Tektronix, Inc. 7A16 User manual

MR

I N
STFR U CTI O
N
MAN UAL
Serial Number
7A16
AMPLIFIER
Tektronix, Inc .
S .W . Millikan Way
" P . O . Box 500
"
Beaverton, Oregon 97005
" Phone [phone] " Cables : Tektronix
070-0980-00

1069

WARRANTY
All Tektronix instruments
are warranted
against defective materials
and workman-
ship for one year . Tektronix
transformers,
manufactured in our plant, are
warranted
for the life of the instrument .
Any questions with respect to the
war-
ranty
mentioned above should be
taken
up with your
Tektronix Field Engineer .
Tektronix
repair and replacement-part
service is
geared directly to the field,
therefore all
requests for repairs and re-
placement parts
should be directed to the
Tektronix Field
Office or representative
in your area . This
procedure will assure
you the fastest possible
service . Please
include the instrument Type
and Serial or
Model Number with all requests
for parts
or
service,
Specifications and
price change privi-
leges reserved
.
Copyright "' 1969 by
Tektronix, Inc .,
Beaverton, Oregon .
Printed in the United
States of America .
All rights reserved .
Contents of this
publication may not be
reproduced in any form
without permis-
sion of the copyright owner
.

SECTION 1
SPECIFICATION
Introduction
Electrical Characteristics
Deflection Factor
Gain
FrequencyResponse
Maximum
Input Voltage
Input Resistance
Input Capacitance
Maximum Input Gate Current
Noise (Tangentially
Measured)
DC
Drift
Environmental Characteristics
Altitude
Transportation
Physical Characteristics
Finish
Dimensions
Weight
SECTION 2 OPERATING INSTRUCTIONS
General
Front Panel Controls and Connector
First Time Operation
Control Setup Chart
General
Operating Information
Basic Applications
SECTION 3 CIRCUIT DESCRIPTION
Introduction
Block Diagram Description
Detailed Circuit Description
Input Coupling
Input Attenuator
Input Stage
First Cascade Stage
Second CascadeStage
Output Stage
Readout Block
SECTION 4 MAINTENANCE
Preventive Maintenance
Cleaning
Lubrication
Visual Inspection
Transistor Checks
Recalibration
Troubleshooting
Troubleshooting Aids
Troubleshooting Equipment
Troubleshooting Techniques
Corrective Maintenance
Obtaining Replacement Parts
Soldering
Techniques
Component Replacement
TABLE
-OF CONTENTS
Page
1-1
1-1
1-1
1-1
1-1
1-1
1-1
1-1
1-1
1-1
2-1
2-1
2-1
2-3
2-3
2-5
3-1
3-1
4-1
4-1
4-1
4-1
4-1
4-2
4-4
4-4
4-6
4-6
4-6
SECTION 6 ELECTRICAL PARTS
LIST
Abbreviations and Symbols
Parts Ordering Information
Index of Electrical
Parts List
3-2
3-2
3-2
3-2
3-3

SECTION 7 DIAGRAMS AND MECHANICAL
3-3

PARTS ILLUSTRATIONS
3-3
Diagrams
Mechanical Parts Illustrations
SECTION 8 MECHANICAL PARTS LIST
Mechanical Parts List Information
Index of Mechanical Parts
Illustrations
Mechanical Parts
List
Accessories
Change Information
Type 7A16
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 .
SECTION
5 PERFORMANCE
CHECK/
CALIBRATION
Introduction
5-1
Test
Equipment Required 5-1
Short Form Procedure
5-2
Performance
Check/Calibration Procedure
Preliminary Procedure
5-3
Preliminary Control Settings
5-4
Check or Adjust
DC Balance
5-4
Variable Balance
5-4
STEP ATTENUATOR Range
5-4
STEP ATTENUATOR
Balance 5-4
Position Centering 5-5
POSITIONRange
5-5
+UP to
INVERT Shift 5-5
GAIN
5-5
VARIABLERange 5-6
Trigger DC Level
5-6
Trigger Gain
5-6
VOLTS/DIV Deflection Accuracy 5-6
Input Compensation
5-7
Series and Shunt
Compensation 5-7
High Frequency Compensation (5 mV) 5-8
High Frequency Compensation (10 mV)
5-8
High Frequency
Compensation (20 mV) 5-8
Step
Response 5-9
Upper -3 dB Point 5-9
Trigger Step Response
5-10
20
Megahertz Bandwidth Limiting 5-11
Noise (Tangentially Measured) 5-11

Fig . 1-1 . Type 7A16
Amplifier_

INTRODUCTION
The Type 7A16 vertical amplifier plug-in unit is part of the
7000-series oscilloscope system . It is a wide band DC coupled
amplifier with calibrated deflection factors from 5 mV/Div to
5V/Div
. Internal gain and compensation circuits are auto-
matically switched to correspond with the setting of the
VOLTS/DIV switch
. A polarity switch provides an inversion of
the signal within
the amplifier . A bandwidth limit switch
allows
low-frequency, low-level signals to be viewed with
reduced interference
from signals above 20 megahertz .
The
upper bandwidth limit of the Type 7A16 is mainly
determined by the oscilloscope
in which it
is
used . For ex-
ample, the
Type
7A16
used with the Type 7504 oscilloscope
will have an upper bandwidth
limit of approximately 90
MHz, and when plugged into a Type 7704 oscilloscope
the
upper bandwidth limit will be
approximately 150 MHz . Re-
fer to the approperiate oscilloscope manual
for complete
information .
This instrument will
meet the electrical characteristics listed
in Table 1-1 following complete calibration as given in Sec-
tion 5 . The performance check procedure given in
Section
5 provides a convenient method to check instrument
per-
formance without making internal adjustments .
The folowing electrical characteristics are valid over
the
stated environmental range for instruments calibrated at
an ambient temperature of +20 ° C to +30 ° C, and
after
a five minute warmup unless otherwise stated .
The Type 7A16 should be calibrated every 1000 hours or
every 6 months if used infrequently .
SECTION 1
SPECIFICATIONS
Change information, if any, affecting
rear of the manual .
TABLE 1-1
ELECTRICAL
this section will be found at
the
TABLE 1-2
ENVIRONMENTAL
Type
7A16
20 Megahertz Band- DC to 20 megahertz within 3
width metahertz .
Risetime 15 nanoseconds to 21 nanoseconds .
Maximum Input Voltage
DC (Direct) Coupled
100 mV/Div to 500 VDC . 500 V, DC + P-P AC at
5 V/Div 1 kHz or less .
5 mV/Div to 100 VDC . 100 V, DC + P-P AC at
50 mV/ Div 1 kHz or less .
AC (Capacitance Cou- 500 V .
pled Input DC Volt-
age
Input Resistance 1 me ohm within 2% .
Input Capacitance 15 picofarads within 0 .5 picofarad .
R and C Product Within 1 % over all deflection
factor settings .
Maximum Input Gate 0 .5 nanoampere or less at 0 ° C
Current to +35 ° C, 3 nanoamperes or less
at +35 ° C to +50 ° C .
Displayed Noise (Tan- 0 .1 division or less at 5 mV meas-
gentially Measured) ured in a 7700-Series Oscilloscope .
DC Drift
Drift With Time (Ambi-
ent Temperature and
Line Voltage Constant)
Short Term 250,u,V/minute (P-P) or 0 .05 divi- ,
sion (whichever is greater) after 1
hour warmup .
Long Term 250 ~V/hour (P-P) of 0 .05 division
(whichever is greater) after 1 hour
warmu w .
Drift With Ambient 100ttV/ ° C or less . -
Temperature (Line
Voltage Constant)
Characteristic Performance
Deflection Factor 5 mV/Div to 5 V/Div, 10 steps in
Calibrated Range a 1-2-5 se i " uence .
Gain Ratio Accuracy Within 2% of gain adjusted at
10 mV Div .
Uncalibrated Continuously variable between cal-
(Variable) ibrated deflection factor settings .
Extends uncalibrated deflection
factor to at least 12 .5 V/Div .
Gain Permits adjustment of deflection
factor for all 7000 series oscillo-
scopes .
Frequency Response ;
System
Dependent (8 With Type 7704 WithType 7504
division reference) Oscilloscope Oscilloscope
Upper
Bandwidth DC 150 MHz 90 MHz
Coupled
Lower Bandwidth AC 10 Hertz or less .
Coupled
With P6053 Probe 1 Hertz or less .
Characteristic Performance
Temperature
O .~ar " ~ 0 ° C to 50° C
Altitude
Non-operatin, To 50,000 feet and -55 ° C
Transportation Qualified under National Safe
Transit Committee test procedure
1A, Category [I .
TABLE 1-3
PHYSICAL
Item
Information
Finish Front Panel is anodized aluminum .
Wei- - ?- :i --_rA m~w W pounds .
Dimensions Fits plug-in compartment of 7000-
Series Oscilloscopes .

