Chapter 11
585
Synthesizer Section
A21 OCXO
A21 OCXO
The spectrum analyzer uses an oven-controlled crystal oscillator
(OCXO). It is deleted in Option 103 and replaced by a
temperature-compensated crystal oscillator (TCXO), located on the
A15 RF assembly. Connectors J305 and J306 on the A15 RF assembly
are located where the TCXO would be installed in an Option 103.
The oven in the OCXO is powered only when the spectrum analyzer is
powered on; there is no standby mode of operation. The OCXO oscillator
operates only when the internal frequency reference is selected. Control
line HEXT (High = EXTernal frequency reference) is inverted by
A15U303B (Refer to the A15 RF assembly schematic diagram, block M,
sheet 2 of 4) to generate LEXT. LEXT is sent to the OCXO via A15J306
pin 4. When LEXT is low, the oscillator in the OCXO will be turned off.
Replacement OCXOs are factory adjusted after a complete warmup and
after the specified aging rate has been achieved. Thus, readjustment
should typically not be necessary after OCXO replacement, and is
generally not recommended.
If adjustment is necessary, the spectrum analyzer must be on
continuously for a minimum of 24 hours immediately prior to oscillator
adjustment to allow both the temperature and frequency of the
oscillator to stabilize. Failure to allow sufficient stabilization time could
result in oscillator misadjustment.
Check operation of the A21 OCXO as follows:
1. Disconnect W49 (Coax 82) from A15J305. Connect the output of W49
to the input of another spectrum analyzer.
2. Check that the fundamental frequency is 10 MHz and that the
power level is 0 dBm
±
3 dB. Also check that the harmonics are at
least
−
25 dBc. Excessive harmonics can generate spurious responses
on the fractional N oscillator on the A14 frequency control assembly.
3. If the OCXO has no output, check A15J306 pin 1 for +15 Vdc. Check
A15J306 pin 4 for a TTL-high level.
4. If A15J306 pin 4 is at a TTL-low level, press
AUX CTRL
and
REAR
PANEL
. Press
10 MHz EXT INT
until INT is underlined. A15J306 pin 4
should read a TTL-high level. Press
10 MHz EXT INT
until EXT is
underlined. A15J306 pin 4 should read a TTL-low level.
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 ...
Page 218: ......
Page 219: ......
Page 220: ......
Page 221: ......
Page 222: ......
Page 223: ......
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 ...
Page 284: ......
Page 285: ......
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 ...
Page 376: ......
Page 377: ......
Page 378: ......
Page 379: ...487 10 Controller Section ...
Page 394: ...521 11 Synthesizer Section ...
Page 451: ......
Page 452: ......
Page 453: ......
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 ...
Page 491: ......
Page 492: ...633 13 Display Power Supply Section ...
Page 504: ......
Page 505: ...671 14 Component Level Information Packets ...
Page 507: ......