Vco Section Inspection - Kenwood NX-3220 K Service Manual

[Inspection procedure]
Unlock[Unlock beep / VCO assist tuning is impossible]
Assist Auto Tuning
Auto tuning NG
Assist Manual Tuning
Manual tuning NG
Check the VCO output signal
Observe the signal at point [A] with spectrum analyzer thru high impedance probe
Signal existence
No signal
Remove <C191><C193><L191> and check whether it is short circuited at point [A]
No short-circuit
Check the VCO power supply
Check the VCO Assist voltage supply circuit
Measure the voltage at point [D] by setting Assist tuning value [4096]
This voltage fluctuate in conjunction
with the change of Assist tuning value
Observe the signal at point [A] with spectrum analyzer thru high impedance probe
This signal fluctuate in conjunction
with the change of the voltage at point [D]
If normal condition,
frequency will be less than 272MHz at assist=1
And frequency will be more than 348MHz at assist=4096.
Check the VCO control voltage supply circuit
Please refer to [Remarks] below.
Modulation trouble / Balance tuning is impossible
Check the VCO modulation circuit
Check the FM deviation in a Balance tuning mode at 2kHz sample tone
When FM deviation don't fluctuate in conjunction
with the change of the Balance tuning value
Check the modulation signal at point [ I ] in a Balance tuning mode at 2kHz sample tone
Signal existence[2kHz tone]
*In case of Balance tuning value is [1024], this signal level is about from 1.1[Vp-p] to 1.5[Vp-p]
Remove <R124><R113> and check the modulation signal at point [H] in a Balance tuning mode at 2kHz sample tone
The modulation signal can be confirmed,
and signal level fluctuate in conjunction with Balance tuning value
There is a problem with the VCO circuit inside a BLS / Please exchange it for a new PCB
[Remarks]
The following things are assumed as causes of trouble besides the above
• PLL data is abnormal
• VCO/PLL lock judgment is abnormal[<IC401>OMAP]
1-160 (No.RA053<Rev.001>)
There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
Measure the voltage at point [B]
The checked voltage is The checked voltage is about from 4 to 5V.
not about from 4 to 5V.
Measure the voltage at point [C]
The checked voltage is
not about from 3 to 3.2V
Remove <R139> and measure the voltage at point [C]
The checked voltage is
aboutfrom 3 to 3.2V
There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
Remove <R116> and measure the voltage at point [B]
The checked voltage is
The checked voltage is not about from 4 to 5V.
about from 4 to 5V.
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
The checked voltage is about 0V.
Remove <R108><R109> and measure the voltage at point [E]
This voltage fluctuate in conjunction
with the change of Assist tuning value
*In case of tuning value is [1] , this voltage is about 0V
In case of tuning value is [4096] , this voltage is about 18.3V
There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
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
This voltage fluctuate in conjunction
with the change of Assist tuning value
Remove <IC102> and measure the voltage at point [G]
This voltage difference between
point [F] and point [G] is more than 0.1V
There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
Short-circuit
The checked voltage is about from 3 to 3.2V.
There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
The checked voltage is not from 3 to 3.2V.
There is a problem outside the BLS. Check the power 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
The checked voltage is about 0V.
There is a problem outside the BLS. Check the Assist voltage supply circuit.
This signal doesn't fluctuate in conjunction
with the change of the voltage at point [D]
There is a problem with the VCO circuit inside a BLS / Please replace to new PCB
When the above condition is not satisfied
There is a problem outside the BLS. Check the circuit around IC303.
This voltage difference between
point [F] and point [G] is less than 0.1V
There is a problem outside the BLS. Please check the circuit posterior to <IC102>