Tektronix 7A13 User manual

INSTRUCTION
MANUAL
Serial
Num ber
TEKTRONIX
CANADA
LTD
.
VANCOUVER
SERVICE
CENTRE
7A13
DIFFERENTIAL
COMPARATOR
SN
B040000 -
up
Tekt ronix , Inc.
 P.O. Box
500
Beaverton ,
Oregon
97005
 Phone : [phone]
 Cables : Tekt ronix
070-1113-00 1070

WARRANTY
All
Tekt ronix
inst rum ent s are
warrant ed against
defective
m at erials
and
workm anship for
one
year
.
Tekt ronix
t ransform ers ,
m anufact ured
in our
plant ,
are warrant ed for the life of the inst rum ent .
7
Any
questions with
respect to the
warrant y
,
m ent ioned
above
should be
taken
up
with
your
Tekt ronix Field
Engineer
or
Representative .
All requests for repairs and replacem ent parts
should be direct ed to the Tekt ronix Field Office or
representat ive in your area . This procedure will assure
you the fastest possible service . Please include the
inst rum ent Type ( or Part Num ber ) and Serial or
Model
Num ber with all
requests
for
parts or
service
.
Specifications and price change privileges reserved .
Copyright  1970 by Tekt ronix , Inc. , Beaverton ,
Oregon . Print ed in the Unit ed Stat es of Am erica . All
right s reserved .
Contents
of
this
publication m ay not
be reproduced in any form without perm ission of the
copyright owner .
U.S.A. and foreign Tekt ronix product s covered
by U.S. and
foreign patent s and
/ or patent s
pending .
1

7A13 (
SN
B040000 - up
)
DISPLAY TIME MULTIVIBRATOR
th :
257
TABLE OF CONTENTS
CR
SAK
RO
120X
SECTION 1 SPECIFICATION
C63
Cho
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8.2
KE
2
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Page
Q73
1-1
1-1
12
1-4
71-4
R
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Vom
HI
:
CO
BV
DB
20V
OOK
3 .
07
Introduction
Electrical
Characterist ics
System
Characterist ics
30
Environm ent al Characterist ics
it
SECTION
2
OPERATING INSTRUCTIONS
Introduction
Front
Panel
Description
55
Test Setup Chart
Fam ili ari zat ion Procedure
General Operat ing Inform at ion
SOOV
3035
4204
1254
Q83
De
30
TOR
OUT
TO 1.2.1
COUNTERS
2-1
2-1
13
2-2
2-4
PRINT
COMMAND
2-5
TO
MEMORIE
VOLINETER
17 1-1662
= 201
DRIVER
201
O.
Q26
PR
OKR63
084
sk
R25
22Y
SECTION 3
CIRCUIT DESCRIPTION
2.3 K
Introduction
Block
Diagram
Description
Detailed
Circuit
Description
3-1
3-1
3-2
SECTION 4
MAINTENANCE
Prevent ive Maintenance
Troubleshooting
STOR
MULT Vige
Correct ive Maintenance
4-1
4-2
4-7
SECTION
5
PERFORMANCE
CHECK / CALIBRATION
To
POO
5-1
5-1
D132
* 12
Introduction
Test Equipm ent Required
Short - Form Perform ance Check / Calibration
Procedure
and
Index
Perform ance
Check
/
Calibration
Procedure
2.OY
192
OK
R21
190
5-3
5-6
BA
20
Q125
o
0173
SECTION 6
ELECTRICAL PARTS LIST
RUL
BOK
RIZAL
ak
Abbreviations and Sym bols
Parts
Ordering
Inform at ion
16
TOBU
RS
22
RESOLUTION
SWITCH ANDGATE
SECTION
7 DIAGRAMS
AND
CIRCUIT BOARD
ILLUSTRATIONS
20
C12
DI
Q9
Sym bols and
Reference
Designat ors
Volt age
and
Waveform
Condit ions
3
MECHANICAL
PARTS LIST
SECTION
8
> 18
START
TO
STOP ZONE
ZG
Mechanical Parts
List
Inform at ion
Index of
Mechanical Parts
Illust rations
Mechanical
Parts List
Accessories
le 20
CI
CHANGE
INFORMATION
Q 163 KA
RICE
370164
Bok
0164
5.
CLOCK
OUT
at algas
Abbreviations
and
sym bols
used in this
m anual are
based on or
taken
direct ly
from
IEEE
Standard
260 "
Standard
Sym bols
for
Unit s " ,
MIL
-
STD - 12B and
ot her standards
of
the
elect ronics
industry .
Change
inf orm at ion , if any
, is
located at
the rear
of this
m anual
.
SEE PARTS
LISTEOR
SEMICONDUCTOR
TYPE
SERIES IM RODEL 112
i
A

.
AIN
00
USE
IN
1-50 m y
VAR IN ONLY
FINE
COMPARISON
VOLTAGE (
Vc )
I
VOLTS
2 :
0076
40 500
MAX
INPUT
VOLTS
AC
+ INPUT
VOLTS /
DIV
UNCAL
GND
VARIABLE
CAD
PULL VAR FOR
X10 Ve
OC
50 m V
20
1MS
20pF
Vc
5
10
5
AC
-
INPUT
2
5
GND
STEP ATTEN
BAL
GAIN
DC
1MS
20pF
Ve
X10 BAL
V
REZIDENT
POSITION
VAR BAL
BW
Ve OUT
0-10V
dit ulo
late
FULL
TEKTRONIX
SMH
DIFFERENTIAL
COMPARATOR
7A13
1
Fig . 1-1 . 7A13 Differenti al Com parat or .
7A13 (
SN
B040000
-
up )
A
.

7A13 ( SN
B040000
-
up )
SECTION 1
SPECIFICATION
Change inf orm at ion , if any , affecting this sect ion will be found at the rear of the m anual .
INTRODUCTION
TABLE 1-1 ( cont )
Characterist ic Perform ance
Requirem ent
The 7A13
Vertical
Plug - in
is a DC
coupled different ial
com parat or with excellent com m on - m ode reject ion and
m edium gain
charact eristi cs
for
m edium level
applicat ions
.
The 7A13 is designed for use in Tekt ronix 7000 series oscil
loscopes . It m ay be used as a different ial input pream pli fier
or conventional pream pli fier in addit ion to it s use as a com
parat or .
Com m on Mode
Signal Range
1 m V / Div to
50
m V
/
Div ;
X10 Vc In
At least +10 V and -10 V
At least +100 V and -100 V
10 m V / Div to
50 m V / Div ;
X10 Vc Out
In the
different ial input m ode ,
the
dynam i c range
allows
the applicat ion of com m on - m ode signals up to +10 or -10
volts to be applied to the unit without at t enuation .
Com m on - m ode reject ion ratio of at least 20,000 : 1 at DC to
100 kHz perm it s m easurem ents of different ial signals less
than 1 m V in am pli tude on 10 volt com m on - m ode signals .
0.1 V / Div to
0.5 V /
Div ;
X10 Vc
In
At least +500 V and --500 V
When used as a different ial com parat or , the 7A13 has an
effect ive offset range of 10,000 divisions .
0.1 V
/
Div
to
0.5
V
/
Div
;
X10 Vc Out
ELECTRICAL CHARACTERISTICS
1 V / Div to 5
V / Div At least
+500 V
and -500 V
X10 Vc In
The elect rical charact eristi cs described in Table 1-1 are
valid over the stat ed envi ronm ent al range of inst rum ent s
calibrated
at an
am bi ent
t em perat ure of +
20  C to
+ 30 
C
and aft er a 20 - m inut e warm up period unless ot herwise
noted .
Frequency
Response
( 8 Div
Reference )
FULL Bandwidt h
Upper
Li m it
See Table 1-2 , System Characteris
ti cs
10. Hz
or less
TABLE 1-1
AC ( Capacit ive )
Coupled Input
Lower Bandwidt h
Frequency
ELECTRICAL CHARACTERISTICS
Characterist ic
Perform ance
Requirem ent
5 MHz
Bandwidt h
DC to 5 MHz within 500 kHz
Deflection Factor
( VOLTS / DIV )
Calibrated
Range
1 m V / Div to 5
V / Div , 12
steps in a
1,2,5
sequence
Overdrive
Recovery
( 1X At tenuator at
1
m V /
Div )
1 us to recover within 1.5 m V and
0.1 m s to
recover within 0.5
m V
aft er the
rem oval of a
+10 V or
-10 V or
less
overdrive
signal
,
regardless
of
overdrive signal
dura
ti on .
Gain Rat io
Accuracy
Wit hin 1.5 % of
GAIN
adjust ed at 1
m V /
Div
See Fig .
1-2 .
Uncalibrated
(
Variable
)
Continuously variable : ext ends
deflect ion factor to at least 12.5
V / Div
Com m on
Mode
Reject ion
Rat io
1 m V / Div to
1-1

