HP 8560A, Service Manual

Page: 340 / 450

6. In Figure 9-11, there is no synchronization between and the video patterns X POS
and Y POS when is TTL high. The Y POS level when is low is the Video In
level.
5 . 0 0 0 . 0 0 v 5 . 0
0 . 0 0 0 s
DEF 1
x
Y
S K 1 1 0 0
Figure 9-11. Synchronization
Frequency-Count Marker Problems
The FREQ COUNT function works by dividing the 10.7 MHz IF signal by two (prescaling)
and counting the divided-down signal using the frequency counter on the A2 Controller
assembly (block Z of the A2 Schematic Diagram). The prescaler is on the A4 Log
Amplifier/Cal Oscillator assembly (block Q of the A4 Schematic Diagram). Perform the
following steps to determine whether the problem is on the A4 Log Amplifier/Cal Oscillator or
A2 Controller assembly:
1.
2.
3.
4.
5.
6.
7.
Disconnect W53 from
Connect the output of a synthesized source, such as an HP to
Set the synthesized source to the following settings:
Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Set the HP 8560A to the following settings:
C E N T E R F R E Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
On the HP 8560A press
COUNT
).
The frequency counter actually reads one half
the frequency of the 10.7 MHz IF. If the CNT frequency display reads all asterisks, the
frequency counter is probably at fault.
If a valid frequency is displayed, troubleshoot the prescaler on the A4 Log Amplifier/Cal
Oscillator assembly.
Reconnect W53 to
Controller Section 13