Chapter 8
401
ADC/Interface Section
A3 Assembly Video Circuits
2. Refer to
and check for correct logic levels at A3U108 pins 1,
15, and 16. Check for proper output signals at TP6. If the select lines
are not changing, suspect the ADC ASM or the VGA/ADC MUX
Control. If the select lines are changing, but the proper video inputs
are not being switched to the output, replace U108. In SAMPLE
mode, the input is MOD_VIDEO (pin 7); in POS PEAK mode, the
input is POS_PEAK (pin 5); and in NEG PEAK mode, the input is
NEG_PEAK (pin 6).
3. Check for the presence of the YTO ERR signal at A3J2 pin 42 with
an oscilloscope probe.
4. If ERR 300 YTO UNLK or 301 YTO UNLK occurs and the voltage is
near zero during a sweep and positive during retrace (YTO is being
locked), the fault is on the A3 assembly. If a constant dc voltage is
present, refer to the Synthesizer section troubleshooting procedure
in Chapter 11.
5. Set the spectrum analyzer to the following settings:
Span ............................................................................. 5 MHz
Sweep time .................................................................... 50 ms
6. Check for the presence of the SCAN RAMP signal by connecting an
oscilloscope probe to A3J2 pin 45 (component side of A3J2). Connect
the negative-probe lead to A3TP4.
7. A 0 to 10 V ramp should be present in both LINE and FREE RUN
trigger modes. If the waveform is present only in LINE trigger, ADC
control signal HBADC_CLK0 may be faulty. Refer to
8. If the scan ramp is present, but is not being switched to the output of
U108, replace U108. If the scan ramp is absent in either mode, do
the following:
a. Connect the oscilloscope probe to A3J400 pin 15 (HSCAN).
b. A TTL signal (high during 50 ms sweep time and low during
retrace) should be present, indicating A3 is working properly.
Refer to the Synthesizer section troubleshooting procedure in
Chapter 11. A faulty TTL signal indicates a bad A3 Interface
assembly.
Table 8-8
Logic Levels at A3U108
Detector
Mode
U108 pin 1
U108 pin 15
U108 pin 16
SAMPLE
H
L
H
POS PEAK
H
L
L
NEG PEAK
L
L
H
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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