Tektronix 5A26 User manual

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T EK T R O N IX
1
1
1
1
1
Te k tronix, Inc .
Ρ . Ο . Box500
Beaverton, O r egon 97077
ι
ο7 α - ιο 47- οο
I N
ST R UCTIO N M A NU A L
Serial Number
F irst P ri n ting JUNE 1975

WARRANTY
All TEKTRONIX instruments
are
w
arrantedagainst
detectivematerials and wor km an shi p for one y ear .
A ny
q u estions
w ith r
espect to' the w arra n t y s h o u ld
betaken up with your TEKTRONIX Field En gi neer - or
representative .
All re qu ests for repairs and replacement parts
sh o u ld b e directed to the TEKTRONIX F iel d Office
or representative in your
area . This
ωίΗassu
re you
t h e fastest possible service . P lease include
instrument
Type
N u mber
o
r P art
Number and Ser
Number w ith all re qu ests fo r parts or ser u ί r e .
Specifications and price change privileges reserved
.
Co p yrig
h
t ,
1975 by Te k tro n ix, Inc ., B eaverto n ,
Oregon . P rinte
d
i n
t he U n ited States of A m erica . All
rig h ts reserved . Contents
of
t h
is p ublicatio
n
m ay not
be re p roduce d i n any fo r m w it hou t p
er
m ission
of
Te k troni x , Inc .
U .S .A .
and
foreig n
T E
KTR ON IX products co vered
by U .S . a nd foreig n paten
ts and/or
pate
n
ts
pe ndi
n g .
T EK TR ON IX is α registere d trademar k
of Tektronix,
Inc .

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TA BLE O F CO N T ENTS
P AG Ε

P AG Ε
LIST O
F
ILLUSTRATIONS

i

S E CTIO N 2 T HE O R YO F O PER ATIO N
L IST
O
F TA BLE S

i

BL OC K DIAG R A M DE SC R I P TIO N 2-1
S E CTIO N 1 O PER ATI NG I N ST RU CTIO N S

CI R CU IT O PER ATIO N 2-2
PREP A R ATIO N F O RU SE

1-1

PRE A MPL I F I ER

2-2
CO N T R O L S, CO NNECTO R S, A ND

1-1

OU T PU T A MPL I F I ER S

2-3
I N DICATO RS

RE ADO U T

2-5
B ASIC O PER ATIO N 1-3
P re p aration

1-3

S
E
CTIO N 3 REPL AC E A BLEELE
CT R ICA L P A R TS
Ste p Attenuator B alance Ad j ustme n t

1-3
Gain
C
h ec k 1-4

S E
CTIO N 4 S ERV ICE I NF
O RM ATIO N
DE
TAI
LE D O
PER ATI N
G
I NF
O RM
ATIO N 1-4

S ERV IC ES A V AI L A BLE

4-1
Applying
Signals

1-4

M
AI N T EN A NC E 4-1
P re-C h arging

1-4

Circ u
it
B
oar d
R emoval

4-1
Sig n
al
In p
ut Connectors

1-4

AD JU ST MEN TS A F T ER
REP AI R

4-1
H ig h Im ped ance In p u t

1-5

DIAG R AM S

4-2
Dis p lay P olarity

1-5

BL OC K DIAG R A M
Deflection F actor

1-5

AD
JUST
MEN T PR
OC
E
D URE
V oltage Comparison M eas urements

1-5

P A R T L OCATIO NS
A
N
D DIAG R AM S
Diffe r en tial
O p
eration

1-5
V oltage
Pr
obes

1-6

S E CTIO N 5 REPL
AC
E A BLE
ME CH AN ICA LP AR TS
Differential M
easurements

1-6
S PE CI F ICATIO N S

1-7

C
H
A
N
G E I NF O RM ATIO N
LIST OF ILLUSTRATIONS
FIG URE

FIG URE
NO .

P AG E NO .
1-1

5 Α 26 Du al Differential Am p lifier .

ii

4-3

A dju stment locations .
1-2

Front-panel cont r ols, conn ectors an d 1-2

4-4

Α 1, A2-Channel 1
and 2
Pr
eam p
lifier circuit
i nd icators .

b
oar d component an d test p oint locations .
1-3

Dimensions .

1-9

4-5

Α 2, A2-Channel 1 a nd2P reamplifier circuit
2-1

F
loating
P
ower Su pp ly d etaile d bloc k 2-4

boar d locatio n s .
d iagram s h owing sta n d i ng cu r re n t p at h s

4-6

A3-Main
circuit boa r d com po n e n t a n d test
t hrough t he P ream p lifie r .

p oint locatio n s .
T he ill u
strations in Section 4 are locate don fol dout pages

4-7

A3-Main ci r c u it b oar d locatio n .
at th e back of the ma n ual .

4-8

A3-Main circ u it b oar d component locations .
4

4-9

A3-Main circuit board location .
-1

Circ u it b oar d locations .
4-2

Common-mode re j ectio n (cm r ) display .
L IST O F TA
BLES
TA BLE
NO .

P AG Ε
1-1

E lectrical Sp ecifications

1-7
1-2

E nvironmental S p ecifications

1-8
1-3

Ph ysical Specifications

1-8
5 Α 26

Fig . 1-1 .
5
Α 26
Dual Differential Amplifier
.

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T he 5 Α 26 Dual Differe n tial Am p lifier is α d ual-trace h ig h -gain d ifferential amplifier plug-in for u se wit
hTe k tronix 5000 Series
Oscilloscopes . T h e unit contains two i d entical in d e p en dent am p lifier chann els t h at feature h ig h sensitivity an
dα h ig h common-
mo d e re j ectio n ratio .
E
achch a
n nel h
as α
ban dwid t h capability of do to 1 mega h ertz, an dα front- p anel pu s h button switch allows the re d uction of
t
he
up p
er b
an d widt
h limit, t hu s increasing t h e signal-to- n oise ratio for low freq u ency applications . E it h er chann el may be
used
for single
c
h annel d isplays, or electronically switche d to p ro d uce dual-trace dis p lays .
An
ill u minate d k no bsk irt provi d es α d eflectio nfactor rea dout, w h ic h is also d isplayed on t h e crt w h en used i nan oscillosco p
e
with rea dou t cap abilities .
PREP A R ATIO N
F
OR US
E

4

V
O
L
TS/DI
V Switc h
es-
V olts per ma j or graticule
Ο
d ivisio n . Selects calibrate dd eflection factors from
'

T he
5
Α
26
is cali b rate d an d ready for use w h en receive d .

50 microvolts/ d ivision to 5 volts/division ; 16 steps
in
T he unit may be installed in any p l u g-in com p artment . R e-

α 1-2-5 se q uence . Kn ob s k irt is illuminate
dto in d i-
fer to t he oscilloscope instruction man u al for information

cate d eflection factor, and 10
Χ scaling
of
bot h k no b
on Χ - Υ operation . To install, align t he u pp er an d lower

s k irt and
crt rea
d
out
is
provi de
d
automatically w h en
grooves of t h e 5 Α 26 with t he plug-in compartment track s,

α 10
Χ
co
d e dp robe is used .
an d fully i n sert t he 5 Α 26 u n til it loc k s i nto place . To
re-
move,
pull
the release latc hto disengage t h e 5 Α 26 from t he
' ~ oscillosco p e . CA L ( V aria b le V O L TS/DI V ) Controls-
P rovi d es υη -
calibrated continuously varia b le d eflection
factors
between t he cali b rate d settings of
t he VO L TS/DI V
CO N T R O L S, CO NNE CTO R S, A N D I N DICATO
R
S

switc
h
and
exten d
st
h e d eflection-factor range to
12 .5
volts/
d ivision .
T he following descri b es t h e
f
u nction of t h e front- p anel
controls, con n ectors, an d indicators . R
efer
to
F ig . 1-2
for
t he locatio nof t h e co n trols, con necto r s and in d icators .
M ore information is given u nder Detaile d O p erating
Information .
DIS PL AY
P
ush B utton-Applies and
removes
logic
levels to t he oscilloscope system to enable or d isa b le
p lug-in operation . Switc h is functional on ly w hen
p l u g-in is op erate d in one of t he vertical d eflectio n
p l
u g-in
compartments .
Ο 2

