Tektronix 511 User manual

TYPE 511
CATHODE-RAY
OSCILLOSCOPE
INSTRUCTION
MANUAL
p j
Manufacturers of Cathode-Ray and V deo Test Instruments
SUNSET HIGHWAY AND BARNES ROAD - P.O.BOX 831 - PORTLAND 7, OREGON, U. S. A.
PHONE: CYp ess 2-2611 CABLES: TEKTRONIX

CONTENTS
GENERAL DESCRIPTION SECTION 1
Character st cs. Funct ons of Controls and B nd ng Posts.
OPERATING INSTRUCTIONS SECTION 2
F rst-T me Operat on.
Sweep C rcu t Adjustments--Adjustment of sweep stab l ty. Funct on
of tr gger selector. Adjustment of tr gger ampl tude. Adjustment of
sweep speed. Recurrent sweep. S ngle sweep. Sweep magn f er. Ext.
sweep nput.
Vert cal Deflect on System--Vert cal ampl f er. D rect connect on to
deflect on plates.
Cal brat on--S gnal-cal brate sw tch. Measurement of s gnal ampl 
tudes .
Intens ty Modulat on (Z axs). Sweep Output. Gate Outputs.
CIRCUIT DESCRIPTION SECTION 3
Cathode-Ray Tube C rcu t.
Sweep C rcu ts--Tr gger phase spl tter. Tr gger Ampl f er. Tr gger
coupl ng d ode. Mult v brator. Unblank ng c rcu t. Gate output genera
tor. Sweep generator. Sweep output cathode follower. Sweep magn f er.
Sweep ampl f er.
Vert cal Deflect on System—Probe. Input attenuator. Vert cal ampl f er.
Cal brator C rcu ts.
Power Supply.
MAINTENANCE SECTION 4
Replacement of Components. Removal of Case. Clean ng. Inspect on.
Trouble Analyz ng and Repa r. Voltage and Cont nu ty Tables. Wave
form Photographs.
ADJUSTMENTS SECTION 5
Operat on on 210-250 Volt L ne. Adjustment of: 225 Volt Regulated
Supply, H gh Voltage Supply, Sweep Speed Cal brat on, Input Attenuator,
Vert cal Ampl f er H.F. Response, Vert cal Ampl f er L.F. Response,
Cal brator Voltage.
Exter or and Inter or Photographs.
PARTS LIST AND DIAGRAMS SECTION 6
VIDEO DELAY NETWORK AND CIRCUIT DIAGRAM SECTION 7
511 AA

NOTE
Th s nstruct on manual has been prepared to
cover TEKTRONIX Type 511, 511A and 511 AD
Osc lloscopes of all ser al number ranges. The
" Type 511A” des gnat on s used throughout the
text and w ll apply to the Type 511 and 511 AD un
less noted otherw se by the nsert on of ser al
number range notat ons. The Type 511 ser al
number range s 101 to 454 and the Type 511A s
455 and up. The Type 511 AD Osc lloscope s
dent cal to the Type 511A except that t ncludes
a factory nstalled Type 1-AD-25 Delay Network.
Text, d agrams, and parts l sts have been expanded
to ncorporate all c rcu t mod f cat ons adopted
dur ng the course of manufacture. The ser al
ranges of nstruments to wh ch var ous mod f 
cat ons were appl ed before sh pp ng from the
factory have been noted wherever necessary.
However, because many nstruments have been
mod f ed n the f eld and out of ser al sequence,
component values and c rcu try of a g ven nstru
ment may d ffer cons derably from those nd cated
n th s manual for ts ser al number. The user s
urged, therefore, to enter whatever changes may
be necessary to br ng th s manual nto agreement
w th the present c rcu try of h s osc lloscope.
When order ng parts, always nclude the fol
low ng nformat on:
1. Instrument Type (511, 511A or 511AD).
2. Instrument Ser al Number (as, SN 9999).
3. Part C rcu t Number (as, R999).
4. Part Descr pt on (value, type, rat ng, toler
ance, etc.).
5. The 6-d g t TEKTRONIX part number (as,
999-999). __________________________________
SAFETY NOTICE
Th s osc lloscope employs dangerously h gh voltages. S nce
some ma ntenance must be performed wth the case removed,
great care should be taken. Use only nsulated tools, stand on
a dry floor and f poss ble keep one hand n your pocket. Care
should also be used n mak ng any connect ons to the deflect on
plates of the cathode-ray tube through the access panel. It s
adv sed that the access panel never be removed unt l the power
has f rst been turned off. The nstrument should not be operated
w th th s protect ve cover removed.
__________________________

SECTION 1
GENERAL DESCRIPTION
!
f
!
The Tektron x Type 511A Cathode-Ray Osc lloscope s a
w de range, portable nstrument, mak ng poss ble the observa
t on of a w de var ety of electr cal waveshapes. It s pr mar ly
ntended for laboratory and shop use, n the development and
test ng of all types of electron c equ pment.
The Type 511AD Osc lloscope s dent cal to the Type 511A
except that t ncludes a factory- nstalled Type 1-AD-25 Delay
Network.
CHARACTERISTICS
S gnals observable:
1. S ne waves from 10 cycles to 10 me.
2. Pulses of .1 m crosecond to 1/50 sec.
Sweep C rcu t
ampl f er.
Max mum deflect on sens t v ty 1.5 v per cm DC
or peak-to-peak AC. Band w dth, DC to 800 kc
(3 db down at 800 kc).
Vert cal Deflect on C rcu t
Hard tube type, e ther tr ggered or recurrent
as des red.
Sweep Speeds
Cont nuously var able from .01 sec. per cm
to .1 m crosecond per cm.
Tr gger Requ rements
.5 to 15 v (Peak) s ne wave or pulse of e ther
polar ty. Pulse as short as .05 m crosecond w ll
tr gger sat sfactor ly. A key connected between
TRIGGER INPUT and GND. s su table for tr g
ger ng s ngle sweeps. Below S/N 720, a3 v bat
tery and key connected n ser es s su table.
Sw tch perm ts s gnal nput connector on panel
to be connected to deflect on plates d rectly, v a
capac tor (RC =.l sec), v a 1 ampl f er stage, or
v a 2 ampl f er stages.
Input Attenuator
Frequency compensated RC type w th attenua
t on rat os of 2, 4, and8. (S/N 101-454, ATTEN.
5X b nd ng post allows add t onal attenuat on.)
Vert cal Deflect on Sens t v ty
Wthout ampl f er 27 v/cm (5CP1A) or 13
v/cm (5ABP) max mum, 200 v/cm m n mum,
DC or peak-to-peak AC.
Sweep Lag
CRT s unblanked and sweep s operat ng
l nearly n less than. 1 m crosecond after rece pt
of an nf n tely sharp tr gger pulse.
Sweep Magn f cat on
Any des red 20% of the sweep can be spread
over the ent re trace except for sweep speeds
faster than .5 m crosecond per cm.
1 Stage, 2.7 v/cm (5CP1A) or 1.3 v/cm (5ABP)
max mum, 40 v/cm (5CP1A) or 20 v/cm(5ABP)
m n mum.
2 Stages, .27 v/cm (5CP1A) or .13 v/cm(5ABP)
max mum, 4 v/cm (5CP1A) or 2 v/cm (5ABP)
m n mum.
(Sens t v ty s reduced by a factor of 10 when
probe s used.)
IN NO CASE SHOULD THE COMBINED AC AND
DC INPUT VOLTAGES EXCEED 600 V PEAK.
External Sweep Input Input Impedance
DC coupled v a 100 K potent ometer and sweep 1 meg shunted by 40 p/ f (+or-5%) for any
TYPE 511-GENERAL DESCRIPTION PAGE 1-1

