Chapter 8
397
ADC/Interface Section
A3 Assembly Video Circuits
Current source U307C provides twice the current of Q316. Resistor
R145 and current source U307D shift the dc level. Resistor R260
terminates the peak detector inputs in 500 ohms. The unterminated
gain is 1.1. Diode CR114 prevents latchup during positive overdrive
conditions while CR113 protects Q318 during overdrive. Diode CR117
is a 12.7 V zener that limits the output of the peak detector to +1.5 V.
Typically, limiting occurs at +1.1 V.
Positive/Negative Peak Detectors
Refer to function blocks Y and Z of A3 Interface Assembly Schematic
Diagram (sheet 5 of 6) in the
8560 E-Series Spectrum Analyzer Component
Level Informatio
n.
The following information pertains to the positive peak detector and is
applicable to troubleshooting the negative peak detector.
The positive peak detector consists of an input amplifier (A3U204 and
A3Q210) followed by detector diodes (A3CR203 and A3CR204) and hold
capacitor A3C217. Output amplifier A3Q206, Q211, and Q212 buffers
the hold capacitor. Both the input and output amplifiers have a gain of
one. Each amplifier has local feedback. On the output amplifier the
emitter of Q212 connects to the gate of Q206. On the input amplifier the
feedback goes through Q209 and Q208 back to the base of U204D.
Global feedback occurs from the output amplifier through R223 back to
the input amplifier U204D. The peak detector resets through Q207.
1. Press
PRESET
and set the spectrum analyzer controls as follows:
Center frequency ..................................................... 300 MHz
Span ......................................................................... 500 MHz
Resolution bandwidth .................................................. AUTO
Video bandwidth ........................................................... AUTO
Log dB/division ...................................................... 10 dB/DIV
2. If the spectrum analyzer does not meet the conditions in steps a
through e below, the positive and negative peak detectors are
probably faulty. Continue with step 3 to check the detectors.
a. The peak-to-peak deviation of the noise in NORMAL detector
mode should be approximately two divisions. Press
TRACE
,
TRACE B
,
CLEAR WRITE B
,
VIEW B
,
TRACE A
,
MORE 1 of 3
,
and
DETECTOR MODES
.
b. Select
DETECTOR POS PEAK
mode.
c. Confirm that the noise is about one-third division peak-to-peak.
The noise should also be no higher than the top of the noise level
in NORMAL detector mode.
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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