Frequency-Count Marker Problems - HP 8560A Service Manual

6. In Figure 9-11, there is no synchronization between DEFl and the video patterns X POS
and Y POS when DEFl is TTL high. The Y POS level when DEFl is low is the Video In
level.
DEF 1
x
Y

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. Disconnect W53 from A2J7.
2.
Connect the output of a synthesized source, such as an HP 3335A, to A2J7.
3. Set the synthesized source to the following settings:
Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +lO dBm
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.35MHz
Frequency
4.
Set the HP 8560A to the following settings:
C E N T E R F R E Q
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz
5. On the HP 8560A press
the frequency of the 10.7 MHz IF. If the CNT frequency display reads all asterisks, the
frequency counter is probably at fault.
6. If a valid frequency is displayed, troubleshoot the prescaler on the A4 Log Amplifier/Cal
Oscillator assembly.
7. Reconnect W53 to A2J7.
5 . 0 0 0 . 0 0 v
Figure 9-11. DEFI Synchronization
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz
).
The frequency counter actually reads one half
COUNT
5 . 0 0 . 0 0 0 s
Controller Section 9- 13
S K 1 1 0 0