General
Installation
O?
SECTION 2
OPERATING INSTRUCTIONS
Change information, if any, affecting this section will be found at the
rear of the manual .
The Type7A16 vertical plug-in unit operates with a Tek-
tronix 7000-series oscilloscope and a 7B-series time base
unit to form a complete oscilloscope system . To effectively
use the Type 7A16, the operation and capabilities of the
instrument should be known . This section describes the op-
eration of the front-panel
controls and connector, gives
first
time operation and general operating information,
and
lists
some measurement techniques using the amplifier .
The Type
7A16 is designed to operate in a vertical plug-
in compartment of Tektronix 7000-series oscilloscopes . For
X-Y operation, the plug-in unit may also be installed in
a horizontal plug-in compartment . (Refer to the indicator
oscilloscope instruction manual for information concerning
X-Y operation .)
To install the Type 7A16 into a plug-in compartment, push
it in until it is seated into the front panel
of
the indicator
unit . Pull the release latch to disengage the
plug-in
unit,
then continue pulling on the release latch
to remove
the
plug-in from the indicator .
FRONT PANEL
CONTROLS AND CONNECTOR
All controls required for operation of the Type 7A16 are
located on the front panel of the unit . A brief description
of the function or operation of the front-panel controls fol-
lows . More detailed information is given under General
Operating Information .
VOLTS/DIV

Selects vertical deflection factor from 5
mV/DIV

to

5 V/DIV

in

1-2-5

sequence
(VAR control must be in the calibrated
position for indicated
deflection factor) .
VARIABLE

Provides variable uncalibrated
deflection
(CAL IN)

factors to at least
2 .5 times the setting of
the
VOLTS/DIV switch . Push knob in and
release
to activate ; the knob moves out-
ward from the VOLTS/DIV control when
activated .
POSITION

Controls vertical position of trace .
IDENTIFY

Moves trace upward about 0 .25 division
for identification . (Also replaces readout
information with the word IDENTIFY .)
Type
7A16
POLARITY

Provides means of inverting the display .
-SUP : A positive-going voltage at the
INPUT
produces a positive de-
flection on the CRT .
BANDWIDTH

Provides limiting of upper bandwidth .
FULL : Normal operation with full band-
width capabilities .
20 MHz : Amplifier

bandwidth

limited

to
20 MHz to provide a reduction
in displayed high-frequency noise
or interference .
AC-GND-DC

Selects method of coupling input signal to
Input Amplifier .
GAIN

Screwdriver adjustment to set gain of the
amplifier .

Gain standardized at 10 mV/
Div .
STEP ATTEN

Screwdriver adjustment to minimize trace
BAL

shift when switching VOLTS/DIV control .
INPUT

Signal input connector . Input impedance
of 1 megohm paralleled
by 15 picofarads .
Similar to standard
BNC
connector, but
with additional conductor to
indicate
to
the readout
circuit the attenuation factor
of the probe
being used .
General
Setup Information
INVERT : A positive-going voltage at the
INPUT produces a negative de-
flection on the CRT .
FIRST-TIME
OPERATION
When shipped
from the factory, the Type7A16 has been
calibrated
to meet the specifications listed in Section 1 and
is ready
to be used with an indicator oscilloscope .
The following steps demonstrate the basic operation of
the controls of the Type 7A16 . It is recommended that this
procedure be followed completely for familiarization with
the instrument . Operation of the indicator oscilloscope and
time base unit is described in the instruction manuals for
these units .
l . Insert the Type 7A16 into a vertical
plug-in compart-
ment of a 7000-series indicator oscilloscope .
2 . Insert a 7B-series time-base unit into
a horizontal plug-
in compartment .
3 . Set the controls as follows :

Operating Instructions-Type
7A16
Type 7A16
VOLTS/DIV

10 mV
VARIABLE
(CAL IN)