sett ng of the nput selector and nput attenuator.
(S/N101-454, 5 meg. shunted by 12 jupf when
us ng the ATTEN. 5X b nd ng post.)
Wth probe, 10 megohms shunted by 14 p/f.
Vert cal Ampl f er Bandwdth
1 stage, down 3 db (Max) (from 1 me response)
at 5 cps and 10 me.
2 stages, down 3 db (Max) (from 1 me response)
at 5 cps and 8 me.
Vert cal Ampl f er Trans ent Response
R set me, 1 stage, .04 m crosecond (10%
to 90%) 2 stages, .05 m crosecond (10% to 90%).
Cal brat ng Voltage
Cl pped s ne wave of power l ne frequency.
S x ranges 0-.3, 0-1, 0-3, 0-10, 0-30, 0-100
volts peak-to-peak. Accuracy for l ne voltages
from 105 to 125 v s +or-5% of full scale. A
pos t on on the SIGNAL CALIBRATE sw tch
allows the use of an external cal brat ng source
when des red. (Below S/N 2406—S ne wave of
power l ne frequency. Three ranges 0-1, 0-10,
0-100 v peak-to-peak.)
Waveforms Ava lable Externally:
Sweep sawtooth, 20 volts peak.
Pos t ve and negat ve gate, 40 v peak, same
durat on as sweep.
Connect on to CRT Cathode
V a .1 / f capac tor. RC=.012 sec.
Accelerat ng voltage on cathode-ray tube, 3KV.
Power Requ rements. 105-125 volts,or210-250
volts, 50-60 cycles, 230 watts. (See Sect on 5.)
We ght, 50 pounds.
D mens ons, 15 1/2” h gh, 121/2" w de,211/2”
deep.
F n sh. P anel, photo - etched alum num w th black
letters. Cab net, gray wr nkle.
FUNCTIONS OF CONTROLS AND BINDING POSTS
A br ef explanat on of the funct on of each control and b nd ng
post s g ven below. For a more deta led explanat on consult
Sect on 3, C rcu t Descr pt on.
PANEL MARKINGS EXPLANATION
INPUT CHAN. SEL.--Gang sw tch perm tt ng the
nput s gnal to be connected to the vert cal
deflect on plates e ther d rectly, v a a .1 pf
capac tor, 1 stage ampl f er, or 2 stage
ampl f er.
INPUT ATTENUATOR--Four pos t on RC com
pensated attenuator located between the SIG
NAL CALIBRATE sw tch and INPUT CHAN.
SEL. for reduc ng the voltage of s gnals wh ch
would otherw se produce excess ve deflect on
or overload the ampl f ers.
VERT. AMPL. ATTEN.--500 ohm potent ometer
n cathode of cathode follower perm ts adjust
ng ga n of s gnal ampl f er.
PANEL MARKINGS EXPLANATION
SIGNAL—CALIBRATE--Sw tch wh ch connects
arm of INPUT ATTENUATOR to EXT. CAL.
b nd ng post, SIGNAL INPUT b nd ng post,
or l ne-frequency cal brat ng voltages.
SIGNAL INPUT--Coax al (b nd ng post,S/N101-
454) connector perm ts connect on of the low-
capac ty probe or b nd ng-post adapter.
ATTEN. 5X--S gnal nput b nd ng post hav ng
h gher mpedance but attenuat ng s gnals 5
t mes (S/N 101-454).
DELAY (511 AD only) --Two pos t on sw tch wh ch
perm ts the Type 1-AD-25 Delay Network to
be sw tched n or out of the v deo ampl f er.
PAGE 1-2 TYPE 511-GENERAL DESCRIPTION

PANEL MARKINGS EXPLANATIONS PANEL MARKINGS EXPLANATIONS
VERT. POSITION--Tw n potent ometers con
troll ng average potent als of vert cal deflec
t on plates and therefore the mage pos t on.
CAL. VOLTAGE--Potent ometer for adjust ng
the cl pped (uncl pped, below S/N 2406) s ne
wave cal brat ng voltage of l ne frequency on
ranges determ ned by the sett ng of the SIG-
NAL-CALIBRATE sw tch.
CRT CATHODE--B nd ng post perm tt ng con
nect on of external modulat ng s gnals to the
cathode of the cathode-ray tube v a a .1 jif
capac tor. RC =.012 sec.
GND.--Connect on to frame of osc lloscope.
ASTIGMATISM--Potent ometer vary ng poten
t al on Anode No. 2 w th respect to the de
flect on plates. Correct adjustment of th s
control makes poss ble a sharp focus of the
mage n both d rect ons s multaneously.
SCALE ILLUM.--Var able res stor controll ng
br ghtness of the lamp wh ch llum nates the
plast c grat cule over the face of the cathode-
ray tube.
INTENSITY--Potent ometer controll ng the av
erage gr d voltage of the CRT and thereby
the br ghtness of the mage.
POWER--On-off sw tch n the AC l ne voltage
supply to the osc lloscope.
FOCUS--Potent ometer controll ng the voltage
appl ed to the focus anode of the CRT and
thereby the sharpness of the mage.
HOR. POSITION--Potent ometer controll ng the
b as appl ed to gr d of one sweep ampl f er
tube and thereby the pos t on of the mage.
SWEEP OUTPUT--B nd ng post connected to
sweep generator v a cathode follower.
SWEEP MAGNIFIER POSITION--Potent ometer
controll ng voltage appl ed to gr d of sweep
magn f er (VI1) and thereby determ n ng por
t on of sweep to be magn f ed. When turned
to OUT sweep magn f er s d sconnected from
the c rcu t.
SWEEP SPEED MULT.--Decade control plus
vern er control sett ng sweep speed and dura
t on wthn range nd cated by SWEEP RANGE.
(A s ngle control, S/N 101-1405).
EXT. SWEEP ATTEN.--Potent ometer control
l ng the fract on of the voltage appl ed to
EXT. SWEEP INPUT b nd ng post wh ch w ll
reach the gr d of the sweep ampl f ers when
the SWEEP RANGE sw tch s set n the EXT.
pos t on.
EXT. SWEEP INPUT - -B nd ng post connect ng to
sweep ampl f er v a EXT. SWEEP ATTEN.
when SWEEP RANGE sw tch s n EXT. pos 
t on. (100 K nput mpedance).
CAL. INPUT--B nd ng post connect ng to EXT.
CAL. pos t on of SIGNAL-CALIBRATE sw tch
perm tt ng an external cal brat ng s gnal
source to be permanently connected to the
osc lloscope.
May be used as aux l ary s gnal nput.
CAL. OUTPUT--B nd ng post connected to arm
of CAL. VOLTAGE potent ometer perm ts
use of nternal cal brat ng voltage as an
external test s gnal of known ampl tude.
+ GATE - - B nd ng post for connect on to the cath
ode of the gate phase spl tter (V8). Th s
furn shes a 40 v peak pos t ve pulse of the
same durat on as the sweep.
-GATE--B nd ng post for connect on v a .1 jif
capac tor to the plate of (V8). Th s furn shes
a 40 v negat ve pulse of the same durat on
as the sweep.
SWEEP RANGE--Gang sw tch select ng appro
pr ate coupl ng capac tors determ n ng mult 
v brator length and sweep speed. When set to
EXT. the sweep ampl f er s connected to
EXT. SWEEP INPUT post n place of the os
c lloscope’s l near sweep.
SWEEP STABILITY--Var able res stor control
l ng b as on gr d of V4 n the mult v brator
c rcu t. Th s b as determ nes whether the
sweep w ll operate recurrently or must be
tr ggered.
TRIGGER SEL.--Sw tch determ n ng source and .
polar ty of tr gger voltage.
TYPE 511-GENERAL DESCRIPTION PAGE |-3

