Sony CRF-230B User manual

CRF-230B
C'S
SONY.
SERVICE
MANUAL
236 3

CRF-230B
Section
1.
TABLE OF CONTENTS
Section
Title Page
OUTLINE? coicccecueticecetecestchec Piste gteiees peed 3
1-1. Specifications 3
1-2. Block Diagram 2.0.0... cece ceeecceceeeeeeoeeee 5
1-3. Technical Features .........ccccccsssccsseeeeees 6
1-4, Circuit Explanations .............cceeeeeeeeee 6
1-5... External “View 2..ceccc.ce.ciiscssuecacavesseneaee 10
1-6. Internal View 0.0... eeesseetseeeeeeeneeeeee 10
V7... Chassis: View ss.icetc.feqvegietssoseceaacstaeute 11
DISASSEMBLY 000... ce ceseeecesseeeeerseeeeee 12
2-1. Rear Cover Removal ..........ccccceseeeeees 12
2-2. Cabinet Removal .0.........cccceeeeseeteees 12
2-3. Front Panel Removal .............:ccceeeeee 13
2-4. Speaker Removal .......ccceeeeeeeenseceeeeees 13
2-5. Fm Front End Block Removal ......... 14
2-6. Main Circuit Board Removal ............. 14
2-7. Sw Front End Block Removal .......... 15
2-8. Cp Circuit Board Removal .......0..0.. 15
2-9. Power Supply Circuit Board
Rei OVal ooo yee scsi let sctececivenetncsaesecs 16
2-10. Dial Cord Stringing ...... eee eeeeeeees 18
CIRCUIT ADJUSTMENTS. ....00... eee 20
3-1. Preparation 00... eee
3-2. A-m I-f Alignment
3-3. Ssb Detector Adjustment ................. 20
3-4. Fm I-f Alignment
3-5. Muting Level Setting ......
3-6. FM1/FM2 Frequency Coverage
and Tracking Adjustment ............. 22
3-7. LW/MW/SW1 Frequency Coverage
and Tracking Adjustment.............. 24
Title Page
3-8. SW2~SW19 Ist I-f Alignment,
Frequency Coverage and
Tracking Adjustment ..............0.06 25
3-9. SW2~SWI19 Frequency Coverage
and Tracking Adjustment ............. 26
3-10. Voltage and Current Adjustment ...... 30
MOUNTING AND SCHEMATIC
DIAGRAMS ooo cece cess netceeeeeeeseeenes 32
4-1. FM1 Front End (P1) ou... cee eees 32
4-2. FM2 Front End (P2) ........ cere 33
4-3. Antenna Terminal (P3) ................0008 34
4-4, Jack Panel (P4) wo... ecceeeeeeceee sees 35
4-5. Cp Circuit Board (P5) ........ece ee eeeeeees 36
4-6. Power Supply Circuit Board (P6) ..... 38
4-7. SW2~SW19 Front End Block (P7)
(SWC-011 D2) ssccnciceceeietnie dew 39
4-8. Switch Circuit Board (P9) ........0.... 44
4-9. Main Circuit Board (P8) .......... eee 45
4-10. Schematic Diagram ............cc.seeeeeeeeeen 47
PACKING AND EXPLODED VIEW .......... 50
S21, Packing +. 2205. kansinic ie etnies 50
5-2. Exploded View (1) ......ccccceecesseeeeeeeeen Sl
5-3. Exploded View (2) vo....cccceccceneeeeeeeen 53
5-4. Exploded View (3) ........ccccecceseeeeereeen 55
5-5. Exploded View (4) .......c..cccceeeseeseeeeen 57
5-6. Exploded View (5) ........cccceccesseeeeneeen 59
5-7. Exploded View (6) .......cccccccsseseeeeeeoen 61
ELECTRICAL PARTS LIST..............::0:0008 62

