Tektronix 7a15 User manual

1 Ν
E3-rFt U CT1C> Μ
ΜΑΝ
V
A L
Se
r
ial Nu m ber
Tektronix, Inc . " Ρ . Ο .
Box
500 " B
eave
r
ton, O r egon 97005 " Ph
o
n
eό
44-0161 "
Ca
b les : Te k tr onix
070-1044-00

670

WARRANTY
All
Tekt r
onix ίη 5tr ιι r η eη t5 are war r a
n
te
d
against-
defective
m
ateriais and workmanship
for one year,
Tektronix
'transfo r
m ers, manufactured
in' o u
r
plant,
are wa r rante d f or
t h e life of the
instrument,
Any
μιι estions
wit h respect to t h e
warranty,
mentioned above -s
h oul d - be ta k
e
n
up'' with your
Tektronix F iel
d Cnginee ι o r Repre'sentativ? .
All
r equests
for re p ai r s and r eplace n ι ent p arts
should
b e di
r ected to t h e Te k t ro n i x Fiel d
Office or
repr esentative
in your area,' This p roce du re
w
ill
assure
yo u
the
fastest
possible ser v ice . P lease include the
instrument Type (or
P
art R lτι r r i b er3 - αη dSer i al
o
r
M o d el
Number ινίΙ h all requests for
parts
or
service .
S p eci f icatio n s an d p rice change
privileges reserve d .
Copyrig h
t 0 1970 by Te k tro n ix, I nc ., B
ea v ertoη , -
O r egon .
Printed . i n t h e U nite d States of America .
All
rig h
ts rese rve d . Contents of t h is
publication
may n ot
be reprod u
ce
d i n
any form-without permiss i on of t h e
co p yrig h t owner :, :. ", .

TABLE OF
CONTENTS
Page

Page
SECTION 1

SPECIFICATION

SECTION
5

PERFORMANCE CHECK/CALIBRATION
Introduction

1-1

Introduction

5-1
Electrical Characteristics

1-1

Test Equipment
Required

5-1
Environmental Characteristics

1-2

Short-Form Procedure
and Index

5-2
Physical Characteristics

1-2

Performance Check/Calibration
Procedure

5-4
SECTION 2

OPERATING INSTRUCTIONS
General

2-1

SECTION 6

ELECTRICAL PARTS LIST
Installation

2-1

Abbreviations and Symbols
Front-Panel Controls

2-1

Parts Ordering Information
First Time Operation

2-1

Index of Electrical Parts List
Control Setup Chart

2-2
General Operating Information

2-4
Basic
Applications

2-5

SECTION 7

DIAGRAMS AND MECHANICAL PARTS
ILLUSTRATIONS
SECTION 3

CIRCUIT
DESCRIPTION
Introduction

3-1
Block Diagram
Description

3-1
Detailed Circuit Description

3-1
SECTION 4

MAINTENANCE
Introduction

4-1
Preventive Maintenance

4-1
Troubleshooting

4-2
Corrective Maintenance

4-5
Instrument Repackaging

4-8
Mechanical Parts Illustrations
Instrument Repackaging
SECTION
8

MECHANICAL PARTS LIST
CHANGE INFORMATION
Mechanical Parts List Information
Index
of Mechanical Parts Illustrations
Mechanical Parts List
Accessories
Abbreviations and symbols used in this manual are based
on or taken directly from IEEE
Standard 260 "Standard Symbols for Units", MIL-STD-12B and other standards of the
electronics industry . Change information, if any, is located at the rear of this manual .

7
Α 15

Intro d uction

TABLE 1-1 (cost)
The 7
Α 15 vertical amplifier p lug-in unit is d esigne d for
u se with Tektronix
7000-series Oscillosco p es . The

7A15 is α

Characteristic

Performance
wi d eband general purpose
am p lifier, with t he upper fre-

Freq uency R esponse

7500-series

7700-series
q uency limit d
etermine d mainly by the oscillosco p e
in

System De pend ent

Oscillosco
pe

Oscillosco p e
which it is u se d . For exam
p le, the 7 Α 15 use d with t he 7504

Up p
er Ban dwidth

60 MHz

75 MHz
oscilloscope will h ave αSystem
Ban dwidth of 60 mega-
hertz ;
an d when use d with t he
7704 oscilloscope, the

(DC Coupled)
system
bandwidth will be 75 megahertz . Α P OLARITY

Lower
Bandwi d th
switch
provides α means
of inverting the d is p lay . The 7 Α 15
can be operate
d
in any p lug-in com partment of the 7000-

(AC Cou p le d )
series oscilloscopes .

W
ithout
P
robe

2
h ertz or less
This instrument will meet the
electrical characteristics
listed in Table 1-1 following
complete calibration as given
in
Section 5 . The p erformance
check proce d ure given in
Section
5p rovi d es α convenient method
of checking instru-
ment p
erformance without making internal
ad justments .
SECTION 1
S PE
CI
F I
CA ΤΙΟΝ
Ch ange
information, if any, affecting t h is section
will
be found at t h e rear of t he man u al .
The following
electrical characteristics are valid over
the

Capacitance

20 picofara d s within 1 .5 p icofarad
state d environmental range
for instruments calibrate d
at an
ambient tem p erature of
+2 ρ° ς
to
+30°C,
and after α
five

R
an d CP roduct

W ithin 1°/ ο over all d eflection factor
minute warmup unless otherwise
noted .

