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1720
Tektronix 1720 User Manual
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V
ARIABLE
DEMOD
OUT
X Y
X Y
X
Y
F
SC
<6>
ERROR
<3>
SCALE
<3>
<3>
B-Y (U)
DEMODULA
T
OR
FOCUS
R
O
TAT
E
PHASE
INTENS
LOCK
DETECTOR
&
BANDWIDTH
SWITCH
ÉÉÉ
ÉÉÉ
ÉÉÉ
FOCUS
CONTROL
R–Y
<1>
<4>
<4>
-X INPUT
+X HI GAIN
+X INPUT
-Y INPUT
+Y HI GAIN
+Y INPUT
X IN
Y IN
TXD
EXT STROBE IN
RXD
MICROPROCESSOR
<5>
<2>
<2>
<2>
<2>
LOW P
ASS
FIL
TER
<2>
LOW P
ASS
FIL
TER
QUAD
PHASE
<2>
<2>
<2>
<2>
<2>
<2>
AL
TERNA
TE
LINE
SWITCHING
LUM
SYNC
SEP
ARA
T
OR
BACK PORCH
SAMPLE
BOWES
OSCILLA
T
OR
<2>
<2>
GAIN CELL
SYNC
TIP
CLAMP
<3>
<1>
LOW P
ASS
FIL
TER
HORIZONT
AL
CENTER DOT
POSITION CLAMP
<3>
B–Y
(U)
<3>
<3>
<3>
QUAD
PHASE
V–AXIS
SWITCHER
VERTICAL
CENTER DOT
POSITION CLAMP
LOW P
ASS
FIL
TER
<3>
R-Y (V)
DEMODULA
T
OR
P
AL PHASE
COMP
ARA
T
OR
<3>
<3>
CAL
UNLOCK
PHASE
SHIFTER
<2>
<2>
<2>
<2>
<2>
<2>
BURST
CLAMP
VOL
T
AGE
CONTROLLED
OSCILLA
T
OR
LOOP
QUAD
<2>
<2>
m
P BLANK
CRT
BLANKING
INTENSITY
CONTROL
<4>
<6>
<8>
<6>
<4>
CENTER
DOT
COMP
ARA
T
OR
<8>
<8>
HIGH
VOL
T
AGE
SUPPL
Y
<4>
<4>
<8>
<4>
<4>
<6>
X Y INPUT
CH - A
CH - B
QUAD PHASE
DETECTOR
LOOP PHASE
DETECTOR
VERT
R–Y
(V)
<8>
HORIZ
GRA
TICULE
ILLUMINA
TION
EXT REF
AUXILIAR
Y
CONTROL
CONTROL LINE
SIGNAL LINE
KEY
SCHEMA
TIC DIAGRAM
NUMBER <n>
1720 / 1721 VECTORSCOPE
GAIN
CAL
INT/EXT
<1>
<1>
<4>
<4>
<5>
<2>
VA
R
75%
100%
EHT
(4X)
TRACE
ROT
A
TION
<1>
C B
C A
NOVRAM
<5>
LINE
SELECT
CHROMA
FRONT P
ANEL
SCREWDRIV-
ER ADJ.