CRF-230B
SECTION 1
OUTLINE
1-1. SECIFICATIONS
Circuit System: Superheterodyne (FM-1, FM-2, MW, LW, SW-1)
Double superheterodyne (SW-2 ~ SW-19)
Semiconductor: 27 transistors, 4FET for reception, 17 transistors
for auxiliary functions, 34 diodes, 2 thermistor
Frequency Coverage: FM-1 ; 76 -90MHz
, FM-2 ; 87.5 - 108 MHz
MW ; 530- 1,605 kHz (566 - 187 m)
LW; 150- 400kHz (2,000 - 750m)
SW-1
;
1.6-
4.5
MHz
(187
-
66
m
;
Marine
Band)
SW-2 ; 2.0-2.6 MHz (120m)
SW-3 ; 3.0-3.6 MHz (90 m)
SW-4 ; 3.5-4.1 MHz (75- 81 m)
SW-5 ; 4.5-5.1 MHz (60 m)
SW-6 ; 5.8-6.4MHz (49 m)
SW-7 ; 7.0-7.6 MHz (40 - 41 m)
SW-8 ; 9.5-10.1 MHz (31 m)
SW-9 ; 11.5-12.1 MHz (25 m)
SW-10; 14.0- 14.6 MHz (20 m)
SW-11; 15.0 - 15.6 MHz (19 m)
SW-12; 17.5-18.1 MHz (16 m)
SW-13; 21.0 - 21.6 MHz (15 m)
SW-14; 21.4- 22.0 MHz (13 m)
SW-15; 25.5 - 26.1 MHz (11 m)
SW-16; 26.8 - 27.4 MHz (11 m)
SW-17; 28.0 - 28.6 MHz (10 m)
SW-18; 28.6 - 29.2 MHz (10 m)
SW-19; 29.2- 29.8 MHz (10 m)
Intermediate Frequency: FM ; 10.7 MHz
MW, LW,SW-1; 455 kHz
SW-2~SW-19; Ist: 1.6- 2.2 MHz
2nd: 455 kHz
Antenna
System:
FM
;
telescopic
antennas
1,000
mm
2
pcs
external
antenna
terminals
(300.2,
75)
are
provided
MW,
LW
;
built-in
ferrite
bar
antenna,
10¢
x
180
mm
external
antenna
terminal
is
provided
SW-!
~
SW-19
;
telescopic
antenna
1,470
mm
external
antenna
terminal
is
provided
Power Requirement: AC 100, 120, 220, 240V, 5%p Hz (c/s)
DC 9V,_ battery (size “D’’) 6 pcs
DC 12V, with SONY car battery cord DCC-2AW (optional)
Power Output: 4W with AC power supply
at 10% distortion 1.5W with DC power supply
Current Drain: AC 180mA
at zero signal DC 90mA
Maximum Sensitivity: FM ; -2dB (0.8yuV)
at output 50 mW, S/N 6dB MW ; 28dB/m (25 4V/m)
LW ; 36dB/m (63 uV/m)
SW ; OdB (1uV); average

CRF-230B
Selectivity:
Muting Level:
Signal-to-Noise Ratio:
Image Rejection:
Frequency Response:
AUX Input Jack
input impedance:
maximum sensitivity:
MPX Output Jack
output impedance:
output level:
Recording Jack
output impedance:
output level:
Recording Connector
output impedance:
output level:
External Speaker Jack:
Headphone Jack:
Earphone Jack:
Other Controls:
Dimensions:
Weight:
Supplied Accessories:
LW, MW, SW-1 ~ SW-19; 40dB at BROAD position
60dB at SHARP position
10 ~ 30 dB (adjustable)
FM; 63 dB at 54dB input, 400 Hz, 30% modulation
MW; 374dB at 60 dB input, 400 Hz, 30% modulation
LW; 30dB at 60 dB input, 400 Hz, 30% modulation
SW; 44dB at 44dB input, 400 Hz, 30% modulation
FM-1 ; 72dB at 77 MHz
FM-2 ; 72dB at 98 MHz
MW ; 60dB at 1,605 kHz
LW; 80dB at 360kHz
SW-1 ; 30dB at 4.5 MHz
SW-2 ; 80dB at 2.5MHz
SW-19; 30dB at 29 MHz
100 - 20,000 Hz within +10dB by tone control
5ka
-53 dB (1.7 mV) at 50 mW output
5 ka
-24 dB (49 mV) at 5k load impedance
2.2 ka
-50 dB (2.5 mV)
80k2
-29.5dB (26mV)
3 ~ 82 speakers can be connected
82 headphone can be connected
82 earphone can be connected
Battery check switch
Calibrator reset knob
AGC/MGC knob
BFO control knob
Selectivity switch
Noise limiter switch
Muting switch
Sensitivity switch
171346" (W) x 121346" (H) x 714" (D)
(452mm x 325mm x 190 mm)
31 lb, 14 kg (without batteries)
AC power cord
polishing cloth

