Ericsson LBI-38505A Specifications download pdf (Page 10)

TROUBLESHOOTING PROCEDURES

SQUELCHED UNSQUELCHED

NOISE SQ OUTPUT U605-2

0.2 VDC 9.9V

CAS U605-1

0.1 VDC 9.9V

RX MUTE U605-14

0.2 VDC 9.9V

RUS U605-13

0.2 VDC 4.9V

SQ DISABLE SW. INPUT U606-1

0.2 VDC 9.9V

AUDIO GATE SW. CONTROL U606-11

0.2 VDC 9.9V

If External Decoder is used (CG, DCG, Type 99, etc.),

RX Mute will remain low (regardless of noise squelch output), until proper

response is decoded.

RX Mute = Noise Sq Output• Decoder Output.

In above cases,

Sq Disable is assumed high (9.9V). If Sq Disable is grounded, U606-10 = 0.2 Vdc, U606-11 = 9.9 Vdc and Unit

is unsquelched for all conditions.

SQUELCH CHECKS

SYMPTOM PROCEDURE

IMPROPER SQUELCH OPERATION

• Check voltages on Schematic Diagram.

• Make gain and waveform checks with noise.

• Make gain and waveform checks with 6 kHz signal.

• Check discrete components in the squelch circuit.

• Replace IC circuit U603.

LOW OR DISTORTED AUDIO

• Check voltages on Schematic Diagram.

• Make gain and waveform checks.

• Check receiver alignment and FM -DET output.

• Check Q601, Q602, Q605 and other discrete components.

SYMPTOM CHECKS Con’t.

LBI-38505 LBI-38505

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Ericsson LBI-38505A Specifications Page 10