Motorola CP160 Detailed Service Manual page 41

1.0 Troubleshooting Tables for Board and IC Signals (includes
Controller, DC Regulation and Audio)
This section contains detailed troubleshooting tables. These tables 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 sections prior to troubleshooting a radio.
Most troubleshooting tables end up by pointing to an IC to replace. It is not always noted, but it is
good practice to verify supplies and grounds to the affected IC and to trace continuity to the
malfunctioning signal and related circuitry before replacing any IC. For instance, if a clock signal is
not available at a destination, continuity from the source IC should be checked before replacing the
source IC.
IC Designator
U310
5V Regulator
U320
3.3V Regulator
U330
3V Regulator
Pin Pin Function
1 Vin
2 Ground
3 Control input
4 Bypass capacitor
5 Vout
1 Ground
2 Feedback
3 Tap (NU)
4 Vin
5 Vout
6 Sense (NU)
7 Error (reset output)
8 Shutdown input
1 Vin
2 Ground
3 Control input
4 Bypass capacitor
5 Vout
TROUBLESHOOTING TABLES
DC Voltage
7.48
GND
7.48
1.26
4.96
GND
1.23
0
7.48
3.23
0
3.20
7.48
7.48
GND
7.48
1.26
3.00
Chapter 2
Comments (Condition)