HP 8560A, Service Manual

Page: 390 / 450

7. If a correct signal is seen at but the signal at is wrong, proceed as
follows:
. Use an oscilloscope to measure the signals at the following test points:
pin 1
Vdc to Vdc Vp-p variation)
pin 3 -1.8 Vdc to -2.4 Vdc Vp-p variation)
If these levels are wrong, perform the “Power and Sampler Match Adjustments” in the
Sampler Oscillator Adjustment procedure. Refer to Chapter 2.
If adjusting the Sampler Match does not bring the signal at within
specification when the signal at is correct, the Sampler is defective.
8. If the signal at is correct, but the signal at is wrong, the fault lies in
the Sampler IF circuitry. Continue with the following steps.
9. Set the HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10. Set a microwave source to the following settings:
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Amplitude
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5
11. Connect the microwave source to
12. Measure the signal at pin 1 using an active probe/spectrum analyzer combination.
13. If a 94.7 MHz signal, approximately -14 is present, but the signal at is
low, suspect
14. When pin 3 is at TTL low, pin 6 should near -15 Vdc and PIN diodes
CR102, and CR103 should be reverse-biased.
15. Set HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 Hz
16. Check that pin 3 is at a TTL high and pin 6 is greater than V. PIN diodes
CR102, and CR103 should all be turned on with about 7 of forward current.
17. Disconnect the power splitter and reconnect W32 to
Synthesizer Section