Comnet MLS II MLSH041, Руководство по обслуживанию

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ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A
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5.3.3 Fixed Squelch Adjustment
1. Disable Channel Guard, if present, (ground J701-7). Set Squelch control RV502 full
CCW.
2. Connect a signal generator to antenna jack J1 and adjust for nominal 8 dB SINAD
signal.
3. Adjust squelch control RV531 to maximum squelch. Receiver must be muted.
4. Adjust squelch control RV531 slowly until receiver unmutes.
5. Check that the squelch opens at an input signal level corresponding to 8 dB SINAD
(±1 dB).
6. Remove ground from J701-7 or re-enable Channel Guard.
5.3.4 Receiver Test Procedures
5.3.4.1 TEST PROCEDURES
These Test Procedures are designed to help you service a receiver that is operating, but
not properly. The problems encountered could be low power, poor sensitivity, distortion,
or low gain. By following the sequence of test steps starting with Step 1, the defect can
be quickly localized. Once the defective stage is pin-pointed, refer to the “Service
Check” listed to correct the problem. Additional corrective measures are included in the
Troubleshooting Procedures. Before starting with the Receiver Test Procedures, be sure
the receiver is tuned and aligned to the proper operating frequency and the transmitter is
operating properly.
5.3.4.2 TEST EQUIPMENT REQUIRED
•
Distortion Analyzer
•
RF Signal Generator
•
dB Attenuation Pad
•
4.0 Ohm, 6 Watt Resistor
5.3.4.3
TEST PROCEDURE
STEP 1: Audio Output and Distortion
Measure Audio Power Output as follows:
1. Apply a 1000 microvolt, on-frequency test signal modulated by 1000 Hz with 3.0
kHz deviation to antenna jack J1.
2. With 4 Watt Speaker: Disconnect speaker plug if present. Connect a 4.0 ohm, 6
watt load resistor across the external speaker loads