P
OS Co
n
trols-
P ositions d is p lay vertically .
ι
BW L I M IT Pu s h B uttons-Allows re du ction of t he
upper b andwi d t h limit to increase t h e signal-to-noise
ratio for low-frequency applications . Selects upp er
ban dwi d t h limit
at
eit h er 1
mega
h ertz ( bu tton o u t) or
10 k ilo h ertz
(
bu tton in) .
O
PER ATI N G I N ST RU CTIO
N S
Section
1-5 Α
26
ST
EP ΑΤΤΕΝ B A L Ad j ustments- B ala n ces t h e in p ut
am p lifier for
minimum trace s h ift t hrou g h o u t t h e
d
eflection
factor
gain-switc h ing ra n ge .
Input Coup li n g P ush B uttons
AC-O U T:DC . B utton pus h e d in selects cap acitive
coupling of
signal app lie d to associate d+ or -
inp
ut
connecto
r ; button out selects d irect couplin g of inpu t
sig n al .
GND . Grou n d s t he preamplifier
in put
an
d connects
input signal to groun d t hroughα
1 mego h m resistor .
PRE CH G . B ot h AC and GN D
buttons pus hed in
p ermits p rec h arging of t
h e cou p ling cap acitor to t h e
input sig n al d o level . R
elease GN D button fo r
measurement .
M OD EP ush B utton s-Select c h annel to b e d is played
an d illumi n ate t h e p ro p er d eflection factor
setting
(1
Χ
or 10 Χ ) on
t he VO L TS/DI V switc h k no bsk irt .
B oth buttons pus hed i n provides α du al-trace d isplay .

Operating
Instructions-5A26
r
ο
Fig
.
1-
2 .
Front-panel controls, connectors, and indicators
.

Operating Instructions-5A26
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AC

O UT : DC
(b
utton out)
+ an d - In p
u t Connectors- BN C connectors for app li-
cation of external voltage signals
. Connector labele d

GND

GND ( bu tton in)
+ indicates t h at α p ositive-going signal will
cause
upwar d d eflectio n ; connector la b ele d - indicates
t
h
at

M OD E

CH
1 an d CH
2
α positive-going
sig n al will cause downwar d d eflectio n .

( b uttons in)
Con nectors
inclu de co d e d -
prob e
input rings for
activating t h e rea dou
t w hen using readout-co d e d
p robes .

d . A d j ust
intensity
control for normal viewing . Traces
sh oul d a pp ear
near gratic u le center .
B ASIC O PER ATIO N
e . Set t he VO L TS/D Ι V switc h es
to .1
. If
traces s h ift,
Preparation

a d ju st t he ST EP ΑΤΤΕΝ B A L control
as d
escri
bed in
'

T he following
procedures are i n te nded to h el p p lace t h e
trace
on t hesc r ee n q uic kly and prepare t he instrument for
immediate use :
'

α .
I n
sert 5 Α 26 all t he way into oscillosco p e plug-in
com p artment
.
ι
T R IGG ER Push Bu tton-Selects
time base triggeri n g
signal from eit h er channel .
b . Turn oscilloscope Intensity control to mi d ra n ge and
t u rn
oscilloscope syste m p ower on . P reset time-b ase
an
d
triggering
controls for 2 millisecon d / d ivision sweep rate
10

and a u tomatic triggeri
ng .
c . Set 5 Α 26 front- pan el controls as follows
:
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DIS
PL AY

ON (butto n in)
T RIGG ER

OU T : CH 1 (b u tto n
out)
P
OS

M i d ra nge
BW L I M IT

OU T : 1 MHz
(b utton o u t)
V O L TS/D 1 V

5
ST EP ΑΤΤΕΝ B A L

M
i d ra nge
C H 1 an d CH2
+Input
Cou p li n g
CH 1
and C
H 2 -
In
p
ut
Coupling
Step Attenuator B alance A dju stment proce
dure .
f .
M ove CH 1 trace 2 d ivisions b elow graticule h orizontal
centerline, and C H 2 trace to b ottom of graticule
with
P
OS controls .
g . Apply400 millivolt pea k
-to- p ea k signal fro m oscillo-
scope cali b rator loop wit hα test lea d or 1 Χ probeto
CH 1 + in p ut connector .
h .
R elease CH 1 + GND b utton . Disp lay will be α s qu ar e
wave 4 d
ivisions in amplitude with bottom of d is p lay at
refere n ce esta b lis hed in step (f) .
i . P osition b ottom of s q uare wave to graticule h
orizontal
centerline .
j . Pu s h in
C
H
1
+
AC button an d note that display s h ifts
d ownwar d 2 divisio n s .
k .
Disconnect test lead from CH 1 + in put an d connect
to CH
2 +
in pu t .
Ι. P ush in T RIGG
ER butto n for CH 2 triggering an d
repeat ste p s (f) t h
ro
ug h (j)
for CH2 operation .
AC

OU
T :
DC (button

Ste p
Attenuator B alance A d j ustment
Out)

Wh en t h e ST EP ΑΤΤΕΝ
B A L control is not properly a dj ust-
ed , t h e d is
p
lay
will s h ift vertically ( d ue to α do imbala nce i n
GND

G ND ( button in)

t he am p lifier)
as t h e VO L TS/DI V switc h is rotate d t h ro ugh -
out its range . T he
s h ift is more noticeable on t he most
sensitive positio n s .

Op
erating Instructions-5A26
α . Set VO L TS/DI V switch to 5 . Ground both
+ an d -

b . Wait about 1 second for coupling ca p acitor to ch
arge .
inputs (G N D bu ttons pu s h e d in) and p osition trace to
graticule h orizontal centerline .
c . R elease GND bu tton a n d ac com p
onent can b e meas u re d
in usual manner .
b . A dj ust ST EP
ΑΤΤΕΝ B A L control for minim u m
trace s h ift as VOL TS/DI V
switch is rotate d t h rou g ho u t
its range .

Signal In p ut Connectors
Wh en
connecting signals to t h e
+
an d - in p ut connectors
on
t he 5 Α 26,
consi d er t h e met h od of co up ling that will be

,
Gain C heck

u se d . Sometimes un s h iel d e d test leads can b e u se d to
Wh en t h e 5 Α 26 is first inserte d into α p lug-in com
p artment,

connect t h e 5 Α 26 to α signal sou rce, p artic
u larly w h e n α
t h e amplifier gain may be c heck e d an d ad
j usted if necessary .

h ig h level, low-frequency signal is
monitore d at α
low
i m -
See A d ju stment Proce d ure in Section 4 of t
h
is
manual for

p ed ance p oint . H
owever, w h en any of t h ese factors are
com p lete i n structions .

missing, it
becomes
i
n creasingly important to use s h iel d ed
signal
cab
les .
In
all cases, t he signal-trans p orting lea d s
s h ou l d be k e p t as s hort as practical .
D E TAI LE DO
PER ATING I NFO RM ATIO N
Applying Signals

Wh en ma k ing si n
gle-e nded
i
nput measurements (conve n tio n al
amplifier operation), b e sure to establis
h α common groun d
con nection between th e
d evice un d er test an d t he 5 Α 26 .
T h e s h iel dofα coaxial
cable is normally u se d for t h is pur pose .
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ι
If t h e maxim u m input voltage rating at t he gates
of t h e input FE T's is exceeded, t he gates a r e

