Tektronix 7A16 User manual

INSTRUCTION
MANUAL
Seriol Number _____ _
7A16
AMPL.IFIER
Tek tr onix, Inc.
S,W. Millikan Way . P. O. Box 500 • Beaverton, Oregon 97005 • Phone 644 ·0 161 • Cables : Tektronix
070 -0980-00 1069

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WARRANTY
All Tektronix instruments are warranted
against defective materials and workman-
ship for one year. Tektronix tran sformers,
manufactured in our plont, are warrante d
for the life of the instrument.
Any questions with respect to the war-
ranty mentioned above should be token
up with your Tektronix Field Engineer.
Tektronix repair and replacement - port
se rv ice is geared directly to the field,
therefore all requests for repairs and re-
pla cement parts should be directed to the
Tektronix Field Office or representative
in your orea. This procedure w ill assure
you the fostest possible service. Please
i nclude the in strumen t Type and SerioI or
Model Numbe r with all reques ts for ports
or service.
Specifications
cnd price c han ge privi-
leges reserved.
Copyright ©
1969 by Tektronix, Inc.,
Beaverton, Oregon . Pr inted in the United
States of America. All rights reserved.
Contents
of this publication may not be
repr o duced in any form without permis-
sion
of the copyright owner.

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

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POSITION
POLARITY
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IfIIVERT .
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FULL .
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Fig _1-1. Tvpe 7A 16 Amplifier _
®
ArtekMedia
Digitally signed by ArtekMedia
DN: cn=ArtekMedia, o=ArtekMedia.com,
ou, [email protected], c=US
Date: 2008.11.16 17:41:57 -06'00'

Type 7A16
SECTION J
SPECIfICATIONS
Change information, if any, affecting this section will be found at the
rear of the manual.
INTRODUCTION
The Type 7A16 vertical amplifier plug-in unit is part of the
7ooo-series oscilloscope system.
It is a wide band DC coupled
amplifier with calibrated deflection factors from 5
mV /Div to
5 V/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.
Characteristic
Deflection Factor
Calibrated Range
Gain Ratio Accuracy
Uncalibrated
(Variable)
Gain
Frequency Response;
System Dependent
(8
division reference)
Upper Bandwidth
DC
Coupled
Lower Bandwidth AC
Coupled
With P6053 Probe
TABLE 1-1
ELECTRICAL
Performance
5 mV /Div to 5 V/Div, 10 steps in
a 1-2-5 sequence.
Within
2%
of gain adjusted at
10mV/Div.
Continuously variable between cal-
ibrated deflection factor settings.
Extends uncalibrated deflection
factor to
at least 12.5 V/Div.
Permits adjustment
of deflection
factor for all 7000 series oscillo-
scopes.
With Type 7704 With Type 7504
Oscilloscope Oscilloscope
150MHz
90 MHz
10 Hertz or less.
1 Hertz
or less.
20 Megahertz Band-
DC to 20 megahertz within 3
width megahertz.
Risetime 15 nanoseconds to
21 nanoseconds.
Maximum Input Voltage
DC (Direct) Coupled
100mV/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-
5OOV.
pled Input
DC Volt-
age
Input Resistance 1 megohm within 2%.
Input Capacitance 15 picofarads within 0.5 picofarad.
Rand C Product Within
1%
over all deflection
factor settings.
Maximum Input
Gate 0.5 nanoampere or less at O°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 250ttV/minute (P-P) or 0.05 divi-
sion (whichever
is greater) after 1
hour warmup.
Long Term 250 ttY/hour (P-P) of 0.05 division
(whichever
is greater) after 1 hour
warmup.
Drift With Ambient 100 ttV/oC
or less.
Temperature
(Line
-
Voltage Constant)
TABLE 1-2
ENVIRONMENTAL
Characteristic
Temperature
OperatinQ
Altitude
Non-operating
Transportation
Item
Finish
Weight
Dimensions
Performance
To 50,000 feet and -55°C
Qualified under National Safe
Transit Committee test procedure
1
A, Category II.
TABLE 1-3
PHYSICAL
Information
Front Panel is anodized aluminum.
About 1.75 pounds.
Fits plug-in compartment of 7000-
Series Oscilloscopes.
1-1
\

