IFR FM/AM-500, Maintenance Manual

Page: 194 / 320

6. Set RF FREQUENCY Thumbwheels to "299 000 0".
7. Connect DVM between wiper of lOK pot and ground.
8. Adjust the 10 K pot to obtain each of the following fre­
quencies and record the corresponding voltage:
a. 1250 MHz
b. 1550 MHz
c. 2330 MHz
If the VCO requires more than 34 volts to pro­
duce 2330 MHz, test the VCO as described in
paragraph 7-4 before proceeding with this pro­
cedure.
9. Connect DVM between center conductor of J4003 and ground.
10. Adjust the 10 K pot to obtain a frequency of 1700 MHz.
11. Adjust Low Limit trimpot R4047 to obtain a voltage equal to
that recorded in Step Ba.
12. Adjust the 10 K pot to obtain a frequency of 1500 MHz.
13. Adjust High Limit trimpot R4042 to obtain a voltage equal to
that recorded in Step Be.
14. Rotate RF FREQUENCY Thumbwheels to "199 000 0".
15. Adjust the 10 K pot to obtain a frequency of 1400 MHz.
16. Adjust 200 MHz Limit trimpot R4024 to obtain a voltage equal
to that recorded in Step Sb.
17. Disconnect the DVM and 10 K pot and recouple P/J4002 and
P/J4003.
18. Rotate RF FREQUENCY Thumbwheels to "999 000 0". Verify the
High Loop phase lock indicator LED is not illuminated.
19. Verify the Spectrum Analyzer displays 1210 MHz at +8 dBm
(±4 dB).
20. Adjust the following trimpots for the minimum spurs at
500 kHz and 1 MHz as displayed on the Spectrum Analyzer.
a. R4045 (Null #2)
b. R4052 (Null #1)
7-31