sw
TEL
ANT
78Q
EXT ANT
FM1
FRONT
END
BLOCK
MAIN
CIRCUIT
BOARD
0212, 0213
S-CURVE
PHASE REVERSE
D212 ~ 0215
S-CURVE
PICK UP
Q201 ~ Q205
FM IF AMP
aad
N
\
oO
—-
je}
2)
R
g
>
Q
Ps
>
s
NOISE AMP
Q206
CARRIER
CONT
Q208, Q209
FEED BACK
SWITCHING
aQ210
DIFFERENTIAL
SWITCHING
Q609
MUTING
D504, D505
ANL
J602
REC OUT
Q601 ~ Q605
AF AMP
POWER AMP
D001, DOG2
RECTIFIER
Q701 ~ Q704
REGULATOR
wee
ee
ee
eee
;
J603
HEADPHONE
J604
EARPHONE
J605
EXT
SP
| DC POWER
| BATTERY
16pcs 9V
CP
CIRCUIT
BOARD
POWER
SUPPLY
CIRCUIT
BOARD
Fig. 1-1

| CRF-230B
1-3 TECHNICAL FEATURES
The SONY Model CRF-230B is a high-perform-
aruc: radio receiver having many features found in
cOmrmunication receivers. Among them are the
fo lbwing:
e 4 total of 23 bands covering the broadcast fre-
quencies of any country in the world. Included
we 2 fm bands, 19 sw bands, a mw band and
alw band.
e (ET (Field Effect Transistor) front ends in fm
and sw bands provide superior sensitivity, image
rejection, and stability.
e fasy-to-tune sw bands due to a dual-conversion
system providing a uniform 600 kHz tuning range
on each band.
e ?roduct detector for receiving ssb signals.
e An fm i-f circuit employing ceramic filters. An
am i-f circuit employing two ceramic filters
with two-step adjustable selectivity.
e Individual tuning knobs for sw2~ 19 bands,
swl/mw/lw bands and fm bands. Preset-tuning
of three stations is available.
e The power supply will operate from household
current in any country of the world (via built-in
voltage selector), internal battery, or car battery.
e Stable, noise-free fm tuning by means of AFC
and a muting system.
e ANL (Automatic Noise Limiter) to minimize
noise.
e Up to 4 watts of undistorted audio power output
with two built-in speakers or external speakers.
TO MUTING
CIRCUIT
1-4. CIRCUIT EXPLANATIONS
AFC (Automatic Frequency Control)
Available for Both FM Bands
In the Model CRF-230B, the local oscillator
frequency is above the signal frequency for the FM2
band, but below the signal frequency for the FM1
band. Because of this, oscillator drift produces a
detector dc output-voltage change of different
polarity on the FM1 band than on the FM2 band.
Therefore, dc control voltages taken directly from
the detector output can not be used to stabilize the
frequency of the local oscillator. To get around this
problem, a comparator circuit with selectable output
polarity is used (Fig. 1-2). The detector output is
devided by equal-value resistors R232 and R233 to
provide two voltages identical in magnitude but
opposite in polarity. These voltages are compared
against a reference voltage of approximately 1.5 volts
produced by the forward voltage drop across D204
and D205. The resultant voltages are applied to the
bases of transistor Q211 and Q212. The each
collector voltage is fed through AFC switch $202
to variable-capacitance diode (DO1 for FM1 band
and D101 for FM2 band). The variable-capacitance
diode is voltage sensitive, so its capacitance (and
hence the oscillator frequency) depends on the mag-
nitude of the control voltage. Load resistors R254,
R255 and also R258, R259 are connected in a
balanced bridge and the contact voltage at the
junction of R260 and R261 is used as a fixed bias
voltage (0.7V) for the variable-capacitance diode
when AFC switch S202 is set to OFF.
IF T204 nee a ie
c circa (DIO!)
TO AFC
CIRCUIT (DON
Fig. 1-2