settings
Deflection
Factor
Calibrate d R ange
GAIN
C
h aracteristic
Gain R atio
Accuracy
Uncalibrate
d
(Variable)
TABLE 1-1
ELECTRICAL C HARACTERISTICS
P erformance
5 mV/ d iv to 5 V/d iv ; 10 ste p s in α
1, 2, 5 se q uence .
W ithin 2% of GAIN ad juste d at 10
mV/ d iv .
W ith Ρ 6053 P robe
Ι
0 .2 h ertz or less
Maximum Input

500 V (DC + Peak AC) .
AC com-
Voltage

I
p onent 1 kHz or less .
In p ut R an d C
R esistance

1 1 megohm within 2°/
ο
7 Α 15
Maximum Input

0 .5 nanoam p ere or less, 0 ° C to
Gate Current

~
+35°C .
2 nanoam p ere or less, +35 ° C to
+50 ° C .
Displaye dN oise

0
.06
division
or less at 5
mV/
d iv
(Tangentially

measure d in 7700-series oscillo-
Measured) scope .
DC Drift
Drift
W ith Time
(Ambient Tem-
perature and
Line Voltage
Constant)
Continuously variable b etween cali-
brated ste p s ; exten d s d eflection
factor
to at least 12 .5 V/ d iv .
Short
Term

250

microvolts/minute

(P-P)

or
P ermits a
d justment of d eflection

0 .05 d ivision (whichever is greater)
factor
for
all 7000-series oscillo-

in
any one minute, after one h our
sco p es .

warmu p .

Specification-7A15
Characteristic
Long Term
Drift With
Ambient Tem-
perature (Line
Voltage Constant
TABLE 1-1 (cont)

TABLE 1-2
ENVIRONMENTAL CHARACTERISTICS
Performance
250 microvolts/hour (P-P) or 0 .05
division (whichever is greater) in
any one
hour, after one hour
warmup .
Refer to the Specification for the associated oscilloscope .
100 microvolt/degree centigrade or

TABLE 1-3
less .

PHYSICAL
Fits all 7000-series plug-in compartments .

SECTION 2
OPERATING
I NSTRU CTIO N S
Ch ange information, if any,
affecting this section will b e found at t h e rear of
this
manual .
General

ID EN TI F Y

Wh en p
resse d , d eflects trace up-
The 7 Α 15 vertical p l u g-i n units o p erates with α Te k -

war d for i d
entification andc h anges
tro n ix
7000-series oscillosco p
e
and
α7Β __
series time- b ase

CRT

rea d out

to

t he

word
u nit to form αcomplete oscillosco pe system .
To
effectively

"ID EN TI F Y" .
u se t he 7 Α 15, t h e op eration an d ca pab ilities
of t
h e instru-
ment s h o u l d b e k nown . T h is section d escribes th e o p eration

P O L A R ITY
of t he front-panel controls, gives first-time op eration and
general o p erating information, and lists some measurement

+
UP

Α ρο p itive- ce s α signal
at t he IN-
PU T

ro du s

p ositive d
eflection
tec h ni q ues using t he am p lifie r .

on t he CRT .
Installat i on

INVER
T

Inverts d is p lay . Α negative-going
The 7 Α 15 is d esigne d to operate in α vertical plug-in

signal at t h e IN PU T pr odu
ces α
compartment of Te k tronix 7000-series oscillosco p es . F or

positive d eflection on t he CRT .
Χ -
Υ
o p eration, t h e 7 Α 15 may also be installe d in α h orizo n -
tal
p
lug-in com p artment (refer to th e Oscilloscope Instruc-

CO
UPL I NG
tion Manual for i n formation on Χ - Υ op eration) . To install

AC

Ca p acitively cou p les t he in p ut sig-
t
he 7
Α 15 into α plug-in compartment, p us h it i n u ntil it is

ηαΙ to t he vertical am p lifier .
seated flus h against t he front p anel of the oscillosco p e .
To
remove, pull the release latc h to d isengage t he 7 Α 15 from

GND

Disconnects the in p ut
signal fr o m
t h e oscillosco
p
e .
Continue to pull t he release latc h to re-

t he am p lifier andground s t he
am
move
t he u nit from t he oscillosco pe .

p
lifier

in p ut .

Allows

the

in p
ut
coupling ca p acitor to be ch arged to
t he DC voltage app lied to the IN-
FRONT P A NEL CO NT R O LS

PU T conn ector .
All co n trols re qu ire d for operation of t he 7 Α 15 are lo-

DC

T he signal is
directly cou p le d to t he
cate d on t h e front panel of t h e unit . Α brief d esc r i p tio n of

am p lifier .
t he function or op eration of t he front p anel
controls
follows . M ore d etaile d infor m ation is given und er
General

GAIN

Screw d
river ad j ustment p ermits
O p erating I n formation .

A dju stment

cali b ration
of d eflection factor .
VO L TS/DI V
Selects calibrate d vertical d eflection
factor from 5 m V / d iv to 5 V / d iv in
α 1, 2, 5 se quence
.
VA RIA BLE

P rovides uncalibrate d varia b
le
d
e
( VO L TS/DI V )

flection factors . E xten
d
s
t he
h ig h est d eflection factor to at least
12 .5 V / d iv . P us h k nob in an d
re-
lease to activate ; the k nob moves
outwar d from t he VO L TS/DI V
control w h en activate d .
VA R B A L

Screw d river a dju
stment p ermits
A d j ustment

b alancing
of the am p lifier for
minimum
trace s h ift w h ile rotating
t he VA R IA BLE
control .
I
N
PU T

BN C connecto r for applying exter-
Connector

ηαΙ signals .
General
FIRST-TIME O PER ATIO N
7 Α 15
Wh
en s h ippe d from t he factory, t he 7 Α 15
h as been cali-
P OSITIO N
Controls vertical p ositio n of oscillo-

br ate d
to meet the s p ecifications listed in
Section 1 and is
sco pe d is p lay .

rea d y
to be u se dwith an in d icator oscilloscope .

