JVC MX-K50R User manual

SERVICE MANUAL
COMPACT COMPONENT SYSTEM
No.21122
Aug. 2002
COPYRIGHT 2002 VICTOR COMPANY OF JAPAN, LTD.
MX-K50R
MX-K50R
Contents
Safety Precautions
Important for laser products
Preventing static electricity
Disassembly method
Wiring connection
Adjustment method
Flow of functional operation
until TOC read
Maintenance of laser pickup
Replacement of laser pickup
Trouble shooting
Description of major ICs
1-2
1-4
1-5
1-6
1-18
1-19
1-23
1-24
1-24
1-25
1-28~41
SP-MXK50 SP-MXK50
CA-MXK50R
DISC
SKIP
V O L UME
V O L UME
+
–
RM – SM XK50R R EM O T E C O N T R O L
S T ANDBY/ O N
12 3
456
78
9
10
+10
S L EEP
S
O UND
M
O DE
T APE A/B FADE
MU T IN G
DISP L AY
M O DE
– SE L EC T +
FM/A M
AUX
CD
T APE
AC T IVE BASS
EX.
L EVE L
FM MODE
P T Y/ E O N
D I S C C H A N G E
CD - R/ RW P L AYBACK
CLOCK
/TIMER
DISPLAY
PH O N E SR
E P E A T
R E C S T A R T
/S T O P
C D R E C
S T A R T
DU BB I N G
PR O G R A MR A ND O M
T A P E B T A P E A
AUX
T APE
CD
FM
/ AM
A C T I V E B A SS
E X. L E V E L
S O UND
M
O D E
MX - K50R
CD2
CD 3
AC T IVE BASS EX T ENSI O N
CD
3
FU LL - L O G IC C O N T R O L
CD SYN CHR O REC O RDIN G
CD1
STANDBY/ON
S T A ND B Y
E C O
D I SP L A Y M O D E
P T Y/ E O N
– S E L E C T +
Area suffix
B ------------------------ U.K.
E ---- Continental Europe
EN ----- Northern Europe
EV ------- Eastern Europe

MX-K50R
1-2
1. This design of this product contains special hardware and many circuits and components specially for safety
purposes. For continued protection, no changes should be made to the original design unless authorized in
writing by the manufacturer. Replacement parts must be identical to those used in the original circuits. Services
should be performed by qualified personnel only.
2. Alterations of the design or circuitry of the product should not be made. Any design alterations of the product
should not be made. Any design alterations or additions will void the manufacturer`s warranty and will further
relieve the manufacture of responsibility for personal injury or property damage resulting therefrom.
3. Many electrical and mechanical parts in the products have special safety-related characteristics. These
characteristics are often not evident from visual inspection nor can the protection afforded by them necessarily
be obtained by using replacement components rated for higher voltage, wattage, etc.Replacement parts which
have these special safety characteristics are identified in the Parts List of Service Manual. Electrical
components having such features are identified by shading on the schematics and by ( ) on the Parts List in
the Service Manual. The use of a substitute replacement which does not have the same safety characteristics
as the recommended replacement parts shown in the Parts List of Service Manual may create shock, fire, or
other hazards.
4. The leads in the products are routed and dressed with ties, clamps, tubings, barriers and the like to be
separated from live parts, high temperature parts, moving parts and/or sharp edges for the prevention of
electric shock and fire hazard. When service is required, the original lead routing and dress should be
observed, and it should be confirmed that they have been returned to normal, after re-assembling.
5. Leakage currnet check (Electrical shock hazard testing)
After re-assembling the product, always perform an isolation check on the exposed metal parts of the product
(antenna terminals, knobs, metal cabinet, screw heads, headphone jack, control shafts, etc.) to be sure the
product is safe to operate without danger of electrical shock.
Do not use a line isolation transformer during this check.
Plug the AC line cord directly into the AC outlet. Using a "Leakage Current Tester", measure the leakage
current from each exposed metal parts of the cabinet, particularly any exposed metal part having a return
path to the chassis, to a known good earth ground.Any leakage current must not exceed 0.5mA AC (r.m.s.).
Alternate check method
Plug the AC line cord directly into the AC outlet. Use an AC voltmeter having, 1,000 ohms per volt or more
sensitivity in the following manner. Connect a 1,500 10W resistor paralleled by a 0.15 F AC-type capacitor
between an exposed metal part and a known good earth ground.
Measure the AC voltage across the resistor with the AC
voltmeter.
Move the resistor connection to each exposed metal part,
particularly any exposed metal part having a return path to
the chassis, and meausre the AC voltage across the resistor.
Now, reverse the plug in the AC outlet and repeat each
measurement.Voltage measured any must not exceed 0.75 V
AC (r.m.s.).This corresponds to 0.5 mA AC (r.m.s.).
1.This equipment has been designed and manufactured to meet international safety standards.
2. It is the legal responsibility of the repairer to ensure that these safety standards are maintained.
3. Repairs must be made in accordance with the relevant safety standards.
4. It is essential that safety critical components are replaced by approved parts.
5. If mains voltage selector is provided, check setting for local voltage.
Good earth ground
Place this
probe on
each exposed
metal part.
AC VOLTMETER
(Having 1000
ohms/volts,
or more sensitivity)
1500 10W
0.15 F AC TYPE
!
Burrs formed during molding may
be left over on some parts of the
chassis. Therefore, pay attention to
such burrs in the case of
preforming repair of this system.
In regard with component parts appearing on the silk-screen printed side (parts side) of the PWB diagrams, the
parts that are printed over with black such as the resistor ( ), diode ( ) and ICP ( ) or identified by the " "
mark nearby are critical for safety.
(This regulation does not correspond to J and C version.)

