Tektronix 791AD User manual

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7912AD
CALIBRATION KIT
067-0854-00
TEKTRCNI~

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Tektronix, Inc.
P.O. Box 500
Beaverton, Oregon 97077
First Printing MAY 1978
COMMITTEDTO EXCELLENCE
7912AD
CALIBRATION KIT
067-0854-00
INSTRUCTION MANUAL
Serial Number
070-2490-00

WARRANTY
All TEl(TRONIX instrtJments are warranted against
defective materials
'cc;•··.,~orkmanship for one
Any questions with f'i'R~!ct to the warranty snc>u1ci.
betaken up with y~yrJiEl(TRONIX Field Engineer
representative.
vy~~"
All requests·~~fottr ·~i~~~~ ... and replacement parts
should be direC'tes o the TEKTRONIX Field Office
or representative ip.your area. This will assure you
the fastest ~si~le •;'~~flice: Plea~f~'rich.ide th~~·
instrument e Nomb~.tlbr Part Nuriltferand Serictl;1
Number wit · U.;~eqo~llt{flor parts dP~ervice.
• ···~
0
$~"C.2g~
1
~~~~~':.:~J·;~'i7~;z.itj~~VTektronix, Inc., Beaverton,
, .• ·oreganf'Printed in. the United States of America. All
rights reserved. Contents of this publication may not
be reproduced in any form without permission of
Tektronix, Inc.
U.S.A. and foreign Tektronix products covered by
U.S. and foreign patents and/or patents pending.
TEKTRONIX is a registered trademark of Tektronix,
Inc.

7912AD CALIBRATION KIT
TABLE OF CONTENTS
SAFETY SUMMARY
SECTION 1 - OPERATION
Calibration Aid
Controls and Connectors
Specifications
Cables and Connectors
Extender Boards
SECTION 2 - SERVICING
Circuit Description
Cathode Blanking
Preamp
Resolution Check
Maintenance
Preventative
Troubleshooting
Corrective Maintenance
Calibration
Introduction
Calibration Procedure
SECTION 3 - ELECTRICAL PARTS LIST
SECTION 4 - DIAGRAMS
SECTION 5 - MECHANICAL PARTS LIST
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1-1
1-1
1-2
1-5
1-6
2-1
2-1
2-2
2-3
2-3
2-4
2-4
2-5
2-5
2-5
2-7

7912AD CALIBRATION KIT
SAFETY SUMMARY
This manual contains safety information which the user must follow to
ensure safe operation of this instrument. WARNING information is intended
to protect the operator. The following are general safety precautions
that must be observed during all phases of operation and maintenance.
WARNING
The following servicing instructions are for use
by qualified personnel only. To avoid personal
injury, do not perform any servicing other than
that contained in operating instructions unless
you are qualified to do so.
Ground the Instrument
To reduce electrical-shock hazard, the 7912AD chassis must be properly
grounded. Refer to the 7912AD Service Manual for grounding information.
Do Not Operate in Explosive Atmosphere
Do not operate this instrument in an area where flammable gases or fumes
are present. Such operation could cause an explosion.
Do Not Service or Adjust Alone
Do not service or make internal adjustments to this instrument unless
another person, capable of giving first aid and resuscitation, is
present.
Disconnect Power Before Servicing
To avoid electrical shock, disconnect the instrument from the power
source before soldering.
To avoid electrical shock, disconnect the instrument from the power
source before replacing components.
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ii

7912AD CALIBRATION KIT
2384-01
The 7912AD Ca1ibration Kit
iii

7912AD CALIBRATION KIT
SECTION 1
OPERATION
The TEKTRONIX 7912AD Calibration Kit provides signals and makes
signal connections for calibration and repair of the TEKTRONIX 7912AD
Programmable Digitizer. For these purposes, the kit contains a
calibration signal source, cables, and extender cards. The calibration
signal source is the same one supplied with the R7912 Calibration Kit;
however, new cables and extenders have been substituted as necessary.
Calibration Aid
The Calibration Aid is a calibration signal source that is used
during several steps in the 7912AD calibration procedure. Also called the
Video Calibrator, it provides special-purpose signals used to adjust the
7912AD video preamplifier and processor and to check the horizontal
resolution of data acquired by the 7912AD. Specific operating
instruct~ons for the Calibration Aid are not given in this manual because
these instructions are part of the 7912AD calibration procedure. More
general operating information is given here, however, to describe the
controls and connectors and to specify performance of the Calibration
Aid.
