HP 8562E, Service Manual

Page: 402 / 482

Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29. Connect an RF signal-generator output to Set the signal generator to the
following settings:
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Amplitude
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30. Monitor pin 1 with a DVM or oscilloscope. Connect ground to pin 6.
31. As the signal generator frequency is increased to 76 MHz, the voltage at pin 1
should change from approximately V to -12 V.
32. Set the signal generator to the following settings and repeat step 30.
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Amplitude
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -15dBm
33. If the voltage monitored in step 30 is correct with a 0 output but not with -15
output, suspect the limiting amplifier function block AE.
34. Place jumper in the NORMAL position and reconnect W32 to
Check YTO FM coil driver and main loop error voltage driver (steps 35-40)
35. To troubleshoot the YTO FM coil driver, refer to step 6 of “first LO Span Problems
(2.01 MHz to 20 MHz).”
36. Steps 36 through 40 verify that the YTO-loop error voltage is reaching the FM coil.
The main loop error voltage driver has a gain of either 1.5 or 15; the analyzer firmware
controls the gain during the locking process. The error voltage is read by the ADC on the
A3 interface assembly.
calibrates out any offsets from true ground.
inverts the sense of the YTO loop to lock the YTO on lower sampler-sidebands (YTO
frequency < (sampler frequency
sampler harmonic)). The fractional N frequency
indicated in the FREQ DIAGNOSE menu will be negative when locking to lower
sidebands. Refer to function blocks E, M, and N of Al4 frequency control schematic in
the
HP 8560
E-Series
Spectrum Analyzers Component Level Information
binder.
Set the spectrum analyzer to the following settings:
Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37. Remove jumper and connect a dc power supply to pin 2. Connect ground
to pin 3. Set the dc power supply to Vdc.
38. Verify the nominal test-point voltages listed in Table 11-8.
39. Change the input voltage to -7.5 volts and re-verify that the voltages listed in Table 11-8
are the same except for a change in polarity.
40. Change the to 678.8 MHz with the SPAN remaining 0 Hz. This will change
the switch setting of and invert the voltages listed in Table 11-8.
11-28 Synthesizer Section