PANEL MARKINGS EXPLANATIONS PANEL MARKINGS EXPLANATIONS
pos t on of TRIGGER SEL. sw tch.
DEFLECTION POLARITY---Three-pos t on le
ver sw tch mounted at the rear s wh ch changes
the V19 operat ng b as and the screen volt
age on V18 and V19, thus prov d ng greater
und storted deflect on when observ ng pulses.
D al read ngs: EXT.
CAL., SIGNAL, X.l,
XI, X10-S/N101-2405
SWEEP SPEED MULT,
was a s ngle d al from
S/N101-1405
TRIGGER AMPL.— Potent ometer controll ng
the b as appl ed to the tr gger ampl f er tube
(V2) and thereby determ n ng the ampl tude
of tr gger s gnals appl ed to the mult v brator.
TRIGGER INPUT— B nd ng post connect ng ex
ternal tr gger sources to +EXT. and -EXT.
+ SIGNAL DEFL. and
arrows added at approx.
S/N 2869
PAGE 1-4 TYPE 5 1 I —GENERAL DESCRIPTION

SECTION 2
OPERATING INSTRUCTIONS
The Type 511A may be operated n any normal ndoor lo
cat on, or n the open f protected from mo sture. If the n
strument has been exposed to dampness, t should be left
n a warm room unt l thoroughly dry before be ng placed
n operat on.
To prevent excess ve nter or temperatures, t s mportant to
allow adequate vent lat on for the osc lloscope. Several nches
clearance should be prov ded at the s des, back and top of the
case.
If the Type 511A s used cont nuously for the same appl 
cat on and only one sett ng of the controls s requ red, t s
adv sable to per od cally check the nstrument at all control
sett ngs to be sure t s n normal operat ng cond t on. For
example, f only d rect connect on to the vert cal deflect on
plates of the CRT s used, a defect n the vert cal ampl f er
m ght not become ev dent. Operat on of the controls also helps
to prevent accumulat on of d rt and tarn sh on the r contacts.
Although the components are well supported and the adjust
ments very stable n sett ng to allow for portable operat on,
the Type 511A should not be subjected to excess ve v brat on
or rough handl ng.
FIRST TIME OPERATION
To place the Type 511A n operat on for the
f rst t me the follow ng procedure s suggested:
1. Connect to a source of 50-60 cycle, 105-
125 v power.
2. Set controls as nd cated below:
INPUT CHAN. SEL ................. 1 STAGE
INPUT ATTENUATOR....................XI
VERT. AMPL. ATTEN ........... Clockw se
SIGNAL-CALIBRATE ........ 3 v(XI, below
............... S/N2406)
VERT. POSITION ............. Index vert cal
CAL. VOLTAGE ............................. 0
ASTIGMATISM ................ Index vert cal
INTENSITY .................... Counterclock-
............................... w se
FOCUS ......................... Index vert cal
HOR. POSITION...................Clockw se
SWEEP MAGNIFIER POSITION ......... OUT
SWEEP SPEED MULT ..................... 5.0
SWEEP RANGE ........................ 10,000
SWEEP STABILITY ........... Counterclock-
...................... w se
TRIGGER AMPL ............... Counterclock-
........................... w se
TRIGGER SEL ........................... + INT.
3. Turn POWER sw tch to ON and wa t about 30
seconds.
4. Advance INTENSITY control unt l a spot s
seen.
5. Adjust VERT. POSITION, HOR. POSITION,
ASTIGMATISM and FOCUS unt l a sharply
focused spot s obta ned at the left center
of the screen.
CAUTION--DO NOT ALLOW THIS SPOT
TO BE EXCESSIVELY BRIGHT OR RE
MAIN FOR LONG IN ONE POSITION.
TYPE 51 t—OPERATING NSTRUCTIONS PAGE 2-1

6. Advance the SWEEP STABILITY control unt l
a sweep appears f then turn t back just under
th s po nt.
7. Set the CAL. VOLTAGE control to 30 (10,
below S/N 2406). A vert cal l ne about 2.5
cm h gh (S/N 5100 and up) should appear.
The vert cal l ne should be about 1.25 cm
h gh for nstruments S/N 2406-5099 and 4 cm
h gh for nstruments below S/N 2406.
8. Advance the TRIGGER AMPL. control unt l a
stable mage of the cal brator waveshape
appears.
The osc lloscope s now d splay ng the 50-60
cycle power l ne waveshape cl pped (uncl pped,
below S/N2406) by the cal brator c rcu ts.
To observe other waveshapes connect them to
the SIGNAL INPUT b nd ng post, turn the SIG-
NAL-CALIBRATE sw tch to SIGNAL, select the
appropr ate sweep speed, etc.
SWEEP CIRCUIT ADJUSTMENTS
Adjustment of Sweep Stab l ty
The sweep c rcu t of the Type 511A s d ffer
ent from the gas tube type usually employed n
portable osc lloscopes. It s much more flex ble
and capable of synchron z ng wth much h gher
frequenc es than convent onal sweep c rcu ts.
Fundamental frequenc es of 10 me and h gher
can be eas ly observed. By one s mple adjust
ment the sweep w ll run recurrently or tr ggered
as des red.
In a recurrent or sawtooth sweep as generated
by a gas tube or s m lar dev ce the synchron za
t on takes place at the end of the sweep. The sync
mpulse causes the beam to return to the left s de
of the tube where t mmed ately starts another
sweep. Thus the sweep t me must be a mult ple
of the s gnal per od, or expressed another way,
the sweep frequency an ntegral fract on of the
s gnal frequency.
In a tr ggered sweep c rcu t each sweep s
started ndependently of the preced ng sweep by a
tr gger or synchron z ng mpulse. When no tr g
ger s be ng rece ved, the beam rema ns at the
left s de of the trace. When the tr gger arr ves,
the beam goes l nearly to the r ght for a t me
n th s case determ ned by the mult v brator
pulse length. At the end of ts sweep t returns
to the left s de aga n to awa t another tr gger.
It s th s var able wa t ng per od wh ch makes
the synchron zat on so easy s nce the sweep t me
s now ndependent of the s gnal per od. The
tr ggered sweep makes t poss ble to v ew pulses
such as used n radar and telev s on where
the length of the pulse s very short compared to
the space between pulses. Th s requ res a fast
sweep wth a long wa t ng per od. Wa t ng per ods
of 2000 t mes the sweep length are frequently
used.
The SWEEP STABILITY control var es the
mult v brator b as and therefore determ nes
whether the sweep w ll osc llate recurrently or
wa t for a tr gger mpulse. Correct funct on ng
for tr ggered operat on s therefore obta ned
when t s set just under the po nt where osc l
lat on takes place. The procedure s to remove
the tr gger source, turn the TRIGGER AMPL.
control counterclockw se, and advance the
SWEEP STABILITY knob unt l a sweep appears
and then decrease t unt l t just d sappears.
NOTE-When us ng the nternal tr gger m
pulses to v ew fundamental frequenc es
above about 2 me t w ll be necessary to
progress vely advance the SWEEP STABI
LITY control somewhat above the normal
operat ng po nt to secure a stable pattern.
Th s control selects the tr gger mpulse to be
used from three sources, the l ne frequency,
(60 cycles), the v deo ampl f er (+ INT and -INT),
or the TRIGGER INPUT b nd ng post. Two pos 
t ons are ava lable for both the INT. and EXT.
sources. When us ng those marked + the sweep
starts at the r s ng port on of the tr gger mpulse.
The -pos t ons start the sweep on the fall ng
port on. When the INPUT CHAN. SEL. sw tch s
n the 2 STAGES pos t on the + INT and-INT pos 
t ons are reversed n polar ty s nce the tr gger
mpulses are sh fted 180° by the pre-ampl f er
stage. For sat sfactory operat on n the EXT.
pos t ons a tr gger of from .5 v to 15 v peaks
should be prov ded. Larger tr ggers should be
reduced by an external attenuator.
Funct on of Tr gger Selector
PAGE 2-2 TYPE 51 1—OPERATING INSTRUCTIONS