Calibrated
POSITION

Midrange
POLARITY

-FUP
BANDWIDTH
FULL
AC-GND-DC
GND
Time Base
Time/Div

0 .5 ms
Variable Time/Div

Calibrated
Slope

0/+
MODE

P-P Auto
Coupling

AC
Source

Int
Position

Midrange
Indicator Oscilloscope
Calibrator

40 mV
Square Wave
Intensity

Counterclockwise
Focus

Midrange
Astigmatism

Midrange
Scale Illum

As desired
4 . Connect
the oscilloscope to a power source
which meets
the voltage
and frequency requirements of the
oscilloscope
power supply .
5 . Turn the
oscilloscope power on and allow about
five
minutes warmup
time
.
6 . Advance the Intensity
and set the time base unit
trig-
gering controls to obtain a
free-running trace on the
CRT .
Adjust the POSITION
controls to center the trace vertically
.
7 . Connect the Calibrator
output to the INPUT connector,
using a 50-ohm BNC cable . Push the
Type 7A16 DC input
coupling button . (Adjust
horizontal and vertical POSITION
controls
as necessary .)
8 .
Set the triggering controls for a
stable display . (Ad-
just
Focus and Astigmatism controls as
necessary .)
9
. Check the display for four divisions of
vertical deflec-
tion (see
Fig . 2-1) . If necessary, adjust the
front panel GAIN
control for four divisions of deflection .
10 . Press
the IDENTIFY button to erase the
readout infor-
mation . When
the IDENTIFY button is pressed and
released,
the display
moves up and down about 0 .25
division . This
movement identifies the
waveformwhen more than one dis-
play is on the CRT .
11 . Press the
INVERT button to display the opposite
po-
larity of the square wave .
(When observing a symmetrical
waveform such as the Calibrator
square wave, inverting
the
signal makes no apparent
change in the display . This is
because the time-base unit triggers on
the indicated slope
of
the displayed waveform .)
12 . Switch the VOLTS/DIV control
through the remaining
positions of the switch, setting the Calibrator
to appropriate
output amplitudes . The STEP ATTEN
BAL control may be
adjusted
to minimize trace shift when
switching the VOLTS/
DIV
control from 5 mV/DIV to 20 mV/DIV .
2-2
MEN
MEMMIMMEME
MOMMIMI ONE
EMEMMINEEME
MEMO =_M1ME_
Fig . 2-1 . 40 mV Calibrator
square wave .
This completes the basic
operating procedure for the Type
7A16 . Instrument operations not explained
here, or opera-
tions which need further explanation, are
discussed under
General Operating Information .
CONTROL SETUP
CHART
Figure
2-2 shows the front panel of the Type 7A16 .
This
chart can be
reproduced and used as a front-panel record
for special
measurements, applications or procedures,
or
it may be used as a
training aid for familiarization with
this instrument .
GENERAL OPERATING
INFORMATION
Signal Connection
In general, probes offer
the most convenient means of
connecting signals to the input of the
Type 7A16 . The Tek-
tronix probes are shielded to prevent pickup
of electrostatic
interference . A IOX attenuator probe
offers a high input
impedance
and allows the circuit under test to
perform very
close to
normal operating conditions . However,
a 1OX
probe also attentuates
the input signal ten times .
To obtain
maximum bandwidth
when using probes, observe the ground-
ing considerations
given in the probe manuals . The probe-
to-connector adapters
and the bayonet-ground tip
provide
the best frequency response .
Remember that a ground strap
only a few inches in length
can produce several percent of
ringing when operating at
the higher frequency limit of this
system (see Fig . 2-3) .
In high-frequency applications
requiring maximum over-
all bandwidth, use a coaxial cable
terminated at both ends
in the characteristic impedance of the
cable
.
To maintain
the high-frequency
characteristics of the applied
signal, use
high-quality, low-loss cable . Resistive coaxial
attenuators
can be used
to minimize reflections if the applied
signal has
suitable amplitude
.

DATA
TYPE 7A16 AMPLIFIER SETUP CHART
POSITION
INPUT
,MR
15pF
TEKTRONIX O
7A16
AMPLIFIER
POLARITY
+UP
0
INVERT
a
BANDWIDTH
FU LL
20MHz
VARIABLE
(CAL IN)
VOLTS/DIV
STEP ATTEN BAL
Fig . 2-2 . Control setup chart .
Operating Instructions Type 7A16
2- 3

Operating Instructions-Type 7A16
MEEM ME M
wo OEM-M-0-mm
IM111011MMEM
ME
MEMOMM
ME 'ZZ' Moro=
ENIMEMENEEN
MEMEMMEM
NERIMMENEME
EMEMEN MEN
MMMM MENEM
MMMEMMMMMM
MoMawd
"" ri i
No
MENEEMME
Fig .
2-3
.
Waveform distortion produced with
incorrect probe ground .
(A)
Eighteen-inch ground strap between generator and
oscilloscope .
(B)
Five-inch ground strap .
High-level,
low-frequency signals can be connected
di-
rectly to
the Type 7A16 INPUT connector
with short
unshielded leads
.
This coupling
method works best for signals
below about one kilohertz
and deflection factors above
one
volt/division . When this
method is used, establish a common
ground between the Type 7A16
and the equipment under
test (common ground provided by
line cords is usually in-
adequate) . Attempt to
position the leads away from
any
source of interference to avoid errors in
the display . If inter-
ference is excessive with unshielded
leads, use a coaxial
cable or a probe .
Input Coupling
The AC-DC-GND pushbutton switch allows a choice
of
input coupling . The type of display desired
determines the
mode of input coupling used . The DC
position can be used
for most applications . However, if the DC
component of the
signal
is much larger than the AC component,
the AC posi-
tion will
probably provide a better
display . DC coupling
2-4
should be used
to display AC signals below
about 10 hertz
as they will
be attenuated in the AC position .
In the AC
position, the DC component of
the signal is
blocked by
a capacitor in the input circuit . The
low-fre-
quency
response in the AC position is about 10 hertz (-3dB
point) . Therefore, some
low-frequency distortion can be
expected near this
frequency limit . Distortion will also
ap-
pear in square waves
which have low-frequency components .
The GND position
provides a ground reference at the
input of the Type 7A16 .
The signal applied to the
INPUT
connector is internally
disconnected but not grounded . The
input circuit is held at ground
potential, eliminating the need
to externally ground the
input to establish a DC ground
reference .
The GND position is also used to
pre-charge the coupling
capacitor to the average voltage level of
the signal applied
to
the INPUT connector . The pre-charging
network allows
the
input-coupling capacitor to charge to
the
DC
source
voltage
level when the Input Coupling
switch is set to GND .
The
procedure for using this feature is as
follows :
1 . Before
connecting the signal containing
a
DC
com-
ponent to
the Type7A16 INPUT connector, push
the Input
Coupling GND
button . Then connect the signal to the
INPUT
connector .
2 . Allow about
one second for the coupling capacitor
to charge .
3 . Push the
Input Coupling AC button . The trace
(display)
will return on the screen
and the AC component of the sig-
nal can be measured in the
normal manner .
Deflection Factor
The amount of vertical deflection
produced by a signal
is determined by the signal amplitude,
the attenuation fac-
tor of the probe (if used), the
setting of the VOLTS/DIV
switch
and the setting of the VARIABLE VOLTS/DIV
control .
The
calibrated deflection factors indicated by
the VOLTS/
DIV
switch apply only when the VARIABLE
control is in
the calibrated (pushed
in) position .
The
VARIABLE VOLTS/DIV control provides
uncalibrated
vertical
deflection between the calibrated settings of
the
VOLTS/DIV switch
. The VARIABLE control extends the
maxi-
mum vertical
deflection factor of the Type 7A16 to at least
12 .5 volts/division (5V
position) .
The GAIN control,
a front-panel screwdriver adjustment,
sets the gain of
the Type 7A16 Amplifier . The vertical
de-
flection of the unit
should be checked for accuracy prior
to making critical measurements,
using either the indicator
unit Calibrator or a Standard
Amplitude Calibrator (067-
0502-00) . If adjustment is necessary,
the GAIN control should
be adjusted with the VOLTS/DIV switch
in the 10 mV posi-
tion . Apply a 40 millivolt Calibrator
signal to the INPUT and
adjust GAIN for four divisions of
display .
Step
Attenuator Balance
To
check the step attenuator balance, push
the Input Coup-
ling GND
button and set the time-base triggering controls
to
provide a
free-running trace . Change the VOLTS/DIV
switch
from 20 mV
to
5
mV . If the trace moves
vertically, adjust
the
front-panel STEP ATTEN BAL adjustment as follows
(allow
O

