Chapter 8
391
ADC/Interface Section
A3 Assembly Video Circuits
A3 Assembly Video Circuits
Voltages from A3J101 to the Variable Gain Amplifier on A3 correspond
(approximately) to on-screen signal levels. (One volt corresponds to the
top of the screen and zero volts corresponds to the bottom of the screen.)
This is true for both log and linear settings except when the spectrum
analyzer is in 1 dB/div or 2 dB/div. In these cases the log expand
amplifier is selected, and 1 V corresponds to top-screen and 0.8 or 0.9 V
corresponds to bottom-screen. The spectrum analyzer can be set to zero
span at the peak of a signal to generate a constant dc voltage in the
video circuits during sweeps.
1. Disconnect W26 from A3J101 and W20 from A2J4.
2. Connect W26 to A2J4.
3. Set the spectrum analyzer to the following settings:
Span ................................................................................. 0 Hz
Sweep time .................................................................... 20 ms
Resolution bandwidth ................................................. 1 MHz
Log/division ............................................................ 10 dB/DIV
4. If a trace is displayed, troubleshoot the A3 assembly. If a trace is
absent, connect an oscilloscope to the rear panel BLKG/GATE
OUTPUT.
5. The presence of a TTL signal (TTL low during 20 ms sweep)
indicates a good A3 Interface Assembly. Troubleshoot the IF section.
6. If the BLKG/GATE OUTPUT is always at a TTL high or low,
troubleshoot the trigger/video gating circuits on A3.
7. Reconnect W26 to A3J101 and W20 to A2J4.
8. Remove the A3 assembly shield.
9. If the video filters appear faulty, see to
10.If there appears to be a peak detector problem, refer to
“Positive/Negative Peak Detectors” on page 397
11.Connect the spectrum analyzer CAL OUTPUT to the INPUT 50
Ω
and set the controls as follows:
Center frequency ..................................................... 300 MHz
Span ................................................................................. 0 Hz
Reference level .........................................................
−
10 dBm
12.If the spectrum analyzer works correctly in 5 dB/div and 10 dB/div
but not in 1 dB/div or 2 dB/div, refer to
Continue with step 13 if the problem involves on-screen
amplitude errors which appear to originate in the video chain.
Summary of Contents for 8564EC
Page 17: ...25 1 General Information ...
Page 37: ...47 2 Adjustment Diagnostic Software ...
Page 77: ...89 3 Manual Adjustment Procedures ...
Page 129: ...161 3a Manual Adjustment Procedures 3335A Source not Available ...
Page 142: ...175 4 Assembly Replacement ...
Page 194: ...Chapter 4 257 Assembly Replacement Procedure 13 A21 OCXO Figure 4 34 A21 OCXO Mounting Screws ...
Page 196: ...259 5 Replaceable Parts ...
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Page 224: ...303 6 Major Assembly and Cable Locations ...
Page 234: ...315 7 General Troubleshooting ...
Page 238: ...Chapter 7 319 General Troubleshooting Introduction Figure 7 2 Ribbon Cable Connections 1 of 3 ...
Page 239: ...320 Chapter7 General Troubleshooting Introduction Figure 7 3 Ribbon Cable Connections 2 of 3 ...
Page 242: ...Chapter 7 323 General Troubleshooting Introduction Figure 7 5 Service Cal Data Menu ...
Page 271: ...352 Chapter7 General Troubleshooting Block Diagram Description Figure 7 6 Functional Sections ...
Page 283: ...364 Chapter7 General Troubleshooting Block Diagram Description ...
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Page 287: ...377 8 ADC Interface Section ...
Page 291: ...Chapter 8 381 ADC Interface Section Introduction Figure 8 2 A3 Test Connector Pin Locations ...
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Page 322: ...427 9 IF Section ...
Page 356: ...Chapter 9 461 IF Section A5 IF Assembly Figure 9 13 Detailed IF Adjust Signature 5 ...
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Page 379: ...487 10 Controller Section ...
Page 394: ...521 11 Synthesizer Section ...
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Page 454: ...593 12 RF Section ...
Page 489: ...628 Chapter12 RF Section A15 RF Assembly Figure 12 10 10 MHz TTL Reference at U304 Pin 13 ...
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Page 492: ...633 13 Display Power Supply Section ...
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Page 505: ...671 14 Component Level Information Packets ...
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