In some cases, d
ifferential meas u rements re q uire no common
clampe d at about + or - 10 volts . If t h e signal

ground connection, a
nd
t
h erefore are less s u sce p tible to
sou r ce
can supply
m ore t ha n 1/16 ampere, t he

interference by ground-loop
currents . Some pro b lems wit h
input protective fuse(s) will o p e n .

stray magnetic co
u pling into t h e signal transporting leads
can also
be minimize d by u sing α d ifferential rat h er t
h
an α
single-en d e d measurement . T h ese consi d eratio n s are d is
Wh en meas u ring unk now n voltages, use t he h ig h
est deflection

cu sse d later in this sectio n under Differential O p eration .
factor first . If t he deflection is too small to ma
ke
t
he
meas u rement, switch to α lower deflectio n factor .
It is always im portant to consi der t h e signal so urce loa
d ing
(an d res u lting ch ange in t he source operating
c h aracteristics)

'
P re-C h arging

d u e to t he signal-trans p orting lea d s an d t he inpu t
circ u it of
Wh
en only t he ac com p onent of α signal having bot
hac and

t h e 5
Α 26
.
T h e circuit at t he in pu t connectors can normally
d o components is to b e measured, t
he
p re-c
h arge circ u it

b e re p rese n te d by α 1 mego h m resistance to ground p
arallel-
permits ch
arging
t
he
co
u p ling ca p acitor to t h e inpu t signal

ed by about 47 p icofarads . Α few
feet
of
s h iel ded ca b le

,
d
o
level .

(20 to 40 p icofara d s p er foot) may
increase t h e p arallel
capacitance to 100
picofarads or more . I n ma ny cases, t he
effects of th
ese resistive and cap acitive loa d s may be too
great and it may be desira b le to minimize t h em t
h
roug
h t h e

,
CAUTION

use of an attenuator pro be .
If t h e 5 Α 26 input is connected to α large d o
voltage sour ce (10 volts pea k or mo r e), use
t he p rech arge provision . Damage to t h e signal

Attenuator probes not only decrease t he resistive-ca p acitive
so u rce could
r esult since t he pea k current

loa d ing of α signal source, but also exten d t he measureme
n t
t hro u gh t h e ac coupling capacitor and t he

range of t h e 5 Α 26 to inclu d e substantially h
ig
h
er voltages .
input
protection
circuitry is limited only by

Passive atten u ator p rob es h avi n g attenuation
factors of 10 Χ ,

,
t
he
signal
source internal resistance .

100 Χ , and 1000Χ , as well as oth er s p ecial- pu r pose types,
are available t h roug h your Te ktronix F ield E ngineer or
F iel d Office .
α . B efore co n necting 5
Α
26
to α signal contai n ing α d o
com p one
n
t, p us
h
in
AC and G N D b uttons . T h en connect

Some measureme n t situations
re q uire an extremely h ig h
inpu t to
circ
u
it u nd er test .

resistance in pu t to t he 5 Α 26 with very
little sou rce loadi n g
ι
ι
1
1

ι
or signal attenuation . In s uc h situatio
n
s, α
passive attenuator

Deflection F actor
p robe cannot b e used . H
owever, t h is proble m may be solved

The amount of trace d eflection
produced by α signal is
'

by using α FE T Pr obe or t
heh ig h-imp e d ance i np ut p rovision

determi n e d by the signal am p litu d
e, t h e
atten
uation (if any)
of t h e 5 Α 26 as described un
d er H ig h -Impe d ance In pu t .

of t h e pro b e, th e setting of t h e
V
O
L TS/DI V switch , an d
t he setting of t h e
V
aria
b le control . T h e d eflection factor
settings
are calibrate d only w h en t he V ariable control is
H ig h-Im p edance In put

rotate d f u lly clockwise i n to t he deten t p osition .
In t h e 50 m t hro u gh 50 μ p
ositions of t he V O L TS/DI V
switch , w here thein
p ut attenuator is not used, t he internal
gate return resistors alone esta
b lis h t he 1 mego h m input

T he range of t he V aria b le control
is at least 2 .5 :1 . It provides
resistance . T he removal of t
he strap from t he P ream p lifier

uncalibrated d eflection factors
covering t h e full ra nge
circuit board (see
F ig . 4-4, C hannel 1 and 2 P reamplifier

between t
he
calibrate d
settings of t h e VO L TS/DI V switch .
circuit board com p onent an d test point
locations in t he

T he V ariable control can be set to exten d t he d eflection
Diagramsan d P arts L ists sectio n ) d isconnects t
hese resis-

factor to at least 12 .5 volts/ d ivision .
tors fro m groun d an d permits t he in pu t FE T
gates
to float,
p rovi d i n gαvery h ig hinput impe d ance
.
To re d uce
noise
and
obtain α more u sa b le d is p lay w he n t
he
V O L TS/DI V switc h is set to t h e more se n sitive p ositions,
T h e in pu t signal m u st be k ept to r elatively low amplit
u des,

p
u s h
in
t he BW L I M IT button to re d uce t h e b a n d wid t
hto
since t h e d eflection factor is restricte d to 50 millivolts/

10 kH z if t h is limit does not a ppreciably d istort t
hed esire d
d ivision t hr oug h 50 microvolts/ d ivision, an d d o cou p li n g

features of t h e signal u nde r ob servation .
must b e u se dto p rovi d eα d o p at h for t he
FE T
gate cu
rre n t .
V oltage Com p arison M easurements
O p
erating Instructions-5A26
NOTE

Some
a pp lications re q uire d eflection factors oth
er t han the
In t h e 0 .1 volt to 5 volt r ange of t he V O L TS/

fixe d values provided by t he V O L TS/DI V switch . One
suc h
DIV switc h , t he input impedance is pa
r alleled

app lication is comparison of signal am p litu d es by ratio
by t he resistors in t he attenuato r . W
h
en
t h e

rat h er th a n by absolute voltage . To accom p lis h t h is,
a
pp
ly
"

strap is removed, t he atten u ation ratio is

αreference
signal to eit h er
+or
- inputs of the 5A26, and
affected, causing t he deflectio nfacto r s in t h is

set the VO L TS/DI V switchand V aria b le con trol so
t h at
range to be incorrect .

To determine t
h e d e-

t he r eference dis p lay covers t h e d esire d
number of graticule
flect ί on factor, c h ec k t h e deflection with
an

d ivisio n s . Do not ch ange t
he V ariable con trol settings
input signal of k nown amplit
u de .

t h roug h out t he subse q uent
comparisons . H owever, th e
settings of t h e VO L TS/DI V switchcan be ch
ange dto
accommodate large ratios . In d
oing
so,
regard t h e nu m b ers
T h e signal source impedance is an
important factor, since

w h ic hdesignate t
h
e switc
h p ositions as r atio factors rat h er
gate cu rrent will p ro d uce an
offset . F or example, α 100

t h an voltages .
p icoampere gate cu
rrent
t
hrou g h 10 mego h ms produces α
1 millivolt
offset, w h ic h may result i n sig n ificant error
w h ere small voltages are of concern .

Differential O p eration
Single-en ded meas u rements
often yield unsatisfactory res u lts
beca
u se
of
interfe r ence resulting from ground-loop currents
T he h ig h -fre q uency res p onse will also d epen d upon t h e

b etween the 5 Α 26 and t he device un d er test . In oth er
signal sou rce im p eda n ce, si nce various s hu nt ca pacitances

cases, it may be d esirable to elimi n ate α do voltage
by means
b etween t h e source and t he input gate
m u
st
c harge an d
ot h er t han t he u se of α do block ing capacitor,
w h ic h co u l d
d isc h arge th roug h t h at i mp ed ance .

limit t he low-frequency res p onse
.
'

Dis p lay
P
olarity
T h ese limitations of
single-en de d measurements are effectively
Single-ended
signals
a pp
lie d to t he + in put connector pro-

eliminated by
connecting t h e
+
inp ut and - in p u t to
'

d uce α d is p lay in phase with
t he in p ut signal . Signals a pp lie d selecte dp oints
in t h e test circuit . Since t h e c h assis of t h e
to t he - i npu t connector
will be inverte d .