FRONT P
ANEL KNOB
<2>
<3>
<1>
<1>
<1>
<2>
<3>
192
194
Table of Contents
Default Chapter
5
Default Chapter
5
Table of Contents
5
General Safety Summary
12
Preface
14
Section 1 Introduction and Specification
17
Accessories
20
Standard Accessories
20
Optional Accessories
20
Options
20
CRT Options
20
Power Cord Options
20
Safety Information
21
Specifications
21
Table 1-1: Signal Input
22
Table 1-2: Vector Mode
22
Table 1-3: XY Mode
24
Table 1-4: CRT Display
24
Table 1-5: Power Source
24
Table 1-6: Environmental Characteristics
25
Section 2 Operating Instructions
27
Front-Panel Controls and Indicators
29
Figure 2-1: Control and Indicator Locations
29
Gain
30
Input
30
Display
31
Miscellaneous
31
Phase
31
Rear-Panel Connectors
32
Figure 2-2: 1720/1721 Rear Panel
33
Using the 1720/1721 in Auxiliary Mode
34
INPUT Switching
34
REF Switching
35
Line Select
35
Store
35
Recall
35
Figure 2-3: Signal Connection for the Operator's Checkout Procedure
37
Figure 2-4: 1720/1721 Typical Vector Display
38
Figure 2-5: Modulated Staircase Waveform Shown on a 1721
39
Figure 2-6: Color Bar and Modulated Staircase Signals both Displayed on a 1721
40
Figure 2-7: Connection for Using Black Burst Signal for External Reference
41
Figure 2-8: 1720/1721 Test Circle Display
42
Measurement Applications
43
Color Measurements
44
Figure 2-9: NTSC Standard Color Phase Vector Diagram
44
Figure 2-10: PAL Standard Color Phase Vector Diagram
45
Figure 2-11: Partial 1720 Graticule Showing the 75% Amplitude Burst Target
46
Figure 2-12: Partial 1721 Graticule Showing the 75% Amplitude Burst Target
46
Functional Use of the Vector Graticule
47
Measurement of Color Bars
47
Figure 2-13: Fine Detail of the 1720 Graticule Magenta Target
48
Figure 2-14: Fine Detail of the 1721 Graticule Target
49
Figure 2-15: Simulated 1720 Graticule Showing the Relationship between Amplitudes on the
49
Differential Gain and Phase Measurements
50
Figure 2-16: Simulation of a 1721 Graticule Showing the Relationship between Amplitudes
50
Figure 2-17: a Simulation of a Part of the 1720 Graticule Showing the Differential Phase and
51
Y Measurements
52
Making Stereo Audio Phase Measurements
52
Figure 2-18: Simulation of the 1721 Differential Gain and Phase Graticule Showing
52
Looking at Incidental Carrier Phase Modulation
53
Service Safety Summary
57
Section 3 Installation
59
Packaging
61
Electrical Installation
61
Power Source
61
Mains Frequency and Voltage Ranges
61
Operating Options
61
Y INPUT Connector
61
Figure 3-1: Plug Jumper Locations
62
Table 3-1: Internal Jumper Selection
62
Auxiliary Connector
63
Mechanical Installation
64
Cabinetizing
64
Table 3-2: AUXILIARY Connector Pin Assignments
64
Figure 3-4: 1700F00 Plain Cabinet
65
Securing the Instrument in Its Cabinet
66
Figure 3-5: 1700F02 Portable Cabinet
66
Rack Mounting
67
Figure 3-6: Cabinet Securing Screws
67
Figure 3-7: 1700F05 Rack Adapter
67
Figure 3-8: 1700F05 Rack Adapter Adjustment
68
Figure 3-9: 1720/1721 and 1700F06 Blank Panel
68
Custom Installation
69
Figure 3-10: Typical Custom Installation Showing the Console
69
Section 4 Theory of Operation
71
Overview
73
Block Diagram
74
Video Input
74
Luminance Processing
74
Microprocessor
74
Section 4 Theory of Operation
75
Gain Cell
75
Chrominance Processing
75
Figure 4-1: Simple Block Diagram of a 1720/1721 Vectorscope
75
Demodulators
76
Output Amplifiers
76
CRT Blanking
76
Circuit Descriptions
77
Diagram 1 Input and Deflection Amplifiers
77
Video Input Amplifiers
77
Gain Cell
78
Diagram 2 Subcarrier Regenerator
78
Reference Switch
79
Sync Separator
80
Bowes Oscillator
80
Back Porch Sample
80
Loop Phase Detector and Amplifier
80
Luminance and Chrominance Amplifiers