Mut ing Crcuit:
Whe: the receiver is detuned from a signal, the
signal deweases. Since less i-f signal is then rec-
tifiecl bydiodes D207 and D208, the negative out-
put voltze of these rectifiers can no longer back
the positie voltage applied to the base of transistor
Q206 though adjustable resistor VR901 (Fig. 1-3).
This allo’s Q206 to conduct lowering its collector
voltage. Since the collector of Q206 is connected
to the bze of PNP transistor Q209, Q209 conducts
wherl its base voltage decreases (with respect to
ground), thereby causing transistor Q208 to con-
duct. Th collector voltage of Q208 then drops to
near grouid potential. The voltage at the collector
of Q208 is fed to the base of transistor Q609
through WUTING switch $203. Since this voltage
is so lowQ609 cannot conduct and complete the
emitter cicuit of transistor Q608. This prevents
Q608 fro: amplifying the detector output.
When tuned to a signal, the opposite actions
occur. IJ-! signal through capacitor C227 is rectified
into negatve d-c voltage by diodes D207 and D208.
This voltae cuts off transistor Q206 and eventually
turns on tansistor Q609, thereby enabling transistor
Q608 to amplify the detector output. The muting
level can be adjusted by potentiometer VR901.
CRF-230B
lower than the signal level. If the receiver tuning
is shifted within range B of Fig. 1-4, the difference
between the collector voltages of transistors Q211
and Q212 becomes large enough drops across re-
sistors R251 and R252, thus lowering the base
voltage of PNP transistor Q209 and results in its
conduction. As before, the conduction of Q209
begins a chain of events which prevents Q608 from
amplifying. If the tuning is shifted within range C
of Fig.14, the difference between the collector
voltages of transistors Q211 and Q212 is so small
that transistor Q210 is turned off within this range
as
well
as
in
range
A.
Noise
components
caused
by detuning, however, are coupled to transistor
Q207 through capacitor C240 and resistor R247
from the detector output.
| |
C—mt— Bf Af Bet — 6
The mutiry level is usually set approximately 20dB Fig. 1-4 Discriminator characteristic
from
discriminator
trol
discriminator = I re
a0 D2i2 D214
G)
D210 R252 D215 D213
CH
“ay,
b2ii 9209 c240
Wy——=1 To AFC
0208 R250) R247 Ps a va Fo
(y’ (Vv NYY
KO) C239 1) &
I Q2it Q212
> +B
to af S
+B circuit << Q6og
S203
MUTING
OFF (fv
p Q609
60n Us
=
Fig. 1-3

