit
again and permit one sweep to be produced up
on reception of a trigger
Manual Trigger
The sweep may be triggered manually, if
desired, by depressing the MANUAL TRIGGER
button C25 is charged to about +20 volts from
the divider R25-R26 When the MANUAL TRIG
GER switch is depressed C25 discharges into C22,
creating a negative pulse at the top of C25 The
negative pulse is coupled through the diode V22
and C26 to the grid of V24 where it activates
the trigger circuitry to initiate a sweep
Sweep Generator Clamp Circuit
In the quiescent state, the parallel clamp tubes
VI64 and VI74 conduct heavily and their plates
are down When the multivibrator is triggered,
the resulting negative pulse at the plate of VI05
is coupled to the grids of the clamp tubes and
interrupts the flow of plate current very rapidly
The plate voltage of the clamp tubes then begins
to rise at a rate determined by the charging
rate of 077 This charging rate is determined
by the value of 077 and R176, both of which
are selected by the MICROSECONDS/CM timing
switch The small choke LI 62 in the grid circuit
of the clamp tubes provides a 10-millimicrosec
ond delay to enable the unblanking circuit to
reach full voltage before the sweep starts
Bootstrap Circuit
For 077 to charge linearly rather than ex
ponentially the voltage across the timing resistor
R176, and hence the charging current, must re
main constant This action is accomplished by
the sweep cathode-follower VI73 and the boot
strap tubes V183-V193 The rise in voltage at the
cathodes of VI73, as 077 charges, pulls up the
cathodes of the bootstrap tubes This rise in
voltage is coupled to the top of R176A and
keeps the voltage across the timing resistor more
nearly constant
Decoupling Diode
A decoupling diode VI72, in series with the
-f-475-volt supply to the plates of the clamp
tubes, offers low resistance to the quiescent
plate current of the clamp tubes but disconnects
the upper end of the timing resistor from the
+475-volt supply when the bootstrap action
raises the cathode of the diode above +475
volts
Sweep Cathode Follower
The sweep cathode-follower VI73 provides the
positive-going sweep sawtooth voltage for the
right-hand deflection plate in the cathode-ray
tube This stage also drives the grid of the
sweep phase inverter to provide the negative
going sweep sawtooth voltage for the left-hand
deflection plate
Sweep Inverter
The phase-inverter V324 (Horizontal Amplifier
diagram) operates as a unity-gain amplifier to
supply the negative-going sawtooth sweep volt
age to the left-hand deflection plate of the cath
ode ray tube The gain of this stage is kept low
by virtue of the frequency-compensated feed
back network between plate and grid V313A
and V313B provide a low-impedance bias and
screen voltage, respectively, for the phase-
inverter tube V324
DC Restoration
Th diodes V332A and V332B remove the accu
mulated charge from the sweep-coupling capac
itors C324 and C325, permitting the sweep to
start at the same position on the cathode-ray
tube regardless of the repetition rate of the
sweep
nblanking Amplifier
During the waiting period, between sweeps,
the bias on the cathode-ray tube is such that the
2-2 CIRC IT DESCRIPTION — TYPE 507

beam current is completely cut off As soon as
a trigger pulse appears and a sweep starts, a
positive pulse of approximately 100 volts is re
quired at the grid of the cathode-ray tube to
turn the beam on This pulse must have a very
fast risetime and a very flat top to insure fast
unblanking and uniform image brightness Both
conditions are accomplished by the unblanking
amplifier V144-V154 and the associated cathode
follower VI53
The negative pulse at the plate of the minus
multivibrator VI05 is coupled to the grids of the
unblanking amplifier via a frequency-compen
sated voltage divider The shunt-compensated
plate-load impedance of the amplifier circuit
produces a positive pulse having a very fast
risetime The cathode-follower circuit VI53 pro
vides a high-impedance, low-capacitance load
to the amplifier, at the same time providing a
low-impedance driving source for the grid of the
cathode-ray tube The cathode-follower VI43
provides a low-impedance source of screen
voltage for the amplifier tubes The UNBLANK
ING ADJ R146 provides a means of adjusting
the screen voltage to obtain the desired 100-volt
unblanking pulse
Trip Pulse
A thyratron pulse generator produces a man
ually-initiated pulse at a rear-panel connector
for triggering a trip-pulse generator In the
quiescent state the divider R52-R53 holds the grid