(A)
mom
MEE
M MM
M
Fig . 2-4 . (A) CRT display showing high-frequency interference when
attempting to view low-level, low-frequency signal, (B) resultant
display when 20 MHz pushbutton is pressed .
at least ten minutes warmup before performing this adjust-
ment) :
1 . With the Input Coupling GND button pressed and the
VOLTS/DIV switch set to 20 mV, move the trace to the center
horizontal line of the graticule with the vertical POSITION
control .
2 . Set the VOLTS/DIV switch to 5 mV
and adjust the STEP
ATTEN BAL adjustment to return the trace to the center
hori-
zontal line .
3 . Recheck step attenuator balance and repeat adjustment
until no trace shift occurs as the VOLTS/DIV switch is
changed from 20 mV to 5 mV .
Signal Polarity
The POLARITY switch provides a means of inverting the
display . With the +UP button pressed, a positive-going
Operating Instructions-Type 7A16
voltage at the INPUT produces a positive deflection on the
CRT
. With
the
INVERT
button
pressed, a positive-going
voltage at the INPUT produces a negative deflection on the
CRT
. However, when observing a symmetrical waveform,
such as the Calibrator square wave,
inverting the signal
makes no apparent change in the display . This is due to
the time-base unit triggering on the indicated slope of the
displayed waveform .
Bandwidth Limiter
The bandwidth switch provides a method of reducing
interference from unwanted high-frequency signals when
viewing low-frequency signals . With the FULL button pressed,
the
full
bandwidth capabilities of the amplifier are avail-
able . When the 20 MHz button is pressed, the upper
-3dB bandwidth point of the amplifier is limited to about
20 megahertz . The unwanted high-frequency signals (such
as television broadcast radiation interference) are reduced
in the displayed waveform . Fig . 2-4 illustrates the use of this
feature . The waveform in Fig . 2-4A is the display produced
when a low-level, low-frequency signal is viewed in the
presence of a strong 50-megahertz radiation (FULL button
pressed) . Fig . 2-4B shows the resultant CRT display when
the high-frequency interference is reduced by pressing the
20
MHz button .
Display
Identification
When
the Type
7A16
IDENTIFY button
is
pressed, the
CRT display is deflected
upward about 0 .25 division for
identification . This feature is particularly useful when the
Type 7A16 is used with an indicator unit designed for use
with more than one vertical amplifier .
When using an oscilloscope system equipped with the
readout feature, information such as polarity, deflection
factor, etc . i s displayed on the CRT . When the Type 7A16
IDENTIFY button is pressed, the readout information per-
taining to the
Type
7A16
is replaced
by
the word IDENTIFY .
BASIC APPLICATIONS
The following information describes
the procedure and
technique for making basic measurements with a
Type 7A16
Amplifier
.
These applications are
not
described in
detail,
since each application must be adapted to the requirements
of the individual measurements . Familiarity with the Type
7A16 will permit these basic techniques to be applied to
a wide variety of uses .
Peak-to-Peak Voltage Measurements-AC
To make a peak-to-peak voltage measurement, use the
following procedure :
1 . Connect
the signal
to
the INPUT connector .
2 . Push the
Input Coupling
AC
button .
3 . Set the VOLTS/DIV
switch
to
display
about
five divi-
sions of the waveform . Make sure the VARIABLE VOLTS/DIV
control is in the calibrated (pushed in) position .
2-5

Operating Instructions-Type 7A16
For
low-frequency signals below about 10
hertz,
push the DC
button .
4 . Set the
triggering controls to obtain a stable
display .
Set the sweep
rate to display several cycles of the
waveform .
5 . Turn the vertical POSITION
control so the lower
portion
of the waveform coincides
with one of the graticule lines
below the center horizontal
line, and the top of the wave-
form is within the viewing area .
Move the display with the
horizontal position control, so
one of the upper peaks lies
near the center vertical line (see
Fig . 2-5) .
6 . Measure the divisions of vertical
deflection from peak-
to-peak
.
This
technique may also be used to make
measure-
ments
betweentwo points on the waveform
rather
than peak-to-peak
.
7 .
Multiply the distance measured in step 6 by
the VOLTS/
DIV switch
setting . Also include the attenuation factor
of the
probe, if any .
Example . Assume a
peak-to-peak vertical deflection of
4 .6 divisions using a 1OX
attenuator probe and a VOLTS/
DIV switch setting of .5 V .
Using the formula
:
Volts vertical
VOLTS/DIV probe
peak to peak = deflection X

setting

X
attenuation
(divisions)

factor
Substituting the given values :
NOTE
NOTE
Volts peak to peak = 4 .6 X 0 .5 X 10
The peak-to-peak voltage is 23 volts .
Fig . 2-5 . Measuring peak-to-peak voltage
of a waveform .
2- 6
Instantaneous
Voltage Measurements-DC
To measure the DC
level at a given point on a waveform,
use the following
procedure :
1 . Connect the signal to the
INPUT connector .
2 . Set the VOLTS/DIV switch to
display about five divi-
sions of the waveform . Make sure the VARIABLE
VOLTS/DIV
control is in the calibrated (pushed in) position
.
3 . Push the Input Coupling GND button .
4 . Set the triggering controls to obtain a
free-running trace .
5 .
Position the trace to the bottom line of the graticule or
other
reference line . If the voltage to be measured is neg-
ative with respect
to ground, position the trace to the top
line of the graticule .
Do not move the vertical POSITION
control after this
reference line has been established .
NOTE
To measure a voltage level with respect to
a
voltage other than ground, make the following
changes in step 5 : Push the Input Coupling
DC
button
and apply the reference voltage to the
INPUT
connector . Then position the trace to the
reference
line .
6 . Push the Input
Coupling DC button . The ground ref-
erence line can be checked
at any time by pushing the GND
button .
7 . Set the triggering controls to
obtain a stable display .
Set the sweep rate to display several cycles
of the signal .
8 .
Measure the distance in divisions between the
reference
line and the point on the waveform at which the DC
level is
to be measured .
For example, in Fig . 2-6 the measurement
is made between
the reference line and point A .
9 . Establish the polarity
of the signal . If the waveform
is above the reference line, the voltage
is positive ; below
the line, negative .
10 . Multiply the distance measured
in step 8 by the
VOLTS/DIV switch
setting . Include the attenuation factor
of the probe, if any .
Example . Assume that the
vertical distance measured is
4 .6 divisions, the waveform is above
the reference line,
using a 1OX attenuator probe and a VOLTS/DIV
switch
setting of 2 V .
Using the formula : Instantaneous Voltage =
vertical

VOLTS/DIV probe
distance X
polarity X

setting

X attenuation
(divisions)

factor
Substituting the given
values :
Instantaneous voltage = 4 .6 X
+1

X
2 V
X
10
The instantaneous voltage is +92 volts .

