Kenwood NXR-700 Service Manual page 45

■ Traceability Procedure of IC34 (The RF control MPU)
Confi rmation of Power Source Voltage
Test Point Normal Output Voltage
IC16 (pin 5)
IC329 (pin 4) 3.3VDC
Correct condition
Confi rmation of Clock frequency
Test Point Proper Frequency
R195 14.7456MHz
(either end of R195 is OK)
Correct condition
Confi rmation of Reset control
Test Point Normal Control Voltage
IC303 (pin 1) 3.3VDC
Correct condition
Parts other than IC34 are malfunctioning.
1-3. Hardware traceability (Method 2)
The NXR-700 control circuit executes the following proce-
dures when the system starts up.
1. An external DC 13.8V power source is applied to the
NXR-700 terminal.
2. The Modem control MPU (IC325) starts up.
3. The Modem control MPU (IC325) initiates all circuit
blocks.
4. The Main MPU (IC703) and the RF control MPU (IC34)
start up.
TROUBLE SHOOTING
5VDC
Abnormal
Confi rmation of IC16 (pin 5) output
condition
Remove R201. If 5 VDC, IC34 is malfunctioning.
Confi rmation of IC329 (pin 4)
Remove R159. If 3.3 VDC, IC34 or IC17 may be
malfunctioning.
If the oscillation of 14.7456MHz cannot be con-
Abnormal
fi rmed:
condition
X1 is malfunctioning or the circuit around X1 is mal-
functioning.
Clock oscillation amplitude is weak:
Drive circuit in IC34 is malfunctioning.
Abnormal
Remove R332 and confirm the voltage of the
condition
pad on the opposite side of IC34:
If 3.3 VDC, IC34 is malfunctioning.
5. The Main MPU (IC703) confi rms the operational status of
the Modem control MPU (IC325) and the RF control MPU
(IC34) by using 115.2kbps UART communications and
then the operation transfer commands will be exchanged
in order to integrate all hardware blocks.
The above steps 1 to 5 will be executed as follows.
NXR-700
45