Specification
-
7A13 (
SN
B040000 - up
)
TABLE
1-1 ( cont
)
TABLE 1-1 ( cont
)
Characterist ic
Perform ance
Requirem ent
Characterist ic
R
and C
Product
Perform ance Requirem ent
Wit hin
1 %
for all
deflect ion
factor
sett ings .
50 m V / Div
X10 Vc In
DC to 100
kHz
At least
20,000 : 1 , 20 V P
- P or less
test signal
At least 10,000 : 1 , 10 V P - P or less
test
signal
100
kHz
to
1 MHz
Maxim um Gate
Current
 C to + 35  C
Both
Input s
+ 35  C
to +
50  C
Both
Input s
0.2 nA
or less
( 0.2 Div
at
1
m V / Div )
1 MHz to 10
MHz
CMRR
=
10,000 / frequency ( MHz )
2 nA or less
( 2 Div at 1 m V
/ Div )
20 MHz
At least 250 : 1 , 1 V P - P or less test
signal
10 m V / Div to
50 m V / Div ; X10
Vc
Out
;
DC Drift
Drift
Wit h Tim e
(
Am bi ent
Tem
perature
and
Line
Volt age
Constant
)
0.1 V / Div to 5
V /
Div ;
X10 Vc In or Out
Short
Term
DC to 10 kHz
AC
Coupled
at
60 Hz
At least
2,000
: 1
At least 500 : 1
1
m V P -
P or less
or 0.1 Div
or less
( whichever
is
great er )
any 1
m inut e
int erval
within
1
hour aft er
20
m in
ut es from turn - on .
Long
Term
Maxim um
Input
Volt age
DC (
Direct )
Coupled
DC + Peak
AC
1
m V /
Div
to
50 m V
/ Div ;
X10
Vc
In
1 m V P
- P or less
or 0.1
Div ( which
ever
is
great er
) during
any
hour
aft er the
first hour and
20
m inut es
from
turn -
on
.
40
VDC
,
40 V
Peak
AC
, 1
kHz or
less
Drift
Wit h
Am bi ent 2
m V
/ 10
 C
or
less ,
0.2
Div
/
10  C
Tem perat ure
(
Line (
whichever is
great er
)
Volt age
Constant
)
10 m V / Div to
50
m V
/
Div
;
X10 Vc
Out
400 VDC , 400 V Peak AC , 1 kHz
or
less
0.1 V / Div to
0.5 V /
Div ;
X10 Vc In
Am pli fier
Crosst alk 1 % or
less shift within
20 ns of step
of fast rise squarewave when
switchi ng
undriven
input from
GND to AC or DC
0.1 V / Div
to
0.5 V /
Div ;
X10 Vc Out
500 VDC . 500 V Peak AC , 1 kHz
or
less
Displayed Noise
( Tan- 400
UV or
less at 1 m V
/ Div in
gent ially
Measured )
Type 7700 -
Series or
7500 -
Series
indicat or
oscilloscope
1 V / Div to 5
V /
Div
;
X10 Vc In
500 VDC
AC (
Capacit ive )
Coupled
Input
Com pari son
Volt age
Range
O V to +10 V
Accuracy
+ ( 0.1 % of
sett ing
+5
m V )
Input
R
and C
Resistance
1 M12 within 0.15 %
Electrical Zero
0.5 m V or less
Capacit ance
20 pF within 0.4 pF at 1 MHz
Vc OUT Resistance 15 k 12 within 5 k 12
1-2
B

 
CMRR
VOLTS
P
-
P
100K
:
1
10K
:
1
Fig
.
1-2
.
Com m on
m ode
reject ion
ratio
graph . It
pertains
to
1
m V /
Div
through
20
m V /
Div
deflect ion
factors
.
1,000
:
1
10
Com m on
Mode
Reject ion
Rat io
Perform ance
Curves
CMRR
Perform ance
Requirem ent
P
-
P
Am pli tude
of
Sinusoidal
Test
Signal
Verificat ion
Point s
100
:
1
DC
10
kHz
100
kHz
1
MHz
10
MHZ
20
MHZ
Specification
-
7A13 ( SN
B040000 - up
)
Frequency
1-3

Specification
-
7A13 ( SN
B040000 - up
)
SYSTEM CHARACTERISTICS
The system charact eristi cs list ed in Table 1-2 are to
specify
the
perform ance of the
plug - in
with
various com
binat ions of
probes and in
various
indicat or
oscilloscopes .
EXTernal CALibrator ,  C to 50  C : The plug - in GAIN is set ( within
10  C of the operating t em perat ure ) using an ext ernal calibrator
signal whose accuracy is within 0.25 % .
* INTernal Calibrator , 15  C to 35  C : The plug - in GAIN is set using
the oscilloscope’s own calibrator and the inst rum ent is operating
within the +
15  C to
+ 35 
C
range .
* INTernal Calibrator ,  C to 50  C : The plug - in GAIN is set ( within
10  C of the operating t em perat ure ) using the oscilloscope’s own
calibrator , and the inst rum ent is operating within the  C to + 50  C
range .
TABLE 1-2
SYSTEM
CHARACTERISTICS
ENVIRONMENTAL CHARACTERISTICS
Probe
Indicator
Oscilloscope
BW
TE
( MHz ) | Ins )
Accuracy ( %
)
Sig
Out
2
EXT
3INT
4INT
BW
TE
CAL CAL
CAL ( MHz ) | Ins )
1.5 2.5
3.5
55
6.4
1.5
2.5
3.5
55
6.4
TABLE
1-3
7A13
test ed
alone (
separat e
from
indicat or
oscilloscope )
)
7500 Series
4.7
75
75
4.7
Characterist ic
Inform at ion
None
P6053
P6048
None
P6053
P6048
7700 Series 100
1.5
3.5
3.5
 
 
2.5
2.5
3.5
3.5
55
55
6.4
6.4
100 1.5
Alt itude
Non
-
Operat ing
Transportat ion
Accuracy
percentages
apply to all
deflect ion
factors .
Plug
- in
GAIN
m ust be set
at the
deflect ion factor
designat ed
at the
applicable
posit ion
of the
VOLTS /
DIV
switch .
When a
probe is
used , the
GAIN
m ust be set
with the
calibration signal
applied to the probe
ti p .
To
50,000
feet
and
-55  C
Qualified under
Nat ional
Safe
Transit
Com m it t ee
test
procedure
1A ,
Cat egory 11
1
1-4
( 

