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1720
Tektronix 1720 User Manual
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/L_SEL_EN
+5V
R245
10.0K
1
6
2
7
3
8
4
9
5
TXD
RXD
EXT_STRB
1A
1
1B
2
2A
3
2B
4
3A
5
3B
6
4A
7
4B
8
5A
9
5B
10
6A
11
6B
12
7A
13
7B
14
8A
15
8B
16
9A
17
9B
18
10A
19
10B
20
11A
21
11B
22
12A
23
12B
24
J933
C239
.1UF
LIN_SEL_BLNK
R235
22.1K
CR137
CR522
H
+5V
-11.8V
-11.8V
R247
6.81K
R872
6.81K
R246
1.00M
R135
2.43K
R137
18.2K
Q248
Q540
R248
221K
CR248
Q343
BLANK
+5V
R542
10.0K
Q541
R448
100
12
J245
+40V
R381
6.19K
R382
6.19K
+11.8V
-11.8V
+11.8V
BROWN
BLUE
R602
20K
C576
.1UF
R484
1.00K
R579
10.0K
R483
100
CR484
CR486
Q481
Q581
+11.8V
R445
10.0K
Q480
Q580
CR476
CR474
R474
100
-11.8V
/uP_BLANK
+5V
R522
1.00K
CR518
Q424
+Y_INPUT
+Y_HGAIN
-Y_INPUT
+X_INPUT
+X_HGAIN
1
9
2
10
3
11
4
12
5
13
6
14
7
15
8
-X_INPUT
-Y_INPUT
+Y_INPUT
C937
100PF
3
2
1
4
1
1
U942A
TL074
C838
100PF
+11.8V
-11.8V
R937
2.00K
R940
10.0K
R841
10.0K
R839
2.00K
R840
20.0K
R842
18.2K
R846
20K
C995
10PF
12
13
14
U942D
TL074
YV
YA
R849
3.01K
R848
10.0K
9
8
14
U446C
LM339
11
10
13
U446D
LM339
15
14
1
6
U585D
DG211
10
11
9
U585C
DG211
+11.8V
R449
11.0K
R549
221
R574
2.21K
Q474
R576
100
C484
2-18PF
-11.8V
R575
100
R582
750
R581
750
Q576
+100V
R857
1.00K
R583
24.3K
-11.8V
R578
20K
C492
.1UF
C591
.1UF
7
6
8
U585B
DG211
6
7
1
U446B
LM339
+11.8V
+11.8V
+5V
-11.8V
R548
11.0K
/XY
VECT
XV
R847
150K
R843
2.00K
12
J920
+Y_HGAIN
1
3
2
1
3
2
1
3
2
1
6
2
7
3
8
4
9
5
+X_INPUT
-X_INPUT
1
2
3
4
5
6
7
8
9
10
1
3
2
1
3
2
1
3
2
C938
100PF
5
6
7
U942B
TL074
C939
100PF
R942
10.0K
R941
10.0K
R938
2.00K
R943
20.0K
R944
18.2K
R939
2.00K
R948
20K
12
J921
10
9
8
U942C
TL074
R946
3.01K
R947
10.0K
2
3
1
1
2
1
3
45
U585A
DG211
C684
.1UF
4
5
2
3
1
2
U446A
LM339
-11.8V
-11.8V
R547
221
VR449
R969
6.3K
C446
.1UF
C448
.1UF
+11.8V
R871
20.0K
C349
47UF
Q966
Q967
R967
100
R957
100
+11.8V
R956
10.0K
R869
6.3K
R858
100
Q867
Q866
+11.8V
-11.8V
GREEN
RED
R502
20K
C856
22PF
-11.8V
R953
100
R856
365
Q856
-11.8V
R958
365
Q855
R954
681
R955
100
P916
12
J916
P917
12
J917
R945
2.00K
P915
12
J915
+X_HGAIN
1
3
2
1
3
2
1
3
2
<6>
A1
CRT
BLANKING
AUXILIARY
CONTROL IN
A11
SERIAL
FIL
TER
BOARD
(SEE
BELOW)
C3
D4
E4
<5>
<5>
C3
<2>
E2
<6>
J245
NOT INSTALLED NORMAL
INSTALLED DISABLE
CENTER DOT BLANKING
C1
AMPLIFIER
VER
TICAL
DEFLECTION
PLATES
TO CRT
VERT
DEFL
<9>
H4
<5>
D3
XY INPUT
REAR
PA
NE
L
INPUT
X Y
AMPLIFIERS
<3>
Y GAIN
D3
G2
CENTER DOT
COMP
ARA
T
ORS
VHF
COMP
AMPLIFIER
ORTHAG
HORIZONT
AL
DEFLECTION
<5>
<5>
<3>
D4
G4
J920
NOT INSTALLED NORMAL
Y HIGH GAIN
INSTALLED X10 GAIN
FL7
FL8
FL9
C13
C14
C15
C16
C17
C18
470PF
470PF
470PF
470PF
470PF
470PF
J2
J1
FL4
FL5
FL6
C7
C8
C9
C10
C11
C12
470PF
470PF
470PF
470PF
470PF
470PF
X GAIN
6.2V
PLATES
TO CRT
DEFL
<9>
H4
HORIZ
J921
NOT INSTALLED NORMAL
X HIGH GAIN
INSTALLED X10 GAIN
SPARE JUMPERS
FL1
FL2
FL3
C1
C2
C3
C4
C5
C6
470PF
470PF
470PF
470PF
470PF
470PF
1720/1721 VECTORSCOPE
A11 SERIAL FIL
TER BOARD
NC
NC
NC
DEFLECTION AMPLIFIER
<4>
NOTE:
P
ART
OF
A3
MAIN
BOARD
SEE P
ARTS LIST FOR EARLIER VALUES
AND SERIAL NUMBER RANGES.
200
202
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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