EMEMENINEME
Refere~lme
Fig . 2-6 . Measuring instantaneous DC voltage with respect
to a
reference voltage
.
Voltage
Comparison Measurements
In some applications, it may be necessary to establish a
set of deflection factors other than those indicated by the
VOLTS/DIV switch . This is useful for comparing signals to
a reference voltage amplitude . To establish a new set of
deflection factors based upon a specific reference ampli-
tude, proceed as follows :
l . Apply the reference signal of known amplitude to the
INPUT connector . Using the VOLTS/DIV switch and the
VARIABLE control, adjust the display for
an exact number
of divisions . Do not move the VARIABLE VOLTS/DIV
con-
trol after obtaining the desired deflection .
2 . Divide the amplitude of the reference signal
(volts) by
the product of the deflection in divisions
(established in step
1) and the VOLTS/DIV
switch setting . This is Deflection
Conversion Factor .
Deflection
Conversion =
Factor
reference signal amplitude (volts)
deflection (divisions) X VOLTS/DIV setting
Operating Instructions Type 7A16
3 . To determine the peak-to-peak amplitude of a signal
compared to a reference, disconnect the reference and apply
the signal to the INPUT connector .
4 . Set the VOLTS/DIV switch to a setting that provides
sufficient deflection to make the measurement .
Do
not
re-
adjust the VARIABLE VOLTS/DIV
control .
5 . To establish an Adjusted Deflection
Factor at any
setting of the VOLTS/DIV
switch, multiply the VOLTS/DIV
switch setting
by the Deflection Conversion Factor established
in step 2 .
Adjusted
VOLTS/DIV
Deflection
Deflection
=

setting

X
Conversion
Factor

Factor
This Adjusted Deflection Factor is correct only
if the
VAR-
IABLE VOLT/DIV control is not moved from the
position
set in step l .
6 . Measure the vertical deflection
in divisions and de-
termine the amplitude by the following
formula :
Deflection
Conversion
=
Factor
Signal
Adjusted
deflection
Amplitude -
Deflection
X
Factor
(divisions)
Example . Assume a reference signal amplitude of 30
volts, a VOLTS/DIV setting of 5 and a deflection of four
divisions . Substituting these values in the Deflection Con-
version Factor formula (step 2) .
30 V
4X5V
_
1 .5
Then, with a VOLTS/DIV switch setting
of 2, the Adjusted
Deflection Factor (step
5)
is :
Adjusted
Deflection =

2 V X

1 .5 = 3 volts/division
Factor
To determine the peak-to-peak amplitude of an applied
signal which produces a vertical deflection of five divisions,
use the Signal Amplitude formula (step 6) :
Signal

=

3
V X 5 = 15 volts
Amplitude

Introduction
This section of the manual contains a description of the cir-
cuitry used in the Type 7A16 amplifier . The description
begins with a discussion of the instrument using the block
diagrams shown in the Diagrams section . Then each circuit
is described in detail using the block diagram to show in-
terconnections between the circuits and the relationship of
the frontpanel controls to the individual stages .
Complete schematics of each circuit are given in the
Diagrams section . Refer to these diagrams throughout the
following circuit description for electrical values and rela-
tionship
.
The following
discussion is provided to aid in
understand-
ing the overall
concept of
the Type
7A16 before the
indi-
vidual circuits
are discussed in detail
.
Each block on
the
Block Diagram, located in the Diagrams section, represents
an individual circuit within the instrument . The number on
BLOCK DIAGRAM DESCRIPTION
SECTION
3
CIRCUIT DESCRIPTION
Change information, if any, affecting
this section will be found at the
rear of this manual .
Fig . 3- 1 . Signal paths through input COUPLING switch .
Type 7A16
each block refers to the diagram on which the complete
circuit is found .
The signal to be displayed on the CRT is applied
to
the
INPUT connector, through the input coupling circuit
to
the
VOLTS/DIV
switch
.
The VOLTS/DIV switch provides the
appropriate input attenuation
and applies the signal to the
first stage of the Input
Amplifier . The signal is coupled
through two emitter followers, Q40-Q50, to the First Cas-
code stage, which operates as a phase-splitter . The First
Cascade stage, Q60A-Q70-Q60B-Q90, contains variable
gain circuits and bandwidth limiting circuits .
The Second Cascade Stage, Q100A-Q120A-Q100B-Q120B,
provides gain-switching, signal polarity inversion, and ver-
tical positioning . The gain-switching relays in the two cas-
code stages are operated by the VOLTS/DIV switch which,
with the input attenuators, sets the overall gain of the am-
plifier . Additional amplification is provided by the Output
Amplifier,
Q125-Q140-Q165-Q180 .
The Trigger Pickoff cir-
cuit,
Q130-Q135-Q170-Q175,
takes the signal from the emit-
ters of Q125-Q165 and amplifies it to provide + and -
trigger signals for the time base unit .

Circuit Description-Type 7A16
In addition
to the functions of the amplifier
just explained,
the Type 7A16
also provides readout logic for
the indicator
oscilloscope, Logic
identifying the Polarity and
the deflection
factor, whether
calibrated or uncalibrated is supplied
. When
the IDENTIFY button is
pressed, the readout is replaced with
DETAILED
CIRCUIT DESCRIPTION
Input Coupling
Input signals applied to
the INPUT connector can be AC-
coupled,
DC-coupled, or internally
disconnected . The input
coupling
relay, K5, a dual pole alternate
throw relay, is
operated by S3,
a three-position pushbutton
switch . Only
one side of the
DPAT relay operates at a time .
When the
AC button is
pressed, K5A is actuated
providing a signal
path from the
INPUT connector through
C3-K5A-K5B-C2-R2
(see Fig . 3-1A) . In this
position, C3 prevents the DC
com-
ponent of the signal
from passing to the amplifier .
When
the DC button is pressed,
K5B is actuated, providing a
sig-
nal path directly through K5B to
Rl (see Fig . 3-1C) . When
the GND
button is pressed, the
input signal is AC-coupled
through
C3 and R3 to ground . The
input circuit is grounded
to
provide a zero volts reference level (see
Fig . 3-113) . Re-
sistor R3 allows
C3 to be precharged in
the GND position
so the
trace remains on screen when the AC
button is pressed
with a
high DC level applied .
Input
Attenuator
The effective
overall deflection factor of
the Type 7A16
is determined by
the VOLTS/DIV switch attenuators
and the
gain-switching relays,
K105-K110-K155-K160 . The 5 mV,
10
mV, and 20 mV switch
positions employ 1 X
attenuators .
In all positions of
the VOLTS/DIV switch above 20 mV,
the
basic deflection factor of
the vertical deflection system
is
20
millivolts per division of
deflection . To increase this
basic
deflection factor to the values
indicated on the front panel,
precision
attenuators are switched into
the input circuit . The
positions
of the VOLTS/DIV switch and
the corresponding
attenuators
are as follows :
The Input Attenuators,
with R14-C14-Rl7-R18-Cl8
form
frequency-compensated voltage
dividers . For DC and low-
frequency signals, they are
primarily resistance dividers
and
the voltage attenuation is
determined by the resistance
ratio
in
the circuit . The reactance of the
capacitors in the circuit
is so high at
low frequencies that their
effect is negligible .
However, at
higher frequencies, the reactance
of the capac-
itors decreases
and the attenuator becomes
primarily a
capacitance voltage
divider .
In addition to
providing constant attenuation at
all fre-
quencies within the
bandwidth of the system, the
Input
Attenuators are designed to
maintain the same input
RC
3-2
characteristics
(one megohm