7A13 (
SN
B040000 -
up )
SECTION 2
OPERATING INSTRUCTIONS
Change inf orm at ion , if any , affecting this sect ion will be found at the rear of the m anual .
INTRODUCTION
tween 1 and 50 m V , VARIABLE
knob is pushed in and 1x probe is
used .
This sect ion opens with a brief functional descript ion of
the front panel cont rols and connect ors ( see Fig . 2-1 ) .
Following the front - panel descript ion is a fam iliarizati on
procedure and finally a general discussion of the operation
of the 7A13 .
NOTE
FRONT - PANEL DESCRIPTION
Wit h VOLTS /
DIV switch set
from .1 V to 5 V ,
lam p
rem ai ns on but input im pedance is 21 M32 and the
input
at t enuator is
uncom pensat ed .
Rin
zo
1-50 m V
VAR IN ONLY
Lam p
Illum inates
when
switch S10 ,
lo
cat ed on
left side of
plug - in , is
turned cw . This indicat es a + IN
PUT and
INPUT
im pedance
of
approxim at ely
infinit y
whenever
the VOLTS / DIV switch is set be
Select s
polarit y of
com parison
voltage .
COMPARISON
VOLTAGE
(
Vc )
+
and
-
Pushbut tons
RINO
USE IN
1-50 m V
VAR IN ONLY
FINE
COMPARISON
VOLTAGE
IVc )
VOLTS
20.76
40
400 500
MAX INPUT
VOLTS
AC
+ INPUT
VOLTS /
DIV
UNCA
GND
CARA
PULL
VAR
FOR
XIO Ve
DC
Rin
Switch
S10
IMA 20pF
AC
INPUT
GND
GAIN
STEP ATTEN
BAL
IMN
20pF
X10 BAL
***
POSITION
VAR
BAL
BW
Ve
OUT 0-10V
F
TE
ONIX
501
,
DIFFERENTIAL
COMPARATOR
7A13
Fig . 2-1 .
Front
panel of
7A13 and
location of Rin
switch S10
.
 
2-1

Operat ing
Instruct ions -
7A13 ( SN
B040000
- up
)
COMPARISON
VOLTAGE ( Vc )
Count er
-INPUT Mode
Switch
Select s
AC ,
DC ,
GND or
Vc
Mode
of
coupling
for
the
-INPUT
chan
nel .
Reads out the equivalent voltage
select ed
by
the
COMPARISON
VOLTAGE ( Vc
) select or switch
in
conj unction
with
FINE ,
VOLTS
/
DIV and
PULL
VAR
for X10
Vc
cont rols
.
STEP ATTEN BAL
Adjust m ent
Adjust s for
no vert ical trace
m ove
m ent
as the
VOLTS
/
DIV
switch
sett ing
is
varied
from 10
to
50
m V
/
DIV .
COMPARISON
VOLTAGE (
Vc
)
Select or
Switch
Select s one
of ten voltage
ranges
from zero to ten volts .
GAIN
Adjust m ent
COMPARISON
VOLTAGE
( Vc
)
FINE Control
Adjust s
the
am pli fier
gain for
dis
play of four divisions upon receipt
of a 4 -
m V
signal when
the
VOLTS /
DIV switch
is set to 1 m V
and the
VARIABLE cont rol is set to CAL .
Select s
a
com parison
voltage som e
where between the lower and upper
li m it s of the select ed band above .
X10 BAL
Adjust m ent
Adjust s for no vert ical trace m ove
m ent as
VARIABLE (
VOLTS / DIV )
knob is
pulled
out
.
+ INPUT
Connector
Provides a m eans of connect ion for
signal
m easurem ent
. It also
cont ains
a third
cont act for probe
at t en
uation
inf orm at ion . This enables
proper
readout
of
deflect ion
factor
on
CRT
screen .
VAR BAL
Control
Adjust s for no vert ical trace m ove
m ent as
VARIABLE (
VOLTS / DIV )
knob is varied throughout it s
range .
+ INPUT Mode
Switch
Select s AC , DC , GND or Vc Mode
of
coupling for
the +
INPUT
chan
nel .
Release
Latch
Pull to withdraw plug - in from in
dicator
oscilloscope .
VOLTS / DIV
Switch
Select s one of twelve volts per divi
sion calibrated deflect ion factors .
BW
Switch
Select s
eit her the
FULL
bandwidth
or 5 MHz .
VOLTS / DIV
VARIABLE Control
Vc OUT 0-10 V Jack
Provides a convenience outlet for
the com parison voltage .
Select s an
uncalibrated
deflect ion
factor som ewhere between the
twelve
sett ings above . A
m ini m um
of 2.5 t im es the VOLTS / DIV
switch sett ing is
provided . The
UN
CAL lam p lights when the
VARIABLE cont rol is out of the
CAL detent .
POSITION Control Posit ions display vert ically on the
CRT face .
Vc REF - IDENT
Pushbut ton
Internally disconnects bot h signals
and applies Vc to bot h inputs .
Readout display is replaced by the
word "
IDENTIFY " .
PULL VAR
FOR
X10 Vc Switch
Select s a Vc range 10X that which
is
select ed by
the
VOLTS / DIV
Switch . This only occurs for 10 , 20 ,
and 50 m V / DIV and .1 , .2 and .5
V / DIV sett ings of the VOLTS / DIV
switch .
TEST SETUP CHART
-INPUT
Connector
Sam e
as
for +
INPUT
connect or
above .
Fig . 2-2 shows a drawing of the front panel cont rols and
connect ors . This chart can be reproduced and used as a test
setup record for special m easurem ents and applicat ions , or
it m ay be used as a training aid for operation of the 7A13 .
2-2
A



Operat ing
Instruct ions
-
7A13 ( SN
B040000
- up )
7A13
DIFFERENTIAL
COMPARATOR
SETUP
CHART

RIN
-
00
USE IN
1-50 m y
VAR IN ONLY

FINE
COMPARISON
VOLTAGE ( Vc )
+
VOLTS
(  )
40
400 500
MAX INPUT
VOLTS
+ INPUT
AC
VOLTS
/ DIV
UNCAL
GND
VARIABLE
CAL
PULL VAR FOR
X10
VC
DC
50
m V
1 2
20pF
20
Vc
5
10
5
AC
-
INPUT
2
2
5
GND
STEP ATTEN BAL
GAIN
DC
1MS
20pF
Vc
X 10 BAL
  -  . .
POSITION
VAR BAL
BW
VC
OUT
6-10V
















FULL
5MHZ
TEKTRONIX 
7A13
DIFFERENTIAL
COMPARATOR
DATA :


Fig . 2-2 . Test set - up chart ,
2-3


U
Operat ing
Instruct ions - 7A13
( SN
B040000 -
up )
FAMILIARIZATION
PROCEDURE
NOTE
First
-
Tim e Operat ion
If
trace is
off screen
,
perform
Front
Panel
Adjust
m ent s
outlined
below
.

The
following
steps are
int ended to help
get the
trace
on
the
CRT screen
quickly
and
to
prepare the
unit
for
im m e
diate use . These
steps are
int ended to
acquaint you with
som e
of the
basic
functions of
the
7A13 .
7. Vary the
VARIABLE
cont rol throughout
it s range
while
observing
the
CRT
trace
.
1. Insert the unit int o the oscilloscope vert ical plug - in
com part m ent .
8.
Adjust
VAR
BAL so
that
there is no
trace
m ovem ent
while
varying
the
VARIABLE
cont rol .
2. Set the 7A13
front panel
cont rols as
follows
:
9.
Vary the
VOLTS
/
DIV switch
from
10
m V
to 50 m V
while observing the CRT
trace .
Pushbut tons
canceled
10.
Adjust
STEP
ATTEN
BAL
so
that the
trace
does
not
m ove
while
varying
the
VOLTS /
DIV
switch
.

