HP 8560E, Service Manual

Page: 564 / 665

Chapter 10 563
Synthesizer Section
Sampler and Sampler IF
Sampler and Sampler IF
The A15U100 sampler creates and mixes harmonics of the sampling
oscillator with the first LO. The resulting sampler IF (60 MHz to 96
MHz) is used to phase-lock the YTO. The sampler IF filters unwanted
products from the output of A15U100 and amplifies the IF to a level
sufficient to drive the YTO loop. When the IF is less than 87.14 MHz,
PIN diodes switch a 120 MHz low pass filter in the sampler IF section.
1. Set HP 8560E/EC to the following settings:
Center frequency .................................................. 300 MHz
Span .............................................................................. 0 Hz
2. Disconnect W32 from A15J101.
3. Connect the input of a power splitter to A15J101. Connect W32 to
one of the splitter outputs. Connect the other splitter output to the
input of another spectrum analyzer.
4. If a 66.7 MHz signal, greater than
−
15 dBm, is not displayed on the
other spectrum analyzer, set a microwave source to the following
settings:
Frequency ......................................................... 4.2107 GHz
Amplitude ...............................................................
−
5 dBm
5. Connect the microwave source to A15U100J1. A 66.7 MHz signal at
approximately 0 dBm 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:
7. If a correct signal is seen at A15TP201 but the signal at A15TP101 is
wrong, proceed as follows:
• Use an oscilloscope to measure the signals at the following test
points:
A15J400 pin 1 +0.8 Vdc to +1.6 Vdc (
≤
0.5 Vp-p variation)
A15J400 pin 3
−
0.8 Vdc to
−
1.6 Vdc (
≤
0.5 Vp-p variation)
A15TP101 66.7 MHz,
−
8 dBm
A15TP201 296 MHz, +9 dBm