Operating Instructions-7A15
T h e following ste p s d emonstrate the basic op eration of
t he co n trols of t he 7
Α 15 . It is recommen d e d t h at t h is pr o-
cedure be
followe d
com
p letely for familiarization with t he
instrument . O p eration of t he oscilloscope an d time-base
unit is d esc r i bed in t he instr u ction ma nu al for t h ese units .
Setu p I n formation
1 . I n sert t he 7 Α 15 i n to α vertical p
lug-in com p artment
of α 7000-series oscilloscope .
2 .
Insert α 713--series time- b ase unit i n to α h o r izo n tal
p lug-in
com partment .
2-2
3 .
Set t
he
controls as follows :

Fig .
2-1 . Oscilloscope dis p lay w h e nch ec k ing amplifier Gain .
7 Α
15 ( L eft V ert com p artment)
P
OSITIO N

Midrange
POLARITY +UP
VO
L
TS/DI V 10 m V
CO
UPL
I N G DC
VA R IA BLE
CA L IN
713511 ( Β H oriz com p
artment)
L evel/Slo p e

Ce n tere d on p ositive slo
p e
Triggeri ng
Mo de

Ρ - Ρ A u to
Coup ling

AC
Source

I n t
Time/Div

1 ms
Variable (Time/Div)

Cal In
M agnifier

Χ 1
ΒDelay
Mode

I ndepen d ent
P osition

Mid range
7504 (Indicator
Oscillosco p e)
V ertical Mo de

L eft
Horizontal Mode

Β
Β
Intensity

CCW
Calibrator

1
kH
z,
40 mV
Β Trigger So u rce

L eft Vert
4
. Connect t he oscilloscope to
αp ower sou r ce w h ic h
meets
t he voltage an d frequency re q
uiremen ts of t h e oscil-
loscope power su pp ly .
7 . Co nn ect
t
he
Cali
b
rator ou t pu t to t h e 7 Α 15 INPU T
conn ector .
8 . C h ec k t he C R T d is p lay for fo u r d ivisions of vertical
deflection (see Fig . 2-1) . If necessary, ad j ust t he fro n t
p anel
GAI N for fo u r d ivisio n s of vertical d eflection .
9 . P ress the ID E NTI F Y b
utton an dch ec k t h at the d is-
play moves
u p ward about 0 .3 divisions . Also ch ec k
t
h
at the
rea dout information
on the
C RT is replace d by the wo r d
"ID EN TI F Y" .
10 . P ress and release the VA R IA BLE control to its out-
ward p ositio n . Turn t h e VA R IA BLE control fully cou nter-
cloc k wise, and ch ec k for 1 .6 d ivisions or less d is p lay am p li-
tude . P ress t he VA R IA BLE control to the CA L IN p osition .
11 . C hange t he VO L TS/DI V to 0 .1 V, Calibrator Volts
to 0 .4 V an d t h e Triggeri n g Sou rce to Ext . Connect the
Calibrator
out p ut t h ro ugh α" Τ " connector to the time b ase
Ext Trig
In an d t he 7 Α 15 I NPU T con nector . Set the
P O L A R ITY
switc h to I NVER T to d is p lay t h e opp osite
polarity of t he
s q
uare
wave .
T h is com p letes t he basic op erating p rocedure for t he
7 Α 15 . I
nstrument operations not ex p lai ned h ere or op era-
tions w h
ic
hneed
furt h er exp lanation are d iscusse d und er
General
O p erating I n formatio n .
5 .
Turn
t he oscillosco pe p ower
on
and allow about 5

CO NTR O L S E T
UP C
H
A R T
minutes warmu p .
Figure 2-2 s h ows t h e front panel of t h e
7
Α 15 . T h is c
h
art
can be re p ro ducedan d use d as α front p a n el record for
6 . A d vance the Β Intensity until α free-r u nning trace is

sp ecial
meas u rements, a pp
lications
or p
roce
du res, or it may
observe d . A d j ust the P ositio n controls to center
t
he t r ace

b
e
used
as α training ai d for familiarization with t h is instru-
οη t he C RT .

ment
.

7 Α 15 T E ST S E T-
UP C H A R T
σ » οί ~ ορρν
POSITION
V A R B A L
INPUT
imp
20 pF
ΤΕΚΤ R ΟΝΙ
%®
7
Α 75
P OLA R ITY
Π
+
UP
-/I NVER
T
V A R IA BLE (CA L IN)
V O L TS/DI V
Ί- Ί AC
GN D
υ DC
AMPL IF I ER
F ig . 2-2 . 7 Α
15 control set u pch
art .
O p erating
Instructions-7A15
2- 3

O pe r ati ng Instructions-7A15
G ENER A
L
O
PER ATI NG I NF O RM ATIO N

T h e GND p osition is also use d to p re-c h arge t h e coup ling
ca p acitor to t he average level of t h e signal app lie d to t h e
Signal
Con n ection

I NPU T connector . T he p re-c h arge network allows t h e i npu t
In general,
prob es offer the most convenient means of

coupling ca p acitor to c h arge to t h e DC source voltage level
con necting α signal to t
he in pu t of t he 7 Α 15 . Tek tronix

whe n t h e CO UPL I N G switc h is set to GN D .
p ro b es are s h iel ded to p
r event p ic k up of elect r ostatic inter-
fere n ce . Α 10
Χ atten u ator p robe offers α h ig h inp u t im-

T he
p edance an d allows t h e circuit un d er test to op erate very

procedure for using th is feature is as follows :
close to normal operati ng con d itions . H owever, α 10 Χ
p robe also attenuates t h e inp u t signal ten times .

