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Tektronix 1720 User Manual
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1721
1721 PAL-M
1720
CKT#
BACK PORCH
SAMPLE
C984
250PF
+5V
R984
16.5K
BOWES
OSCILLA
TOR
R683
6.81K
R781
3.92K
+11.8V
+11.8V
CR682
SYNC
SEP
ARA
T
OR
R691
10.0K
+11.8V
C675
27PF
R684
4.75K
R675
22.1K
R680
3.92K
R674
6.81K
R687
22.1K
+11.8V
+11.8V
Q688
Q687
CR680
CR781
Q680
CR681
C686
.027UF
C776
.001UF
C881
3300PF
C781
.1UF
R780
8.25K
R677
1.00K
R676
47.5K
R775
10.0K
R776
3.32K
R777
30.1K
R883
5.23K
R782
2.55K
+5V
+11.8V
+5V
Q780
CR776
Q880
W986
0 OHM
R884
39.2K
R786
10.0K
R878
10.0K
R882
10.0K
+5V
-11.8V
+5V
9
1
0
8
U876C
74LS00
12
13
11
U876D
74LS00
C
X
1
4
R
X
1
5
A
1
B
2
C
L
3
Q
13
Q
4
U884A
74LS221
Q781
W987
R348
2.00K
+5V
D
12
Q
9
CK
11
Q
8
P
R
1
0
C
L
1
3
U774B
74LS74
P
AL PHASE
COMP
ARA
T
OR
NC
C348
.1UF
+11.8V
2
3
7
6
8
5
1
4
U348
LM311
NOT INSTALLED
C336
C337
C437
C548
C791
R647
U348
W986
W987
Y129
INSTALL
INSTALL
340.0
INSTALL
130PF
100PF
850PF
130PF
390PF
3.579545MHZ
4.433619MHZ
R253
4.99K
+5V
R637
10.0K
R252
1.13K
NOT INSTALLED
NOT INSTALLED
NOT INSTALLED
INSTALL
INSTALL
100PF
422.0
340.0
850PF
130PF
390PF
253PF
85PF
550PF
56PF
85PF
130PF
3.575611MHZ
10.0K
8.2K
NOT INSTALLED
ERROR AMPLIFIER
<3>
A2
IN
1720
C352
.1UF
R644
2.74K
D
+11.8V
-11.8V
LOOP PHASE
DETECT
OR
A2
<3>
E1
<4>
H
+5V
<3>
A3
/H
CR876
-11.8V
-11.8V
J696
EXT SYNC REF
1-2 EXT REF
2-3 CH A INPUT
R685
100K
R686
10.0K
-11.8V
-11.8V
Q685
R682
825K
C685
1UF
REFERENCE SWITCH
R692
13.0K
R693
20.0K
-11.8V
Q693
<1>
LUMINANCE
E3
C787
.1UF
2
3
1
1
2
1
3
4
5
U889A
DG211
INT_REF_VIDEO
+5V
4
5
6
U876B
74LS00
R694
100
123
J696
P696
CHROMINANCE
C788
.1UF
C985
.1UF
R892
392
+11.8V
+11.8V
-11.8V
Q794
Q795
J796
EXT CHROMA REF
1-2 NORMAL
2-3 CW
10
11
9
U889C
DG211
+11.8V
8
10
1
4
6
12
5
23
1
4
U646
1496P
C645
.1UF
C949
.001UF
R745
1.00K
R746
6.81K
-11.8V
R744
475
R645
100
R646
100
R642
475
3
2
6
7
4
8
15
U640
LM318
C844
10UF
C534
410PF
L642
100UH
C540
790PF
C644
.001UF
R643
4.32K
R743
2.74K
+11.8V
R741
562
<5>
NC
D4
C640
.1UF
C641
.1UF
C738
.02UF
R530
2.00K
R528
10.0K
/CAL
+5V
+11.8V
-11.8V
NC
Q532
3
2
1
8
4
U734A
1458
C637
.1UF
C734
.1UF
+11.8V
+5V
-11.8V
C733
1UF
C632
.02UF
C532
2200PF
C732
1UF
R631
47.5K
R632
33.2K
R634
10.0K
LOOP
BAL
BURST
CLAMP
R633
1.00M
R734
100
+11.8V
+11.8V
-11.8V
R637
10.0K
R639
4.75K
R534
20K
CR639
Q732
R832
1.00K
R855
2.74K
+11.8V
+11.8V
R845
4.32K
R636
549
R831
221K
C748
.1UF
8
10
1
4
6
12
5
23
1
4
U854
1496P
C854
.1UF
R649
475
R748
1.00K
R749
475
R747
8.25K
-11.8V
-11.8V
NC
7
6
8
U889B
DG211
C952
.001UF
R893
2.43K
P796
1
2
3
J796
L791
15UH
C791
130PF
R891
6.19K
R791
2.00K
R890
10.0K
R895
2.00K
-11.8V
<5>
<1>
C5
D3
L533
15UH
C437
850PF
15
14
1
6
U889D
DG211
INT_/EXT
EXT_REF_VIDEO
& AMPLIFIERS
C432
.001UF
R433
3.32K
+11.8V
<3>
A2
L433
3.9UH
C428
.1UF
C328
.1UF
C452
2200PF
R432
20.0K
R428
10.0K
R328
33.2K
R334
825K
SUBC
-11.8V
-11.8V
-11.8V
C333
.1UF
R431
825
Q434
CR428
Q334
VCXO
Y129
3.5795MHZ
R222
56.2K
-11.8V
R333
33.2K
C235
9-45PF
R232
121K
Q222
L437
15UH
L337
15UH
C336
390PF
C337
130PF
C548
100PF
L750
15UH
R224
75.0
Q333
Q328
QUAD PHASE
DETECT
OR
R647
340
R648
100
R952
100
NC
C543
790PF
L845
100UH
C536
410PF
C842
10UF
C855
.001UF
3
2
6
7
4
8
15
U739
LM318
R742
2.74K
+11.8V
+11.8V
R740
562
5
6
7
U734B
1458
R736
2.7M
C836
.02UF
C824
267PF
C826
100PF
C832
.1UF
R638
47.5K
R735
432K
R737
47.5K
R738
1.00K
R830
2.21K
+11.8V
Q733
R635
3.92K
Q632
CR632
LOCK DETECTOR
& BW SWITCH
C737
.02UF
R834
2.21K
R833
15.0K
-11.8V
Q836
CR837
C741
.1UF
C743
.1UF
R837
549
-11.8V
NC
R739
20.0K
J428
A4
A2
CONNECTS
PHASE
BOARD
<7>
SHIFTER
C223
.001UF
C222
.1UF
R331
100
R234
75.0
-11.8V
R223
1.00K
R233
2.00K
& J112
TO J100
1
2
3
4
J428
C234
470PF
C134
2200PF
R332
10.0K
R221
150K
CR235
R239
121K
PHASE SHIFTER
OUTPUT AMPLIFIER
1720/1721 VECTORSCOPE
SUBCARRIER REGENERA
T
OR
<2>
P
ART OF A3 MAIN BOARD
196
198
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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