Adjustment of Tr gger Ampl f er
The TRIGGER AMPL. control adjusts the b as
n the tr gger ampl f er and therefore the ampl 
tude of the mpulse wh ch reaches the mult 
v brator. After the SWEEP STABILITY s set
as descr bed prev ously, and the TRIGGER SEL.
sw tch set to the correct pos t on, advance the
TRIGGER AMPL. control unt l a stable mage s
obta ned. When the tr gger source s a slowly
chang ng wave such as a s ne wave or sawtooth,
adjustment of the TRIGGER AMPL. sett ng w ll
change the phase of the s gnal relat ve to the
start of the sweep.
In general, t s des rable to use the m n mum
TRIGGER AMPL. sett ng requ red to nsure a
stable mage.
If poor synchron z ng s exper enced when the
Type 511A s used to observe repet t ve s gnals
conta n ng errat c peak voltages, such as pro
duced by v brat ng contacts, t may be poss ble
to form a stab l zed tr gger s gnal by the use of
aux l ary l m t ng and d fferent at ng c rcu ts.
The TRIGGER SEL. sw tch should then be set to
the proper EXT. polar ty, and connect on made
to the TRIGGER INPUT.
Adjustment of Sweep Speed
The comb nat on of SWEEP RANGE and
SWEEP SPEED MULT, controls allows the op
erator to vary the sweep speed so that the marked
port on of the grat cule (10 cm) s covered by the
trace n any t me from .1 sec tol m crosecond.
The number of m croseconds requ red for the
sweep to traverse the 10 cm. scale s determ ned
by mult ply ng the SWEEP RANGE read ng by the
sum of the read ngs of the SWEEP SPEED
MULT, d als (by the read ng of the SWEEP
SPEED MULT, d al, below S/N 1406). Th s
nd cated read ng s accurate w th n 5% (10%,
below S/N 1406) when cal brated at the factory.
Prov s on has been made to compensate for
var at ons caused by d fferent tubes, etc., by a
screwdr ver adjustment ns de the case. Pro
cedure for adjustment of th s control s descr bed
n Sect on 5.
Recurrent Sweep
In case t s des rable to have a sweep w thout
us ng any sort of tr gger, merely advance the
SWEEP STABILITY control unt l a stable sweep
s obta ned. Th s sweep s the convent onal saw
tooth var ety as used n most osc lloscopes.
S ngle Sweep
The tr ggered sweep c rcu t used n the Type
511 nherently prov des for s ngle sweep opera
t on. The beam s blanked out unt l the tr gger
s multaneously turns t on and starts the sweep.
For s ngle sweep operat on a mechan cal contact
or hand key can be connected between the TRIG
GER INPUT b nd ng post and ground. In nstru
ments below S/N720 a hand key can be con
nected n ser es w th a 3v battery between the
TRIGGER INPUT b nd ng post and ground. If
repeated sweeps occur due to nterm ttent or
bounc ng contact, a capac tor of .1 juf to 1 pf
should be connected across the contact for
nstruments S/N720 and up. Th s capac tor s
charged through 22 megohms and the long t me
constant prevents an mmed ate recurrence of
the sweep.
Sweep Magn f er
Frequently t s des rable to exam ne n some
deta l a port on of the waveshape under observa
t on , for nstance the rate of fall of the end of a
fa rly long pulse. In the Type 511A the sweep
magn f er c rcu t makes t poss ble to expand
any des red 20% of the sweep to cover the
ent re tube face. When the SWEEP MAGNIFIER
POSITION control s moved from the OUT
pos t on, the sweep s delayed for a var able
t me and then goes at about 5 t mes ts normal
rate. The operat ng procedure s to turn the
SWEEP MAGNIFIER POSITION to OUT. Adjust
the sweep speed controls so that the port on of
the wave to be magn f ed s at the r ght s de
of the tube. Now turn the SWEEP MAGNIFIER
POSITION knob clockw se unt l the des red
s gnal moves n from the r ght to the center
of the tube face. The magn f ed sweep s not
l near over ts ent re trace so that t s des r
able to use only the center two nches f pos
s ble. If h gher magn f cat on than f ve s
wanted t s only necessary to change R47 to a
larger value. A value of 10 K w ll g ve a mag
n f cat on of about 10. The somewhat lower
value chosen appears to be a more usable value
n most cases.
NOTE--A sweep of 10 cm per m cro
second s about the l m t of the sweep
ampl f ers, so that care must be taken
that the magn f ed sweep does not exceed
th s value.
TYPE 51 1—OPERATING INSTRUCTIONS PAGE 2-3

