406
Chapter 8
ADC/Interface Section
A3 Assembly ADC Circuits
1. Set the spectrum analyzer controls as follows:
Center frequency .................................................. 300 MHz
Span .............................................................................. 0 Hz
Sweep time .................................................................... 60 s
Detector mode ....................................................... SAMPLE
2. Trigger an oscilloscope on HSTART_ADC (U506 pin 15) and monitor
the outputs of the SASM (U527 pins 18 and 19; U528 pins
14 through 23). Each bit should start high and be switched low. It
will either stay low or return to a high state 1
µ
s later, depending on
the comparison at U512.
3. If the outputs do not exhibit this bit pattern, and the ADC ASM
checks are working properly, suspect A3U527, U528, or one of the
latches (U514/516). If the output of comparator U512 does not toggle
back and forth during a conversion, suspect either U512 or one of the
clipping diodes (CR500/CR501).
NOTE
Because currents are being summed at U512 pins 2 and 3, voltage
levels at these points are difficult to interpret.
Ramp Counter
Refer to function block D of A3 Interface Assembly Schematic Diagram
(sheet 2 of 6) in the 8560 E-Series Spectrum Analyzer Component Level
Information.
The ramp counter is used for sweeps with widths greater than 2.0 MHz
times N. The analog sweep ramp is compared to the digital ramp
counter. When the analog sweep ramp exceeds the DAC output
generated for that ramp counter setting, HRAMP_COMP toggles high,
indicating the end of a bucket. The ramp counter counts horizontal
buckets. There are 601 buckets per sweep, so the ramp (bucket) counter
counts from 0 to 600. The ramp counter is incremented by
HRST_PK_ENA.
1. Press
PRESET
on the spectrum analyzer and set the controls as
follows:
Span .......................................................................... 5 MHz
Detector mode ....................................................... SAMPLE
2. For spans greater than 2.0 MHz times N0, HODD (A3U525 pin 3) is
a square wave with a period defined by (2
×
sweep time/600). For
example, for a 6 s sweep time, HODD has a period of 20 ms. The
ramp (bucket) counter will be odd every other bucket.
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 286: ......
Page 287: ...377 8 ADC Interface Section ...
Page 291: ...Chapter 8 381 ADC Interface Section Introduction Figure 8 2 A3 Test Connector Pin Locations ...
Page 321: ......
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 ...
Page 504: ......
Page 505: ...671 14 Component Level Information Packets ...
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