Chapter 9 471
IF Section
Cal Oscillator (P/O A4 Assembly)
Inadequate CAL OSC AMPTD Range
Refer to function block AC of A4 Log Amplifier Schematic Diagram in
the 8560 E-Series Spectrum Analyzer Component Level Information.
1. If A4R826, CAL OSC AMPTD, has inadequate range to perform the
IF Amplitude Adjustment, press
CAL.
2. Rotate A4R826 fully clockwise and disconnect W52 (coax 9) from
A5J4.
3. Connect A5J4 to the input of a second spectrum analyzer.
4. Set the other spectrum analyzer controls as follows:
Center frequency .................................................... 10.7MHz
Reference level ......................................................... −30dBm
5. Observe the spectrum analyzer display while pressing
FULL IF
ADJ. The signal level should be greater than −34.55 dBm. If the
signal level is incorrect, continue with step 7.
6. Rotate A4R826 fully counterclockwise. The signal should be less
than −36.25 dBm. If the signal level is correct at both settings,
troubleshoot the A5 IF assembly. If the signal level is incorrect,
continue with step 7.
7. Troubleshoot the ALC loop on this assembly using the following
steps:
a. Connect a positive DVM probe to A4J9 pin 4.
b.On the 8564EC or 8565EC spectrum analyzer, press
CAL.
c. Press
FULL IF ADJ. Observe the DVM reading between the
displayed messages IF ADJUST STATUS: 300 kHz RBW and IF
ADJUST STATUS: 3 kHz RBW. During this time period, the voltage
should be within a 2 to 10 Vdc range.
d. Observe the DVM reading while IF ADJUST STATUS: AMPLITUDE
is displayed. The reading should be within the 2 to 10 Vdc range.
e. If the DVM reading is outside the range in step c but inside the
range in step d, suspect one of the reactive components in the
filter.
8. If the ALC loop is working correctly (A4J9 pin 4 within the test
tolerances given), then either the output attenuator is defective, or
A4U810 pin 6 (in ALC loop integrator) is outside of its +3 to +6 Vdc
range.
9. Reconnect W52 (coax 9) to A5J4.
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