As is
COMPARISON VOLTAGE
(
Vc
)
Polarit y
COMPARISON VOLTAGE
( Vc ) Count er
+ INPUT Mode
 INPUT Mode
VOLTS / DIV
VARIABLE
STEP ATTEN BAL
GAIN
X10 BAL
VAR BAL
BW
POSITION
11. Set the
VOLTS / DIV
switch to 10
m V . Pull
out the
PULL VAR FOR X10 Vc range knob while observing
the
CRT
trace
.
Gnd
Gnd
1
V
in ( CAL )
As is
As is
As is
As is
5
MHZ
Midrange
12. Adjust X10
BAL so that
there is no
trace m ove
m ent
while m oving
the
PULL VAR
FOR X10
Vc
range
knob in
and out .
|
13.
Repeat steps 7
through
12 unt il
opt im um
sett ings
are
achieved
.
|
3. Turn the
Intensit y cont rol
fully count erclockwise
and turn
the
oscilloscope
Power ON ,
Preset the t im e
- base
plug - in cont rols for a .5 m s / div sweep rate and aut om at ic
triggering .
14. Push
in the PULL
VAR FOR
X10 Vc
Range
knob and set
the
VOLTS / DIV switch
to 1 m V ;
posit ion the
trace two
divisions below
graticule
cent er .
1
4. Wait about five m inut es for the 7 A13 and the oscillo
scope
to
warm
up .
15.
Apply a 4
m V peak
- to -
peak
calibrator
signal
through
a coaxial
cable
to
the =
INPUT
connect or on
the
7A13 .
NOTE
About five m inut es is sufficient warm up t im e when
using the 7A13 for short - term DC m easurem ents . For
long - term DC
m easurem ents
using the lower
deflec
ti on factors , allow at least one hour .
16. For DC
coupled , single
- ended
operation , set the +
INPUT Mode Switch to DC . The display should be 4 divi
sions of
square
wave
am pli tude
with
the
bot tom of
the
display at the reference est ablished in step 14 .
U
NOTE
5. Adjust the Intensit y cont rol for norm al viewing of
the trace . The trace should appear near the graticule cent er .
If the
display
am pli tude
is not 4
divisions
, adjust
GAIN cont rol unt il
it is .
6. Using the POSITION cont rol , posit ion the trace two
divisions below graticule cent er . Set VOLTS / DIV to 1 m V
posit ion
.
17. For AC coupled , single - ended operation , re - posit ion
the display to place the bot tom of the display at the grati
cule cent er line .
u
2-4


Operat ing Instruct ions - 7A13 ( SN B040000 - up )
X10
BAL
Adjust m ent
18.
Set the
+
INPUT
Mode
switch to AC
and
note that
the
display
shift s downward
about two
divisions to
it s
average
level
.
1. Set
the
VOLTS / DIV
switch
to
10 m V .
Pull out
the
PULL
VAR
FOR
X10 Vc
Range
knob
while
observing
the
CRT
trace .
19.
Disconnect
the
calibrator
signal from the +
INPUT
connect or . Set bot h the
and
INPUT
Mode
switches to
GND .
-
2.
Adjust
X10 BAL so
that
there is no
trace
m ovem ent
while m oving
the knob in and
out .
Front
Panel
Adjust m ents
3.
Repeat
all
balance
adj ust m ent s
unt il
opt im um set
ti ngs are
achieved .
These
adj ust m ent s m ust be
accom plished each
t im e the
7A13
is
placed
in
a
different
oscilloscope and
should be
checked in the
given
sequence
prior to any
crit ical
m easure
m ent
of
waveform s .
GAIN
Adjust m ent
1.
Using the
POSITION
cont rol
,
posit ion the CRT
trace
two
divisions
below
graticule cent er .
Preset
7A
13
cont rols as
follows :
2.
Set VOLTS /
DIV
to
1
m V
posit ion .
3. Apply a 4
m V peak - to -
peak
calibrator signal
through
a coaxial cable to the + INPUT connect or on the 7A 13 .


1


n








n

r
COMPARISON
VOLTAGE
( Vc )
Polarit y
Count er
+ INPUT Mode
 INPUT Mode
VOLTS
/
DIV
VARIABLE
STEP
ATTEN BAL
GAIN
X10 BAL
VAR
BAL
BW
POSITION
Pushbut tons canceled
As is
GND
GND
1 V
In (
CAL )
Midrange
or as
is
As is
Midrange or as is
Midrange
or as
is
5 MHz
Midrange
4. Set the
+
INPUT Mode
switch to DC .
5. Adjust GAIN cont rol so that the display is four divi
sions of square wave am pli tude with the bot tom of the
display at the reference est ablished in step 1 .
GENERAL OPERATING INFORMATION
Allow 20
m inut es
warm up t im e .
Signal
Connection
VAR
BAL
Adjust m ent
1. Set the
VOLTS
/ DIV
switch
to 1
m V .
In general , probes offer the m ost convenient m eans of
connect ing signals to the inputs of the 7A13 . The Tek
tronix probes are shielded to prevent pickup of elect rost at ic
int erference . A 10X
at t enuator probe offers a
high input
im pedance
and
allows the circuit
under test to
perform very
close to norm al operating condit ions . ( For further infor
m at ion on the use of probes , see Use of At tenuator Probes
in this sect ion of the m anual , and in the probe inst ruct ion
m anual . )
2.
Vary
the
VARIABLE
cont rol
throughout it s
range
while observing the CRT trace .
1
3. Adjust
VAR BAL so that
there is no
trace
m ovem ent
while varying the VARIABLE cont rol .
STEP
ATTEN
BAL
Adjust m ent
In high - frequency applicat ions requiring m axim um over
all bandwidth , use a coaxial cable t erm inat ed at bot h ends
in the charact eristi c im pedance of the cable . To m ai nt ain
the high -
frequency charact eristi cs of the applied
signal , use
high - quality , low - loss cable . Resistive coaxial at t enuators
can be
used to
m ini m ize
reflect ions if the
applied signal has
suitable
am pli tude .
1. Vary the VOLTS / DIV switch from 10 m V to 50 m V
while observing the CRT trace .
2. Adjust STEP ATTEN BAL so that the trace does not
m ove while varying the VOLTS / DIV switch .
High - level , low - frequency signals can be connect ed
direct ly to the 7A13 input with short unshielded leads . This
A
2-5


U
Operat ing
Instruct ions -
7A13 ( SN
B040000
- up
)

m ust be
set to
one of
the six
posit ions
from 1 to
50 m V
;
( 2 ) the
VARIABLE (
VOLTS / DIV ) knob
m ust be
pushed
to
the IN
posit ion
; ( 3 ) the
INPUT
Mode
switch of
the
signal
channel m ust
be set to DC
.

coupling
m ethod
works best
for
signals
below
about one
kilohertz
and
deflect ion
factors
above
one voit
/ division
.
When this
m ethod is used
, est ablish a
com m on
ground be
tween the
7A13
and the
equi pm ent
under test
( com m on
ground
provided
by line
cords
is
usually
inadequat e
) .
At t em pt to
posit ion the
leads away
from any
source of
int erference
to avoid
errors
in
the display
. If int erference
is
excessive with unshielded leads , use a coaxial cable , probe ,
or different ial
am pli fier
operation
. ( Differenti al
am pli fier
operation
m ay
require
special
considerat ions for
signal con
nections
. See
Differenti al
Operat ion in this
sect ion of the
m anual
.
)
If the ext ernal device does not provide a DC return path
for the input
FET gat e
, an
ext ernal resistance
( adequately
shielded ) m ust
be
connect ed
between the
input
connect or
and
ground .
|
CALIBRATED
DIFFERENTIAL
COMPARATOR
OPERATION

Bandwidt h Li m it er
Introduction

The BW (
bandwidth
)
switch provides a
m ethod of re
ducing
int erference from
unwant ed high -
frequency signals
when
viewing
low -
frequency
signals
.
Wit h the
FULL
but t on
pressed , the full bandwidth capabilit ies of the am pli fier are
available . When the 5 MHz but t on is pressed ,
the
dB bandwidth
point of
the am pli fier
is
li m it ed
to
about 5
MHz . The
unwant ed high -
frequency signals
are
reduced
in
the
displayed
waveform .