1 .
Before connecting the signal con taining α DC com-
p onent to t he 7 Α 15 INPU T, set the CO UPL I NG switc h to
GND . T h en connect t h e signal to the I NPU T connector .
In h ig h -fre qu ency a pp lications re q uiring maximum over-
all b andwid t h , use α coaxial ca b le terminate d at both end s
in t h e ch aracteristic imp e dance of the ca b le . To maintain
t h
e
h ig h
-fre q
uency c h
aracteristics of
t he
a pp
lie d signal, use
h ig h - q
uality low-loss cable .
R
esistive coaxial attenuators
can be u se d to min imize reflections if t h e a pp lie d signal h as
s
u ita b le
am
p
litu
de .
In p ut Cou p ling
T h
e AC-G N D-DC lever switc h allows α c h oice of in p ut
co
u p ling . T he ty pe
of
d
is p lay d esire d d etermines t h e mo d e
of in pu t co u pling u se d . T h
e
DC p
osition can be use d for
most a pp lications . However,
if t he DC com ponent of t h e
sig n al is muc h larger t han t he
AC com p one n t, t h e AC
p osition will p robably p rovi d eα better d is p
lay . DC coupling
s h ould be use d to d isplay AC signals b
elow about 2 h ertz
an dsqu a r e waves containing low-frequency
com ponen ts, as
t hey will b e attenuate d in t he AC p osition .
Ι
η the AC p osition, t he DC com p onent is bloc kedby α
ca p acitor in t h e in p ut circ u it . T h e low-frequency res p onse
in t he AC position
is
abou
t 2 h ertz (-3
dB
point) .
Th ere-
fore, some
low-frequency
attenuation
can
be exp ecte d near
t h is fre q uency limit . Distortion will also app ear in s q uare
waves w h ic h h ave low-fre q uency com p onents .
2- 4
2 .
Allow
a bo u t
two
seconds for the coup ling ca p acitor
to ch arge .
3 . R eset t h e CO UPL I N G switc h to AC . T he trace
( d isplay) will remain on t h e scree n and t he AC com p on ent
of t he signal can b e meas u re d in th e normal manner .
H ig h -level low-frequency
signals
can b
e
con n ecte d direc-
tly
to the
7
Α 15 I NPU T conn ector with sh ort unsh ielded

Deflection F actor
leads using α BN C to Banana J ack A da p ter . T h is met ho d
wor k
s best for signals below about one k ilo h ertz an d d eflec-

T he amou nt of vertical d eflection p ro du ce d by α signal is
tion factors above one volt/ d ivisio n .
Wh en t h is met hod is

d etermine d by t he sig n al am p litu d e, t h e atten u ation factor
u se d , esta b lis hα common ground
between t he 7 Α 15 and of t he p ro b e (if any), t he setting of t he
VO
L TS/DI V switc h
t he
e q
uipment
un d er test
(common
groundp rovi d e dby

and t he setting of the VA R IA BLE control (if co n trol is i n
line cord s is usually
ina
deq
uate) . Attem p t to p osition t h e

t he outwar d p ositio n ) . T h e calib r ate d d eflection factors
in-
lea d s away from any source of interfere
n ce to avoi d errors

dicated b y t h e VO L TS/DI V switc happ ly
only w h en t he
in t he d is p lay . If interfere n ce is excessive
with uns h ielded

VA R IA BLE control is in t he inward (CA
L IN) p osition .
leads, use α coaxial cable or α p ro b e .
T he VA R IA BLE control p rovides uncali b
rated vertical
d eflection b etween t he calibrate d
settings of t he VO L TS/
DI V switc h , an dexten d s the maximu m d
eflection factor to
at
least 12 .5 volts/ d ivision .
T h e GAI N
control, α fro n t- p anel screwd river ad j ustment,
sets
t he gai n of the 7 Α 15 in t he 10 m V / d iv p osition of t he
VO
L TS/DI V switc h . T he gain calibration of t he unit s hou
l d
be ch
ec k ed for acc u racy p rior to ma k i n g critical measure-
ments, using eit h er t he oscillosco p e cali b rator ou t p ut or α
sta nd ar d am p lit ude calibrator . If a d j ustment is necessary,
t he GAI
N
s h oul
d b e a d ju ste d with t he VO L TS/DI V switc h
set to 10 m
V .
V
ariable B
alance
To c
h ec kan d /o r a dju st the VA R B A L, p roceed as fol-
lows :
1 . Set the CO UPL I N G to GND an d a d just the time- b ase
T he GND position p rovi d es α ground reference at t he

controls for α free-running trace .
am p lifier in p ut . T h e signal a pp lied to t h e I NPU T connector
is p resente d wit hα one mego h m load, w h ile the am p lifier
in
pu t is grounded . T h is eliminates the nee d to externally

2 . P ress and release t h e
VA R IA BLE control to its o u t-
gro und the I NPU T to esta b lis hα DC gro u n d reference .

war d p osition .