External Sweep Input
Prov s on has been made for the connect on
of external sweep generators to the Type 511 A.
Th s m ght be a s ne wave osc llator for fre
quency compar son, the sweep obta ned from a
" Frequency sweep” s gnal generator, etc., or an
aux l ary slow sweep generator. The EXT.
SWEEP INPUT b nd ng post s connected to
the hor zontal deflect on plates v a, the EXT.
SWEEP ATTEN. and a one stage push-pull
ampl f er. The ent re system s DC coupled,
perm tt ng the use of very slow sweeps. Wth
the EXT. SWEEP ATTEN. fully clockw se the
deflect on sens t v ty s approx mately 1.5 volts
per cm, DC or peak-to-peak AC.
VERTICAL DEFLECTION SYSTEM
The Type 511A s equ pped wth a very flex
ble vert cal deflect on system capable of ampl 
fy ng or attenuat ng as necessary a w de range
of waveshapes. S nce the best ampl f ers and
attenuators have faults, t appeared undes rable
to f rst attenuate large s gnals and then ampl fy
them back to someth ng l ke the r or g nal
s ze. It was therefore dec ded that the Type
511A should have a sw tch ng system so that
only as much ampl f cat on as needed to get a
reasonably s zed mage would be employed. Th s
sw tch called the INPUT CHAN. SEL. has four
pos t ons, DC, VIA COND, 1 STAGE and 2
STAGES. In the DC pos t on the SIGNAL INPUT
connector s connected v a the INPUT AT
TENUATOR to the upper deflect on plate w thout
a coupl ng capac tor. The lower plate s con
nected to the VERT. POSITION control and by
passed for s gnals. The VIA COND. pos t on s
s m lar to the DC except a ,1 |f capac tor s
n ser es w th the deflect on plate. On these
two pos t ons the deflect on sens t v ty s ap
prox mately 27 v per cm (13v per cm, S/N
5100 and up) DC or peak-to-peak AC, wth the
attenuator n the XI pos t on.
Normally, connect on to the SIGNAL INPUT
s accompl shed by attach ng the B nd ng Post
Adapter, wh ch s suppl ed, and a s ngle lead.
When reduced load ng on the c rcu t under test
s des red, the Input Probe should be used.
CAUTION--THE PEAK POTENTIAL AP
PLIED TO THE PROBE SHOULD NOT
EXCEED 600 VOLTS.
S nce the probe ntroduces an attenuat on of
10X, t w ll be advantageous to employ a com
mon sh elded lead (no attenuat on) to prevent
p ckup of stray f elds when deal ng w th very
low s gnals, f the add t onal c rcu t load ng s
perm ss ble. A ground lead to the equ pment un
der observat on should be prov ded, and often an
earth ground s des rable.
Vert cal Ampl f er
Wth the INPUT CHAN. SEL. sw tch n the 1
STAGE pos t on the SIGNAL INPUT connector
s connected to the deflect on plate v a the IN
PUT ATTENUATOR, a cathode follower, the
VERT. AMPL. ATTEN., and a one stage push-
pull ampl f er. The VERT. AMPL. ATTEN. s
a 500 ohm potent ometer n the cathode of the
cathode follower, allow ng the ga n of the ampl 
f er to be cont nuously adjusted over a range of
two to one, thus f ll ng n the INPUT ATTEN
UATOR steps. Both low and h gh frequency com
pensat on s employed to produce a w de band of
un form ampl f cat on. Careful attent on has
been pa d to the trans ent response so that square
wave pulses, etc. w ll be fa thfully reproduced.
The ampl f ers are adjusted at the factory for
opt mum trans ent response rather than flat
frequency response. A much flatter response s
obta nable f des red by ncreas ng L6, and read
just ng L7, L8, L9, and L10, but overshoot w ll
occur on steep wave fronts. Wth opt mum tran
s ent response, the r set me (10% to 90% of full
ampl tude) s .04 m croseconds or better. At the
low frequency end of the band, the top of a
10,000 m crosecond square pulse w ll not depart
by more than 5% from flatness. The deflect on
sens t v ty s approx mately 2.7 v per cm (1.3 v
per cm, S/N 5100 and up) peak-to peak max mum.
CAUTION--CARE MUST BE TAKEN TO
AVOID OVERLOADING THE AMPLIFI
ERS. THIS WILL BE AVOIDED IF THE
IMAGE IS NOT ALLOWED TO EXCEED
THE RULED SECTION OF THE GRATI
CULE, WITH THE VERT. POSITION CON
TROL SET SO THAT WITH NO SIGNAL
APPLIED THE SWEEP LINE IS CEN
TERED.
PAGE 2-4 TYPE 51 1—OPERATI NG INSTRUCTIONS

In the 2 STAGES pos t on a w de band pre
ampl f er stage s nserted between the INPUT
ATTENUATOR and cathode follower. S nce the
bandw dth and trans ent response of the two
stage ampl f er are nfer or to a s ngle stage
ampl f er, th s pos t on should not be used unless
t s necessary, n order to obta n a suff c ently
large mage. R set me s .05 m croseconds.
The ga n of the two stage ampl f er s about
100 (S/N5100 and up, 200) mak ng the max mum
deflect on sens t v ty approx mately .27 vper cm
(.13 v per cm, S/N5100 and up) peak-to-peak.
The deflect on polar ty s nverted when the
2 STAGES pos t on s used, result ng n down
ward deflect on on the CRT for pos t ve nput
polar ty.
In nstruments S/N845 and up, a three pos t on
lever type sw tch s mounted at the rear of the
Type 511A Osc lloscope. Th s sw tch changes
the operat ng b as on gr d No. 1 of VI9 and the
screen voltage on VI8 and VI9. Wth the sw tch
set at the center (normal) pos t on, the b as
appl ed to V19 s equal to the b as of V18,
result ng n balanced operat on and equal upward
and downward und storted deflect on of the trace.
For normal operat on, the DEFLECTION PO
LARITY sw tch should be n th s pos t on.
If t s des red to observe pulses, the sw tch
should be set n e ther the upward or downward
pos t on, correspond ng to the deflect on of the
mage on the cathode-ray tube. In the upward
pos t on, the b as of V19 s decreased,result ng
n ncreased output of VI9 and decreased output
of VI8, thus perm tt ng greater und storted
upward deflect on. These cond t ons are re
versed when the deflect on polar ty sw tch s n
the downward pos t on.
D rect Connect on to Deflect on Plates
To allow d rect connect on to the deflect on
plates w th the lowest capac ty, banana jacks
(S/N101-454, screw term nals) are prov ded on
a panel access ble through an open ng n the
left s de of the case. By remov ng the jumpers
the nterval c rcu ts may be d sconnected. The
term nal marked Y1 s the top plate and the one
marked X2 s the r ght plate. Deflect on sens 
t v ty s approx mately 27 v DC per cm ( S/N
5100 and up, 13 v DC per cm) on the vert cal
plates and 32 v per cm (S/N 5100 and up, 18 v
per cm) on the hor zontal.
If pos t on ng control s des red, the jumpers
should be replaced wth 1 megohm res stors
and a ser es coupl ng capac tor employed. Un
less balanced nput s des red, the unused de
flect on plate should be bypassed to ground.
CALIBRATION
Wh le the cathode-ray osc lloscope s usually
employed only as a qual tat ve rather than a
quant tat ve dev ce, t s the only nstrument
capable of mak ng many types of voltage and
current measurements on non-s nuso dal wave
shapes. To a d n th s work the Type 511A
ncorporates an nternal cl pped (uncl pped,
below S/N 2406) s ne wave voltage cal brator and
assoc ated SIGNAL-CAL IB RATE sw tch, allow
ng the operator to select e ther the nternal
cal brat ng voltage or a su table external source
of cal brat ng voltage to subst tute for the s gnal
be ng measured.
S gnal Cal brate Sw tch
Th s sw tch perm ts the vert cal deflect on
system of the osc lloscope to be conven ently
changed from the SIGNAL INPUT connector to
two d fferent sources of cal brat ng voltages.
In the EXT. CAL. pos t on t s connected to
the b nd ng post marked CAL. INPUT, wh ch
n turn may be connected to a source of known
voltage. In the rema n ng s x pos t ons (S/N
2406 and up) t s connected to the center arm of
the CAL. VOLTAGE potent ometer mak ng ava l
able the nternal cl pped s ne wave source of
voltage at power l ne frequency n s x cont nuous -
ly var able ranges. These s x ranges furn sh the
follow ng peak-to-peak voltages: 0-.3, 0-1,0-3,
0-10, 0-30, 0-100 Vj and are accurate w th + or-5
% of full scale for l ne voltages from 105 to 125v.
For osc lloscopes below S/N 2406 n the re
ma n ng three pos t ons the vert cal deflect on
system s connected to the arm of the CAL.
VOLTAGE potent ometer mak ng ava lable the
nternal s ne wave source of voltage at power
l ne frequency n three cont nuously var able
ranges. These three ranges furn sh the follow ng
TYPE 51I-OPERATING INSTRUCTIONS PAGE 2-5