X15 pF) for
each setling of
the VOLTS/DIV
switch . The attenuators
contain adjustable
shunt
capacitors to provide input capacitance
.
Input
Stage
The
signal from the Input Attenuator is
connected to the
Input Stage
through the network Rl4-Cl4-Rl7-Rl8-Cl8
. These
resistors are part of
the attenuation network at all
VOLTS/
DIV switch
positions . Variable capacitor C18
adjusts the
basic input
time constant for a nominal value of one
meg-
ohm X 15 picofarads .
R14-C14 isolate the input
from the
gate of the input
field-effect transistor, Q20 .
Resistor R14
also limits the gate current
of Q20 .
FET Q20B is a constant
current source for the source fol-
lower, Q20A . The DC Bal
adjustment, R34, varies the gate
level of Q20B to provide a zero
volt level at the base of
Q60A
with no signal applied . Low-frequency
by-pass ca-
pacitors
C34 and C36, with L34, filter
noise from the gate
of
Q20B . L20-C20 and L30-C30 are
decoupling networks .
Damping
for Q20A is provided by R23 . The
source of Q20A
is isolated
from the base of Q40 by R28-C28 .
Resistor R28
sets the bias
of Q20A, preventing the gate
from going more
positive than the source
. Damping for Q20B is
provided by
R38 . The bias for Q20B
is set by R30 . Diode CR29
clamps
the gate of Q20A
at about -12 volts, protecting
the FET
from large negative voltage
swings .
Two emitter followers,
Q40 and Q50 couple the input
sig-
nal through R52-C52
to the First Cascade Stage .
Capacitors
C45 and C52 are adjustable
for high frequency peaking .
In
the collector of each of the
emitter followers is a damping
adjustment . Maximum damping
for Q40 is achieved
when
R40 is adjusted away from the collector
of Q40 . Maximum
damping
for Q50 is achieved when R55
is adjusted away
from
the collector of Q50 . These two
damping adjustments
are set for
a compromise between maximum
risetime and
minimum ringing
. Capacitors C23 and C56
assure that no
feedback
signals are seen by the input FETs .
First Cascode
Stage
The first
cascade stage is a paraphase
amplifier . With
R34 adjusted for zero
volts at the base of Q60A,
the quies-
cent current through
both sides of the paraphase
amplifier
is approximately 10
milliamperes . The input signal drives
the base of Q60A, and the
base of Q60B is grounded through
R82 . A positive signal at
the base of Q60A increases
the
current through
R60-Q60A-R68-R71-Q70-R100 and reduces
the current through R80-Q60B-R88-R90-Q90-Rl50,
producing
push-pull signals at the bases of Q100A
and Q100B . Resistor
R68,
paralleled by C68-1_68, and R88,
paralleled by C88-1_88,
provide thermal
balance for the stage . Resistors
R70, R71
and R90 provide
damping . The divider R73-R74
sets the
base voltage of Q70
and Q90 at approximately 6 .7
V . The
common-emitter circuit
contains two high-frequency peaking
adjustments, C61 and R61 .
The voltage gain of this stage,
from single-ended to push-
pull, is approximately 1 .6 and is set by the
ratio of R100
or R150 to
R60 and R80 . With K65 as
shown (VARIABLE
pushed in),
the exact gain of the amplifier is
set by R66
(VOLTS/DIV
switch set to 10 mV), which adjusts the
amount
of shunt current
through R64-R66-R84 . Relay K65,
actuated
in the uncalibrated
position, switches in the
R65-R85-RB6
O
i
5 mV 1X
.2V
lox
10mv
1X .5V 25X
20 m V
1
X
.1 V 50X
50 mV 2 .5X
2 V l00X
.1 V 5 X
5 V 250 X
the word IDENTIFY .
At the same time, the collector
of
Q120B is grounded
through R200, shunting some of
the
collector current which moves
the trace upward approxi-
mately 0 .25 division .