3 . Wh ile
rotati ng the V A R IA BLE co n trol t h roug h out its
range, a dju st the VA R B A L ( α front p an el screwdriver ad-
ju stment) for minim u m trace s h ift (0 .5 div or less s h ift as
VA R IA BLE co n trol is turned from fully cloc
k
wise to
fully
cou n te r cloc k wise) .
Signal
P olarity
The P O L A RITY switch p rovides α means of inverting
t h e d is p lay . W it hthe P O L A R ITY set to + UP, α positive-
going voltage at t he I NPU T produces an upward deflection
of t he C R T d isplay . W it h
P
O L A R ITY set to I NVER T, α
p ositive-going voltage at t he I NPU T will
p rod
uce α d
own-
ward deflection of t he C
R
Td
isplay . If
α
symmetrical wave-
form s u c has t he calibrator square-wave is to be ob served,
t h e time-base must be triggere d externally to observe t he
p olarity i nversion . T h is is d ue to the time-base unit trigger
ing on t h e in d icated slo pe of t he d is p laye d waveform w hen

F ig . 2-3 .

Oscilloscope display w h en making Ρ - Ρ voltage measu re-
it is trigge r e d internally .

m ents .
Display Identification
2 . R eset the CO UPL I N G to AC, ad ju st the time-b ase
Wh en the 7 Α 15 ID EN TI F Y button is p ressed, t h e C RT

triggering co n trols for α stable d is p lay an d set the Time/Div
dis p lay representing t he out put of the 7 Α 15 is deflected

to d is p lay several cycles of the waveform .
upward abo u t
0 .3
d ivision for identification
. T
h
is feature is
p articularly useful in oscilloscopes h aving multi-trace d is-
p lays .

3 . Set t he VO L TS/DI
V switc h
to d isplay a b out
five
vertical d ivisions of the waveform . C heck t h at the V A R -
IA BLE control is in the CA L
IN
( push ed in) p osition .
Wh en u sing an oscilloscope system eq uipped with t h e
readout feature, information such as p olarity, d eflection
factor, etc ., is displayed on the CR T . Wh en t he ID EN TI F
Y
bu tto n is p ressed, the readout i n formation p ertaining to t h e
7
Α 15 is re p laced by the
word "ID EN TI F Y" to ai d in locat-
i n g the 7 Α 15 reado u t w hen more t h an one vertical u nit is
used .
T he following informatio nd escri b es the p rocedure
an dtech ni qu
es for ma
k
ing basic meas u rements wit h t he
am p lifier . T hese app lications are not d escribe d in d
etail
since each a pplicatio n must be a d apted to t he re q uirements
of the individual meas u
rement .
F
amiliarity wit h t he 7 Α 15
will permit t hese b asic tec hn iques to
be a
p
plie d to α wide
variety of uses .
P eak -to- P ea k V
oltage M easurement-AC

6 . M ulti p ly the d ista nce (in d ivisions) meas u re d in step
5
by t he
VO
L TS/DI V switch settings . Incl ude t h e attenua-
Το ma k e αpeak -to- p ea kvoltage measurement, u se t he

tion factor of t h e p robe being used .
following p roced u re :
E
xam p le : Assume α p eak -to-pea k vertical
d eflection of 4 .6
1 . W it h t he CO UPL I N G set to GN D, co
n nect t he signal

d
iviso n s using α 10 Χ atte nu ator p robe and α V
O L TS/DI V
to t he I NPU T con nector .

setting of 0 .5 V
.
BASIC A PPL ICATIO N S
Ope r ati ng Instructions-7A15
4 . W it h t h e P OSITIO N control, p ositio n the d is p lay so
t h e lower portion of the waveform coincides with one of
t h
e gratic
ule
lines
b
elow
t hecenter h
orizontal refere nce
line, and the to p of the waveform is in the viewing area .
M ove the d isplay wit hthe h orizontal P ositio ncontrol so
on e of the upper p eak s is aligned wit h t he cen ter vertical
reference line
(see
F
ig . 2-3) .
5 . M easure the vertical d eflection from pea kto pea k
(divisions) .
NO ΤΕ
T his technique may
also
be used
to
make
measure-
ments between two points on the waveform, rather
than peak to peak .
2-5

O p e r ating Instructions-7A15
V olts
(peak-to- p eak) _
vertical V OLTS/DIV
probe
d eflection Χ switch Χ
attenuation
(divisions) setting
factor
Substituting
the
given
values :
V olts ( p eak-to-peak) = 4
.6
Χ
0 .5
Χ
10
The peak-to- peak voltage is 23 volts .
Instantaneous V oltage M easurement-DC
To
measure
the DC level at α given point on α waveform,

F ig .
2-4 .

Oscilloscope d isplay w hen
measuring i nstantaneous DC
use the following proced
ure :

level .
1 . Set the COUPLING to GND
an dp
osition
the trace to
the b ottom line of the graticule (or other selecte d
reference
line) . If the voltage
to be measure d is negative with respect
to ground, p osition the trace to the to p line of
the grati-
cule
. Do not move the vertical P OSITION control after this
reference h
as been established .
ΝΟΤΕ
To
measure α voltage level wit h respect to a voltage
ot h er t h an ground,
ma
ke
t h e following c h anges to
step 1 : Set t h e CO UPL I N
G to DC and apply the
r eference voltage to t h e I NPU T
connecto r , t h en
position t he tr ace to t h e reference line .
2 . Connect
the signal to the INPUT connector .
3 . Set the COUPLING
to DC (the ground reference can
b e checke d at any time by
setting the COUPLI NG to
GND) .
1 η some ap p lications, it may be necessary to establish α
set of deflection factors other than those in d icate dby the
4 . Set the V OLTS/DIV switch to d is p lay about five ver-

V OLTS/DIV switch . This is useful for
comparing
signals
to
tical divisions of the waveform . Check t hat the V ARIABLE

α reference signal am p litu de . To establish α new set of d e-
control is in
the CAL IN position . A d just the time-base

flection factors base d upon αs p ecific reference am p litu d e,
triggering controls for α stable d is p
lay .