Controls and Connectors
Power Connector: Mates with the 7912AD PROBE POWER outlet to power
the Calibration Aid.
VIDEO CALIBRATION Connector: Provides either the CATHODE BLANKING or
PREAMP signal (selected by switch).
CATHODE BLANKING: A negative-going pulse used to blank a small area
in the center of the 7912AD scan converter target.
PREAMP: A standard-amplitude signal to check the gain of the 7912AD
video preamplifier.
1-1

7912AD CALIBRATION KIT
RESOLUTION CHECK Connector: Provides a fast-rise signal as selected
by the VERTICAL DELAY switch. This signal is used to check the 7912AD
data resolution. When the VERTICAL DELAY switch is set to the IN
position, the signal is delayed by about 1.25 nanoseconds from the
triggering signal.
TRIG OUT Connector: Provides a triggering signal for the other
outputs. The CATHODE BLANKING/PREAMP switch must be set to PREAMP to get
either the PREAMP or RESOLUTION CHECK triggering signal.
CAL Connector: Provides input for a clock signal from the 7912AD.
SYNC IN Probe: Provides input for a sync signal from the 7912AD.
Specifications
The electrical specifications listed in Table 1-1 are valid within
the environmental limits in Table 1-2. Also, the Calibration Aid must be
calibrated within each 1000 hours of operation or each six-month period
if operated infrequently; it should be calibrated at an ambient
temperature of +20 to +30 degrees C after a five-minute warm-up.
Statements in the Performance Requirements column are verified by
performing the calibration procedure. Statements in the Supplemental
Information column are not to be construed as performance requirements,
but indicate expected performance.
1-2
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7912AD CALIBRATION KIT
TABLE 1-1
CALIBRATION AND ELECTRICAL CHARACTERISTICS
CHARACTERISTICS
PREAMP signal output
(CAL input connected
to 7912AD TP28302)
Amplitude
Rise time
Pulse duty factor
Frequency
CATHODE BLANKING out-
put (SYNC input con-
nected to 7912AD
TP28402)
Amplitude
Fall time
Pulse width
Frequency
TRIG OUT
Amplitude
PREAMP or RESO-
LUTION CHECK
PERFORMANCE REQUIREMENTS
20 millivolts ±.1%
into 50 ohms
6 nanoseconds or less
-5 volts ±.10%
1-3
SUPPLEMENTAL
INFORMATION
50%
250 kilohertz
Approximately 300
nanoseconds
3.2 microseconds
±.10%
60 hertz (50 hertz
for 7912AD Option 13)
Approximately 600
millivolts into 50 ohms

CATHODE BLANKING
Frequency
RESOLUTION CHECK
(CAL input connected
to 7912AD TP28302)
Amplitude
Pulse duty factor
Frequency
VERTICAL DELAY IN
CHARACTERISTICS
Temperature
Operating
Storage
Altitude
Operating
Nonoperating
7912AD CALIBRATION KIT
Pulse is delayed 1.25
nanoseconds ±.10% compared
to VERTICAL DELAY OUT
TABLE 1-2
ENVIRORMENTAL CHARACTERISTICS
Approximately 4.8
volts (unterminated)
Divided by two from
freqency of main
output
Approximately 200
millivolts
50%
250 kilohertz
PERFORMANCE REQUIREMENTS
+20 to +30 degrees C.
-55 to +75 degrees C.
Up to 4570 meters (15,000 feet)
Up to,15,200 meters (50,000 feet)
1-4 @

7912AD CALIBRATION KIT
Cables and Connectors
In addition to the cables and connectors attached to the Calibration
Aid and extender cards, some other cables and connectors are supplied in
the 7912AD Calibration Kit. These are shown in Fig. 1-1. The use of the
cables is called out in the 7912AD calibration procedure.
Jumper with
female connectors.
50-ohm coaxial
cable
with BNC
and TEKTRONIX®
connectors; length
approximately 30
inches. Two provided.
BNC-to-clip
lead adapter.
50-ohm BNC
feed-through
terminator.
2384-02
Fig. 1-1. 7912AD Calibration Kit cables and connectors.
