Failure Diagnosis Of The Vco Section - Kenwood NX-3220 K Service Manual

5.4 Failure diagnosis of the VCO section (NX-3220)
[Overview]
The VCO circuit is mounted inside the BLS. BLS stands for "Board Level Shield".
This BLS has no lid and provides high shielding performance. Because BLS is difficult to solder, components inside the BLS can't be
soldered.
When there is a problem with the VCO circuit, the VCO can't be repaired.
If the VCO function doesn't work, use this flow chart to identify the problem.
The following is explained about failure diagnosis of VCO circuit inside a BLS<E101>.
[About a BLS]
BLS is shielding case
BLS for VCO area is integrated type and can not be removed
[Prediction problem related to the VCO circuit]
• PLL Unlock
<Radio state>
- Unlock beep
- VCO Assist voltage tuning is impossible
<The cause>
- VCO control voltage is abnormal
- VCO Assist voltage is abnormal
- VCO power supply is abnormal
- VCO signal output circuit is abnormal
[VCO circuit inside a BLS<E101>]
R 1 0 2
0
$Q101
R106
10
C104 100p
C 1 0 5 1 u
50
Q102
IC101
EM6M2
OPA170AIDRL R
IN+
V+
V-
IN-
oUT
R108
C103 33p
R105 1 2 0 k 1 0 M
[E] [D]
ASSIST
[G]
IC102
BU7295HFV
CV amp
C N 1 0 1
IN+
VDD
VSS
R11 2
IN-
oUT
1k
C106
0.1u
1-158 (No.RA053<Rev.001>)
[F]
L 1 2 1
LB73H0AY-00 4 D134 D135
L41-2785-53
R128 R132 C133 SMV1801-079LF SMV1801-079LF
R127 R126 L131
2 7 0 n
0
0 390 (D) 0 1 0 0 0 p
L136
LB73H0AY-00 4
50C
L11 2
LB73H0AY-00 4
4.3V
Q11 3 Q11 4
VT6M1
2SD2654/W/
VCO circuit inside a BLS (in a dotted line)
R134
L139
10 RN(D)
VCO
270n
L41-2785-53
C141
L41-3378-08
Q131 C144
C134 L138 9p R135
33n 0.5p
1000p 0
BLS
E101
F1B-0095-00
[H]
[C]
[B]
R124
4.1V
R140
4 7 k
470k
R141
[ I ]
470k
VCO Buffer
[A]
This point is inside other BLS<E301>
Q151
2SC5108FT/Y/ C146
CN191
6p
C193
Q181
2.5p (B)
2SC5108FT/Y/ C183
L191
27n
4p (H0AM)
(B)
3.2V
R139
0
C197
470p
C198
2.5p (B)
L192
R195 R194
2 7 n
0 33
(H0AM)