proceed
as
follows
:
5 . M easure the vertical distance in divisions between the
reference line and the p oint on
the waveform at which t he
DC level is to be measured . F or exam p le, in F ig . 2-4 the
measurement is made between t he reference line an d p oint
Α .
EMENEEMEME
M11111111M
ON
MEN MENEM
6a R ι R EE "
// "
MENEM
_
MEMEMEMM
7 . M ulti p ly the d istance measured in step 5 by the
V
OLTS/DIV switch setting . Inclu de the attenuation factor
of
the p robe, if any . E xample : Assume that
the vertical
distance
measure d is 4 .8 divisions, the waveform is above
the reference line, u
sing α10 Χ attenuator probe and α
V OLTS/DIV switch setting
of 0 .5
V .
U sing the formula :
Instantaneous _
V oltage
vertical P olarity V OLTS/DIV probe
distance Χ P olarity Χ Switch Χ attenuation
( d ivisions)

setting factor
Substituting the given
values :
Instantaneous V oltage = 4 .8 Χ
+1
Χ
0 .5
V
Χ 10
The instantaneous voltage is +24 volts
.
V oltage Com p arison M easurements
1 . Apply α reference signal of k nown amplitude to the
INPUT connector . U sing the V OLTS/DIV switch and the
V ARIABLE
control, adjust the d is p lay for an exact number
of d ivisions . Do not move the V ARIABLE
control after
obtaining the d esire d deflection .
2 . Divide the
amplitu d e of the reference signal (volts)
6 . E stablish t he polarity of the signal . If
the waveform is

by the p ro d uct of the d eflection ( d
ivisions) from step 1 an d
a bove the reference line, the voltage is p ositive ; below the

the V OLTS/DIV switch setting . This is the Deflection Con-
reference line, negative
.

version F actor .
2-6

Operating Instructions-7A15
Deflection

6 . M easure the vertical d
eflection in d ivisions an d d eter-
reference
signal amp l itude ( vo lts)
Conversion =

mine the am p litude b y
the following formula :
F actor

d eflection (divisions) ΧV OLTS/DIV setting
3 . To d etermine the amplitu de of α signal compare d to α
reference, d isconnect the
reference signal and apply the sig-
nal to b e com p are d to the 7 Α 15 INPUT connector .
4 .
Set the V OLTS/DIV switch to α setting that p rovi d es
sufficient d
eflection to make the measurement (do not
readjust the V ARIABLE control) .
5 . To establish an A d juste d Deflection F actor at any
setting
of the
V
OLTS/DIV switch, multi p ly the V OLTS/
DIV switch setting b y the Deflection
Conversion F actor
established in ste p 2 .
Adjusted
Signal Am p litude
= Deflection

Χ

d eflection
F actor ( d ivisions)
E xample : Assume
α reference signal
amplitude of 30
volts, α V OLTS/DIV
switch setting of 5 V an
dα vertical
deflection of four divisions . Substituting
these values in the
Deflection
Conversion F actor formula (step
2) :
Deflection

30 vo lts
Conversion =

= 1 .5
F
actor

4
( d iv) Χ 5 V
T hen with α V OLTS/DIV switch setting of 2 V, the
A d juste d Deflection
F
actor (step
5) is :
V OLTS/DIV

Deflection

Adjusted
Deflection F actor = 2 V Χ 1 .5 = 3
A d juste d Deflection F actor
=

switch

Χ

Conversion

volts/division
setting
F actor
To d etermine the amplitude of
an a p plied signal which
produces α vertical d eflection of five divisions,
use the Sig-
This Adjuste d Deflection F actor is correct if the V AR-

ηαΙ Am p litude formula (step 6) :
IABLE control h as not been move d from the p osition
set in
step 1 .

Signal
Am p litu de = 3 VΧ 5 ( d iv) = 15 volts

NOTES

Introduction
T h is section of t he manual contains αd escri p tion of t
he
circ u itry u sed i n t h e 7 Α 15 amplifier . T h e d escription begins
wit h αd isc u ssion of t he instrument using t h e block d iagram
s h own in t he diagrams section . T hen each circ u it is d es-
cribed in detail u si n g t he b loc kd iagram to s h ow intercon-
nections b etween t h e circuits an d relations h i p of t he front
p anel controls
to t
he in
d ivi
du
al stages .
SECTION
3
CIRCUIT
DESCRIPTION
C h ange information, if any, affecting t h is section will be found at t h e r ear of t h is manual .
I NPU T connector,
t
h roug h the in pu t
cou p ling circuit to t he
VO L TS/DI V switc h . T he VO L TS/DI V switc
h p rovi d es t he
a p pro p riate in p ut attenuation an d applies t he sig n al
to t
he

Input Attenuator
7 Α 15
In a dd ition to t h e fun ctions of t he amplifier j
ust ex-
p lai ne d , th e 7 Α 15 also p rovi d es rea d out logic for the i n d i-
cator oscillosco pe . L ogic is s up plie d w h ic h identifies t he
dis p lay
P
olarity and t h e d eflection factor, w h et h er cali b ra-
ted or u ncali
b rated . Wh en t
he
ID EN TI F
Y
button is pressed,
t he rea d out is erase d an d t he word ID EN TI F Y
app ears . At
t h e same time, the bottom of R 274 is groun de d to d eflect
t h e trace up ward a pp roximately 0 .25 d ivision .
D E TAI LE D CI RCU IT D E SC R I P TIO N
Com p lete sc h ematics of each circ u it are given in t h e
Diagrams section . R efer to these d iagrams t h roug h out t he

Input Cou p ling
following
circuit descri p tion fo r electrical values and rela-
tionsh i p .

