Microprocessor - Motorola 6864115B62-C Detailed Service Manual

3-4
2.2

Microprocessor

Power Up Alert Tone is OK but volume knob does
not operate and no indicator is on
EXTAL
U0831 Pin 31
= 8.00 MHz ?
RESET
TP0833
= HIGH ?
Measure with scope while
rotating Volume Pot
Data Signal
on J0801 Pin 5
BUS+ ?
Data Signal
on TP0836
SCI_RX ?
Data Signal
on TP0837
SCI_TX ?
NO
Check / Replace
R0831 / U0833 / U0831
YES
NO
Check / Replace
C0833 / R0832 / U0831
YES
NO
Check radio controller
YES
Check / Replace
NO
YES
NO
YES
TROUBLESHOOTING CHARTS
R0837 / R0836
Check / Replace
U0831
Check / Replace
D0831 / R0838