of the thyratron below cutoff When the MAN
UAL TRIP PULSE switch is depressed C50 charges
and the positive pulse developed at the grid fires
the thyratron Since the thyratron is connected
as a cathode follower, the cathode pulls up
sharply to develop the output pulse of approxi
mately 700 volts In producing the output pulse,
however, the cathode voltage approaches suf
ficiently close to the voltage at the plate to
extinguish the thyratron and return the circuit to
its quiescent state
VERTICAL DEFLECTION SYSTEM
Since the Type 507 does not contain a vert
ical amplifier, the vertical defection circuit con
sists mainly of an attenuator and a positioning
network
The input signal is developed across the 72-ohm
attenuator resistance The desired percentage of
the input signal is selected from a tap on the div
ider by means of the ATTENUATOR switch, from
where the signal is coupled to one of the ver
tical-deflection plates in the cathode-ray tube
The other vertical deflection plate is connected
to ground to accommodate the single-ended
input signal
When the SIGNAL MODE switch is in the EX
TERNAL NORMAL position, positive-going por
tions of the input signal produce upward deflec
tion in the cathode-ray tube; in the EXTERNAL
REVERSED position, positive-going signals pro
duce downward deflection In the INTERNAL
MARKER position of the switch, time markers
from the Time-Mark Generator are coupled to
the lower deflection plate and the upper plate is
connected to ground
Either of two positioning circuits may be con
nected into the vertical deflection circuit When
fin
the toggle switch SW435 is in the 50 VOLT
STEPS position, a tapped divider connected be
tween +150 volts and —150 volts is connected
into the circuit By means of the POSITIONING
switch, the positioning voltage may be selected
in 50-volt steps between these two limits Test
points and adjustments are provided to accur
ately set the upper and lower voltage for the
divider
When SW435 is in the VARIABLE position,
a continuously variable positioning control is
connected into the circuit The VARIABLE posi
tioning control is part of a divider connected
between +225 volts and —250 volts The resis
tance values in the divider are such that the
range of positioning voltage is about 325 volts,
a bit greater than the 300-volt range provided
by the 50 VOLT STEPS control Front-panel EX
TERNAL VOLTMETER connections are provided to
monitor the VARIABLE positioning voltage The
VARIABLE DEFLECTION SENSITIVITY MONITOR
switch may be used to reverse the voltmeter
connections, or to disconnect the VARIABLE
position control from the front-panel voltmeter
connections if desired
®CIRC IT DESCRIPTION — TYPE 507 2-3

CATHODE-RAY T BE CIRC IT
The NE2 neon glow lamps across the INTEN
SITY control potentiometer and MAX INTENSITY
variable resistor maintain the INTENSITY poten
tiometer terminal voltage constant regardless of
cathode-ray tube cathode current, thereby
stabilizing the intensity adjustment
The purpose of the MAX INTENSITY control
is to adjust the minimum grid bias setting avail
able by the INTENSITY control to a safe value
thus preventing damage to the cathode-ray tube
screen in case the INTENSITY control is ad-
HIGH-VOLTAGE
All accelerating potentials for the cathode-
ray tube are provided by a high-voltage supply
employing an audio oscillator operating at a
frequency of approximately 1500 cycles Four
high-voltage rectifier tubes in a voltage-quad-
van ced too far
The FOCUS control potentiometer varies the
voltage at the focusing ring to focus the trace;
the ASTIGMATISM control potentiometer varies
the voltage at the astigmatism anode to focus
the spot in both dimensions simultaneously
The GEOM ADJ potentiometer varies the
field as the beam emerges from the deflection
system to control the linearity at the extremes
of deflection
POWER S PPLY
k
rupling circuit provide +20,000 volts; a single
half-wave rectifier tube provides —4000 volts
The high-voltage rectifiers, capacitors, resistors
and transformers are all oil-immersed
HIGH-VOLTAGE OSCILLATOR AND REG LATOR CIRC IT
The screen voltage of the high-voltage oscil
lator V820 is regulated to maintain a con
stant —4000 volts of rectified output so that
the deflection sensitivity of the cathode-ray
tube will not be affected by line-voltage
or load changes A sample of the —4000-volt
output, obtained from a tap on the divider con
sisting of R212 and R213, is compared to the
regulated —250-volt supply through V814A Any
“error” voltage that may exist is amplified by