In p ut signals
a p plie
dto
t
h
e
I
NPU T connector can be
AC-co up le d , DC-cou p led, or internally d
isconnecte d . W it h
t he cou p li ng switch set to AC, t h e signal p at h
is t
h
roug h
C1- R 1-CO UPL I NG switch -C3- R 3 and t h roug h t he VO LTS/
BL OC K DIAG R A M D E SCR I P TION

DI V switchto the in pu t am p lifier . Ιη t h is p osition, C1 p re-
vents
the DC com p onent of t he signal from passi ngto t he
T he following d iscussion is p rovi d ed to ai d in und er-

am p lifier . W
it
hthe
CO UPL I NG switch set to DC, t he signal
stan d ing t h e overall conce p t of the 7 Α 15 before t he in d i-

p at
h is throug h C3- R 3 and the VO
L TS/DI V switc h to t h e
vidu
al circ u its are d iscu sse d in d etail . E ach b loc k on t he

am p lifier in p ut . W it hthe CO UPL I NG
switch set to G N D,
B loc k Diagram, (in t he Diagrams section)
rep
resents
an indi-

the in
p
ut sig n al is AC-cou p le d throug h C1- R
1- R 2 to ground
vi d ual circuit wit h in the instrument . T he nu m b er
on
each
to p
rovi d e α constant load for the signal
source
.
At t h e
block refers to t h e d iagram on w h ic hthe com p lete circ u it is

same time,
t he am p lifier in pu t is groun d e dtoprovide
α 0
found
.

volts reference level . R
esistor R2 allows C1 to b e p
re-
charge d in the GND position so the
trace will remain
on
screen w h en the AC bu tton is p
ressed wit hα h ig h DC level
T he signal to be displayed on the C R T is a pp lie d to t he

a pp
lie d .
I npu t Am p lifier (Q103A-Q103 B -Q110-Q210-Qll2-Q212) .

T he effective overall d eflection
factor of t h e 7 Α 15 is
T he gain setting,
variable gai n , an d variable balance ad ju st-

d etermi
ned by the VO L TS/DI V switch
attenuators . T he
ments

are contained

in t h is stage .
T
h
e in put signal

is

b asic d eflection
factor of t h e 7 Α 15 is 5 m V p er d
ivision of
ch anged from single-ended to differential
by this stage and

d
eflection . To increase this b
asic d eflection factor to the
a pp lied to the p olarity selection stage . T he P olarity
Selec-

values in d
icate don the front p anel, p
recision attenuators
tion stage
(Q130-Q230-Q140-Q240) p rovi d es sig n al polarity

are switched
i
nto the inpu
t circuit . T he i npu t
atte nuators
inversion w h en the front
p anel POLARITY switch is set to

form fre q uency-com
p ensated voltage d ividers . For
DC and
I NVER T .

low-frequency signals,
they are p rimarily resistance d
ividers,
an d
the voltage attenuation is d
etermine d by the resistance
ratio in
the circuit . T he reactance of
t h e cap acitors i n t h e
T
he
Out put Am p lifier stage (Q160-Q260-Q170-Q270)

circuit
is so h ig h at low fre q uencies t h
at thei r effect is
provides vertical p
ositioni ng of the C R T dis p lay and im-

negligi b le . H
owever, at h ig h er fre q ue n
cies, t he reactance of
ped ance matc h ing
betwee
n
the 7 Α 15 and the oscillosco pe

the capacitors d
ecreases an d the attenuator
becomes p ri-
vertical

i np ut .

T he

Trigger

P ic k off

circuit,

marily α capacitance
voltage divider .
0180-Q280-Q185-Q285, ta kes the signal from t he
emitters
of Q170-Q270 and am p
lifies it to p rovi de + an d - trigger

In a d dition to provi d ing constant
attenuation at all fre-
sig n als for the time
b ase u nit .

q uencies within the b andwidth of t h e
system, the in p ut

Circuit
Description-7A15
attenuators are designe d to
maintain the same in p ut R C

and Q260 is p rovided by R
161-C161 an d R 261-C261

'
c h aracteristics for eac h
setting of t he VO L TS/DI V switch .

res p ectively .
R 171-C171 and R 271-C271 p rovi d e thermal
T h e attenuators contain
a
d ju
stable s h unt ca p acitors to p ro-

compensation

for

Q170

an d Q270

res p ectively .
vi d e in p ut ca p acitance .

C253-C175- R 175 are h ig h -fre q
uency p ea k ing a d j ustments
for cali b ration of t he 7 Α 15 .
In put Am p lifier
The sig n al from the in put atte n
uator is connecte d to t he
In p ut Am p lifier t h roug h R 109- R 100-
R 101-C101 . T h ese
resistors are p art of t he attenuation networ
k at all VO L TS/
DI V switch p ositions . R esistor R 101 limits
the overd rive
gate current of i np ut FE T Q103A
. C101-CR 102-C102 p ro-
vi de an in pu t protection circ u
it to p rotect Q103A from
large negative voltage swings . Protection
from lar ge p ositive
voltage swings is p rovi d ed by Q110, w
h ic h effectively
clam p s the source of in put FE T Q103A
to the +15 volt
sup p ly
.
T he i nput signal is coupled t h roug hsou
rce follower

R ea d out B loc k
Q103A an d emitter follower Q110
to the base of Q112,
one- h alf of t h e input p araphase am p
lifier . T he ot her h alf of