network and switches out the R64-R66-R84 network .
The
VARIABLE control (R86) affects the gain of the amplifier by
a greater degree than R66, due to the
comparatively small
values of R65 and R85 . With R86 set to minimum resistance,
the gain of the amplifier is reduced by a factor of at least
2 .5 . TheVar Gain Bal control, R89, is adjusted for no trace
shift when K65 is switched .
With the BANDWIDTH switch FULL button pressed, the
output of the first cascode stage is connected directly through
K75 to the second cascode stage . With the 20 MHz button
pressed, the bandwidth limiting circuit, C77-C97-L76-L96-L97,
is switched in by K75 . This sets the upper frequency limit of
the amplifier to approximately 20 MHz .
Second Cascode Stage
The second
cascade
stage, formed by QIOOA-Q120A-
Q100B-Q120B, contains gain switching, signal inversion, and
vertical positioning circuits . The gain of this stage in the
5
mV position of the VOLTS/DIV switch is set by the ratio
of 8123 or R163 to R102 or R151 . With the POSITION con-
trol and R117 set to midrange, the quiescent current through
Q100A and Q100B is
approximately 15 milliamperes, set
by
R104-R106-R156
.
The quiescent current through Q120A
and Q120B is
approximately 10 milliamperes, set by R118-
R166 . In the 10 mV position, Kl 10 and K160 switch
in shunt
resistor R161, reducing the gain by a factor
of two . In the
20 mV position, K105 and K155 switch in shunt
resistor R159
and series resistors R108 and R158, reducing
the
gain by
an
additional factor of two . The deflection factor at the
out-
put of this stage is 15 mV/Div per side .
The emitter circuit of Q100A-Q100B contains high-fre-
quency peaking adjustments C102-R103-C103 . Compensation
in the 10 mV position is provided by C111-R111 .
Additional
compensation in the 20 mV position is provided by C109-
R109 . Thermal compensation networks for Q100A and Q100B
are formed by R105-C105 and R155-C155 . Resistors R106
and R156 set the voltage drop across the gain-setting di-
viders to zero volts . The Step Atten Bal control, R153, is
adjusted for no trace shift when switching K105 and K155
or K110 and K160 . Thermal compensation networks for
Ql20A and
Q1 20B
are formed by C124-R124 and C164-R164 .
The polarity inversion circuit consists of a DPDT relay,
K115, and a front panel push-button POLARITY switch . With
the +UP button pressed, the relay is as shown in the schemat-
ic . With the INVERT button pressed, Kl15 is actuated, in-
verting the signal outputs and the trigger outputs .
The vertical
POSITION control, R115, applies DC voltages
of opposite
polarity to the two sides of the amplifier through
R114 and R160 . This offset voltage is
DC-coupled to the
output moving the trace upward
or downward on the CRT .
With the vertical POSITION control set to
midrange, the
position centering network, R117-R118-R168, applies a posi-
tive voltage to one side of the amplifier,
centering
the
trace
vertically on the CRT .
Output Stage
The output stage consists of the
emitter-feedback and
shunt-feedback amplifiers, Q125-Q165 and Q140-Q180, and
the trigger pick-off amplifier Q130-Q135-Q170-Ql75 .
The
gain of the output amplifier is approximately five, set by
Readout Block
Circuit Description-Type 7A16
the ratio of R142-R182 to R128-R168
.
Thermistor (RT128) and
Varactors (CR128-CR168) provide proper compensation
for
transient response variations with temperature . Thermal
compensation for Q125 and Q165 is provided by
R125-C125
and R165-C165 . Resistor R129 provides the DC
current
source
for Q125 and Q165 . Decoupling
for the output amplifier
is
provided by L140 and C140 . The -15 volt supply is decou-
pled in the common-emitter circuit of Q140-Q180 by L143
and C143 . R141-R181-R143 provide approximately 18
milli-
amperes DC current for each output transistor . The output
signals are reverse terminated by C145-R145 and C185-R185 .
These networks, with the 50-ohm terminations in the indicator
oscilloscope, produce an output deflection factor of 25 milli-
volts/division per side .
The trigger pickoff amplifier takes the output signal from
the emitters of Q125 and Q165 and amplifies it to a level
near that of the output amplifier . Resistor R131 sets the DC
current for Q130 and Q170 through R130 and R170 respec-
tively . Capacitor C130 provides high-frequency peaking .
Thermal compensation for Q130 and Q170 is provided by
C133-R133 and C173-R173 . Divider R172-R174-R137-R177
provides approximately 15 milliamperes each for Q135-Q175 .
The output signal from the trigger pickoff amplifier is reverse
terminated by C138-R138 and C178-R178 .
The readout block consists of switching resistors and a
probe sensing device . The switching resistors, selected by
the setting of the Readout Switch (part of the VOLTS/DIV
switch), are used to signal the Indicator Oscilloscope the
setting of the VOLTS/DIV switch .
Refer to Schematic Diagram 4 (Section 7), Switching and
I : ;terconnecting Plug, to find the resistors associated with
a particular setting of
the VOLTS/DIV switch . The number
1, 2, or 5 is selected by R207-R208-R209 . R207 selects
the
numeral
1, R207-R208 selects the numeral 2, and R207-R209 .
selects the numeral 5 . R226-R228-R234 and
the output of
the probe sensing device (Q200) selects the decimal
point
(number of zeroes) .
R224-R225, when switched in, gives the
Volts sub-unit m (milli) . R205-R206 selects the symbol V (volts)
.
R218-R220 selects the symbol > when the VARIABLE VOLTS/
DIV knob is in the uncalibrated position . R219-R222 selects
the symbol + when the INVERT pushbutton is pressed in .
The probe connected to the INPUT connector forms a
voltage divider with R202 to the -15 volt supply . The
amount of probe resistance will determine the bias applied
to the base of Q200 .
With a 1 X probe connected, Q200 is biased off by the
-15 volt supply, and the deflection factor (in the readout
display) is determined by the setting of the Readout Switch
(part of the VOLTS/DIV switch) .
With a IOX probe connected to the INPUT connector,
the bias applied to the base of Q200 will allow 1001(A of
collector current to flow . When the clock pulse interrogates
interface connector B33, this current is added to the current
corresponding to the setting of the Readout Switch to in-
crease the deflection factor (in the displayed readout) by 10 .
The Indicator Oscilloscope displayed readout will give the
correct deflection factor from the probe tip (using the
3-3

Circuit Description-Type 7A16
recommended attenuator
probes) whereas the VOLTS/DIV
knob on the Plug-In will display
only the Plug-In deflection
factor .
The trace IDENTIFY button, when
pressed, does two things :
l .
It causes the trace, representing
the output of the Type
7A16,
to move upward a small amount
by inserting R200
from
the collector of Q120B to ground . This
shunts a small
amount of
the collector current causing the
trace to move .
2 .
It also grounds the base of Q200 .
This causes Q200
to turn on hard
erasing the displayed readout
and causing
the word IDENTIFY
to appear .
These two
actions aid in identifying the
Type 7A16 trace
when multiple
traces are displayed .
When the IDENTIFY
button is released,
the readout is restored to
its previous
display .
For more specific
information on the operation of
the Indi-
cator Oscilloscope refer
to the appropriate Indicator
Oscillo-
scope Manual .

Introduction
This section of the manual contains maintenance infor-
mation for use in preventive maintenance, corrective main-
tenance
and troubleshooting of the Type 7A16 .
General
Preventive maintenance consists of
cleaning, visual inspec-
tion, lubrication, etc . Preventive maintenance
performed
on a regular basis may prevent instrument breakdown
and
will improve the reliability of this instrument
.
The severity
of the endironment to which the Type 7A16 is subjected
determines the frequency of maintenance . A convenient time
to perform preventive maintenance is preceding recalibration
of the instrument .
Cleaning
O
i
PREVENTIVE MAINTENANCE
The Type7A16 should be cleaned as often as operating
conditions require . Accumulation of dirt in the instrument
can cause overheating and componentbreakdown . Dirt on
components acts as an insulating blanket and prevents ef-
ficient heat dissipation . It may also provide an electrical
conduction path .
The covers of the indicator oscilloscope
minimize
the a-
mount of dust which reaches the interior of the Type7A16 .
Operation of the system without the indicator oscilloscope
covers in place necessitates more frequent cleaning . When
the Type7A16 is not in use, it should be stored in a pro-
tected location such as a dust-tight cabinet .
CAUTION
Avoid the use of chemical cleaning agents which
might damage the plastics used in this instrument .
Avoid chemicals which contain benzene, toluene,
xylene, acetone
or
similar solvents .
Exterior . Loose dust accumulated on the outside of the
Type
7A16 can be removed with a soft cloth or small paint
brush . The paint brush
is particularly useful
for dislodging
dirt
on and around the front-panel controls . Dirt which
re-
mains can be removed with a soft cloth dampened in a
mild detergent and water solution . Abrasive cleaners should
not be used .
Interior . Dust in the interior of the instrument should be
removed occasionally due to its electrical conductivity under
high-humidity conditions . The best way to clean the interior
is to blow off the accumulated dust with dry, low-velocity
air . Remove any dirt which remains
with a soft
paint brush
or a cloth dampened with a mild detergent and water solu-
tion
.
A
cotton-tipped applicator is useful for cleaning in
narrow
spaces .
SECTION 4
MAINTENANCE
Change information, if any, affecting this section will be found at
the
rear of the manual .
Lubrication
Visual Inspection
Transistor Checks
Recalibration
Introduction
TROUBLESHOOTING
Type 7A16
General . The reliability of
potentiometers and other
moving parts can be maintained if they are kept properly
lubricated . Potentiometer shaft bushings should be lubricated
with a light-weight lubricant (e .g ., Tektronix Part No . 006-
0172-00) . Do not over lubricate . A lubrication kit containing
the necessary lubricants and instructions is available from
Tektronix, Inc . Order Tektronix Part No . 003-0342-01 .
The Type 7A16 should be inspected occasionally for such
defects as broken connections, broken or damaged circuit
boards,
improperly seated transistors or relays,
and
heat-
damaged parts .
The corrective procedure for most visible defects
is
obvi-
ous ; however, particular care must be taken if
heat-damaged
components
are found . Overheating usually indicates other
trouble in the instrument ; therefore, it is important that the
cause of overheating be corrected to prevent a recurrence
of the damage .
Periodic checks of the transistors in the Type7A16 are
not recommended . The best check of transistor performance
is actual operation in the instrument . More details on check-
ing transistor operation is given under Troubleshooting .
To ensure accurate measurements, check the calibration
of this instrument after each 1000 hours of operation or every
six months if used infrequently . In addition, replacement of
components may necessitate recalibration of the affected
circuits . Complete calibration instructions are given in Section
5 .
The Performance Check/Calibration Procedure can also be
helpful in localizing certain troubles in the instrument . In
some cases, minor troubles may be revealed and/or cor-
rected
by
calibration .
The following information is provided to facilitate trou-
bleshooting of the Type 7A16 . Information contained in other
sections
of
this
manual should be used along with the follow-
ing
information to aid in locating the defective component .

