592 Chapter11
RF Section
A9 Input Attenuator
A9 Input Attenuator
1. Perform the "Input Attenuator Accuracy" test in the HP 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 HP 8560E/EC, press AMPLITUDE, and ATTEN AUTO MAN until
MAN is underlined.
4. Step the input attenuator from 0 dB to 70 dB. A "click" should be
heard at each step. The absence of a click indicates faulty attenuator
drive circuitry.
5. Monitor the pins of A14U420 with a logic probe or DVM while
setting the input attenuator to the values listed in Table 11-3 on
page 593.
NOTE The logic levels listed in Table 11-3 on page 593 show the default AC
usage (Pin 5 low, Pin 6 high). DC usage (Pin 5 high, Pin 6 low) is not
shown.
6. If one or more logic levels listed in Table 11-3 on page 593 is
incorrect, disconnect W11 from A14J6 and repeat step 4 checking
only pins 3, 5, 11, and 13 of A14U420. Pins 4, 6, 10, and 12 should all
read low TTL levels.
7. If one or more logic levels listed in Table 11-3 on page 593 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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