peak-to-peak voltages: 0-1, 0-10, 0-100 v and
are accurate to +or-10% w th normal l ne
voltage (approx mately 117 v).
The CAL. INPUT b nd ng post may be used
as an aux l ary s gnal nput. Th s connect on
s not recommended for observ ng h gh speed
trans ents, due to the sl ghtly greater capac ty.
Measurement of S gnal Ampl tudes
To measure the ampl tude of any s gnal under
observat on, adjust the s ze of the mage to
correspond to a conven ent pa r of hor zontal
l nes on the grat cule. Move the SIGNAL CALI
BRATE sw tch to the appropr ate source of cal 
brat on voltage and adjust ts output unt l the
mage matches the same grat cule l nes to wh ch
the s gnal had been prev ously set. The cal bra
t on voltage s now equal to the s gnal ampl tude.
CAUTION -- IF THE INPUT PROBE (AT-
TEN. 10X) IS USED, THE SIGNAL AMPLI
TUDE IS EQUAL TO TEN TIMES THE
CALIBRATION VOLTAGE.
The scale on the CAL. VOLTAGE potent om
eter s cal brated n peak-to-peak volts. If a
s ne wave s be ng measured, th s may be con
verted to R.M.S. by d v d ng by 2.828.
CAUTION--DO NOT OVERLOAD THE
AMPLIFIERS WHEN MAKING AMPLI
TUDE MEASUREMENTS.
Another method wh ch s less accurate but
more rap d s to cal brate the osc lloscope t
self. Select a su table conven ent voltage n
the range needed, for example 10 volts, and
adjust the VERT. AMPL. ATTEN. unt l a
conven ent deflect on, say 5 scale d v s ons, s
obta ned. The sens t v ty s now 2 volts per
d v s on and ampl tudes may be read d rectly.
The range may be extended f des red by the
INPUT ATTENUATOR and probe wh ch has an
attenuat on of 10X. For nstruments S/N101-454
the range may be extended by the ATTEN. 5X
b nd ng post.
CAUTION--THE DEFLECTION POLAR
ITY SWITCH MUST BE IN THE NORMAL
(CENTER) POSITION DURING CALIBRA
TION TO PREVENT ERROR IN THE INDI
CATED AMPLITUDE. (S/N 845 and up).
INTENSITY MODULATION (Z AXIS)
If des red, s gnals may be mpressed on the
cathode of the cathode-ray tube thus modu
lat ng ts br ghtness. The CRT CATHODE b nd
ng post s connected to the cathode v a a .1
pf capac tor. The cathode res stor s 120 K.
SWEEP OUTPUT
The SWEEP OUTPUT b nd ng post makes
ava lable the waveshape appear ng on the plate
of the sweep generator tube. V10 s used as a
cathode follower to solate the sweep generator
from whatever s connected to the SWEEP
OUTPUT post. The ampl tude s approx mately
20 v peak-to-peak.
S nce the t me constant s only .012 sec. long,
square pulses cannot be transm tted w thout
some loss of shape. Its pr mary purpose,
however, s to transm t short pulses such as
t memarkers, etc.
GATE OUTPUTS
V8 s used as a phase spl tter to prov de pos t ve
and negat ve square waves of the same durat on
as the sweep. The + GATE s taken from the cath
ode and DC coupled, thus prov d ng an accurately
square-topped pulse even at the longest sweep
t mes. The -GATE s taken from the plate v a a
.05/f capac tor to remove the DC component.
PAGE 2-6 TYPE 51 l—OPERATING INSTRUCTIONS

SECTION 3
CIRCUIT DESCRIPTION
Major c rcu t number changes and mprovements occurred n
the Type 511 Osc lloscope start ng wth S/N 455. At th s t me the
Type 511 des gnat on changed to Type 511A. Numbers n paren
thes s nd cate the earl er values. If your osc lloscope has a ser
al number between 101 and 454, please use the part number n
parenthes s. For greater clar ty and conven ence to you, t may
be des rable to cross out all of those part numbers and text sec
t ons wh ch do not apply to your part cular Tektron x nstrument.
CATHODE-RAY TUBE CIRCUITS
The Type 511A uses a type 5CP1A (101-
5099) or 5ABP (5100 and up) cathode-ray
tube. Th s tube has a f ve nch screen and
ut l zes electrostat c focus and deflect on. A
post-accelerat ng electrode ( ntens f er) s used
to prov de ncreased br ghtness. The total
accelerat ng potent al s about 3000 v, g v ng a
sharp br ght mage v s ble n normal room l ght.
The var ous negat ve voltages necessary to
operate the tube are obta ned from a voltage
d v der network across the -1500 v supply.
R142 prov des the b as voltage wh ch controls
the beam current and thereby mage br ght
ness. Th s control s labeled INTENSITY. C60
serves to bypass the cathode to ground v a the
f lter capac tor C77 (C69) n the power supply.
In order to br ng the electron beam to a sharp
focus at the screen, the potent al of the second
anode s adjusted by the FOCUS potent ometer
R140. The ASTIGMATISM control s the poten
t ometer R135 connected between the +225 v
(+125 v) and -140 v suppl es. Th s control adjusts
the potent al of the second anode so that good
focus s obta ned on both hor zontal and vert 
cal l nes s multaneously. In order to transm t
unblank ng pulses to the gr d of the cathode-ray
tube, the .1 pf, 2000 v capac tor, C58 s used.
A s m lar capac tor, C59, s used to transm t
external mpulses such as t m ng markers from
the CRT CATHODE b nd ng post.
The twin potent ometers, R131A and R131B,
prov de a means of vary ng the average poten
t als of the vert cal deflect on plates and there
fore vary the pos t on of the mage. These
potent ometers are connected between the + 225 v
(+125 v) and -140 v suppl es so that as one plate
s made more negat ve the other s made an
equal amount pos t ve. By th s means the aver
age potent al of the vert cal plates s not changed
by adjustment of the VERT. POSITION control.
Th s s essent al n order to ma nta n good
focus over a w de area of the screen. When
the DIRECT pos t on of the INPUT CHAN.
SEL. sw tch s used, the VERT. POSITION con
trol adjusts the potent al of the lower plate only.
In th s case t may be found necessary to adjust
the ASTIGMATISM control to obta n the best
focus.
SWEEP CIRCUITS
The sweep chass s conta ns the c rcu ts
necessary to deflect the electron beam hor 
zontally across the screen at a un form rate,
start ng each sweep n synchron sm w th the
tr gger mpulses. C rcu ts are prov ded wh ch
cut off the beam between sweeps. Prov s on s
made to feed var ous sweep c rcu t waveforms to
b nd ng posts for external use.
Tr gger Phase Spl tter
The TRIGGER SEL. sw tch, operat ng n con
junct on wth VI, the tr gger phase spl tter,
selects the source of tr gger s gnal and reverses
ts phase f necessary. The tr gger ampl f er,
V2, requ res a pos t ve mpulse on ts gr d to
prov de the correct tr gger to the mult v brator.
TYPE 5 t f —Cl RCUIT DESCRIPTION PAGE 3-1