Type 7A16
SECTION 2
OPERATING INSTRUCTIONS
Change information, if any, affecting this section will be found at the
rear of the manual.
General
The Type 7A16 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 7A 16, 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.
Installation
The Type 7A 16 is designed to operate in a vertical pl'ug-
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 7A 16 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
VARIABLE
(CAL IN)
POSITION
IDENTIFY
®I
Selects vertical deflection factor from 5
mV /DIV to 5 V /DIV in 1-2-5 sequence
(V AR control must be in the calibrated
position for indicated deflection factor).
Provides variable uncalibrated deflection
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.
Controls vertical position of trace.
Moves trace upward about 0.25 division
for identification.
(Also replaces readout
information
with the word IDENTIFY.)
POLARITY
BANDWIDTH
AC-GND-DC
GAIN
STEP ATTEN
BAL
INPUT
General
Provides means of inverting the display.
+UP: A positive-going voltage at the
INPUT produces a positive de-
flection on the CRT.
INVERT: A positive-going voltage at the
INPUT produces a negative de-
flection on the
CRT.
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.
Selects method of coupling input signal to
Input Amplifier.
Screwdriver adjustment to set gain of the
amplifier. Gain standardized at 10 mV /
Div.
Screwdriver adjustment to minimize trace
shift when switching
VOLTS/DIV control.
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.
FIRST-TIME OPERATION
When shipped from the factory, the Type 7A16 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.
Setup Information
1. Insert the Type 7A 16 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:
2-1

Operating Instructions-Type 7A16
VOLTS/DIV
VARIABLE (CAL IN)
POSITION
POLARITY
BANDWIDTH
AC-GND-DC
Time/Div
Variable Time/Div
Slope
MODE
Coupling
Source
Position
Type 7A16
10 mV
Calibrated
Midrange
+UP
FULL
GND
Time Base
0.5 ms
Calibrated
0/+
P-P Auto
AC
Int
Midrange
Indicator Oscilloscope
Calibrator
Intensity
Focus
Astigmatism
Scale Ilium
40 mV Square Wave
Counterclockwise
Midrange
Midrange
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 hori.zontal 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 waveform when 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 A HEN 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
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 10X attenuator probe offers a high input
impedance and allows the circuit under test to perform very
close to normal operating conditions. However, a lOX
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 signa1, use
high-quality, low-loss cable. Resistive coaxial attenuators
can be used to minimize reflections if the applied signal has
suitable amplitude.
®

DATA:
®
Operating Instructions--Type 7A16
TYPE 7A16 AMPLIFIER SETUP CHART
POSITION
@
DAC
DGND
POLARITY
+upD
INVERT 0
BANDWIDTH
FULL 0
20MHz 0
VARIABLE (CAL IN)
VOLTS/DIV
~~
@(~
lMO
15pF
TEKTRONIX®
\7A16\
STEP ATTEN BAL
AMPLIFIER
Fig. 2-2. Control setup chart.
2-3

Operating Instructions-Type 7A 16
Fig. 2-3. Waveform distortion produced with incorrect probe ground.
(AI Eighteen-inch ground strap between generator and oscilloscope.
(BI 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 (-3 dB
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 n.etwork 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 Type 7A16 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 (5 V 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 A HEN BAL ad justment as follows (allow
®

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 mY, 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
A TTEN 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 mY.
Signal Polarity
The POLARITY switch provides a means of inverting the
display. With the +UP button pressed, a positive-going
®I
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
whp.n
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 7A 16 I DENTI FY button is pressed, the
CRT display is deflected upward about 0.25 division for
identification.
This feature is particularly useful when the
Type 7A
16 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. is 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
7A 16 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
NOTE
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.
. NOTE
This technique may also be used to make measure-
ments between two points on the waveform rather
than peak-to-peak.
7. Multiply the distance measured in step 6 by the YOLTS/
DIY 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 lOX attenuator probe and a YOLTS/
DIY switch setting of .5 Y.
Using the formula:
Yolts vertical YOLTS/DIY
peak to peak = deflection X setting
(divisions)
Substituting the given values:
Yolts
peak to peak = 4.6 X 0.5 X 10
The peak-to-peak voltage is 23 volts.
probe
X attenuation
factor
Fig. 2-5. Measuring peak-Io-peak vollage 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 YOLTS/DIY switch to
display about five divi-
sions of the waveform. Make sure the YARIABLE YOLTS/DIY
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
YOLTS/DIY 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 lOX attenuator probe and a YOLTS/DIY switch
setting
of 2 Y.
Using the formula: Instantaneous Yoltage =
vertical
distance X
(divisions) polarity X
Substituting the given values:
YOLTS/DIY
setting
probe
X attenuation
factor
Instantaneous voltage = 4.6 X +1 X 2 Y X 10
The instantaneous voltage is +92 volts.
®I
i
.J
J