upper
-3
When
one
of the
INPUT
switches
is set to
Vc and
the
ot her is set to AC or DC , the 7A13 is operating as a cali
brated different ial com parat or or slide - back volt m et er . The
calibrated
com parison
voltage , Vc , can
be added
differen
ti ally
to
the
input signal
to
obt ain
null ,
For
linear
opera
ti on ,
Table 1-1 in the
Specification
sect ion list s the
m axi
m um input
signal or
voltage that
can be
applied to
the
7A13 INPUT connect or at a given VOLTS / DIV switch posi
ti on
.
U
Display
Ident ification
When the 7A13 Vc REF - IDENT but t on is pressed , the
signal is
int ernally
disconnected and the
trace
is
returned
to
the
cent er
graticule area
for
ident ification .
This feature
is
particularly
useful
when the
7A13 is used
with an
indicat or
unit designed for use with m ore than one vert ical am pli fier .
In different ial
com parat or
operation
the
calibrated DC
com parison voltage
is
int ernally applied , to
different ially
offset any unwant ed portion of the applied signal . This
allows m easurem ents of relatively sm all AC or DC signals
riding on top of relatively large AC or DC signals .
U
||
When using an oscilloscope system equipped with the
readout feature ,
the 7A13
deflect ion factor is
displayed on
the CRT . When the Vc REF - IDENT but t on is pressed , the
readout inf orm at ion pertaining to the 7A13 is replaced by
the word IDENTIFY .
The DC
com parison voltage
is set by two
cont rols
: the
COMPARISON VOLTAGE ( Vc ) switch and FINE cont rol .
The switch has ten ranges , from 1 to 10 volts in 1 volt
steps ; and the FINE cont rol select s a voltage within the
select ed
range .

Rin
Switch
Equivalent
Vc
L
1
The Rin switch
S10 ( located on
left side of the
unit )
select s the input resistance to ground ( + and
INPUT
sim ult aneously
) to be eit her =
1 M12 or zoo . The
Rin switch
is norm ally set to the = 1 MS2 posit ion . A front - panel lam p
is illum inated to indicat e when the Rin switch is set to 300 .
When a signal is applied to the 7A 13 INPUT con
nector ( s ) , it is
at t enuated in
the Input
At tenuators before
being applied to
the + or - Input
stage . In
cont rast , the Vc
Supply voltage is not
at t enuated , but
is
applied ( via relays )
direct ly
to
the Input
stage .


The high input im pedance obt ained by sett ing Rin to
zoo is useful for m easuring voltages in high - im pedance cir
cuit s where m ini m um loading is necessary , and the voltage
to be m easured is within the 10 volt range of the 7A13 .
Differenti al com parat or operation is used to m ak e the
m easurem ent . At null , the com parison voltage is equal to
the voltage being
m easured .
Direct applicat ion of the Ve to the Input stage m ak es
the 110 - V Vc appear equivalent to the product of the Vc
and the at t enuation factor of the Input At tenuator . Like
wise , the use of an at t enuator probe m ult ipli es the Vc by
the at t enuation factor of the probe .
}
!
Vc Count er
Several precaut ions m ust be observed when using the
200 posit ion of the Rin switch ( 1 ) the VOLTS / DIV cont rol
The Vc Count er
reads out four digit s
of the Vc select ed
by the COMPARISON VOLTAGE ( Vc ) switch and FINE

2-6
 )

Operat ing Instruct ions - 7A13 ( SN B040000 - up )
of the
7A13
need
not
be
connect ed
in any
way
to
the test
circuit , there are few li m it at ions to the select ion of these
test point s .
cont rol
.
An
illum inated
deci m al
point
in
the
Count er is
switched
aut om at ically by
int ernal
circuit ry
for
readout
of
the equivalent Vc . Special probes which correct the Vc
Count er for the probe
at t enuation m ay be
used .
Divi der
probes not having the sensing capabilit y m ay be used with
the
inst rum ent
,
but
they will
not
operate the
sensing
system . The operator m ust take this int o account in reading
the Vc
Count er
.
Am pli tude and Com m on - Mode Reject ion
Vc
OUT
0-10 V
Jack
The VC
OUT 0-10
V jack ,
m ount ed on the
front panel
of the
7A13
,
perm it s
m onit oring of the
com parison
voltage
.
The voltage at the jack is set up by the COMPARISON
VOLTAGE ( Vc )
switch , FINE
cont rol
, and
polarit y
switch
.
Im pedance
is 15 ks
within 5 k.12
.
In the text
which follows ,
the term "
Input Signal
Range " m eans the com m on - m ode operating range of volt
age through which the am pli fier will produce a usable out
put . This should not be confused with the m axim um ( non
destruct ive ) input voltage , which is related to the break
down
li m it s of
the
am pli fier
com ponent s .
Factors Which Affect CMRR
When
m onit oring
the
voltage
at
the jack , the
voltage
is
not affected if
an " infinit e -
im pedance
type "
volt m et er
( such as a digit al volt m et er or any null type m eter which
draws
negligible
current
)
is used
for
m onit oring
purposes
.
Frequency . Since the com m on - m ode output voltage is a
factor of phase differences as well as gain between channels ,
the frequency
of the input
com m on - m ode signal
has a
direct bearing on the CMRR . Generally , as the frequency of
the input signal increases , the CMRR decreases . ( Except ion :
with AC - coupled input , the CMRR will becom e higher as
frequency is increased from DC to over 100 Hz . )
1


n

n
n







n




If the Vc
OUT - 0-10
V jack
is
loaded by an
ext ernal
m eter , the com parison voltage available at the jack and
applied to the input of the am pli fier will not be the sam e as
indicat ed by the Vc Count er . However , the volt m et er which
is connect ed to the jack will indicat e the act ual slideback
voltage . Therefore , it is possible to load the circuit con
siderably
and
still be able to
read the
com parison
voltage
accurately as
long as the reading
of the
volt m et er is used
inst ead of the Vc Count er readout .
Source Im pedance . The specified CMRR assum es that
the point s being m easured have ident ical source im pedance .
The source im pedance and the am pli fier input im pedance
form an RC divider which determ i nes the portion of the
signal that appears across the am pli fier input , and the
apparent
effect
on
CMRR
.
Differenti al
Operat ion
The user m ay desire to const ruct a graph of CMRR
versus frequency for specific applicat ions where the source
or signal
transporting lead
im pedances are
unbalanced .
Differenti al m easurem ents are m ade by applying the
signals to the + INPUT and -INPUT connect ors . Then , bot h
input Mode switches should be set to the sam e posit ion : AC
or DC , depending on the m ethod of signal coupling desired .
When using the 7A13 for different ial operation , only the
voltage difference between the two signals is am pli fied and
displayed . Com m on - m ode signals ( signals that are com m on
in am pli tude , frequency , and phase ) are reject ed and not
displayed .
Signal Transporting Leads . A principal requi rem ent for
m axim um CMRR is that the signals arrive at the am pli fier’s
two inputs with no change in phase or am pli tude . Slight
differences in at t enuation factors , or phase shift between
two input at t enuators m ay reduce the CMRR 20 % or m ore .
a
The 7A13
different ial input
provision m ay be
used to
elim inat e int erfering signals such as AC line - frequency hum .
Single - ended m easurem ents oft en yield unsatisfactory infor
m at ion because of int erference resulting from ground - loop
current s between the oscilloscope
and the device
under test .
At tenuator probes ext end the usable voltage range of a
different ial am pli fier by reducing the input signal level be
low the m axim um com m on - m ode input voltage . However ,
reduction in the apparent CMRR will usually occur because
of com ponent
value
differences within
the
probes . ( See Use
of At tenuator Probes in this sect ion . )
These li m it at ions of single - ended m easurem ents are vir
tually
elim inat ed in different ial
m easurem ents .
A
differen
ti al
m easurem ent is
m ade by
connect ing
each of
the two
inputs
to
select ed
point s in the
test
circuit .
Since the
chassis
Ground
Connections
. Proper
grounding reduces signals
generated from ground loop current s . It is usually best to
elect rically connect the probe or signal lead shields together
at the probe body or signal source , but not to the inst ru
m ent
ground .
1
 
