TEST PROCEDURES
These Test Procedures are designed to help you to service a
receiver that is operating---but not properly. The problems en-
countered could be low power, poor sensitivity, distortion, limiter
not operating properly, and low gain. By following the sequence
of test steps starting with Step 1, the defect can be quickly
localized.
TEST EQUIPMENT REQUIRED
•
Distortion Analyzer similar to:
HP331A, or an equivalent average response meter
•
Signal Generator similar to:
HP8640B
•
6-dB attenuation pad, and 8.0 ohm, 2-Watt resistor
Once the defective stage is pin-pointed, refer to the "Service
Check" listed to correct the problem. Additional corrective meas-
ures are included in the Troubleshooting Procedure. Before
starting with the Receiver Test Procedures, be sure the receiver
is tuned and aligned to the proper operating frequency.
PRELIMINARY ADJUSTMENTS
1. Connect the test equipment to the receiver as shown for all
steps of the receiver Test Procedure.
2. Turn the SQUELCH control fully clockwise for all steps of
the Test Procedure.
3. Turn on all of the equipment and let it warm up for 20
minutes.
TEST PROCEDURES
STEP 1
AUDIO POWER OUTPUT AND DISTORTION
TEST PROCEDURE
Measure Audio Power Output as follows:
A. Apply a 1,000 microvolt, on frequency test signal modulated by 1,000 Hertz with 3.0 kHz deviation to antenna jack A301-J1.
B. Disconnect speaker lead pin from System Plug P701-11 (on rear of Control Unit).
Connect an 8.0-ohm, 2-Watt load resistor from P904-19 (SPKR H1) to P904-18 (SPKR LO) or from P701-4 to P701-17
(SPKR HI) on the System Plug. Connect the Distortion Analyzer input across the resistor as shown.
OR WITH HANDSET:
Lift the handset off of the hookswitch. Connect the Distortion Analyzer input from P904-19 to P904-18.
C. Adjust the VOLUME control for one Watt output using the Distortion Analyzer as a Voltmeter.
D. Make distortion measurements according to manufacturer’s instructions. Reading should be less than 3%. If the receiver
sensitivity is to be measured, leave all controls and equipment as they are.
SERVICE CHECK
If the distortion is more than 3%, or maximum audio output is less than 1 Watt, make the following checks:
E. Power Supply and regulator voltage---low voltage will cause distortion. (Refer to Receiver Schematic Diagram for voltages.)
F. Audio Gain (Refer to Receiver Troubleshooting Procedure.)
G. FM Detector Alignment (Refer to Receiver Alignment.)
LBI-38505 LBI-38505
7
(3 pages)
(197 pages)
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