Maintenance-Type
7AII6
An understanding
of the circuit
operation is very helpful
in
locating troubles
. See the Circuit
Description section
for
complete
information .
Troubleshooting
Aids
Diagrams . Circuit
diagrams are given on
foldout pages
in section 7 . The
componentnumber and
electrical value
of each component in
this instrument are
shown on the dia-
grams .
Switch Wafer Identification
. Switch wafers
shown on
the diagrams are coded
to indicate the position
of the wafer
in the complete switch assembly
. The numbered
portion of
the
code refers to the wafer
number counting from the
front,
or
mounting end of the switch,
toward the rear . The
letters
F and R indicates whether the
front or rear of the wafer
per-
forms the
particular switching
function . For example,
a
wafer
designated 2R indicates
that the rear of the
second
wafer is used for this particular
switching function .
Wiring
Color-Code . All
insulated wire and cable used
in
the Type 7A16 is color-coded
to facilitate circuit
tracing .
Signal
carrying leads are identified
with one or two colored
stripes on
white insulation . Voltage
supply leads have col-
ored insulation
indicating the polarity
of the supply ; red for
positive
supplies, violet for negative supplies .
The stripe on
a voltage lead
indicates the number of the
supply, using the
Composition Resistors :
Metal-Film Resistors :
Ceramic Capacitors
:
Resistor and Capacitor
Color Code
Signifi-
Multiplier
I Tolerance
cant Resis- Capaci-
Resis- Capaci-
Figures tors - toys 1 tors

tors
10

10

i-1 %

±l % or
0 .1 pF*
%
or
pF*
or
or
1 pF*
(D@
and
O
-1 st,
2ndand 3rd significant figures ;
-multiplier ;
O
-tolerance ;
@
-temperature
coefficient .

NOTE : OT and/or ©C color code
for capacitors depends upon
manufacturer and capacitor type . May not be
present in some cases .
*For capacitance of 10 pF or
less .
4-2
Fig . 4-1 . Color-code
for resistors and ceramic capacitors
.
EIA color
code, counting in
sequence from ground
all supplies
in the
oscilloscope system
. The +15-volt supply lead
is
identified
by a brown stripe
on red insulation,
indicating
the second
positive supply
from ground . (The -f-5-volt
supply
is the
first positive supply .)
The -15-volt supply
lead is
identified by
a black stripe on violet
insulation .
Resistor
Color-Code . Brown
composition resistors
and
metal-film
resistors are used in the
Type 7A16 . The resistance
values of
composition resistors and
metal-film resistors
are
color coded
on the components
(some metal-film
resistors
may have
the value printed on the
body) with EIA
color-
code . The
color code is read
starting with stripe
nearest
the end of
the resistor . Composition
resistors have
four
stripes which
consist of two significant
figures, a multiplier
and a tolerance
value (see Fig . 4-1) .
Metal-film resistors
have five stripes
consiting of three
significant figures, a
multiplier and a
tolerance value .
Capacitor Marking
. The capacitance
values of common
disc capacitors and
small electrolytics are
marked in micro-
farads on the side of
the component body .
The white ceramic
capacitors used in
the Type7A16 are color coded
in pico-
farads using amodified EIA
code (see Fig . 4-1) .
Diode Color Code .
The cathode end of
each glass-
encased diode in indicated
by a stripe, a series of
stripes
or
a dot . For most silicon
or germanium diodes with
a series
of stripes, the color code
also indicates the type of
diode
Red 2 10 2
10 2
±2% ±2%
Orang e 3 ~_ 103
10 3 1 _L3% -L30/ .
Yellow 4 10 4
10 4
±4%
+100
-0
Green 5 10 5
10 5 ±0 .5% ±5%
0 .5 pF*
Blue 6 10 6
10E
___ ---
Violet 7 --- --- --- ---
Gray 8---
10-2
---
+80%
-20%
or 0 .25
White
9
--- lp-1 ---
±10%
1 pF*
(none)
---
±20%±10%

Insert the Type 7A16 and a
calibrated time base unit into
a calibrated oscilloscope . Turn
the power on and allow several
minutes warmup .
POLARITY,
BANDWIDTH
and COUPLING
buttons light
when pressed
Set horizontal and vertical
POSITION controls to mid-
range VOLTS/DIV to 10 mV,
POLARITY to +UP, BAND-
WIDTH to FULL
and Time/
Div
to 0 .5 ms .
Free run the
sweep and advance the inten-
sity .
Press IDENTIFY button .
Check
that
the readout is
replaced by the word
IDEN-
TIFY
and
that the trace moves
upward about 0
.25 divisions .
Yes
Connect the oscilloscope cali-
brator 40 mV square wave
output through a BNC cable
to the Type 7A16 INPUT .
Check for four divisions of
square wave amplitude .
Yes
Trigger the sweep using
inter-
nal triggering . Check for stable
display .
Remove the Type 7A16
from
the oscilloscope and
check for
a free running trace .
If part of
the readout is miss-
ing or
incorrect, check the
Type 7A16
readout circuit
using the
Circuit Description
(Section 3) and the diagram in
Section
8 . Refer to oscillo-
scope
manual for oscilloscope
readout circuitry .
Check output
amplifier . Check
positioning circuit .
Still no trace
Check
time base
unit control
set-
tings . Check sweep
output .
Fig . 4-2 . Troubleshooting chart for Type 7A16 .
Maintenance-Type 7A16
4- 3
Readout
stays Check IDENTIFY Switch,
on CRT
Q200
and associated circuitry
.
Trace does
not
shift
Check
IDENTIFY switch,
0120B and output amplifier .
Check waveforms and voltages
No Deflection
using
Schematic Diagrams .
Near four divi-
Check inputattenuator
.
sions of deflec-
tion
Adjust front panel
GAIN for
four divisions of
deflection .
Near eight divi-
Check relays K110
and K160 .
Check for
+15
V
at the relay
sions of deflec-
coil .
tion
Stable display
cannot be
ob-
tained
Check
trigger pickoff circuit
for same
output signal as out-
put
amplifier .