2-7

U
Operat ing
Instruct ions
-
7A13 ( SN
B040000 - up )
USE
OF
ATTENUATOR
PROBES
U
General
NOTE
If
two
probes
with
different
divider
ratios are
con
nected
to the
INPUT
connect ors
( e.g. ,
10X and
100X
) ,
the
deflect ion
factor
readout ,
Vc
Count er ,
and MAX
INPUT
VOLTS
indicat or
will be
corrected
for the
probe
with
the
larger
division
ratio (
100X ) .
U
At tenuator
probes
reduce
the
resistive and
capacit ive
loading
of the
signal
source
and
ext end the
m easurem ent
range
to
include
subst ant ially
higher
voltages
. Passive
at t en
uator
probes
having
different
at t enuation
factors as
well as
special
- purpose
types
are
available
from
Tekt ronix
, Inc.
Probe Select ion
The P6055
probe
is
recom m ended for
m easurem ents
where
CMRR up
to
20,000
: 1
m ust be
m ai nt ained
(
100 : 1 at
20
MHZ ) . The
at t enuation
ratio is adjust able
to X10
to
com
pensate
for
differences in
input
resistance
of
the
am pli fier
.
U
4
Special
probes
which
correct
the
readout
deflect ion
fac
tor
,
Vc
(
com parison
voltage
)
Count er ,
and
MAX
INPUT
VOLTS
indicat or for
probe at t enuation
m ay be used
. ( The
+
and
INPUT
connect ors
have an outer
ring
which
is
connect ed to
the Probe
Sensing circuit
. )
Divi der
probes
not
having
the sensing
capabilit y
m ay
be
used
with
the inst ru
m ent , but
they will not
operate
the
sensing
system
.
There
fore ,
the
operator
m ust
supply
the
probe
at t enuation
factor
for
m easurem ents
involving
the three
indicat ors
affected
.
L
The
P6053 probe is
recom m ended
for
m easurem ents
requiring
the
full
bandwidth of
the
7A13
( see
Table
1-2 in
the
Specification
sect ion )
. The
P6053 also
has the
sensing
capabilit y
for
deflect ion factor
and Vc
Count er
readout
com pati bi lit y .


|
U
U
U


U
4

U
2-8
U

7A13
( SN
B040000 - up )
SECTION 3
CIRCUIT
DESCRIPTION
Change inf orm at ion , if any , affecting this sect ion will be found at the rear of the m anual .
INTRODUCTION
stant
at t enuation at all
frequencies within the
bandwidth
of
the
inst rum ent
.
This
is
done
while
m ai nt aini ng
the
sam e
input t im e const ant ( 20 Us ) for all posit ions of the
VOLTS /
DIV
switch .
A block
diagram
descript ion
covering
the
general con
figuration of each circuit in the 7A13 is included in this
sect ion . Following the block diagram descript ion is a m ore
detailed descript ion , particularly for circuit s unique to this
inst rum ent . If m ore inf orm at ion is desired on com m only
used
circuit s
, refer
to the
following
:
Input Source and Em it ter Followers
Tekt ronix
Circuit Concepts Book (
order from
your local
Tekt ronix
Field Office or
representat ive ) :
The
Input Source and
Em it ter
Followers
are
designed to
present a very high input im pedance at the at t enuator’s
output . Bootst rapping is incorporat ed in these stages for
each of the
+
and
inputs . A Current Source is used to
supply the
proper
am ount of current for
these stages .
Each
side
also
cont ains an
overload
protection
circuit to
guard
against
signals
larger than
approxim at ely  15
volts .
Vertical Am pli fier Circuit s , Tekt ronix Part No.
062-1145-00 .
Differenti al
and
Com m on
Mode
Signal
Clam ps


















1

A block diagram and com plete schem at ic diagram s are
included in the Diagram s sect ion at the back of this m anual .
These should be referred to throughout the circuit des
cript ion .
The
Differenti al
and
Com m on
Mode
Signal
Clam ps
allow
the
following
Differenti al
Com parat or
stage to
operate linearly for all input condit ions . The Differenti al
Mode
Signal
Clam p
li m it s
the
output
levels
to
approxi
m at ely
+1
volt ,
whereas the
Com m on Mode
Signal Clam p
allows
a
window of at
least 10
volts
.
1
For m ore inf orm at ion relating to the function and / or
adj ust m ent of variable com ponent s , refer to the Perfor
m ance Check / Calibration procedure in Sect ion 5 .
a
BLOCK DIAGRAM DESCRIPTION
( See Block Diagram Pullout preceding schem at ics . )
Differenti al
Com parat or
The
Differenti al
Com parat or
operates upon the
li m it ed
output of the Differenti al and Com m on Mode Signal
Clam ps . The am pli fied signal is then applied to the gain
switchi ng
am pli fiers . The
gain of the
Differenti al Com
parat or is approxim at ely one .
INPUT Mode Switches
A signal
applied
to
eit her the
+ or
INPUT
connect or ,
as shown by the heavy lines on the Block Diagram , passes
through the INPUT Mode switches to the Input At ten
uators . The signals can be AC coupled , DC coupled or dis
connect ed int ernally . ( See schem at ic diagram No. 1. )
1
1X , 2X , and 5X Gain - Switching Am pli fier
The 1X , 2X , and 5X Gain - Switching Am pli fier receives
the different ial signals from the Differenti al Com parat or .
Gain switchi ng is accom plished by the VOLTS / DIV switch
through
relays
.
Input
At tenuators
The Input At tenuators for the + and
inputs
are
iden
ti cal and are conventional RC type at t enuators . The adjust
able resistive elem ent s facilitate m at ching the
and +
at t enuators to obt ain opt im um DC com m on - m ode reject ion
and
precise at t enuation
ratios .
1X
and
10X
Gain
-
Switching
Am pli fier
The 1X , 10X Gain - Switching Am pli fier receives the
different ial signal from the 1X , 2X , and 5X Gain - Switching
Am pli fier . The gain of this stage is switched through relays
by the VOLTS / DIV switch in conj unction with the PULL
VAR FOR X10 Vc switch .
The at t enuators ( Schem at ic Diagram No. 1 ) are fre
quency
com pensated
voltage
dividers
which
provide
con
A
3-1