5 Α 26
nee d not be connecte d in any way to t he test circ u it,
t h ere are
few limitations to t h e selection of t h ese test points .
In any case, d
o
not
excee d t he maxim u m safe in pu t voltages .
Α similar
polarity relations h ip exists for d ifferentially a pp lie d
.

s ί gnals, but p
ertai ns
to
t h e direction of voltage c h ange at
one in put with res p ect to th e ot h e r , rat h er t han with res p ect

T h e + an d -AC bu ttons sh ou l d bothbe set to t
he
same
to c
h assis potential .

p
ositions, d epending on t he met hod of
signal coupling requ ire d .

O p
e
r ating Instructions-5A26
Only t hevoltage d
ifference between two signals is am p lifie
d pro
b es are s h iel d ed to prevent pick up of electrostatic inter-
an d d isplaye d in
differential measurements, w h ile t h e common-

ference . Α
10 Χ attenuator probe offers α h ig h in put
mode signals (commo n i n
am p
lit
ude, fre q uency and ph ase)

impedance and allows t he circuit under test
to
perform very
are re j ecte d .

close to normal operating con d itions . See your Te k tronix,
Inc ., catalog for c h aracteristics and compati b ility of probes
for u se with t h is system .
T he ab ility of th e 5 Α 26 to re j ect common-mo
d
e
signals is
in d icated by t he commo n-mo de re j ection
ratio (cm r r) .
Cmrr
is at least 100,000 :1 at t h e input
con n ectors from 50
microvolts/ d ivision to
50
millivolts/
d ivisio n w hen signals
between do an d 30 k ilo h ertz are do
cou p led to t he in p uts .
To illustrate t h is ch aracteristic,
assume t hat α si n gle-en d ed
i npu t signal consists of an
unwante d 60 h ertz signal of 1
volt pea k -to-pea k , p lus α d esire d
signal of 1 millivolt p ea k -
to-peak . If an attem p t is ma d e
to display th e describe d
signal (single-e nd e d meas u rement)
at 0 .2 millivolts/ d ivision,
t he 60 h ertz signal will prod uce α
deflectio nequ ivalent to
5000 d ivisions an d t h e 1 millivolt signal will b e
lost .
Outsi d e infl uences such
as magnetic fiel d s can also degrade
t h e performance,
partic u larly w hen low level signals are
involved . M agnetic i nterference
may be minimize d by using
i d entical sig n al-t r ansp orting leads
to t he two in pu ts an d
twisti ng t he two lea d s toget h er
over as much of t h eir lengt h
as p ossi b le .
COD E D PR O BE S . T h e 5 Α 26 is d esigne d for
com p
atibility
wit h co d e d pro b es, suc h as t he Te ktronix Ρ 6062 Α 1 Χ /10 Χ
P assive P robe . T h e + an d - i npu t connectors
h
ave
an ou
ter
ring to w h ic h t h e cod ing pin
on t
he
probe connector ma kes
contact . T h is typ e
of
probe
allows t he vertical d eflection
factor in d icate d by t he rea d out to corres pon d wit h t h e
actu al voltage at t h e probe ti p , elimi n ating t he need to
consid er t he atte nu ation factor w hen meas u ring t h e signal
am p lit ude on t h e graticule scale .
If t he same
1 millivolt signal is meas u re dd ifferentially with
Differential M easurements
t he 60 h ertz signal
common to both inputs, no more t han

T
he
following a d ju stment procedure is recommen d ed w hen
one part in 100,000 of t h e
common-mode signal will a pp ear

p re p aring to u se twoTe ktronix Ρ 6062 Α probes for differen-
in t
he display . T h e d esire d signal will
produce α dis p lay of

tial measurements in t h e 10 Χ mo de .
5d
ivisions, with not more t han 0 .1 division
of d is p lay
pro d uce
d by t h e common-mo d e signal (cmrr n ot s p ecifie
d
w h en resi d
ual dis p lay is 0 .1 d ivision or less)
.

α . Connect one probe for d c-cou p le d , si n gle-e n ded
operation to C H 1 + in put . Obtain triggere d d is p lay of
an app ropriate s quare wave, such as t h at from α calibrator
T here are α
n umber of factors w h ic h
can
degrad
e common-

or square-wave generator . Com p
ensate prob e s quare-
mode
re j
ectio n . T he princi p le requirement for maxim u m

wave response wit h p robe com p e n sation a dju stment-
re j ection is t h at t h e
com m on-mode signal ar r ives at t he input
FE T gates in p recisely
t
he
sameform . Α d iffere nce of
only
0 .01% in t h e atte nuation factors
of t
h
e in put atte nu ators

b . Connect
α secon d p robe for dc-cou p le dop eratio n
may re d uce t here j
ectio n ratio to 10,000 :1 .

L i k ewise, any

to C H 1 - in put .
Apply 100 volt p eak -to- peak sq uare
d ifference in source im p e d ance
at t h e two p oi n ts in t h e

wave to both pro b es . F ree-ru n swee pand a dju st p robe
source un d er test will
d egrade t he re j ection ratio . Atten u ator

com p ensation a d j ustme n t of secon d p ro b e for minim u m
p ro b es w h ic h
do not have ad j usta b le resistance
an dca p aci-

d is p lay am p litu de .
tance
may
red
uce t h e re j ection ratio to 100 :1 or less .
c . Steps ( α ) an d (b) matc h t he probes for use
at any
sensitivity t h at employs t he partic u lar input attenuator
(1 Χ
or 100 Χ ) used in steps ( α ) and (b) . Wh en it is
necessary to u se
t
h e
oth
er input atten u ator, steps
(
α
)
an d (b) s hou l d b e repeated .
d . R epeat steps ( α ), (b), and ( ε ) fo r C h annel 2 .
V oltage P robes

e . Wh en examining αsmall d ifferential signal in t h e
In general, probes offer t h e most conve n
ient means of

presence
of
relatively
large common-mo d
e components,
connecting
α signal to t h e in pu t of t he 5 Α 26 . Te k t r
on ix

ad j ust pro b e by temporarily connecting b ot h prob es to
eit h er of t h e two signal sources .

Deflection Factor
Cali b rated R ange
Accuracy
U ncali b rate d R ange
Fre q uency R es p o n se
Ban
d wid t h (8 Div R eference)
DC (Direct) Co u pled
1 MH z
10 kH z
AC (Ca p acitive) Co up le d
1 MH z
10 kH z
Ste
p
R es po n se
A b errations
Input R and C
M aximu m Safe Input
Voltage
DC (Direct) Co up le d
50 μ V /Div to 50 m V /Div
100 m V /Div to 5 V/Div
AC (Ca p acitive) Co up le d
50 μV /Div to 50 m V /Div
100 m V /Div to
5
V/Div
DC R e j ection
AC (Capacitive) Co up le d
Inp u t Gate Current
Common
Mo
d e R e j
ectio n
DC
(Direct)
Coupled
C h
aracteristics
50 μ V /Div to
50
m V /Div
100 m V /Div
to
5 V/Div
SPE
CI
F ICATIO N S
TA BLE 1-1
Electrical Sp ecifications
50
μ V / d iv
to 5 V/ d iv in α 1, 2, 5 seq u ence .
W it h in 2% of d eflection factor setting .
Variable VO L TS/DI V control p rovi d es con ti nuou sly
variable d eflectio n factor b etwee n cali b rate
d
settings
an d exten d s d eflection factor range
to 12 .5
V/
d
iv .
Dc to at least 1 MH z .
Dc to 10 kH z with i n 20% .
Performance R e qu irement
2 Hz or less
to at least
1
MHz .
2 Hz or less to 10 kH z wit h in 20% .
O p erating Instructions-5A26
+2°/ ο , -2°/ ο or less . Total not to exceed 4°/ ο ρ - p .
1 ΜΩ with in 0 .15% pa r allele d by
a p p
roximately 47 p F .
10 V ( d c + pea k ac) .
350 V ( d c
+
pea k ac) .
350 V do (co up ling ca p acitor pre-c h arge d ) 10 V p ea k ac .
350 V (dc + pea k ac) .
At
least 100,000 :1 after 20 min ute warmu p .
100 ρΑ or less
(100
μ V or
less dep ending
on exter n
al
loadi n g) at +25 ° C .
At least 100,000 :1 from do to 30 kH z with up to
20
V ρ - ρ
sine wave .
At least 300 :1 from d o to 30 kH z wit h up to 100 V
ρ - ρ sine wave .

