QEI 675 - Alignment and Troubleshooting; Equipment Required for Alignment; FMO and Phase Lock Assembly Alignment

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SECTION 5
ALIGNMENT AND TROUBLESHOOTING
5-1 EQUIPMENT REQUIRED BUT NOT SUPPLIED
l. RF Load (50 ohms - 20 watts min.)
2. RF Wattmeter (Bird 43 or equivalent)
3. FM Modulation Monitor (QEI 671 or equivalent)
4. Audio Generator (less than .1 % distortion)
5. Distortion Analyzer (Hewlett Packard 331 or equivalent)
6. Dual Trace 10 MHz Oscilloscope (Telequipment 054 or
6
equivalent
7. 110 MHz Counter (Stability better than l part in 10 )
8. Signal Sampler (-20 to -30 dB output)
9. Spectrum Analyzer
NOTE: DO NOT ATTEMPT TROUBLESHOOTING OR ALIGNMENT OF THIS
UNIT WITHOUT ADEQUATE TOOLS AND TEST EQUIPMENT.
Before starting alignment of this unit, verify that three supply
voltages are present and correct. Connect the Exciter to a
suitable (50 ohm - 20 watt) RF load through the signal sampler.
- 5-2 FMO AND PHASE LOCK ASSEMBLY ALIGNMENT
l. AFC Adjustment
a . Connect a scope to test point
11
L" . A ct j us t A 2 R 4 7 for the
greatest amplitude linear 5 KHz sawtooth obtainable.
b. Connect a scope to pin 6 of A2Ull. Adjust trimmer access-
ible through hole in FMO can until pin 7 shows a DC level.
Either side of lock will give a sawtooth signal whose
frequency becomes lower as lock is approached.
2. Modulation Level Adjustment
a. Connect an FM Modulation Monitor to the low level output
of the signal sampler.
b. Connect a 400 Hz +10 dBm signal to TBl. Place S3 in MONO
position. Adjust A2R31 until monitor reads 100%.
C.
Connect a 400 Hz 4Vpo (l .41Vrms) signal to COMP jack J2.
Place S3 in COMP pos1tion. Adjust A2R65 until monitor
reads 100%.
3. Coarse Frequency Adjustment.
a. Connect a counter to the low level output of the signal
sampler.
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