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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
(LINEI
to turn the HP 85623 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 HP 85623 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-1
eve1
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
+lO
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
a
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 9-21, A4 log amplifier/Cal oscillator Block Diagram.
Inadequate
CAL
OSC
AMPTD
Range
Refer to function block AC of A4 Log Amplifier Schematic Diagram in the
HP
8560 E-Series
Spectrum Analyzer Component Level Information.
1. If A4R826, CAL OSC AMPTD, has inadequate range to perform the IF Amplitude
Adjustment, press
LCAL).
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
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 MHz
Reference level
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30
dBm
5. Observe the spectrum analyzer display while pressing FULL IF ADJ . The signal level
should be above -34.55
dBm.
If the signal level is incorrect, continue with step 7.
6. Rotate A4R826 fully counterclockwise. The signal should be below -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 HP 85623 spectrum analyzer, press (CAL).
IF Section 9-33