Operating Instructions-5A26
Common M
ode
R e j
ection (continue d )
AC (Cap acitive)
Coupled
50 μ V /Div to
50 m V /Div
W it h2Ρ
6062
Α P
robes
Displaye d
N oise (Tangentially M easure d )
C h a n nel Isolation
at 1 MH z (Single- E n d ed)
C h a n nel
Isolation at 30 kH z (Common M
od
e)
Tempe r atu re
Altitu de
Sh oc k
Operati ng
Storage
O p erating
Storage
V ibratio n
Operati ng
Operating
a nd Storage
W eig h
t
Dime n sions
C h aracteristics
C h aracteristics
C h aracteristics
TA BLE
1-1 (CO N T .)
E lectrical Sp
ecifications
TA BLE 1-2
E
nvironmental S p ecifications
At
least 20,000 :1 at 5 kH z and ab ove, d ecreasing
to
not less t han 2000 :1 at 60 Hz .
400 :1 at 10 Χ p ro b e atten uation .
30μ V or less at full ban d wid t h .
At least 100 :1 wit h8d iv sine wave applie d to o n e
ch annel at 2 V /d
iv and oth er chan n el at 1 m V / d iv
with no signal
applied .
50 μ V or less at any d eflection
factor wit h 20 V ρ - ρ
si ne wave a p plie d to + an d - i nputs of eit her
c hannel .
0 ° C to +50
° C .
-55 0 C to +70 ° C .
To 15,000 F eet .
To 50,000 F eet .
TA BLE 1-3
Ph
ysical Specifications
See F
ig . 1-3, Dimensions .
P erformance R equ irement
P erformance R e q uireme n t
15 minutes alo ng eac hof
3 ma j or axes at α total d is-
placement of 0 .015 inc h wit h
frequency varie d from
10 H z to 50 H z to 10 H z in 1 minute
swee p s . H ol d
for 3 minutes
at 50 H
z .
All ma j or resonances must
be above 50 H z .
To 30 g's, 1/2 sine, 11 ms d uration, 2 sh oc ks per
axis in
eac h d irection for α total of 12 s h
oc
k
s .
Description
Ap p roximately 2 I b s, 3 oz .
(1
kg) .

ι
ι
σσ 0
00 (j
σσ
Νφ
σσσσ σσσσ 0
ι
°
000000
ο
F ig . 1-3 . Dimensio ns
.
Op
erating Instructions-5A26

ι
1
ι
ι
T h is sectio nof
t
h e
manual d escri b es t h e operatio nof t he circ u its in t he 5
Α 26 Dual Differe ntial Am p lifier unit .
Complete
sch ematic diagrams a nd
an overall b loc k d iagram of t he u nit are given
on pullout pages at t he b ac kof t h is manual . T h
e chann el
'

1 and channel 2
circuitry is essentially i d entical . T he following
bloc k d iagram and circuit operation d iscussio n s a p p ly
to
c h annel 1
with exce p tio n s i n clu ded w h ere applicable .
ι
Wh
en t h e DIS PL AY b utton is presse d , α
logic
level
is
a pp
lie d

T h e BW L I M IT 10 kH z switc h p laces α ca p acitor across t h e
'

to t
h
e oscilloscope to ena b le 5 Α 26 o pe r ation (switc h f u
nc-

two out p ut Ι ines to re d uce t h e ban d wi d t han d, t h us, limit
tion is
limited to operation i n α vertical d eflection
com p art-

t h e noise . T he signal is t h en p asse d to the Output Amplifier
ment)
.

t
h
roug
han
emitte
r -follower
isolation stage
.
'

Signals a pp lie dto
t h e
+
and - input connectors can be
p asse d d irectly
t
h
roug h t he i nput cou p li n g switch es to t h e
atten u ators ( d c
cou p le d ) or t h ey can be capacitively (ac)
couple d to block t h e do
component of th e signal . T h e GND
switch p rovi d es αgro u nd reference to
t he
P reamplifier
i npu t .
'

T h
e In p ut Atten uator consists of fre quen
cy-compensated
voltage d ivi d ers
.

1 Χ attenuation is p rovi d e d for t h e 50 μ
to
50 m p ositions of t he
V O L TS/DI V switch , and100 Χ
'

.

atte n uation is p rovi d
ed
for
t h
e
.1 to 5 p ositions . B alance
to α low-frequency common-mode
signal b etween t he
attenuators of t he two inputs is set by a dju
stment of t h e
i n ternal LF C MR
potentiometer .
C h annel
switch ing is accom p lis h e d by t h e p l ug-i n M OD E
bu ttons an d t h e
chan nel switc h signal from t h e oscillosco p e .
F rom t h e In p
ut Atte n uator, t he signal is p asse d d irectly to

E lectronic switch i ng p rovi d
es αd is p lay of eit h er or bot h
t h e Pr eam p lifier . T h e
inpu ts to t he P ream p lifier are fu se

channels ( du al-trace) . T heswitch ing
rate in d ual-trace
'

a n d d io de protected
.
T
he Pr eamp lifier consists of two

o peration is d etermine d by t he channel-switch
sig n al re p eti-
i d entical
operational am p lifiers connecte d in αd iffere n tial

tion rate from t he oscilloscope,
configuration . Common-mo
d e signals between groun d an d
t h e two in pu
ts
are
re j ected, d ue to α bootstra pp e d floating
p ower supply
t
hat
moves wit h t h e common-mo de signal
to

T he VO L
TS/DI V switc hcontrol is ma d e up of α series of
maintain consta n
t op erating c h aracteristics of t he active

cams and contacts t h at switch in pu t atten u ators, select t he
devices . T he d ifference
b etween t he two in pu ts is amplified .

pro p er gai n
-setting resistors in t he Gain Switc h ing Am p lifier,
'

T h e co n stant c u rrent
return facilitates t h e d o balance of t h e

and p rovi de the proper
crt readout d ata .
P reamplifier outputs .
'

F
rom t he P ream p lifier, t he
signal is cou p le d d irectly to t he
Gai n Switc h ing Amplifier .
Two
i
d
e
n tical o p erational ampli-
fiers an d α series- p arallel resistor
network provide t heprop er
'

gain for each VO L TS/DI V
switch setting .
T HE O R Y O
F O PER ATIO N
BL OC K DIAG RA M D E
SC
R
I P TIO N
Section 2-5 Α 26
T h e output diffe r e n tial
am p
lifier
is o p erate d push-pull,
presenting αsig n al to t h e
outpu t terminal t h at is of t h e same
p olarity as
t
h
at a
p
plied to the P ream p lifier in put . T he
front-panel V ariable VO L TS/DI V (CAL ) an d internal gain
controls provi de α means of varying t he gain of t he 5 Α 26 .
Α p
ositioning-current d river is co n necte d to t he ou t put lines
to alter t heq uiescent trace p osition .
Α
triggering signal is tap p e d from t h e emitter-follower isola-
tion stage,
amplifie d an d ma d e available to an associate d
time-base p
lug-in u n it . Triggering signal am p lit u de is abo ut
0.25 volts p er d is p laye d d ivision .
E ither of two lam p bulbs be h i nd t hek
no
bsk
irt on the
VO L TS/DI V switch ill u minate
t he selecte d d eflectio nfacto r .
One lam p lig h
ts
for
1 Χ deflectio n factor ; t h e ot h er lig h ts
w h en α rea d
out-code d p robe is attac he d to t he+ or - input
con n ectors to in
d icate α 10 Χ deflection factor .