U
Circuit Description - 7A13 ( SN B040000 - up )
Driver
Am pli fier
DETAILED
CIRCUIT
DESCRIPTION
At tenuator and Switching
The Driver Am pli fier receives the different ial signals
from the 1X , 10X Gain - Switching Am pli fier . The gain of
the Driver Am pli fier is approxim at ely 2.5 . It s output signals
are applied to the Out put Am pli fier .
The
At tenuator and
Switching
circuit ry
determ i nes the
operating
m ode and
deflect ion
factor of
the
7A13 .
Also
included is the
circuit ry
which
provides the
readout logic to
the
indicat or
oscilloscope , and
that
which
drives
the
deci
m als in the
Vc Count er
.
Out put Am pli fier
The
Out put Am pli fier
further am pli fies
the different ial
signals and then applies them to the input of the oscillo
scope through pins A11 and B11 of the int erface connec
tor
.
INPUT Mode Switches
Trigger Am pli fier
The Trigger Am pli fier receives a portion of the Out put
Am pli fier signal
in order
to
provide
+
and -
int ernal
triggers to drive
the Trigger
Generator circuit
in the t im e
base plug - in unit
.
The separate
+ and -
INPUT
switches
cont rol the
m ode
of operation
for the 7A13
. Si
cont rols the + input
side of
the
am pli fier , and
S21
cont rols
the
input
side .
These
switches perm it connect ing one input or the other , or bot h ,
to the Input
Source
and
Em it ter
Follower stages
. The Vc
posit ion of the INPUT switches applies the com parison
voltage ,
inst ead of the
signal ,
to one or
bot h sides
of the
am pli fier
1
NOTE
Feedback Li m it er
The 7 and
input
channels of the
7A13 are
sim ilar ,
To m ini m ize duplicat ion , only the + input channel is
described in detail throughout this descript ion .
The Feedback Li m it er is driven by signals from the
Trigger Am pli fier when the output am pli tude exceeds a
cert ain li m it . These signals are fed back to the 1X , 2X , and
5X Gain - Switching Am pli fier stage to li m it the incom i ng
signal and prevent the signal from over - driving the suc
ceeding
stages
int o sat uration
.
Readout
Logic
The
Readout
Logic
circuit provides the
necessary
logic
for the oscilloscope readout system . Logic is supplied to
indicat e the deflect ion factor and the uncalibrated sym bol
( when the VARIABLE cont rol is not in the CAL posit ion ) .
An input from the Probe Sensing circuit provides probe
at tenuation factor and trace ident ification logic .
When the INPUT switch is in the DC posit ion , the input
signal is coupled direct ly to the Input At tenuator . In the
AC posit ion , the AC com ponent of the signal is coupled
through capacit or C1 , while the DC com ponent is blocked .
The GND posit ion int ernally disconnects the signal from
the 7A13 and connect s ground to the Input At tenuator .
This provides a ground reference for the am pli fier without
requiring rem oval of the input probes .
Vc
Decim al
Light
Driver
When the INPUT switch is set to Vc , relay K10 ( relay
K30 for
input ) disconnects the signal while the com
parison voltage
Vc is applied
to the gate
of the input FET
.
This
provides
a
DC reference for
one input of the
Differen
tial
Com parat or
while the
signal is
applied
to the
other . The
front - panel Vc REF - IDENT pushbut ton 540 , when
pressed , act uates bot h relays K10 and K30 to apply Vc to
bot h input channels sim ult aneously .
U
The Vc
Decim al Light
Driver
illum inates a lam p
pro
viding a deci m al point to the Com pari son Voltage ( Vc )
Count er . This enables the Vc Count er to read out the equi
valent com parison voltage as determ i ned by the total at ten
uation of the input signal by the Input At tenuator and
divider
probe .

VOLTS / DIV and PULL VAR FOR X10 Vc
Switches
u
Probe Sensing and Trace Ident ify
The Probe Sensing circuit senses the at tenuation factor
of a divider probe connect ed to an input . The output of
this circuit then adjust s the output s of the Readout Logic
and Vc Decim al Light Driver circuit s to include the probe
at tenuation factor . The inputs to this circuit also provide
the trace ident ify signals to the Readout Logic and Out put
Am pli fier
circuit s .
The VOLTS / DIV switch , S50 , sets the overall deflect ion
factor of the 7A13 . The PULL VAR FOR X10 Vc switch ,
$ 80 , m ult ipli es the equivalent Vc range ten t im es and in
creases the m axim um input voltage rating of the 7A 13. $ 80
is act uated by pulling the VARIABLE ( VOLTS / DIV ) knob
to its outer posit ion . A latch on the cont rol shaft prevent s
the knob from being pulled out unless the VOLTS / DIV
switch is in one of its cent er six posit ions ( 10 m V- , 5 V ) .
U
3-2
 

Circuit
Description -
7A13 ( SN
B040000 - up
)
The
functions of
these
two
cont rols are
accom plished
by switching relays to switch input at tenuators and set the
gain of
the two
gain -
switching
am pli fier
stages . The
switches also
provide
signals
indicat ing
deflect ion
factor
and Vc range
to the
Readout
Logic and
Vc
Decim al Light
Driver
stages
.
In the 1X
at tenuator
setting ,
the input
resistance con
sists of two
resistors
series
returned to
ground
through
Rin switch S10 . The ground return is disconnected when
S10 is set
to
Rin
500
.
S50 and
580
cont rol the
switching
relays
associated
with the
following circuit s
:
Variable com ponent s in the input to the FET adjust to
est ablish the input R and C at 1 MS and 20 pF . Variable
com ponent s in the at tenuator networks adjust to provide
the following
charact eristics :
1. The input R and C is norm alized at all settings of the
VOLTS / DIV switch .
1. Input At tenuators . Relays KO - K26 and K7 - K27
switch the input signal ( bot h + and - input channels sim ul
taneously
) to
pass
direct ly to the input
FET ( 1X ) ,
pass
through one
at tenuator
network ( 10X ) ,
or pass
through
two
at tenuator
networks (
100X
) .
The
current to
energize
the switching relays passes through cont act s on bot h S50
and $ 80
.
Wit h
$
80
pushed in ,
the
Input
At tenuators
are
select ed
by
S50 to be
1X for S50
settings
of
1-50 m V ; 10X
for S50 settings
of .1 - .5 V ; and
100X for S50
settings of 1-5
V. Pulling S80 out increases the input at tenuation to 10X
for S50 settings of 10 to 50 m V , and 100X for settings of
.1 to .5 V.
2.
Precise
at tenuation
ratios
and
high
-
frequency
com
pensation
.
Wit h these
adj ust m ent s
accurately
set ,
opt im um
com m on - m ode reject ion through the at tenuators is
achieved .
1
Vc
Decim al
Lights and
Light
Drivers
The Vc
Decim al Lights circuit
consist s of
DS65 , DS70 ,
and DS75 . When illum inated , DS65 indicat es act ual Vc
range of 9.999 V ; DS70 indicat es equivalent Vc range of
99.99 V ; DS75 indicat es equivalent Vc range of 999.9 V.
n



n


n
n


n




n



2. 1X - 10X
Gain -
Switching
Am pli fier . The gain
of this
stage is
switched
by relays
K60 - K61 .
The stage gain
is
m axi
m um when
the relays
are in the 1X
setting . The
relays in
the 10x
posit ion
switch in
an
at tenuator to divide
the gain
by a
factor of
10.
The
relay
energizing
current
passes
through cont act s on S50 and $ 80 .
3. 1X ,
2x , and
5X Gain -
Switching
Am pli fier .
Relays
K47 - K48 switch at tenuator networks to reduce the gain of
this stage by a factor of 2 or 5. These relays are cont rolled
by $ 50 only , giving the VOLTS / DIV switch the 1-2-5
sequence .
The Vc Decim al Lights Driver circuit consist s of 065 ,
070 , and Q75 act ing as switches between ground and their
associated lights . This circuit illum inates DS65 ( X1 ) unless
adjust ed by the input ( s ) for a Vc m ult ipli er of X10 or X 100
( com bined at tenuator ratio of probe and Input At tenua
tor ) . Mult iplier inputs indicat ing 10X or 100x Input
At tenuator settings are current s through resistors R66 and
R65 switched through cont act s on the VOLTS / DIV and
PULL VAR FOR X10 Vc switches . An input from the
Probe Sense circuit corrects for the probe at tenuation ratio .
Thus
,
S50
select s the
am pli fier
gains
and
input
at ten
uation as necessary for any specific deflect ion factor .
Pulling out S80 m ult ipli es the equivalent Vc by switching in
an at tenuator to divide the input signal 10 t im es ; sim ul
taneously , the am pli fier gain is m ult ipli ed by 10 to retain
the
deflect ion
factor set by
S50 .
The bias levels on Q65 , Q70 , and Q75 are est ablished by
the resistor - diode network R64 - R63 , CR67 - R71 - R72 - R73 ,
CR66 - CR77 - R
77 - R76 - R75 ,
and R74 .
Wit h no
m ult ipli er
inputs , the bias levels are such that Q65 is sat urated . This
provides a ground ( lights com m on ) return for DS65 . Due to
sat uration , the collect or of 065 is near zero volts , to reverse
bias Q70 and 075 through CR67 and CR66 , which are
forward biased .
.
Input
At tenuators
The Input At tenuator circuit consist s of two 10X RC
divider
networks in
each input
channel .
Switching
relays
K6 -
K26 and K7 -
K27 switch the
input
signals to
bypass the
RC
divider
networks for 1X
at tenuation ; pass
through one
divider
network for
10X
at tenuation ;
or pass
through
bot h
networks for 100X
at tenuation . ( The
am ount
of
input
signal
at tenuation
is
determ i ned
by
the setting of
the
VOLTS
/ DIV
and PULL
VAR FOR X10
Vc
switches
.
For
m ore inf orm at ion , refer to the discussion of these switches
and to
the
schem at ic
diagram . )
An input current level indicat ing a X10 m ult ipli er
( eit her through R66 or from the Probe Sense circuit )
adjust s the bias levels to reverse bias 065 to cut off . The
voltage level on the collect or of Q65 is now near +5 V to
reverse bias CR67 and CR66 . This results in Q70 being for
ward biased to sat uration to illum inate DS70 . The near
zero voltage level on the collect or of Q70 applies reverse
bias to the base
of 075 through
CR77 and
R76 .
A
3-3

