HP 8560A, Service Manual

Page: 363 / 450

3. If pin 1 does not appear to be correct, verify that the sweep ramp is reaching the
Sweep Switch as follows:
Change the oscilloscope’s amplitude scale to 1.25 and monitor the pin 14.
The waveform should be a 0 V to -10 V sweep of 50 ms duration. See Figure 10-7.
Check for a 0 V to -10 V ramp at
pin 13. Refer to function block H of Al4
Frequency Control Schematic (sheet 2 of 5).
Check that state of the
S weep Switches as indicated in Table
Note
Switches and can change the polarity of This
allows the Roller Oscillator to sweep backwards when the YTO is locked to
a lower sideband of a Sampling Oscillator’s comb tooth. The YTO always
sweeps forward (lower frequency to higher frequency), but the Roller Oscillator
sometimes sweeps backwards (higher frequency to lower frequency). The
FREQ
DIAGNOSE
menu will indicate a negative Main Roller frequency in this instance.
S o u r c e C h o n 1
1 S l o p e 1 A u t o S c a l e E n a b l e d
1
I A d j u s t 1 - 2 . 5 0 0 v
O n E v e n t 0000 1
P r o b e
1
i n g Cdc 1 Cl Mnl
X S e l e c t e d
C u r s o r 0
C u r s o r O - X
0 . 0 0 v
0 . 0 0
Figure 10-7. Input to Sweep Switch
Table Settings of Sweep Switches
Open 1
Open
9
Open 16
Closed
1
Closed
8
Closed
9
High
High
High
High
High
High
Switch
Switch State Switch Control Line Control Line State
Synthesizer Section O-1 9