T heory of Operation-5A26
CI R C UIT
O PER ATIO N
Circuits
uni q ue to t h is i nstrumen t are descri b e d
in d etail in t h is discussion . Circ u its commo n ly use d
in
t
he electronics in d ustry
are not d escribe d in d etail . If more information
is desire don t h ese co m monly u se d circ
u its, refer to t h e following text b oo k s .
Ph illi p Cutler, "Semicon du ctor
Circ u it Analysis", M cGraw- H ill, N ew Yor k , 1964 .
J acob M illman an d H e r bert Taub, "
P ulse Digital an d Switc h ing W aveforms",
M cGraw- H ill, N ew Yor k , 1965 .
Al b ert Paul M alvino,
"Transistor Circuit Ap p roximations", M cGraw- H
ill, N ew Yor k , 1973 .
Gor d on V . Deboo, "Integrated
Circ u its and Semicon d uctor Devices",
M cGraw- H ill, N ew Yor k , 1971 .
L loy dΡ . H unter (E d .), "
H
an
d b
oo
k of Semiconductor E lectronics", th ir d ed itio
n
,
M cGraw- H ill, N ew Yor k , 1970 .
T h e n umbers insi d e t he d iamon d s after α h ea d
i ng refer to t h e sc h ematic diagram
for
t
h at circ u it locate d at t h e back of t
h
is
man u al .
ι
ι
ι
1
ι
ι
ι
PRE A MPL I F I ER

1 Ο

In p ut
Attenuators
T
heInp u t Attenu ators consist of fre qu ency-com
p e n sate d
ΡΙυ g- Ιη L ogic

voltage
d ivi d ers t h at p rovi de 100 Χ atte n uation
in t h e .1 to

,
Wh en DIS PL AY button is
presse d ,
α
logic level is

5p
ositions of t h e VO L TS/DI V switc h . F or do and low-
applied to t he electronic switc
h ing circuit in t h e oscillosco p e

fre
quency sig n als, t he d ivi d ers are esse n tially resistive
to en able plug-in o p eration . P
ower
is a pp
lied to ill umin ate

(attenuation
ratio d etermi ned by t h e resistance
ratio) .
t h e VO L TS/DI V knob s
k irt b e h in d t h e p ro p er d eflection

B alance
between t he atten u ators of t he two inputs
for
low-
factor w hen t he M OD
E bu tton is p resse d in .

fre quen cy common-mode signals is set by a d j usting
R 9, LF
C MR . At h ig h er fre q uencies, t he ca p
acitive r eacta n ce
b ecomes effective and t h e im p
edance ratio d etermines t h e
Input Cou p ling

atten u ation .

6'
Signals a pp lied to t
h e front-panel
+an
d - i npu t connectors
may b e ca p acitive couple d (ac), d irect coup le d ( d c) or
internally grounded t h roug h α capacitor and resistor .
Input

In a dd ition to providing constant
100 Χ attenuation at all

'
coupling is selecte dby means of two pus h bu tton
switc h es

fre qu encies with in t h
e
b an dwidth
ca
p
abilities of t he instr u -
at
each in pu t ; S2C an d D for t he
+
input an
d S2A and Β for

ment, t h e In p ut Atte n uator
maintains α constant in p ut R C
t h e - inp u t .

ch aracteristic (1 mego
h m paralleled b y about 47 p icofara
d s)
for
t
h e .1 to 5p ositio n s of t h e VO L TS/DI V switc
h .
Α signal a pp lie d to t h
e + inp u t wit h b ot h bu ttons in t he out
position ( d c cou ple d ) is p asse d
directly
to
t h e Inpu t Atten u -

In
p ut
P
rotection
ator . Wh en t he AC bu tton
is p resse d i n, C12 is place d in

I
n p
ut p
rotection consists of f u ses F 20 and F 30
and dio d es
t h e circuit to ac couple
signals of abou t 2 h ertz (-3 d B

C R 21, CR 24, CR 31, and CR 34 . If th e
signal s h o u ld reac h
point) andh ig h
e r
to
t h e attenuator . Ca p acitor C12 bloc k
s

α level s u fficient to forward b ias one of t he p
rotection dio d es
any do component
of t he signal . Wh en t he GND bu tton is

(
α potential greater t h a n about 12 .5 volts),
cu rrent will be

,
p resse d in,
α groun d reference is p rovi ded to t he inp u t of

con
d ucted t h ro u gh t h at d io d e, p rotecting t
h e inp u t FE'r"
.
t he
amplifier wit h o u t t h e need to remove t h e app
lied signal

If t h at curre n t s h oul dexceed t h e fuse
rati n g, t h e f u se(s) will
from t he
i np
ut
connector .

open .
2-2
NOTE

P ream p lifier
Wh en ac
coupled with do levels of 10 volts or

T h e Pream p lifier consists of two i d entical op
erational
mo r e, bot h t
h e Α Cand G N D b u ttons should

amplifiers connecte d in αd ifferential
config u ration .
b e p r essed in (PRE C H G) w h ile inputconnec-
tions are made or brok en, or w h en voltage
levels are c h anged .

This allows t he co u
pling

Th e op erational amplifiers con sist of 054A,
Q60A, and
capacitor to c ha r ge without opening
t h einput

Q64A on t he - inp u t
side, and 054 Β , 060 Β an d Q64 B on
f u ses or overdriving t
h e amplifier .

t h e + i np ut si d e .
Transistors Q54A a n d 054 Β provi de α

.
` ι

ι
ι
ι
ι
ι
ι
ι
ιι
ι
ι
ι
ι
ι
ι
To minimize trace s h ift as d iffere n t vertical deflection factors
are selecte d , t he o ut pu ts at t h e Q64A and Q64 B collectors
are do balanced at equal p otentials so t hat the voltage across
t
h e gain-setting
resistors in t
he Gain-Switc h ing Am p lifier is
zero at all settings of the VO L TS/DI V switc h .
T h
is do
balancing is ach ieve d by a dj usting R 89, Atten ΒαΙ R ange
an d R 72, ST EP ΑΤΤΕΝ B A L
.
Common-
M
o de
R
e j ection
F loating P owerSupp ly
Α F loating P ower Supply consisting of Ο 39, Q44, Q48, and
Ze n er d io d es VR 40 an d VR 42 mi n imizes i nherent common-
mo d e d iffic u lties an d , t h erefore, im proves t h e common-mo de
re j ection ratio (refer to F ig . 2-1 ) . Transistor Q44 is α
constant-current h ig h -impedance sou r ce, and Q39 is t he
current retur n .
Gain-Switc
h
ing
Am p lifier
Th eory of Operation-5A26
'

voltage follower in put to
outp
u
t
transistors Q64A
and
Q64 B constant op erating c h aracteristic of t he elements in t he
w h ile Q60A provi d es a dd itional open-loop gain . Total gain

P ream p lifier stage . Since no common-mo de signal c u rrent
'

of t h e stage is determine d by R 58 and R 18 between t he two

is
d eveloped ,
t
heoutpu
t at
t h e collectors
of
Q64A
an
d Q64 B
amplifiers, and resistors R 64 an d R84 .

remains u nc h ange d ; t h at is, t h e common-mo d e signal is
re j ecte d .
Quiescently, t h e two si d es of t he am p lifier are balance d .
Wh en α d iffe r e n tial signal is a p plie dto t h e gates of Q54A

V ariable capacitor C59, H
F
C MR, is ad j usted to normalize
a nd Q54 B , sig n al cu rrent is develo p ed t h roug h resistors R 58

t he
effective
capacitance of t
h e
active devices on
one si d e
an d R 78 . Cond u ction of Q64A an d Q64 B is ch ange d by

of t h
e
am p lifier to t heoth er .
t h e amount of signal current with t he o utpu t voltage develo p -
ed across R 64 and R 84 . T h e out pu t is α push-pull signal,
op p osite in p olarity to t he signal a pp lie d to the in pu ts .

