Troubleshooting Flow Chart For Microprocessor - Motorola CDM Series Service Manual

Chapter 2: 3-4 Control Head CDM1250 / PRO5100 / CDM1550 Series / PRO7100 Troubleshooting Flow Charts
2.2

Troubleshooting Flow Chart for Microprocessor

6881091C63-A
Power up alert tone sounds, but Volume knob
does not operate and indicator does not light up
EXTAL
U0831 Pin 31
= 8.00 MHz?
YES
RESET
TP0833
= HIGH?
YES
Measure with scope while
rotating Volume Pot
Data Signal
on J0801 Pin 5
BUS+?
YES
Data Signal
on TP0836
SCI_RX?
YES
Data Signal
on TP0837
SCI_TX?
NO
Check / Replace
R0831 / U0833 / U0831
NO
Check / Replace
C0833 / R0832 / U0831
NO
Check radio controller
Check / Replace
NO
R0837 / R0836
NO
Check / Replace
U0831
YES
Check / Replace
D0831 / R0838