CRF-23 0B
The noise is amplified, rectified into negative
d-c voltage by diodes D210 and D211, and applied
to the base of transistor Q209 to turn it on. Since
the base voltage of Q207 is controlled by the collec-
tor voltage of Q209, the amplification of transistor
Q207 increases due to increased base bias, and
transistor Q209 is held conducting quite reliably.
As before, transistor Q608 cuts off the detector
output.
Positive feedback through resistor R250 and
capacitor C239 from transistor Q209 aids in turning
off Q208.
CF501 ($501-1)
R528 C526
330 33P
R528 C524
330 150P
Adjustable Selectivity Employing Ceramic Filters:
The bandwidth in a-m reception can be altered
by changing the coupling between the sections of
ceramic filters in the a-m i-f circuit. Ceramic filters
CF50!1 and CF502 can be manually set to narrow
or wide bandwidth by switch S501.
The net result of the switch manipulations on
the ceramic filter circuits are summarized in Table.
The overall selectivity curves of the a-m i-f strip
are shown in Fig. 1-5.
Overall
CF502 ($501-2 ~ 3) response
(Fig. 1-5)
C527 R530
36P 2K
fe
mn [__]
C526 R529
100P 1K

CRF-230B
Product Detector for Single-Sideband Reception:
Input Level (dB)
30
A product detector is a type of heterodyne
detector. Single-sideband signals can be recovered by
passing them through nonlinear device after being
mixed with a carrier identical in frequency to that
used during modulation at the transmitter. That is,
these two signals, sideband and carrier, are converted
into two beat signals, upper and lower, against the
carrier frequency by heterodyne action. The upper
beat signal is eliminated by passing through the filter
circuit and the lower beat signal is fed to the next
stage as audio signals.
In the model CRF-230B, the detector utilizes
the square-law characteristic (output current pro-
portional to the square of the effective value of the
input voltage) of a diode for the nonlinear device.
To minimize distortion, two diodes D502 and
D503 are connected in reverse each other and applied
the signals respectively positive in phase. That is
- ia ae - < because the range of square-law curve of one diode is
narrow causing distorted detection for strong input
signal.
The BFO injection voltage used for carrier re-
insertion is comparatively high (about 0.8 volt is
optimum) to set the operating point of the detector
within a linear portion of the diodes’ characteristic.
This results to minimize distortion of the recovered
40
50
60
70
BO
Fig. 1-5 — Overall i-f response curve
ANL (Automatic Noise Limiter):
This limiter in the a-m section clips any noise audio signal.
pulses accompanying the signal to a level no longer
than the signal amplitude. The clipping level is auto- IFT504 —
matically adjusted to match the variations in signal ras T —1¢ 7 ‘ pa Lis
level. The collector voltage of i-f amplifier Q502 for- if signal ad
7 Wy ~—we- detected
Rsi7 | Rs20 | signal
Cae Csi9
ward biases diodes D504 and D505 through resistors
R509 and R521, while the output voltage of detector
D501 provides a reverse-bias voltage (Fig. 1-6). These
two
bias
voltages
adjust
the
clipping
level
of
diodes
habit
D504
and
D505
to
match
the
average
signal
level.
|
Lov 2i a
Fig. 1-7 Production detector
D504 | 0505
detected clipped
signal signal
Fig. 1-6 | Automatic noise limiter circuit

4 iy Ye)
1-5. EXTERNAL VIEW
X-38276-86
knob ass’y,
calibrator
X-38276-85
knob ass’y, TREBLE,
BASS and MGC
control
X-38276-84
knob ass‘y, BFO and
VOLUME control
1-6. INTERNAL VIEW
1-401-348-31
ferrite bar antenna,
MW/LW
7-501-103
telescopic antenna, FM
3-841-371 :
Panel, antenna terminal
717-514-304
slide switch,
ROD ANT/EXT ANT
171-222-985
adjustable resistor,
MUTING level
Fig. 1-8.
7 O.—
171-502-210
speaker
3-828-422
push button, band
selector
X-38276-83
tuning knob ass’y
X-38276-87
lever ass’'y, BFO select
8-981-411-5717
SW front end, SWC-011D2
1-50 1-104
telescopic antenna, SW .
1-526-165-27
voltage selector
1-533-048
fuse post
1-508-377-1711
connector, ac/ext dc poner supply
1-509-029-02
jack, TAPE
1-507-169-13
jack, REC/AUX IN/
MPX OUT/EXT SP