1-3
MX-K50R
1. Service should be performed by qualified personnel only.
2.This equipment has been designed and manufactured to meet international safety standards.
3. It is the legal responsibility of the repairer to ensure that these safety standards are maintained.
4. Repairs must be made in accordance with the relevant safety standards.
5. It is essential that safety critical components are replaced by approved parts.
6. If mains voltage selector is provided, check setting for local voltage.
1.This design of this product contains special hardware and many circuits and components specially
for safety purposes. For continued protection, no changes should be made to the original
design unless authorized in writing by the manufacturer. Replacement parts must be identical to
those used in the original circuits.
2. Any unauthorised design alterations or additions will void the manufacturer's guarantee ; furthermore the
manufacturer cannot accept responsibility for personal injury or property damage resulting therefrom.
3. Essential safety critical components are identified by ( ) on the Parts List and by shading on the
schematics, and must never be replaced by parts other than those listed in the manual. Please note
however that many electrical and mechanical parts in the product have special safety related
characteristics. These characteristics are often not evident from visual inspection. Parts other than
specified by the manufacturer may not have the same safety characteristics as the recommended
replacement parts shown in the Parts List of the Service Manual and may create shock, fire, or
other hazards.
4. The leads in the products are routed and dressed with ties, clamps, tubings, barriers and the
like to be separated from live parts, high temperature parts, moving parts and/or sharp edges
for the prevention of electric shock and fire hazard. When service is required, the original lead
routing and dress should be observed, and it should be confirmed that they have been returned
to normal, after re-assembling.
!Burrs formed during molding may be left over on some parts of the chassis. Therefore,
pay attention to such burrs in the case of preforming repair of this system.
(U.K only)

MX-K50R
1-4
Important for laser products
1.CLASS 1 LASER PRODUCT
2.DANGER : Invisible laser radiation when open and inter
lock failed or defeated. Avoid direct exposure to beam.
3.CAUTION : There are no serviceable parts inside the
Laser Unit. Do not disassemble the Laser Unit. Replace
the complete Laser Unit if it malfunctions.
4.CAUTION : The compact disc player uses invisible laser
radiation and is equipped with safety switches which
prevent emission of radiation when the drawer is open and
the safety interlocks have failed or are de
feated. It is dangerous to defeat the safety switches.
5.CAUTION : If safety switches malfunction, the laser is able
to function.
6.CAUTION : Use of controls, adjustments or performance of
procedures other than those specified herein may result in
hazardous radiation exposure.
!Please use enough caution not to
see the beam directly or touch it
in case of an adjustment or operation
check.
Position of labels
WARNING LABEL
CLASS 1
LASER PRODUCT

