Chapter 5 Troubleshooting Charts
5.1 Introduction
This chapter contains detailed troubleshooting flowcharts and tables. These should be used as a
guide in determining the problem areas. They are not a substitute for knowledge of circuit operation
and astute troubleshooting techniques. It is advisable to refer to the related detailed circuit
descriptions in the theory of operation chapter prior to troubleshooting a radio.
5.2 List of Troubleshooting Charts
Most troubleshooting flowcharts (see Table 5-1) end by pointing to an IC to replace. Before replacing
any IC, it is good practice to verify power supplies and grounds to the affected IC and trace continuity
to the malfunctioning signal and related circuitry. For example, if a clock signal is not available at a
destination IC, continuity from the source IC should be checked before replacing the source IC.
Table 5-1. List of Troubleshooting Charts
Description Page
VHF (136–174 MHz)
Poor RX Sensitivity or No RX Audio 5-12
RX IF—Poor SINAD or No Audio 5-14
RX Back-End—Poor SINAD or No Audio 5-15
Low or No RX Injection Signal 5-18
Low or No TX Injection Signal 5-19
TX or RX VCO Unlock (Fail 001) 5-20
No Output Power at TX Mode 5-22
No Output Power and IDC < 2A at TX Mode 5-23
UHF Range 1 (380–470 MHz) and UHF Range 2 (450–520 MHz)
No 16.8 MHz Reference Oscillator Frequency 5-24
Poor RX Sensitivity or No RX Audio 5-25
RX IF—Poor SINAD or No Audio 5-27
RX Back-End—Poor SINAD or No Audio 5-29
Low or No RX Injection Signal 5-32
Low or No TX Injection Signal 5-33
No TX Audio 5-34
TX or RX VCO Unlock (Fail 001) 5-35
RF Power Amplifier (RFPA)—No or Low TX Power Output 5-37
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