O U T PU T A MPL I
F
I ER S

2 Ο
T
he Gain
-Switc h ing Am p lifie r consists of two
i den tical
o p erational amplifiers .
T he o
p
erational am p lifiers consist
of
Q205A,Q208A, an d
Q21 OA
on t
h e - in
pu t si de an
d Q205 B ,
Q20813, and Q21OB
on the
+input
si d e . Total gain of t
he
stage
is determine d by
R
210,
R 220
a
nd t he setting
of
the VO L TS/DI V control
w h ic h selects t h e series- p arallel combi nation of R 203, R 213,
an
d R 228 t hrough R 236 .
One of t h e primary functions of t h e P reamplifier is to re j
ect
any
common-mode com p onent of th e in pu t signal
an
d
am p lify only t he d iffe r ence . Assume t h at the in p uts are tie d

P otentiometer R 225, V ar ΒαΙ 1, located in t h e collector
togeth er and α voltage is ap plie d to t he commo n input . T h e

circ
u
it of transistors Q21 OA, an d Q21 013, is a d j uste d with
amplifier d
iffere n tial out p ut is i d eally zero, and wo u l d no
inpu t signal
to
set t he voltage across t he V aria b le V O L TS/
actu ally be zero provi
d
e d t h at t he ch aracteristics
of all

DI V control, R 264, in t he O u t put Am p lifier stage to zero
corres p on d ing elements on t he two si d es of t h e am p lifier

volts . W it hbot h sides of t he am p lifie r balance d , trace
werematc h e d (e .g ., Q54A an d Q54 B transcon du ctance an d

d eflectio n is p revente d as t he V ariable V O L TS/D I V co n trol
μ ,
Q60A an d Q60 B beta, c urrent sou rces, etc .) . In practice,

is rotate d t h ro ugh out its range
.
any mismatc h will
cause αd
ifferential
output .
N ormally, t h e frequency response of t h e Gain Switc h ing
Am p lifier is from do to at least 1 mega h ertz, h owever, for
low-frequency a pp licatio n s w h ere h ig h i nput sensitivities
are u se d , t h e overall fre q u ency response can b e limite dto
abo u t 10 k ilo h ertz to re d uce n oise referred to t h e in pu t .
T h is is ach ieved by pus h ing in t he BW L I M IT 10 kH z switch ,
S239, w h ic hco nnects C239 across t he out p ut of t h e Gain
Switc h ing Am p lifier-
T h e in pu t to t h e bootstrap ( Χ 1 gain) am p lifier is connecte d

Isolation Stage
'

to the j unction of R 58 and R 78 . T he bootstra p amplifier

T
he
d ifferential signal d evelope d at t
h
e collectors of
Q210A
p ortion of t he supp ly co n sists of emitter-follower 048 and

an d Q210 B is passed t hroug h emitter followers
Q242
and
do level-s h ifting Zener diodes VR 40 an d VR 42 . T he collec-

Q252 to t he Out pu t Am p lifier . Transistors Q242 an d Q252
'

f or im p e d ance of Q39 presents minimum loa d ing to t he

isolate t he Gain Switc h ing Amplifier from t he loa d ing of
Q48 out p ut a nd maintai ns t he gai n of t h e am p lifier (boot-

t he Output Am p lifier a n d Trigger Amplifier .
stra p efficiency) very close to one .
Out p ut Am p lifier
T h e entire p ower s u pply an d am p lifier voltages move an

The
Output Amplifier consists of push-pull amplifiers 0260
amount equ al to t h e common-mo d e voltage to maintain α
and Q270 . W it hα sig n al applied, pote n tiometer R 273,Gain 1,

T h eory of
Operation-5A26
provides emitter d egeneration
.

T h e gain is d etermined
by

Ch annel Switching

I
t h e total emitter
resistance w h ic h allows the overall gain of

Channel switch
ing is accomplis hed by Q282,Q292, Q286
t he 5 Α 26 to be ad
j
usted
to matc h t he mai n frame re qu ire-

and Q386 . T h e c hannel
switc h sig n al from the m ai n frame
ments . Also, t he V aria b le VO L
TS/DI
V
con trol, R 264,

th roug h p in Β 21 sets t h e b ias
on
Q386
w
h
ile t he bias on
p rovi d es continuo u sly variable gain to 2 .5 times t he calibra-

Q286 is d etermined by t h e M OD E butto n s . T h e bias level
te d d eflectio n
factor setting .

at t h e base of
Q286 relative to t h at at t h e base of Q386
d etermines w h ic h
of t h ese transistors is on . W it h t he C H 1

,
M OD E bu tton
pressed i n a nd t he C H 2 M OD E bu tton o u t,
Transistors Q267 and Q277 are p
ositioning-curre n t dr ivers .

the b ias level
on
Q286
is lowe r (more negative) t h an t h at at
P osition ( P OS) control, R 274, p rovi d
es an ad j ustable

Q386,
w h ic h tur n s Q286 off a nd
Q386 on . W it h Q286
c h ange i n t h e con duction of t he
transistors to provide α

turned off, +5 volts do t h roug h R286
reverse-biases d io d es

'
curren t t h at eit h er a dds to
or sub stracts from t he Q260-0270

CR283 and CR 293, w h ic hturns
on
Q282
an d Q292 i n t h e
cu rrents to alter the q uiesce nt vertical p osition
of t
h e
d is p lay .

channel switch
stage
.
T h
us,
t h
e ch
annel 1 signal is co upled
to t he mainframe t hr oug h interface
connector p ins Α 7 and Β 7 .

I
+30 V
+30 V
F
ig . 2-1 . F loati n g P ower Supply d etailed
bloc k d iagram sh owing stan d ing c ur re n t p at h s t hr o ugh t h e P
reamplifier .
ι
ι
ι
lei
ι
ι
ι
ι
ι
ι
ι

Wh ile
Q286 is off, Q386 is on an d d raws current from
t
he

tion factor to p r
ovide α d ir ect rea do ut . N ormally, DS421 is
+5 volt d o su pp ly t hrough R386 . T he resultant voltage

lit to indicate α
1 Χ d eflection factor . Co nn ecting α rea do u t-
across
R 386 turns off Q382 an d Q392 i n t he C han nel Switc h co ded 10 Χ prob e
to eit her inpu t (wit h t h e GND bu ttons
stage . T hu s, t h e
ch annel 2 signal is n ot co up le d to t he

out) a u tomatically
ch anges t he crt r eado ut b y αfactor of
mainframe .

