Agilent Technologies 856290216 Frequency-Count Marker Problems, Controller Section lo

DEF 1

xPOS

Y POS

5 . 0	0I	V/div 0 . 0 0 v		5 . 0 m s / d i v	0 . 0 0 0 s
			I

SK1 100

Figure 10-l 1. DEFl 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.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 Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.35MHz

4. Set the spectrum analyzer to the following settings:

Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...300 MHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz

5.On the spectrum analyzer, press (FREQ 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.

6.If a valid frequency is displayed, troubleshoot the prescaler on the A4 log amplifier/Cal oscillator assembly.

7.Reconnect W53 to A2J7.

Controller Section lo- 13