1-5

7912AD CALIBRATION KIT
Extender Boards
Three extender boards are supplied in the 7912AD Calibration Kit to
accommodate the several sizes of circuit boards in the 7912AD. These
extenders are used to make 7912AD boards accessible for service while the
7912AD is in an operating condition. Each extender board includes a
ground clip; connect the clip to the 7912AD chassis ground to reduce
noise while operating the instrument with the extenders.
CAUTION
Turn power ofC before removing or inserting
any of the 7912AD plug-in boards while using
the extenders.
1-6
I '

7912AD CALIBRATION KIT
SECTION 2
SERVICING
This section contains the Calibration Aid circuit description and
servicing instructions for the Calibration Kit.
Circuit Description
The Calibration Aid converts two internal 7912AD signals into test
signals for calibration of the 7912AD. The Calibration Aid provides four
kinds of signals: blanking, calibrated square wave, fast-rise pulse, and
triggering.
Cathode Blanking
The CATHODE BLANKING output is used to blank a small portion of the
7912AD TV frame during calibration. The output is synchronized so that
the blanked portion appears in the middle of the center TV scanning line.
To do this, the SYNC IN probe is connected to TP402 on the 7912AD Video
Processor and Scan Control board (A28). The negative transition of the
sync signal marks the beginning of the center TV scan line. This
transition triggers one-shot U101A, which is adjusted to delay the
CATHODE BLANKING output pulse about 30 microseconds. Thus, blanking
occurs at the center of the TV line. After the delay, U101B is triggered
by the trailing (low-to-high) edge of the U101A 0 output pulse. The
output pulse width of U101B is approximately 3.2 microseconds, setting
the width of the blanking pulse.
The blanking pulse is inverted and amplified by Q111. R115 is a
front-panel control that varies the baseline of the blanking pulse as
needed to match the 7912AD circuit.
Since the 7912AD scans in the standard interlaced format, the
Calibration Aid is triggered to produce two blanking pulses per frame as
shown in Fig. 2-1. The normal adjustment of R101, however, positions the
blanking pulse for field 2 offscreen so only the blank spot in the center
of the screen is visible.
2-1

7912AD CALIBRATION KIT
--_ .....
--FIELD #1
- - -FIELD #2
-
-
2384-03
Fig. 2-1. A TV scan showing both CATHODE BLANKING pulses;
noraally the field 2 pulse is off-screen when
R101 is adjusted correctly.
The TRIG OUT signal supplied in the CATHODE BLANKING mode comes from
flip/flop U212A, which divides the CATHODE BLANKING output frequency by
two.
This eliminates double-triggering when looking at an oscilloscope
display of the CATHODE BLANKING pulse while triggered on the TRIG OUT
signal.
Preamp
The PREAMP output provides a calibration signal for the 7912AD video
preamplifier. This square-wave output is used for adjustment of both gain
and transient response of the video preamplifier. The CAL input of the
Calibration Aid is connected to a 500 kilohertz signal from TP302 on the
7912AD Video Processor and Scan Control board (A28). The CAL input on the
Calibration Aid is marked 1 MHz only because that was the frequency used
with the R7912 Transient Digitizer. U121B operates on the CAL input as a
divide-by-two in the same manner as U121A. The 250 kilohertz square wave
from U121B's 0
output drives amplifier Q131 through an RC network that
sets the PREAMP output gain and transient response. Low-frequency signal
2-2

7912AD CALIBRATION KIT
drive to Q131 is adjusted by R135 and high-frequency drive by C136. The
output is AC-co~pled through C139. R140 and C140 compensate for the
inductance in the output switch, S101.
The PREAMP triggering signal is provided through Q141, driven by the
output of U111B. The PREAMP trigger signal is in phase with the PREAMP
signal even though the two outputs of U121B are complementary. The phase
inversion is cancelled by the two output transistors, one of which is
inverting (Q131), and one of which is not (Q141).
Resolution Check
The RESOLUTION CHECK output provides a fast-rise signal used to
check the horizontal resolution of data acquired by the 7912AD. To do
this, two pulses, one delayed 1.25 nanoseconds from the other, are
digitized. They are then displayed on a monitor and compared. If the
rising edge of each pulse is distinct, the 7912AD has adequate
resolution; if not distinct, the resolution is inadequate.
The RESOLUTION CHECK output provides a fast-rise pulse, either
delayed, or not delayed with respect to the trigger, according to the
position of S102.
As in the case of the PREAMP output, the CAL input signal from the
7912AD is divided by two by U121B. Q141 provides both the output and the
trigger signal; the two signals are isolated by R146. To get the trigger
signal, S101 must be in the PREAMP position. DL161 provides the delay if
inserted in the output circuit by S102.