1-5
MX-K50R
Preventing static electricity
1. Grounding to prevent damage by static electricity
Electrostatic discharge (ESD), which occurs when static electricity stored in the body, fabric, etc.is discharged,
can destroy the laser diode in the traverse unit (optical pickup). Take care to prevent this when performing repairs.
2. About the earth processing for the destruction prevention by static electricity
In the equipment which uses optical pick-up (laser diode), optical pick-up is destroyed by the static electricity of
the work environment.
Be careful to use proper grounding in the area where repairs are being performed.
2-1 Ground the workbench
Ground the workbench by laying conductive material (such as a conductive sheet) or an iron plate over
it before placing the traverse unit (optical pickup) on it.
2-2 Ground yourself
Use an anti-static wrist strap to release any static electricity built up in your body.
3. Handling the optical pickup
1. In order to maintain quality during transport and before installation, both sides of the laser diode on the
replacement optical pickup are shorted.After replacement, return the shorted parts to their original condition.
(Refer to the text.)
2. Do not use a tester to check the condition of the laser diode in the optical pickup.The tester's internal power
source can easily destroy the laser diode.
4. Handling the traverse unit (optical pickup)
1. Do not subject the traverse unit (optical pickup) to strong shocks, as it is a sensitive, complex unit.
2. Cut off the shorted part of the flexible cable using nippers, etc. after replacing the optical pickup. For specific
details, refer to the replacement procedure in the text.Remove the anti-static pin when replacing the traverse
unit.Be careful not to take too long a time when attaching it to the connector.
3. Handle the flexible cable carefully as it may break when subjected to strong force.
4. It is not possible to adjust the semi-fixed resistor that adjusts the laser power. Do not turn it
Conductive material
(conductive sheet) or iron plate
(caption)
Anti-static wrist strap
Attention when CD mechanism assembly is decomposed
1. Remove the CD changer unit.
2. Remove the CD changer mechanism.
3. Solder is put up before the card wire is removed from the pickup unit
connector on the CD mechanism assembly.
(When the card wire is removed without putting up solder, the CD pick-up
assembly might destroy.)
4. Please remove solder after connecting the card wire with the pickup unit
connector when you install picking up in the substrate.
*Please refer to "Disassembly method" in the text for pick-up and how to
detach the CD mechanism assembly.
Soldering
Fig.1
Fig.2
Card wire
Card wire
Picup unit
connector
Picup unit
connector
CD changer unit
CD changer
mechanism

MX-K50R
1-6
Remove the three screws Aattaching the metal
cover on the back of the body.
Remove the six screws Battaching the metal cover
on both sides of the body.
Remove the metal cover from the body by lifting the
rear part of the cover.
1.
2.
3.
Disassembly method
Removing the metal cover (See Fig.1)
ONE POINT
How to eject the CD tray (see fig.2)
Although it will end if the OPEN/CLOSE
button is pushed when a power supply can
be taken, when that is not right, CD tray will
be opened manually.
Turn the loading pulley gear at the bottom of
the CD changer unit as shown in Fig.2 and
draw the CD tray toward the front.
Removing the CD tray fitting (See Fig. 3)
Prior to performing the following procedure, eject the
CD tray.
After drawing the lower part of the tray fitting toward
the front, remove the five claws. Then, while moving
the tray fitting upward, remove it.
1.
Prior to performing the following procedure, remove
the metal cover and CD tray fitting.
Remove the card wire attached to CD changer unit
on the adhesion tape.
Disconnect the card wire from the connector CW105
on the CD board.
Disconnect the harness from the connector RCW6
on the main board and CW107 on the CD board.
Remove the two screws C attaching the CD changer
unit to the rear panel.
Remove the two screws Dattaching the CD changer
unit to both sides of the front panel assembly.
Draw the CD changer unit upward from behind while
pulling the rear panel outward.
1.
2.
3.
4.
5.
6.
Removing the CD changer unit
(See Fig.4 to 7)
Fig.1
Fig.2
Fig.3
Metal cover
A
B
(both sides)
Loading pulley gear
(See <CD changer unit>fig.1)
Fig.4
CD changer unit Card wire
Adhesion tape
Joint
Claw
CD tray fitting

