Chapter 12 605
RF Section
A9 Input Attenuator
A9 Input Attenuator
1. Perform the "Input Attenuator Accuracy" performance test in the
8560 E-Series Spectrum Analyzer Calibration Guide.
2. If there is a step-to-step error of approximately 10 dB or more,
continue with step 3.
3. On the spectrum analyzer, press AMPLITUDE, and ATTEN AUTO MAN
until MAN is highlighted.
4. Step the input attenuator from 0 dB to 60 dB. A "click" should be
heard at each step. The absence of a click indicates faulty attenuator
drive circuitry. It will be necessary to use the DATA keys to enter an
input attenuator setting of 0 dB (the step key will not allow selecting
0 dB input attenuation).
5. Monitor the pins of A14U421 with a DVM while setting the input
attenuator to the values listed in Table 12-2 on page 606.
6. If one or more logic levels listed in Table 12-2 on page 606 is
incorrect, disconnect W11 from A14J6 and repeat step 5 using
Table 12-4 on page 607.
NOTE When W11 is disconnected, the +28 V levels listed in Table 12-2 on
page 606 are floating and will read approximately 0.2 V. Refer to
Table 12-4 on page 607.
7. If one or more logic levels listed in Table 12-4 on page 607 is
incorrect with W11 disconnected, troubleshoot the A14 frequency
control assembly.
8. If all logic levels are correct, the A9 input attenuator is probably
defective.
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