An analog coding
system is u se d in t he 7 Α 15
to convey
t he para ph ase am p lifier, Q212, is
α groun d ed -base con-

information from
the p l u g-in to t he oscilloscope
rea d ou t
figuratio n . Th e reference voltage
level at t he base of Q212

section . E ach sym
b ol used by t he 7 Α 15 re q uires
two cur-
is set by the VA R B A L
control, α fro n t panel ad j ust . T he

re n ts to d efine
it . T h is read out information is
encoded on
p ara ph ase am p lifier
converts t h e single-en de d in pu t
into α

~°
output lines,
interface connectors Α 37 an dΒ 37,
by the

,
d ifferential ou tput . T
he gain of t he am p lifier is set in t
h is

A3 0t ο rs between out pu
t
and B33 .
and interface
connectors
stage by front p anel GAI N
control R 121 wit h t he variable

Α
30, Α 32, Α 33, Β
29, Β 32 and

33 .
control set to t he CA L
IN p osition . W it h the VA R IA
BLE
control in t he o u
twar d (uncalibrated) p osition a nd t u r
ned

R
efer
to Sc h ematic Diagram 3 in t h
e Diagrams section to

'
fully co unterclock wise
to minimum resistance, t h
e gai
n
of
fin d t
h ititdithilif
h
t h e am p lifier is reduce dby
α factor of at least 2 .5 .
T h ise
ressors assocae

w

α p
artcuar settng o te
exten d s the maxim u m uncalibrate
d d eflection factor to at

Ti ηα

resistors
switch .
least
12 .5 volts/ d ivision . Dam p ing resistors
R 114 and R214
i
n
t
he collector circ u its of Q112 and
Q212 res p ectively,

T h e pro b
e connecte d to t h e I N PU T
connector forms α
serve
to dam p out any ringing
or oscillations . C1 14-R 115

voltage divi der
wit h 1175 to the -15 volt p
ower su p p l

T h y e .
an d C214-
R215 are t h ermal com p ensation
networ k s,
amount
of p robe resistance will d etermine
the b ias a pp lie d '
to t he base of
Q80 . F or exam p le, wit
h α 10 Χ attenuator
P olarity Selection
Stage

p robe s uch as the Ρ
6053 P robe connecte
d to t he I NPU T
connector, t he
bias a pp lie d to t he
base of Q80 will allow
T h e

P olarity
Selection Stage ma d e
up
of

100 microam p eres
of collector cu rrent
to flow . Wh en t he
Q130-Q230-Q140-Q240 V r
ονί des α means of ίην . ι rt ίη g t he

t ί me slot p ulse from
the oscillosc

itt

itf
op
enerrogaes n erace
in p ut signal . W it h t h e P O L A R ITY
switch set to
+U
P , Q130

connector Β 33,
t h is 100 microam p eres of
current is a dd e d
an d
Q230 are biase d on and the
sig n al is p asse d straig h t

to t he current
correspon d ing to t he
setting of t he VO L TS/
t hro u gh to
t he out put am p lifier . W
it h t he P O L A R ITY

DI V
switch to
increase t he d eflection
factor (in the d
is-
switch
set to I NVER T, Q130 an d Q230
are biased off an d

p laye
d reado u t) by
α factor of 10 . R
efer to t he a pp ro p
riate
Q140-10240
are turned on to p
rovide signal inversion .

oscillosco p e
Instruction Manual for
more ίηf οrm α
+ ίοη on
C131- R 131
an d C231- R 231 are
thermal
compensation net-

t
h e Readout System .
System .
wor k s .
Out p ut Am p lifier
T h e
Out p ut Am p lifier is com p ose d of
Q160-Q260-Q170-Q270 an d t h eir
associate d circuitry . T he
vertical P OSITIO N control
is located in t he in p ut to t h is
stage . T h ermistor R T151 and varactors
CR 154-C R 254 pro-
vi d e prop er com p ensation for transient
res p onse with
ch anges
of tem p erature . T h ermal compensation
for Q160
3-2
Trigger P ic k off Stage
T h e Trigger P ic k off stage
consists of
Q180-Q280-Q185-Q285 an d t h eir
associate d circuitry .
E mitter followers Q180 an d Q280
provi de isolation b e-
tween the trigger out p ut
circuit an d t he signal output cir-
cuit to p revent load ing
of t he signal out put am p lifier .
R 186-C186 and R
284-C284
p
rovi d e thermal com p ensation
for Q185 and Q285 res
p ectively . T he trigger ou t p ut ampli-
t ude is a pp roximately
t
he
same as t he signal out p ut
ampli-
tude .
T h e oscillosco p e d is played readout
will
give t
he correct
d eflection factor from the p robe ti p (using t he recom-
men ded attenuator p robes), w hereas the VO L TS/DI V k nob
on the p lug-in will d is p lay only t he p lug-in d eflection fac-
tor .
ι
T h e trace ID EN TI F Y
button, w
h en p resse
d , d
oes two
th ings :

I
ι

Circuit Description-7A15
1 . It groun d s t he j unction of R
75- R
274
(bottom en d

h ard, an d t h e displayed rea do u t is re p lace d by t h e word
of R 274) to d eflect t he trace u p war d about 0 .25 d ivi-

ID EN TI F
Y .
sion .
T hese two actions ai d in i dentifying t he 7 Α 15 trace
w henmultip le traces are d is p laye don the CRT . Wh e n t he
2 .
T he b ase of Q80, w h ic h is connected to th e ju nc-

ID EN TI F Y b utton is release d , the rea d o ut is restored to its
tion of R 75- R 274,
is also gro u n d ed . T h is t urns Q80 on

p revio u s d
is p lay .

NOTES