V814A and V814B and is applied to the screen
of the oscillator tube V820 This will change the
output of the oscillator in a direction to compen
sate for the error The —4KV ADJ R814 controls
the bias on V814A and is adjusted so that the
output voltage is exactly —4000 volts This same
circuit indirectly regulates the +20,000-volt sup
ply since the oscillator furnishes energy for both
supplies
The time-constant network associated with the
V804 circuit delays the application of screen
voltage to the oscillator tube slightly when the
power is first turned on This permits the oscil
lator circuit for the heaters (V830) to bring the
heaters up to emission before the application of
plate voltage in the rectifier tubes
TIME-MARK GENERATOR
An electron-coupled Colpitts oscillator V250B
is gated off and on by a free-running multi
vibrator circuit V225A and V225B through the
cathode-follower V250A The gated time markers
are then amplified in V264 and are coupled to
the cathode-ray tube vertical deflection circuit
when the SIGNAL MODE switch is in the MARK
ER position
The time markers are also coupled through
C267 to the grid circuit of the cathode-follower
V243A, where they are superimposed on the
multivibrator waveform and fed to the trigger
circuitry so that the sweep can be triggered by
the markers when the TRIGGER SELECTOR switch
is in the MARKER position The diode V242
clamps the grid of V243A to prevent the nega
tive pulses of the differentiated multivibrator
waveform from producing a trigger
i t
2-4 CIRC IT DESCRIPTION — TYPE 507 ®

EXTERNAL POWER S PPLY
-2 5 0 -V o lt Supply
The -250-volt supply employs a full-wave
rectifier tube V612 and a capacitor-input filter
system The supply is regulated by comparing
the voltage across V619, a gas-diode voltage-reg
ulator tube, to that obtained from a divider con
nected across the output, through a comparator
tube V614 The —250V ADJ control R625 de
termines the percentage of total voltage that
appears at the grid of V614 and thus determines
the total voltage across the divider
If line-voltage or load fluctuation tend to
change the output voltage, an error signal
exists between the grid and cathode of V614
The error signal is amplified by V614 and
V627A The resulting change in voltage at the
plate of V627A, which will be in a direction to
compensate for any change in output voltage,
is coupled through the rectifier to the output to
keep this voltage constant
+ 225-Volt Supply
The + 225-volt supply employs selenium recti
fiers in a full-wave, bridge circuit This supply is
regulated by comparing to ground (the cathode
of V634) the voltage of a point near ground
potential obtained from the divider R644-R645'
connected between the +225-volt bus and the
regulated —250-volt supply Any error signal
that exists is amplified and inverted in polarity
by V634 and coupled through the paralleled
cathode-followers V647A, V647B and V627B to
the output to prevent the output voltage from
changing C644 improves the response of the cir
cuit to sudden changes in output voltage This
supply also provides a +360-volt unregulated
output for the oscillator tube in the high-voltage
supply
A small sample of the unregulated bus ripple
appears at the screen of V634 through R637
This produces a ripple component at the grids of
the cathode followers that is opposite in polarity
to the ripple appearing at the plates, and tends
to cancel the ripple at the cathodes and hence
on the +225-volt bus This same circuit also im
proves the regulation in the presence of line-
voltage variations
+ 475-Volt Supply
Rectified voltage from terminals 9 and 10 of
the power transformer isx added to the voltage
supplying the +225-volt regulator to supply
power for the +475-volt regulator The reg
ulator circuit of this supply functions in the same
manner as that of the +225-volt supply
+ 750-Volt Supply
A full-wave rectifier V672 is employed in the
-j-750-volt supply The rectified output of this
tube is added to voltage supplying the +475-
volt regulator to supply power for this supply
This supply is regulated by comparing to the
regulated +475-vo!t bus (the cathode of V674) a
voltage near +475 volts obtained from the
divider R684-R685 connected between the +750-
volt bus and ground Any error signal is am
plified by V674 and is applied to the grid of the
cathode-follower V687 The cathode of V687
then acts to prevent the voltage on the +750-
volt bus from changing
CIRC IT DESCRIPTION — TYPE 507 2-5

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