When the TRIGGER SEL. sw tch s n the -INT
or +EXT. pos t ons, s gnals are taken off the
cathode of VI and do not change n polar ty.
Therefore a pos t ve mpulse must be suppl ed
by the external source or vert cal ampl f er
as the case may be. Wth the TRIGGER SEL.
n the + INT. or -EXT. pos t ons, s gnals are
taken off the plate and reversed n polar ty,
thus prov d ng the requ red pos t ve output from
negat ve tr gger sources.
Tr gger Ampl f er
The 6AG7 tube, V2, serves to ampl fy and
nvert the pos t ve tr gger mpulses rece ved
from VI. The TRIGGER AMPL. potent ometer,
R6, var es the b as and thus controls the po nt
on the pos t ve tr gger waveform at wh ch V2
beg ns to conduct. R12 n conjunct on w th
C4A (C3) furn shes the small amount of cathode
b as necessary when the TRIGGER AMPL.
potent ometer s operated n ts extreme clock
w se pos t on.
Tr gger Coupl ng D ode
The negat ve tr gger mpulses from the plate
of V2 are mpressed on the plate of V4 by
means of the coupl ng d ode V3. The d ode s
used n preference to a coupl ng capac tor be
cause t d sconnects the tr gger ampl f er from
the mult v brator once the mult v brator s tr g
gered. When the mult v brator s tr ggered the
plate of V4 falls, mak ng the d ode plate nega
t ve wth respect to ts cathode and therefore
non-conduct ng. Th s cond t on s ma nta ned
unt l the mult v brator completes ts cycle and
s ready to be tr ggered aga n.
Mult v brator
To convert the var ous shapes of tr gger
mpulses nto square waves of controllable
durat on, su table for operat ng the sweep gener
ator and unblank ng the cathode-ray tube, a
mult v brator s prov ded. Th s cons sts of two
tubes V4 and V5. Dur ng the wa t ng per od V5
s fully conduct ng s nce ts gr d s at cathode
potent al and therefore ts plate s held at a low
value due to the voltage drop n R23. Wth V5
n th s cond t on and the SWEEP STABILITY
correctly adjusted, the gr d of V4 s held well
below the cut-off by the voltage d v der, R17
and R18. The c rcu t rema ns n th s cond t on
unt l a tr gger mpulse s rece ved. The plate
of V4 s dr ven down by the tr gger pulse and
also the gr d of V5, because of the coupl ng
capac tor C7. The plate of V5 therefore r ses
carry ng wth t the gr d of V4 caus ng t to
conduct. Th s act on cont nues unt l V4 s
conduct ng and V5 cut off. Th s cond t on s
ma nta ned unt l the capac tor C7 d scharges,
ra s ng the gr d voltage of V5 to such a po nt
that t starts to conduct. Th s makes the plate
of V5 fall, carry ng w th t the gr d of V4 and
start ng a regenerat ve cycle wh ch ends w th
V5 conduct ng and V4 cut off, the cond t on
wh ch ex sted before the tr gger mpulse oc
curred. Thus the plate of V4 produces a square
negat ve pulse and s multaneously the plate of V5
produces a pos t ve pulse. The negat ve pulse
s used to control the operat on of the sweep
generator and the unblank ng of the cathode-ray
tube. The pos t ve pulse s used to furn sh the
plus and m nus GATE voltages ava lable at the
front panel b nd ng posts.
In nstruments S/N1406 and up, the durat on of
the t me V5 s cut off s determ ned by the t me
constant of C7, R20C, R20C1 through R20C9 (de
pend ng upon the pos t on of S10A).The voltage
appl ed across the c rcu t s substant ally nde
pendent of the character st cs of the tr gger m
pulse. To cover a range of sweep t me from .1
sec to 1 m crosecond, C7 has f ve values as
selected by the SWEEP RANGE sw tch. The cal 
brated var able res stor R20C s returned to
+ 225 volts. Th s makes poss ble the use of a lar
ger value of C7 than would otherw se be poss ble,
thus reduc ng the voltage d v der act on of the
stray capac tances to ground n the gr d c rcu t
of V5. Var at on of R20C, R20C1-9, n conjunc
t on w th the f ve values of C7 g ves a cont nuous -
ly var able adjustment of mult v brator pulse
length.
In nstruments S/N101 to 1405, the durat on
of the port on when V5 s cut off s determ ned
by the t me constant R20A, R21, R22,C7 and the
voltage appl ed to R20A, and s substant ally n
dependent of the character st cs of the tr gger
mpulse. To cover a range of sweep t me from
.1 sec. to 1 m crosecond, C7 has f ve values as
selected by the SWEEP RANGE sw tch. In the
three slowest pos t ons R20A s returned to
ground, but for the two fastest t s returned
to +225 v. Th s makes poss ble the use of a
larger value of C7 than would otherw se be
poss ble, thus reduc ng the capac ty voltage d 
v der act on of the stray shunt capac t es to
ground of the gr d c rcu t of V4. Var at on of
R20A n conjunct on w th the f ve values of C7
g ves a cont nuously var able adjustment of the
PAGE 3-2 TYPE 511—CIRCUIT DESCRIPTION

i
I
mult v brator pulse length.
Unblank ng C rcu t
Dur ng the wa t ng per od the b as on the
cathode-ray tube s such that t s completely
cut off. As soon as a tr gger appears and the
sweep starts , t s necessary to prov de a
pos t ve pulse on the gr d of the cathode-ray
tube and thus turn on the electron beam. Th s
pulse should have an extremely fast r se and a
very flat top so that the br ghtness of the mage
s un form.
To secure a pulse of th s nature, n nstru
ments S/N2869 and up, the negat ve pulse from
the gr d of V5 s l m ted by plate current cutoff
n V7.1A before t reaches full ampl tude.
The voltage d v der R37, R38, sets the d.c.
b as on the gr d of V7.1A at approx mately 0
volts and suppl es a negat ve pulse of 45 volts
ampl tude. C l2 nsures that the lead ng edge w ll
be coupled through wthout loss of r set me due
to gr d and w r ng capac t es to ground. The
45 volt negat ve pulse s more than adequate
to dr ve V7.1A nto cutoff, thus produc ng at
the plate a square, flat-topped pos t ve pulse
hav ng an ampl tude of 80 volts. To prov de
ncreased r set me, L2.1 s employed n the
plate c rcu t of V7.1A. The cathode follower,
V7. IB, serves to solate the plate c rcu t of V7.1A
from the capac ty-to-ground of the cathode-ray
tube gr d and assoc ated w r ng, thus prevent ng
any apprec able reduct on n r set me due to
the r effect. Th s c rcu t s capable of un-
blank ng the tube n less than .1 m crosecond
after a sharp tr gger pulse reaches the TRIGGER
INPUT b nd ng post.
To secure a pulse of th s nature, n nstruments
S/N101 to 2868, the pos t ve pulse from the
mult v brator s cl pped before t reaches ts
normal ampl tude by the d ode V6. The cathode
of V6 s held at approx mately + 55 v and thus
the plate cannot r se more than a few volts
above th s value. In order that the capac ty - to-
ground of the cathode-ray tube gr d and ts
assoc ated components and w r ng should not re
duce the rate of r se apprec ably, the cathode
follower V7 s used. Th s c rcu t s capable
of unblank ng the tube w thn .1 m crosecond
after a sharp tr gger mpulse reaches the TRIG
GER INPUT b nd ng post.
Gate Output Generator
V8 serves to solate the gate output b nd ng
posts from the mult v brator. It rece ves a pos 
t ve pulse on ts gr d of the same durat on as
the sweep from the plate of V5 v a the voltage
d v der R32 and R33. CIO ma nta ns the steep
s des of the pulse. S nce the plate and cathode
load res stors are equal, pulses of equal s ze
but oppos te polar ty appear at the plate and
cathode. The + gate from the cathode has no
block ng capac tor and therefore preserves the
square pulse for the longest sweeps. It was
not felt des rable to have the -Gate b nd ng
post carry the +225 v potent al of the plate;
therefore a block ng capac tor s used.
Sweep Generator
The sweep generator c rcu t produces the
bas c wave necessary to sweep the beam l nearly
across the tube and return t to ts start ng
po nt. Dur ng the wa t ng per od the 6AG7 tube
V9 s held fully conduct ng s nce t has no b as
and therefore ts plate s about at ground poten
t al. When a tr gger occurs the negat ve pulse
from the mult v brator cuts the gr d of V9 off
very rap dly.
In nstruments S/N 1406 and up the plate r ses
n exponent al fash on at a rate depend ng upon
R20D, R20D1-9 ( as determ ned by sett ng of
S10B), R39, the voltage appl ed across the c r
cu t, and C15. When the mult v brator pulse
ends V9 conducts aga n, thus d scharg ng C15.
S nce C15 s charged to only about 5% of the
supply voltage the rate of r se s very nearly
l near. F ve values of C15 as determ ned by
the SWEEP RANGE sw tch n comb nat on w th
the var able res stors R20D and R20D1-9 pro
v de a cont nuous var at on of sweep speed of
from .1 sec to 1 m crosecond for a 10 cm
sweep. In order to ma nta n the correct mult 
v brator pulse length as the sweep speed s
ncreased, the SWEEP RANGE sw tch changes
C7 n the mult v brator and C15 s multaneously.
In a l ke manner the SWEEP SPEED MULT,
controls are dual controls chang ng R20C, R20D
and R20C1-9, R20D1-9 s multaneously. In order
to ma nta n the cal brat on of the SWEEP SPEED
MULT, d als when tubes are changed, etc.,
the voltage appl ed to R20D may be var ed by
R42 wh ch sets the gr d potent al of the cathode
follower V15. The use of the cathode follower
nstead of a potent ometer ma nta ns a con
stant charg ng potent al as R20D, R20D1-9 s
TYPE 51 -CIRCUIT DESCRIPTION PAGE 3-3

