HP 8560A, Service Manual

Page: 389 / 450

3. If the signal at is low, but the signal at is correct, press
INTERNAL SIG ID OFF.
4. Check that PIN diode switches CR603 and CR605 are reverse biased by approximately
+10 Vdc. Refer to function block F of Al5 RF Schematic (sheet 1 of 3).
5. Measure 300 MHz signal at using an active probe/spectrum analyzer
combination. If the signal is not approximately refer to “Unlocked Reference
PLL” in this chapter.
6. If the level at the TP503 is correct, but signal at TP504 is too low, the fault is probably in
the amplifier.
Sampler and Sampler IF
The Sampler creates and mixes harmonics of the sampling oscillator with the first LO.
The resulting sampler IF (63 MHz to 105 MHz) is used to phase-lock the YTO. The Sampler
IF filters unwanted products from
output and amplifies the IF to a level sufficient to
drive the YTO loop. When the IF is between 78 and 87 MHz, PIN diodes switch a 120 MHz
notch filter in the sampler IF section.
1. Set HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Disconnect W32 from
3. Connect the input of a power splitter to Connect W32 to one of the splitter
outputs. Connect the other splitter output to the input of another spectrum analyzer.
4. If a 94.7 MHz signal, greater than -15 is not displayed on the other spectrum
analyzer, set a microwave source to the following settings:
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5
5. Connect the microwave source to A 94.7 MHz signal at approximately 0
should be displayed on the other spectrum analyzer.
6. Use an active probe/spectrum analyzer combination to measure the signal at the following
test points:
94.7 MHz, -25
294 MHz, +17
Synthesizer Section