Maintenance
Although some specific maintenance is described here, more general
maintenance information can be found in the 7912AD Service Manual.
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2-3

7912AD CALIBRATION KIT
Preventative
Cleaning and visual inspection of the Calibration Aid and items in
the 7912AD Calibration Kit are recommended when the time comes to
recalibrate the Calibration Aid. Cleaning should be done more often, if
required. Exterior surfaces can be cleaned with a soft cloth. If
necessary, use a small brush to dislodge dirt on and around front-panel
controls. A mild detergent and water solution can also be used, but do
not use abrasive cleaners.
Dust can be removed from the inside of the Calibration Aid by clean,
·dry, low-pressure air. To clean etched circuit boards, wash with warm
water and a mild detergent solution such as Kelite mixed at a ratio of
about one 1 part detergent to 20 parts water. Keep water and detergent
out of potentiometers and switches. Special products are available from
Tektronix Field Service Centers to clean these parts. Dry the card
thoroughly before operating.
CA UT I OH
Do not use chemicals that can damage the
components in the Calibration Kit. Such
chemicals as benzene, toluene, zylene,
acetone, and similar solvents are especially
harmful and should never be used.
Troubleshooting
For troubleshooting, an understanding of the circuit description is
helpful. A component locator diagram is printed adjacent to the schematic
diagram in Section 4 as an aid in finding components shown on the
schematic or mentioned in the circuit description. Before beginning to
troubleshoot Calibration Aid circuitry, recheck front-panel settings,
then check the power supply voltages, and then inspect circuit components
for clues to any malfunction.
If the instrument is operable, but is not performing correctly in
some respects, the calibration procedure can be a troubleshooting aid. By
attempting to complete the procedure, the source of a malfunction may
become evident.
2-4

7912AD CALIBRATION KIT
Corrective Maintenance
Parts in the electrical and mechanical parts list can be ordered
from Tektronix, Inc., or purchased through field service centers. If
parts other than those purchased through Tektronix are to be used,
carefully check that they are adequate as replacements by noting the
descriptions in the parts list and the use of the parts in the
instrument. When ordering replacement parts from Tektronix, Inc., include
the instrument type, instrument serial number, a description of the part
including circuit number if an electrical part, and the Tektronix part
number.
Use care if electrical parts are soldered or unsoldered to prevent
damage due to heat. Use a small soldering iron: 15 to 35 watts is
recommended. Apply only enough heat and apply it directly to the solder
connection either to unsolder if removing a part, or to form a good bond
if installing a part. Use a heat sink where needed. Use only rosin core
solder.
Calibration
Introduction
Perform the calibration procedure as required by repair or at the
intervals stated in the specifications in Section 1. The test equipment
required is listed in Table 2-1. All equipment used must be operating
within its own specifications. The calibration procedure is written to
use the equipment suggested; if other equipment is substituted, different
setup or operation may be needed. Refer to the instruction manual for the
test equipment if you need more operating instructions than those given
in this procedure.
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7912AD CALIBRATION KIT
TABLE 2-1
TEST EQUIPMENT USED IN CALIBRATION PROCEDURE
Equipment
Test Osilloscope
Pulse Generator
Description
TEKTRONIX 7000-Series
oscilloscope with probe
power connector, 100
MHz bandwidth, 5 milli-
volt/division sensi-
tivity, and two ver-
tical channels.
Pulse repetition rates
from 60 hertz to
500 kilohertz with
output amplitude up to
+4 volts.
Suggested Equipment
TEKTRONIX 7603 Oscillo-
scope with 7A26 Dual
Trace Amplifier and
7B53A Dual Time Base.
TEKTRONIX PG501 Pulse
Generator with TM500
power module.
In addition to a terminator in the Calibration Kit, the following
items are used in the calibration procedure. These items are available
from Tektronix, Inc. They are:
Item
Coaxial cable (2),
50-ohm, BNC connectors
BNC-to-post adapter
BNC T connector
Feedthrough terminator,
50-ohm, BNC connectors
Tektronix Part No.
012-0057-01
012-0092-00
103-0030-00
011-0049-01
It is not necessary to make an adjustment if a previous CHECK step
in the procedure is within limits. A checkmark indicates those steps that
check Performance Requirements as listed in the specifications in Section
1•
2-6