the s gnal on the gr d of V11A, w thout change
of polar ty. The SWEEP MAGNIFIER POSITION
potent ometer ra ses the potent al on the gr d
of VI IB above ground and thus the cathode
potent al of VI1 A. No sweep appears on the
plate of VI IB unt l the plate of the sweep genera
tor overcomes th s b as, then the ampl f ed
sweep appears. Suff c ent b as s ava lable on the
SWEEP MAGNIFIER POSITION to make t pos
s ble to start the magn f ed sweep at any po nt on
the normal sweep. V6 s employed as a DC re
storer, n nstruments S/N455 and up, to nsure
that the magn f ed sweep w ll start at the same
potent al each t me, thus prevent ng j tter or n
stab l ty of the trace. When the magn f ed sweep
s not des red, the SWEEP MAGNIFIER POSI
TION knob s turned to the OUT pos t on wh ch
operates a SPDT sw tch connect ng the sweep
ampl f er d rectly to the plate of the sweep
generator.
Sweep Ampl f er
The sweep voltage at the plate of V9 s only
about 20 v ampl tude. To sweep the spot across
the screen, about 350 v s necessary. The sweep
ampl f er prov des the necessary ampl f cat on
and n add t on converts the s ngle s ded voltage
from the sweep generator nto a balanced voltage
su table for deflect ng the beam. Th s balanced
voltage s necessary to ma nta n the average po
tent al of the deflect on plates constant over the
ent re sweep, and thus prevent defocuss ng. The
ampl f er wh ch does th s uses a cathode-coupled
c rcu t cons st ng of the tr ode connected 6AU6
tubes V13 and V14. The act on of th s c rcu t
s the same as descr bed for the sweep magn 
f er except that load res stors are present n
both plates. The HOR. POSITION control var es
the b as on VI4 and thus determ nes the pos 
t on from wh ch the sweep starts. To nsure
that the sweep w ll always start at the same
po nt on the screen each t me (at a g ven sett ng
of the HOR. POSITION control), the 6AL5 restor
er d ode VI2 s connected between the gr d of
V13 and ground. Th s d ode removes any charge
wh ch C20 may have ga ned dur ng the sweep.
var ed. Deta ls of th s adjustment may be found
n Sect on 5. The two res stors R39.ll andR39.12
connected n ser es are shunted across R20D1-9
to compensate for the plate c rcu t loads of V9.
In nstruments S/N101-1405, the plate r ses
n exponent al fash on at a rate depend ng on
R20B, R39, and C15. When the mult v brator
pulse ends V9 conducts aga n, thus d scharg ng
C15. S nce C15 s charged to only about 5% of the
supply voltage, the rate of r se s very nearly
l near. F ve values of C15 as determ ned by
the SWEEP RANGE sw tch n comb nat on w th
the var able res stor R20B prov de a cont nuous
var at on n sweep speed of from less than .1
sec. to 1 m crosecond for 10 cm sweep. In
order to ma nta n the correct mult v brator pulse
length as the sweep speed s ra sed, the SWEEP
RANGE sw tch changes C7 n the mult v brator
and C15 s multaneously. L kew se the SWEEP
SPEED MULT, s a twn control chang ng R20A
and R20B s multaneously. To ma nta n the cal 
brat on of the SWEEP SPEED MULT, d al
when tubes are changed etc., the voltage appl ed
to R20B may be var ed by R42 wh ch sets the
gr d potent al of the cathode follower VI5. The
use of the cathode follower n place of a poten
t ometer ma nta ns a constant charg ng potent al
as R20B s var ed. To ma nta n the cal brat on
of the SWEEP SPEED MULT, d al n nstruments
S/N 101-454 a voltage regulator tube V15 holds
the voltage constant. The voltage appl ed to R20B
from VI5 may be var ed by R42. Deta ls of th s
adjustment w ll be found n Sect on 5.
Sweep Output Cathode Follower
To prov de the necessary solat on between
capac t es fastened to the SWEEP OUTPUT
b nd ng post and the sweep generator, the cath
ode follower V10 s prov ded. The gr d of V10
s connected to the plate of the sweep generator.
The SWEEP OUTPUT b nd ng post s connected
to the cathode of V10 w thout a block ng capac tor.
Sweep Magn f er
The funct on of th s c rcu t s to delay the
start of the sweep for a var able t me, and then
cause t to go at f ve t mes ts normal speed.
Th s s accompl shed by the b ased, cathode-
coupled ampl f er Vll. In th s type of ampl f er
a pos t ve change n the gr d potent al of Vll A
ra ses both cathodes and therefore corresponds
to a negat ve change on the gr d of VIIB. Thus
the plate of Vll g ves an ampl f ed vers on of
H gh frequency compensat on prov des suff 
c ent band wdth to ampl fy the 1 m crosecond
sweep wth good l near ty.
Th s s accompl shed by the bypass ng effect
of C22, wh ch at h gh frequenc es reduces the
degenerat on ntroduced n the cathode c rcu t
by R65 and R66.
PAGE 3-4 TYPE 51 t-CI RCUIT DESCRI PTI ON