10 an d lig h ts DS417
to indicate α 10 Χ d eflection factor .
Wh en t h e CH 2 M
OD
E
button is p resse d i n, t he bias level
on Q286 is h ig h er (less
negative) t h a n t h at at Q386, w h ic h
t u rns Q286 on an d
Q386
off .
T he con d itions d escribe d for
t h e c hannel 1 mo de are th en
reversed .
T h eory of
Operation-5A26
W it h α 10 Χ rea
d out-co d e d p robe co nn ected
to
the - input,
t he pr o b e-cod ing resistor
is con necte d in p arallel wit h R410
t h roug h t h e probe-co d i ng
ring . T h e pro b e resistor biases
Q417 on, w h ic hturns
on
in d icator
DS417 . Conse q ue n tly,
Q421 t urns off and exti ngu is hes in d icator
DS421 . T he
probe-cod
ing resistor i n p arallel with R
410 also
c
h an ges t h e
b
ias on Q450 w hic hch anges t h e crt rea
d out . Wh en t he
DIS PL AY
button is ou t, illuminating voltage is remove
d
from i n d icators
DS417 an d DS421, and 0484 is gate d off .
T h us, i nd icators DS417
an dDS421 are extingu is he d , an d
t h e crt reado u t is b lan k
ed .
F
or d ual-t r ace op eration (b ot h CH 1
and CH
2
M OD E
bu ttons pus h e
d in), α 0 to +5 volts repetitive signal is
a pp
lied
from t h e mai n frame to t heb
ase of Q386 t h roug h p in Β 21 .
T hu s, t h e bias level on Q386 alternates
above a n d below t h e
b ias level
on Q286 w h ic hturn s
on
ch annel 1, t hen c
ha nn el
2, at α rate d
etermine d by t h e re p etition rate of t he c h
ann el
switch signal at
p
i
nΒ21 .
W it h α 10 Χ rea d ou t-co d e d p
ro
b
e connecte d to t he+ in pu t,
R 413 f un ctions t he same
as
R
410 i n t h e - in pu t circ u it .
Trigger Amplifier

T hu s, α 10 Χ rea d out-code d p ro b e
connected to eit h er or
Differential am p lifier Q245 and
Q255 receives t h e triggering

both
in p uts will p rovi de α
10 Χ reado u t on t he VO L TS/DI V
signal from t he emitters of Q242
and Q252 in the isolation

k nob s k irt an don
t h
e
crt .
stage of t h e Output Am p lifier . T h e
triggering signal is
am p lified
and
passe d t h ro u gh
T R IGGER switc h S401 to
transistor Q404 w here
it is m ade availa b le to an associated

When p r esse d i n, contacts
of
GN
D switch es S2D (+ in pu t)
time- b ase unit via pin Α 4 . T
he triggering signal is of t h e

and S213 (- in pu t) open t h e
circuit between t h e
+
and -
same polarity as t h at a pp lie dto the
gate of
Q54
B an d h as

in pu t prob e-coding rings
and t he rea d ou t circ u itry . Co n se-
αη amplitu d e of abo u t 0 .25 volts per displaye
d d ivisio n .

qu
ently, with α rea dou t-co d e
d pro b e connecte d to bot h
inputs an d both
+
απd -G ND b
uttons p resse d in, t he
V O L TS/DI V k no bsk irt and crt
will i nd icate α1 Χ d eflection
V ertical Switch ing

factor . If only one of t h e GND buttons
is p ressed in, t h e
V
O L TS/DI V k nob s k irt and crt will in d icate α
10
Χ
deflection
V OL TS/DI V switch S20 co n tains α series
of cam lo b es

factor .
w h ic h engage an d d ise n gage vario u s
contacts at different
positions of t h e switch . Cams 1, 2, 4,
a nd 5 control switch -
i n g of t he In p ut Attenuator
an dcams 11 t h ro ugh 19 control

If t he probe-co d i ng ring
on t
he +
or - in p u t connector is
switch i n g of gain-setting networ k
resistors R 228 t h roug h
groun ded , DS417 lig h ts
to indicate α 10 Χ d eflection factor
R 236 in t he
Gain-Switc h ing Am p lifier stage . T h
ose co n tacts

an d t he crt rea dou t is extingu
is
h
ed . T h
ecr
t r ead o u t is
t h at are engaged
at any VO L TS/DI V switchposition are

d etermined b y
t h e VO L TS/DI V control w h
ic
h
esta b lis h es
s h own
by blackd ots on t h e switch logic diagram .

t h e b ias on Q458,
Q466 and Q474 . C h anging t h e bias
on
t h e base of t h ese transistors
also ch anges t he emitter voltage
t hereb y ch angi n g t he voltage across
t
h eir
associate d emitter
RE ADO U T

3 Ο

resistors . T he current d rawn
from pi n Α 28 t h ro ugh Q458,
Q466, or Q474 and t h eir
associate d emitter resistors d ete r -
Deflection F
actor ( VO L TS/DI V K nob S
k irt and
mines t h e crt rea d out .
CR T)
E
it
h er
of two lamp bulbs (DS417
or D5421) locate d be hin d
t
he
VO L TS/DI V k no bs k irt illuminate
t
he
selected d eflec-

REPL AC E A
BLE
ELE CT R ICA
L P A R TS
PA R TS
ORDERING I NF
O
RM ATIO N
R e p lace m e n t p arts a r e available from o rt hroughyour local Te k t r on
ix, I n
c .
Fiel d Office
o
r
re p rese
n tative .
C h a n ges to Te k tro n ix i n str u me n ts a
r
e someti
m es ma de to accommo d ate i mp rove d
com pon e n ts as t h ey beco m e availa b le, a nd to give you
t h e be n efit o f t he latest ci r cu it
improve m en ts develo ped i n o ur e n gi n eeri n g de p a r t m e n t . It is t h erefo r e im p o
r tant, w h
e
n
or d eri n g pa r ts, to i n cl ud e t he followi ng i n fo rm ation i n yo u r o rd e r : Part nu
m
ber,
i n st rum en t
ty p e or numbe r , serial nu mbe r , a nd m o d ificatio
nn
u
m
be
r if a p plicable .
If α part you h ave ordere dh as been re p lace
d wit hαn ew or i mpr oved p a r t, your local
Te k tro n ix, Inc . Fiel d Office o
r r
ep
rese n tative will con tactyo u co n ce rn i ng any c h a n ge i n pa r t
num b er .
C hange
i
n
for m atio n , if
any,
is locate d at t h e rea r of t h is ma nu al .
S
PE CIA L N OT E S A N D SY MB O L S
ΧΟΟΟ

Pa r t fi r st a dd e d at t h is serial numb e r
ΟΟΧ

Pa r t removed afte rt h is serial number
.
ITEM NAME
In t h e Parts List, an Item Na m e is se p a r ated
f r
om
t he desc r i p tio nb yα colon ( :)
.
Because of s pace li m itatio n s, an Ite m N a
m
e
may sometimes a pp ea r as i n com p lete . Fo r
furt h e rIte mN a m e i d en tificatio
n ,
t
h
e U .S . Fe
d e r al Catalogi n g H a nd book Η 6-1 ca n be
utilized w h ere p ossible
.
ABBREVIATIONS
ACT R ACT U ATOR

PL STC PL ASTIC
ASSY ASS EMBL Y

QTZ Q U A R TZ
CA
P CA P ACITO R

RE C P RE C EP TAC LE
C ER C ER A M IC

RE S RE SISTO R
C K
T

CI
R
C U
IT

RF

R ADIO FRE QUEN CY
CO MP CO MP OSITIO
N

S EL S ELE CT E D
CO NN CO
NNE
CTO
R

S EM ICO N D S EM ICO N D U CTO R
EL CT LT ELE CT R O L YTIC

S EN S
S EN SITI VE
ELE C ELE CT R ICA L

V A R V A
R
IA
BLE
I N CA N D I N CA N D E SC EN T

WW

W
I REW
O UN
D
LE D

LIG H T EM ITT J N G DIOD E

X FMR

T R A N S F O RMER
N O NW I R

NON W I REW O UN D

XTA L

C R YSTA L
Section 3-5Α 26