HP 8560A, Service Manual

Page: 310 / 450

Common IF Signature Problems
n
Region A of Figure
8-4
is noisy:
Suspect the first LC pole.
n
Region B of Figure
8-4
is flat:
Suspect the third step-gain stage, the fine attenuator, or the
fourth LC-pole output amplifier.
Region C of Figure 8-4 has no
15
step:
Suspect the reference 15 attenuator.
n
Region D of Figure
8-4
is flat:
Suspect the second step-gain stage.
n
Entire signature noisy:
If the signature resembles Figure 8-9, suspect a broken first
step-gain stage or a break in the signal path in the input switch, first crystal pole, or second
crystal pole.
n
Correct shape but noisy:
If the signature resembles Figure 8-10, suspect the second
crystal-pole output amplifier.
n
Amplitude of Region B of Figure
8-11
varies more than
12 Suspect the third step-gain
stage output amplifier.
n
Region
B
of Figure
8-12
is kinked:
Suspect the fourth LC-pole output amplifier.
R E F 1 0 . 0
2 0
I I I
5
S A M P L E
C E N T E R 1 0 7 0 0 S P A N 0 H z
R E S B W 3 0 0
V B W 3 0 0 S W P 5 0 0
S K 1 7 8
Figure 8-9. Noisy Signature
8-28 IF Section