Circuit
Description -
7A13 (
SN
B040000 - up
)
U
U
Sim ilarly
, an
input
current level
indicat ing
a
X100
m ult ipli er
( X
100 through
R65
,
X100
from the
Probe
Sense
circuit ,
or
X10
from each
input ) will
result
in
bot h
065
and
070
being cut off
;
CR66
-
CR67 -
CR77 reverse
biased ;
and
Q75 turned on
, to illum inate
D $ 75 .
When
different
-
at tenuation
divider
probes
are
connect ed
to the +
and --
INPUT
connect ors , the
output s
of the
Probe
Sense
circuit
will
indicat e the
at tenuation factor
of the
probe
having
the larger
divider .
u
Readout
Logic
Vc REFerence and Trace IDENTify
The Vc REF
- IDENT
pushbut ton
, when
pressed , does
two things :
U
The
Readout
Logic
circuit
consist s of
Q20
to
encode
the uncal
logic
(
uncalibrated
deflect ion
factor
)
and
resistors
switched
by
the
VOLTS
/
DIV switch
to
encode
deflect ion
factor
logic
.
U
1. Vc is
connect ed
to the
gates
of
the
input
FET’s via
relays
K10
-
K30
,
while
the
input
signal
( if
any ) is
discon
nected .
This returns the
trace
representing the
7A13
output
to
cent er screen
.
The switching
is
accom plished by
breaking
the
ground return for
the relay
arm atures
.
Uncalibrated
inf orm at ion is
generated
when
-15 V
clock
pulses
from
int erface
connect or
B32 add
current
to
the
colum n
current
through R
45 -
CR45 and
int erface
con
nector A37
.
When the
VARIABLE
(
VOLTS / DIV
) cont rol
is in the
CAL
posit ion ,
Q20 is
sat urated
to
apply
+50 V
through
R36 to
the
junction
of
CR45 -
CR46
- R45
- R36
. This
posit ive
voltage
reverse
biases
CR
45 , to
block
current flow
between
B32 and
A37
.
When the
VARIABLE cont rol
is not
in the
CAL
posit ion , +50
V
from S35
reverse
biases
CR36
and Q20
through
CR35 . This
rem oves
the
reverse bias
volt
age
from
CR45 to
provide
a
current
path
between
int erface
connect ors
B32
and
A37 .
1
2.
Connects
ground
to
the bases
of
Q40
and
060
through
CR43
and
CR44 ,
This
low value
of
bias
will :
( 1 )
cause
040
to
turn on
hard
when
int errogated
,
replacing
the
deflect ion
factor
readout
display
with
the
word
"
IDENTIFY " ; (
2 )
m ove
the Vc
Count er
deci m al
to
the far
right .
Probe
Sense
When
the probe
Ident ify
pushbut ton is
pressed
,
the
effect
on the
Readout
Logic
and Vc
Decim al
Lights
Driver
circuit s
is the
sam e as
when the
Vc
REF -
IDENT
front - panel
pushbut ton
is
pressed
.
However
,
the trace
is
not
returned to
cent er
screen
,
but is
shift ed
upward
slightly
. This
is
accom
plished
by
insert ing
a
resistor ,
R376
,
from ground
through
CR46 or
CR47
to the base
of
Q470 (
Trigger
Am pli fier ,
diagram
3 ) .
This shunts
a sm all
am ount
of the
output cur
rent ,
causing
the
trace to
m ove
.
The Probe
Sense
circuit
consist s
of
Q40
and
Q60
and
associated
com ponent s
.
This
circuit
ident ifies
the
at tenua
tion factor of
the probe
connect ed to the
front - panel con
nector
by
sensing
the
am ount
of
current
flowing
from the
current
sink through
the
probe
coding
resistance
.
The out
puts of
this circuit
adjust the
Readout
Logic
and Vc
Deci
m al
Lights Driver
circuit s so their
output s include
the
probe
at tenuation
factor
.
}
These
two
act ions aid
in
ident ifying
the 7A
13
trace
when m ult iple traces are displayed .
INPUT
AMPLIFIER
The third cont act
of the +
( or - ) INPUT
connect or
provides
the
input
to
the
Probe
Sense
circuit
from the
probe coding resistance ( coded probes only ; see Operat ing
Instruct ions
) .
The third
cont act
is
also
used for
the
IDEN
TIFY
input .
The coding
resistor
form s
a voltage
divider
with R40 ( R42
through
CR42 ) to the
-15 V supply
. The
resultant
voltage
sets the
bias on
040 and
Q60 , and
deter
m ines
( along
with their
respect ive
em it t er
resistors
)
their
collect or
current s .
U
Input
Source
and
Em it ter
Followers
The
Input Source
and
Em it ter
Followers
stage
provides
a
very
high
input
im pedance ,
so as
to
not
load
the
at ten
uator
circuit
elem ent s . This
stage includes
Q120
,
source
follower
;
0130A ,
em it t er
follower ;
and the
following :
Q140 -
Q145 ,
const ant
current
source ;
Q115 -
Q118 ,
boot
strap
em it t er followers
; Q105 ,
const ant
current
source
; and
Q110
- CR
110 -
CR112 - CR 101 -
CR 102 - CR
134 ,
overdrive pro
tection . The
overdrive
protection
circuit ry
act s
to prevent
com ponent
dam age
within
this
stage
.
The
Differential
and
Com m on
Mode
Signal
Clam ps
protect the rest
of the
am pli
fier
from an
input
overdrive .
The collect or
current
of Q60
adjust s the
bias levels
in
the Vc
Decim al
Lights
Driver circuit . The
output of
040
affects the
Readout Logic
output
( deflect ion
factor
) in
the
following
m anner :
when the
 15
V
clock
pulse
is applied
to int erface
connect or
B33 , 040
is
int errogated
and its
collect or current
is added to
the colum n
current
through
int erface connect or A37 .
U
U
Wit h a
1x
probe ( or
no
probe )
connect ed
,
040
and
Q60
are turned off , and thus have no output .
A
sim plified
schem at ic
diagram
of
this
stage is
shown in
Fig . 3-1
.
The
pri m ary
signal
path ,
through
Q120
and
Q130A ,
is
shown by a
heavy
line on
the
diagram . The
3-4
A
U