-
~ .
..,
~
y
. _.
~
.. ::iI
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:
1. 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 7A 16
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
Deflection
Factor
VOLTS/DIV Deflecti.on
tf X Conversion
se
mg Factor
This Adjusted Deflection Factor is correct only if the VAR-
IABLE VOLT / DIV control is not moved from the position
set
in step 1.
6. Measure the vertical deflection in divisions and de-
termine the amplitude by the following formula:
Signal
Amplitude Adjusted d
fl t·
. e ec Ion
Deflection X (d. .. )
Factor
IVlslons
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).
Deflection
30V
Conversion = 4 X 5 V = 1.5
Factor
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 15 I
A I· d = 3 V X 5 = vo
ts
mp Itu e
2-7

Type 7A16
SECTION 3
CIRCUIT DESCRIPTION
Change information, if any, affecting this section will be found at the
rear of
this manual.
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.
BLOCK DIAGRAM DESCRIPTION
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
(A) C2
~
r!J
C3
K5A
SIGNAL
~I
~
INPUT
R2
NO
I GND I
C2
(B)
rA~
~
SIGNAL
AA
INPUT
v v
R2 R3
[§J
(C)
R1 K5B
-
each block refers to the diagram on which the complete
ci rcuit 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
Cascode stage, Q60A-Q70-Q60B-Q90, contains variable
gain circuits and bandwidth limiting circuits.
The
Second Cascode Stage, Ql OOA-Q120A-Ql OOB-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.
K5B
=0--0
----------l .. ~ To S10
NC
To S10
K5B
K5A
-
NC -NC 1
I
SIGNAL
5
; 'VV\
_---------------~._ ToS10
~
INPUT
NO
Fig. 3-1. Signal paths through input COUPLING switch.
® 3-1

Circuit Description-Type 7A 16
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
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.
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. 3-1 A). 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 R1 (see Fig. 3-1 C). 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. 3-1 B). 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-KllO-K155-K160.
The 5 mY, 10
mY, and 20 mV switch positions employ 1X attenuators.
In all positions of the VOLTS/DIV switch above 20 mY, 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:
5mV 1X .2V
lOX
10 mV 1X
.5V
25X
20 mV
1X .1 V SOX
50 mV
2.5X 2V
100X
.1 V
5X
5V 250X
The Input Attenuators, with R14-C14-R17-R18-C18 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 X 15 pF) for each setl ing 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 R14-C14-R17-R18-C18. 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 Cascode 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 cascode 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-RlOO and reduces
the current through R80-Q60B-R88-R90-Q90-R150, producing
push-pull signals
at the bases of Q100A and Q100B. Resistor
R68, paralleled by C68·L68, and R88, paralleled by C88-L88,
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 mY), which adjusts the amount
of shunt current through
R64-R66-R84. Relay K65, actuated
in the uncalibrated position, switches in the R65-R85-R86
®I

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. The Var 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 cascode stage, formed by Q100A-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
R123 or R163 to R102 or R151. With the POSITION con-
trol and Rl17 set to midrange, the quiescent current through
Q100A and Q100B is approximately 15 milliamperes, set
by
R1 04-R1 06-R156. The quiescent current through Q120A
and Q120B is approximately 10 milliamperes, set by R1l8-
R166. In the 10 mV position, K110 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 Cll1-Rlll. 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
Q120A and Q120B 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, K115 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
Rl14
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, Rl17-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 Q130Q135-Q170-Q175. The
gain of the output amplifier
is approximately five, set by
Circuit Description-Type 7A 16
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 Rl72-R174-R137-Rl77
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.
Readout Block
The readout block consists of switching resistors and a
!)I'obe 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, :terconnecti ng PI ug, to fi nd 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
numeralS. R226-R228-R234 and the output of
the probe sen"ing 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 t 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 1X 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
lOX probe connected to the INPUT connector,
the bias applied to the base of Q200
will allow 100 ItA 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 7A 16
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:
1. It causes the trace, representing the output of the Type
7A16,
to move upward a small amount by inserting R200
from the collector of 0120B to ground. This shunts a small
amount of the collector current causing the trace to move.
2. It also grounds the base of 0200. This causes 0200
3-4
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.
®

