Chapter 12 Uhf1 Troubleshooting Tables; Troubleshooting Table For Receiver (Uhf1); Table 12-1. Troubleshooting Table For Receiver (Uhf1) - Motorola EP350 Service Manual

Chapter 12 UHF1 Troubleshooting Tables

12.1 Troubleshooting Table for Receiver (UHF1)

Symptom
Radio Dead (no 1. Battery dead or
turn–on beep, no defective
LED indication)
2. Defective battery
contacts
3. Microprocessor not
starting up
4. Regulator fault
5. Flexible Cable fault
No RX Audio (with 1. Speaker dead or
LED indication) defective
2. Audio Processor IC
not starting up
3. Audio Amp IC not
starting up
No Receive (with 1. IF IC dead or fault
no LED indication)
No RX 1. RX–B+

Table 12-1. Troubleshooting Table for Receiver (UHF1)

Possible Causes Procedure
Substitute good battery or battery
eliminator
Inspect battery contacts for
corrosion or bent terminals
Verify clock input to U101 Pin 13 is
7.3728 MHz using high impedance
probe.
Verify U101 Pin10(reset) is high.
Verify U506 Pin 4 is 3.3V
Verify U505 Pin 4 is 5.0V
Check connection of the 12 pin
flexible cable between J104 & J105
Substitute a good housing (with
speaker)
Verify J603 connection
Verify clock input U102 Pin 14 is
3.5795 MHz using high impedance
probe.
Verify U601 Pin 6 is battery voltage.
If battery voltage is being supplied to
Pin 6, then verify audio output at
Pin 5 & 8.
Verify clock input to U201 Pin 1 & 2
is 44.645Mhz using high impedance
probe.
Verify Q304's collector voltage is
4.8V when RX–EN is high.
Corrective Action
Change or replace battery.
Clean/Repair/Replace J602
Troubleshoot/Replace FL101.
If reset is Low, troubleshoot
regulator U506 or U107.
Check for shorts on outputs
Troubleshoot/Repair as
needed, replace faulty regulator
Re–assemble or replace flexible
cable
Change the housing (with
accessory)
Change the housing (with
accessory)
Troubleshoot/Replace FL102
Troubleshoot/Replace U601
Troubleshoot/Replace FL201
Check/Replace Q304