Kenwood NX-3400, Service Manual

Page: 67 / 98

(No.RA070<Rev.001>)1-67
[Inspection procedure]
[Remarks]
The following things are assumed as causes of trouble besides the above
• PLL data is abnormal
• VCO/PLL lock judgment is abnormal[<IC401>MPU/DSP IC]
● Unlock [Unlock beep / VCO assist tuning is impossible] *Include modulation problems
↓
↓
↓
↓
↓
↓
○ Check the VCO output signal
↓ ↓
↓ ↓
↓
↓
↓ ↓
↓ ↓ ↓
↓ ↓ ■There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
↓ ↓
↓ ○Check the VCO power supply point B *In case, Radio frequency is set under 870MHz
↓ point C In case, other than those above
↓ ↓ ↓
↓ ↓ ↓
↓ ↓ ■There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
↓ ↓
↓ ↓ point B *In case, Radio frequency is set under 870MHz
↓ point C In case, other than those above
↓ ↓ ↓
↓ ↓ ↓
↓ ↓ □There is a problem outside the BLS. Check the power supply circuit.
↓ ↓
↓ ■There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
↓
↓
○ Check the VCO Assist voltage supply circuit
*When measuring this point, please use a multimeter with sufficiently high input impedance
↓ ↓
↓ ↓
↓ *Assist voltage switch<Q102> is on in the state of Assist tuning mode
↓ ↓ ↓
↓ ↓ ↓
↓ ↓ □There is a problem outside the BLS. Check the Assist voltage supply circuit.
↓ ↓ *In case of tuning value is [ 1 ] , this voltage is about 0V
↓ ↓ In case of tuning value is [ 4096 ] , this voltage is about 15V
↓ ↓
↓ ■There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
↓
↓
↓ ↓
↓ ↓
↓ ↓
↓ ↓
↓ ■There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
↓
○ Check the VCO control voltage supply circuit
↓
↓
↓
↓
↓ ↓
↓ ↓ ↓
↓ ↓ ↓
↓ ↓ □There is a problem outside the BLS. Check the circuit around IC303.
↓ ↓
↓
↓
↓ ↓
↓ ↓ ↓
↓ ↓ ↓
↓ ↓ □There is a problem outside the BLS. Please check the circuit posterior to <IC102>
↓ ↓
↓ ■There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
↓
Please refer to [Remarks] below.
Assist Auto Tuning
Assist Manual Tuning
Measure the voltage at point B or C
Observe the signal at point A with spectrum analyzer thru high impedance probe
Remove <R198> and check whether it is short circuited at point A
Measure the voltage at point F
*
In case of Assist tuning value is [ 1 ] , this voltage is about 4.7V
In case of Assist tuning value is [ 4096 ] , this voltage is about 0.1V
Remove <R108><R109> and measure the voltage at point E
Remove <R116> or <R117> and measure the voltage at point B or C
Observe the signal at point A with spectrum analyzer thru high impedance probe
Remove <IC102> and measure the voltage at point G
Remove <C118> and measure the voltage at point D by setting Assist tuning value [ 4096 ]
No signal
Signal existence
The checked voltage is
not about 4.2V.
This voltage fluctuatein conjunction
with the change of Assist tuning value
When the above condition is not satisfied
The checked voltage is about 0V. *Modulation problems may occur if this point[ D ] be abnormally condition.
This voltage fluctuatein conjunction
with the change of Assist tuning value
This signal doesn't fluctuate in conjunction
with the change of the voltage at point
E
Auto tuning NG
Manual tuning NG
No short-circuit
This voltage fluctuatein conjunction
with the change of Assist tuning value
This voltage difference between
point
F and point G is more than 0.1V
Short-circuit
The checked voltage is
about 4.2V.
The checked voltage is about 4.2V.
The checked voltage is to greatly differ from 4.2V.
The checked voltage is about 0V.
This signal fluctuate in conjunction
with the change of the voltage at point
E
This voltage difference between
point
F and point G is less than 0.1V