Type 7A16
SECTION 4
MAINTENANCE
Change information, if any, affecting this section will be found at the
rear of the 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.
PREVENTIVE MAINTENANCE
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 en
..ironment 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
The Type 7A16 should be cleaned as often as operating
conditions require. Accumulation of dirt in the instrument
can
cause overheating and component breakdown. 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 Type 7A16.
Operation of the system without the indicator oscilloscope
covers
in place necessitates more frequent cleaning. When
the Type 7A16 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 deaning in
narrow spaces.
®I
Lubrication
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.
Visual Inspection
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.
Transistor Checks
Periodic checks of the transistors in the Type 7A16 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.
Recalibration
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 Pr~cedure 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.
TROUBLESHOOTING
Introduction
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.
4-1

Maintenance-Type 7A16
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 component number 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:
Ceramic Capacitors:
00 and 0 -1 st, 2nd and 3rd significant figures;
® -multiplier; 0 -tolerance;
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 +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 Type 7A16 are color coded in pico-
farads using a modified
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
Resistor
and Capacitor Color Code
Color
Signifi- I Multiplier
.cant I Resis- I Capaci-j
Figures _t~ tors
Silver I I 10-2 I
Gold I I 10-1 I
Tolerance
Resis- Capaci-
tors tors
+10%
+5%
I 0 I 1
+20% or
2 pF*
Black
Brown I I 10 10 + 1% + 1% or
0.1 pF*
~-I 2 I 102 102 +2% I +2%
Orange I 3 I 103 103 +3% I +3%
Yellow I 4 1----:
1
:-::
0
-;-4 ~~~-_-:-1.."._07.4=~-{1- -~-4-:-:0:71o-1::='=+=_:1~:~~:,-1o~~1
Green I 5 1 105 105 +0.5% +5% or
0.5 pF*
Blue
I 6 I 106 106
Violet I 7 I
Gray
8 10-2
+80%
-20%
or 0.25 pF*
White 9 10-1 +10% or
1 pF*
(none)
+20% +10% or
1 pF*
*For capacitance of 10 pF or less.
@ -temperature coefficient.
NOTE: 0 and/or ®. color code for capacitors depends upon
manufacturer
and capacitor type. May not be present In some cases.
Fig. 4-1. Color-code for resistors and ceramic capacitors.
4-2
®

Maintenance-Type 7A16
Insert the Type 7A 16 and a
Buttons
do not t Check for +5 volts
at +5 V TP
calibrated time base unit into
on the main circuit board.
a calibrated oscilloscope. Turn
the power on and allow several light
when press·
minutes warmup. ed
POLARITY,
BANDWIDTH
and COUPLING
buttons
light
Remove the Type 7A 16 from
Check time base
when pressed Still
no trace
unit control set·
r ....... '- .. · .........
tings. Check sweep
a free running trace.
Set horizontal and vertical
output.
POSITION controls to
mid· Trace does
not
range VOLTS/DIV to 10 mV, appear
POLARITY to +UP, BAND· Yes Check signal
output
WIDTH to FULL and Timel
DC balance. Check
Div to 0.5 rns. Free run the Correct
readout
output amplifier.
sweep and advance the inten·
does not appear
sity. If
part of the reedout is miss·
ing
or
incorrect, check the
Type
7A16
readout circuit
Trace
Appears
~
using the Circuit Description
Readout appears (Section 3) and
the diagram in
Section
8.
Refer to oscillo·
scope manual
for oscilloscope
Rotate the POSITION control readout circuitry.
and check for movement of
Trace does
not
trace. move l Check
output amplifier. Check
positioning circuit.
Yes
Press IDENTIFY button.
Readout
stays
Check
IDENTIFY
switch,
Check
that the reedout is
on CRT
Q200 and associated circuitry.
replaced by
the word IDEN·
TlFY and that the trace moves Trace does
not
upward about 0.25 divisions.
shift
Check
IDENTIFY switch,
Q120B and
output amplifier.
Yes
Connect the oscilloscope cali· No Deflection Check waveforms
and voltages
brator 40 mV square wave
using
Schematic
Diagrams.
output through a BNC cable Near
four
divi· Check
input attenuator.
to
the Type 7A16
INPUT. sions
of deflec·
Check for four divisions of
~on
square wave amplitude. Adjust
front panel GAIN for
four divisions of deflection.
Yes
Near eight divi· Check relays K110
and K160.
Check
for +15 V at the relay
sions
of deflec· coil.
Trigger the sweep using inter·
tion
nal triggering. Check for stable
Stable display
display.
cannot
be
ob· L
tained Check trigger pickoff circuit
for same
output signal as out·
put amplifier.
Fig. 4-2. Troubleshooting chart for Type 7A 16.
® 4-3