Agilent Technologies 8564EC, Service Manual

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470 Chapter 9
IF Section
Cal Oscillator (P/O A4 Assembly)
NOTE
If error messages
ERR 581 AMPL
or
ERR 582 AMPL
appears, refer to
error message
ERR 582 AMPL
in Chapter 6 and perform the procedure
provided.
1. The oscillator output frequency should exceed 11.5 MHz if the
CAL OSC TUNE line, A4U804 pin 14, e9 V. The oscillator
frequency should be less than 9.9 MHz if CAL OSC TUNE is less
than
−
9 V. The oscillator only operates when CALOSC_OFF is low
(0 V).
2. If the cal oscillator remains locked (no error code
ERR 499
displayed)
but does not have the correct output level, troubleshoot the output
leveling circuitry (function blocks AA, AB, and AC) or output
attenuator (function block AD).
Cal Oscillator Unlock at Beginning of IF Adjust
1. Press
LINE
to turn the 8564EC or 8565EC spectrum analyzer off
and then on. The words
IF ADJUST STATUS
appear on the display
10 seconds after the instrument is turned on (assuming the rest of
the instrument is working correctly). Immediately observe the lower
right corner of the display for error messages. If the message
ERR 499 CAL UNLK
appears (before errors
ERR 561
,
ERR 562
and
ERR 565
), the cal oscillator is unable to phase-lock. Expect to see the
ERR 499
message for only about 1 second.
2. If the 8564EC or 8565EC spectrum analyzer registers an
unlocked cal oscillator, continue with step 3 to verify the presence of
externally supplied signals.
3. Check A4U811 pin 9 for a 100 kHz TTL-level square wave verifying
operation of A4U811, A4Q802, and the 10 MHz input signal from
A4J7.
4. Check the +15 VF, +5 VF and
−
15 V power supplies, and +10 V
reference on the A4 assembly.
5. Check that A4U807 pin 5 (CALOSC_OFF) becomes TTL low (0 V) at
the start of a FULL IF ADJ (press
CAL
and
FULL IF ADJ
). The phase
modulation output at A4U804 pin 8 should also remain at 0 volts. If
these checks are correct, troubleshoot blocks V, W, X, and Y. See
Figure 9-26, “A4 Log Amplifier/Cal Oscillator Block Diagram (2 of
2).”