Chapter 11 571
Synthesizer Section
Frequency Span Accuracy Problems
6. The rest of the procedure troubleshoots the YTO FM coil driver.
Refer to function block M of A14 frequency control schematic (sheet
2 of 5).
7. Set the spectrum analyzer to the following settings:
Center frequency ..................................................... 300MHz
Span .................................................................................0Hz
Trigger ............................................................ SINGLE,EXT
a. On the spectrum analyzer press
SAVE, SAVE STATE, STATE 0.
b. Remove A14J23 jumper and connect a dc voltage source to
A14J23 pin 2. Connect the voltage source ground to A14J23 pin 3.
c. Connect a microwave frequency counter or another spectrum
analyzer to the spectrum analyzer 1ST LO OUTPUT. (front panel
output)
d. Set the dc-voltage source output for 0 Vdc and note the 1st LO
frequency.
e. Set the dc-voltage source output for +10 Vdc. The 1st LO
frequency should momentarily increase approximately
+15.6 MHz.
f. The voltage at A14U332 pin 2 should be approximately 19% of
the voltage at A14J23 pin 2.
g. If the 1st LO frequency did not change in step e, press
LINE to
turn spectrum analyzer off and disconnect W10 from A14J3.
h. Place a jumper between A14J3 pins 9 and 10. Place a 50 Ω,3watt
resistor across A14J3 pins 5 and 6 (resistor, part number
0811-1086). Press
LINE to turn spectrum analyzer on.
i. On the spectrum analyzer, press
RECALL, STATE, STATE 0.
Table 11-14 Settings of Sweep Switches
Switch Switch State Switch Control
Line (Pin #)
Control Line
State (TTL)
U318A Closed 1 High
U318B Open 16 High
U318C Closed 9 Low
U318D Open 8 Low
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