80
Quadrature Phase Detector and Amplifier
81
Burst Clamp
81
Lock Detector and Bandwidth Switch
81
Error Amplifier
81
PAL Phasing
82
Vcxo
82
Diagram 3 Demodulator
83
V-Axis Switcher
83
Chrominance Demodulators
84
Sync Tip Chrominance Clamp
84
Demodulator Output Filters and Amplifiers
84
Vector Center Dot Position Clamp
84
Diagram 4 Deflection Amplifier
85
XY Input Amps
86
Deflection Amplifiers
86
Center Dot Comparators
86
CRT Blanking
86
Diagram 5 Microprocessor
87
Microprocessor
87
Table 4-1: U613 Switching Control Outputs
88
Diagram 6 Control Circuit
89
Z-Axis Control
89
Trace Rotation
90
Graticule Illumination
90
Post Regulators
90
Diagram 7 Low Voltage Power Supply
91
Output Filters
92
Error Amplifier
93
Feedback Transformer Driver and Peak Detector
93
Output HV Shutdown
93
Diagram 8 High Voltage Power Supply
94
Focus Amplifier
95
Grid Drive Circuit
95
Z-Axis Amplifier
95
Section 5 Checks and Adjustments
97
Recommended Equipment List
99
Electrical Instruments
99
Section 5 Checks and Adjustments
100
Auxiliary Equipment
101
Performance Check Procedure Short-Form Reference
103
Table 5-1: Performance Check Procedure Short-Form Reference
103
Performance Check Procedure
104
Figure 5-2: Loop–Through Connection of Black Burst Signal to both EXT REF and CH-B
105
Figure 5-3: Using the Vector Graticule –3 Db Markings to Measure Bandwidth
106
Figure 5-4: Signal Connection for Checking CH-A/CH-B Phase Matching
108
Figure 5-5: Rear-Panel XY INPUT Connector Showing Inputs
112
Figure 5-6: Audio Frequency XY Display
113
Adjustment Procedure
115
Signal Connections
115
Adjustment Procedure Short-Form Reference
116
Figure 5-8: Starting Connections for the Adjustment Procedure
116
Table 5-2: Adjustment Procedure Short-Form Reference
117
Long-Form Adjustment Procedure
118
Figure 5-9: Test Points and Adjustment Locations for the 11.8V Supplies
119
Section 6 Maintenance
125
Preventive Maintenance
127
Cleaning
127
Visual Inspection
128
Table 6-1: Static Susceptibility
128
Performance Checks and Readjustments
129
Troubleshooting
130
Foldout Pages
130
Parts Lists
131
Major Assembly Interconnection
131
Specific Troubleshooting Procedures
134
Power Supply
134
Introduction
134
Low Volts Supply
135
High Volts Supply
135
Table 6-2: Power Supply Fault Symptoms
135
Table 6-3: Low Volts Supply Voltages
135
Table 6-4: Control Circuit Test Points
137
High Volts Supply
138
Table 6-5: High Volts Supply Fault Symptoms
138
Table 6-6: High Voltage Oscillator Test Points
139
Serial Port and LED Driver Diagnostics
140
Corrective Maintenance
141
Mechanical Disassembly/Assembly
142
Bezel Removal
142
Graticule Light Removal and Replacement
143
CRT Removal
144
Replacement of the CRT
144
Removing the Rear Panel
145
Removing the Front Panel Circuit Board
146
Removing the Main Board
147
Removing the Power Supply Board
148
Repackaging
149
Identification Tag
149
Repackaging for Shipment
149
Figure 6-8: Repackaging
150
Section 7 Options
151
Options
153
Power Cord Options
153
Field Upgrade Kits
153
Cabinets
153
Plain Cabinet (1700F00)
154
Carrying Case (1700F02)
154
Side-By-Side Rack Adapter (1700F05)
154
Ordering
154
Section 8 Replaceable Electrical Parts
155
Parts Ordering Information
157
Using the Replaceable Electrical Parts List
157
Section 8 Replaceable Electrical Parts
163
Section 9 Diagrams/Circuit Board Illustrations
189
Section 10 Replaceable Mechanical Parts
213
Section 10 Replaceable Mechanical Parts
218
4
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Tektronix 1720 Specifications
General
Brand
Tektronix
Model
1720
Category
Measuring Instruments
Language
English
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