Ericsson LBI-38505A manual Test Procedures, Test Equipment Required, Preliminary Adjustments

LBI-38505 TEST PROCEDURES LBI-38505

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.

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.)

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