1-7
MX-K50R
Prior to performing the following procedure, remove
the metal cover and the CD changer unit.
Disconnect the card wire from the connector FCW3
on the main board.
Disconnect the harness from the connector JCW1,
JCW2 and HCW3 on the main board.
Remove the screw Eattaching the earth terminal
extending from the cassette mechanism assembly.
Remove the two screws Fattaching the front panel
assembly to both sides of the body.
Remove the screw Gattaching the main board to the
front panel assembly.
Remove the screw Hattaching the front panel
assembly to bottom of the body.
Release the two joints1 and two joints2, and detach
the front panel assembly toward the front.
1.
2.
3.
4.
5.
6.
7.
Removing the front panel assembly
(See Fig.8 to 10)
Fig.6
Fig.7
Fig.5
RCW6
CD changer unit
Main board
Rear panel
C
D
(both sides)
Rear panel
CD changer unit
Front panel
assembly
Fig.8
Fig.9
Main board
Amp. board
FCW3
JCW2
JCW1
HCW3 ACW1
ACW2
Front panel
assembly
Joint1
(both sides)
F
(both sides)
Joint1
(both sides)
F
(both sides)
E (fixing the earth wire)
Front panel
assembly
G
Main board
CD board
CW105
CW107

MX-K50R
1-8
Prior to performing the following procedure, remove
the metal cover and the CD changer unit.
Disconnect the card wire from the connector ACW1
and the harness from the connector ACW2 on the
amp. board.
Remove the four screws Iattaching the heat sink
cover to the rear panel. Remove the heat sink cover.
Remove the four screws Jattaching the heat sink
and two screws K attaching the speaker terminal to
the rear panel.
After moving the heat sink upward, remove the
claws. Then pull out the heat sink & amp. board
inward.
1.
2.
3.
4.
Removing the heat sink & amp. board
(See Fig.8, 11 and 12)
Prior to performing the following procedure, remove
the metal cover.
Disconnect the card wire from the connector CON01
on the tuner board.
Remove the two screws L attaching the tuner board
to the rear panel.
1.
2.
Removing the tuner board
(See Fig.12 and 13)
Prior to performing the following procedure, remove
the metal cover, CD changer unit and heat sink &
amp. board.
Disconnect the power cord from the connector PJ2
on the ECO board.
Disconnect the harness from the connector PJ3 and
RCW5 on the ECO board.
Remove the two screws M attaching the ECO board
to the rear panel.
1.
2.
3.
Removing the EOC board
(See Fig.12 and 13)
Prior to performing the following procedure, remove
the metal cover, CD changer unit, heat sink & amp.
board, tuner board and ECO board.
Remove the two screws N and three screws O
attaching the rear panel.
1.
Removing the rear panel (See Fig.12)
Fig.10
H
Joint2 (Bottom side)
Fig.11
Rear panel
Heat sink
cover
I
I
Fig.12
Heat sink
Speaker
terminal
K
N
M
O
L
Rear panel
J
J
Fig.13
Main board
ECO board
Tuner board
CON01
PJ3
RCW5
PJ2
Rear panel

1-9
MX-K50R
Prior to performing the following procedure, remove
the metal cover, CD changer unit and heat sink &
amp. board.
Unsolder the power IC solder point.
Remove the two screws Qattaching the power IC to
the heat sink.
1.
2.
Removing the power IC
(See Fig.15 and 16)
Prior to performing the following procedure, remove
the metal cover, CD changer unit and rear panel.
Disconnect the card wire from the connector FCW3
and the harness from the connector JCW1, JCW2
and HCW3 on the main board.
Disconnect the harness from the connector PCW1
on the fuse board.
Remove the screw Gattaching the main board
holder to the front panel assembly. (See Fig.9)
Remove the two screws P attaching the heat sink to
bottom chassis.
1.
2.
3.
4.
Removing the main board (See Fig. 14)
Removing the power cord (See Fig. 14)
Prior to performing the following procedure, remove
the metal cover, CD changer unit and rear panel.
Disconnect the power cord from the connector PJ2
on the ECO board (see fig.13) and pull up the power
cord stopper upward.
1.
Prior to performing the following procedure, remove
the metal cover, CD changer unit and heat sink &
amp. board.
Disconnect the power cord from the connector RCW1
on the trans. board.
Disconnect the harness from the connector PCW1 on
the fuse board.
Remove the four screws Rattaching the power
transformer on the bottom chassis.
1.
2.
3.
Removing the power transformer
(See Fig .17)
Fig.16
Fig.17
Fig.15
Fig.14
Fuse board
Trans. board
Fuse board
Trans. board
Power cord
Bottom chassis
Power cord
stopper P
Q
R
Heat sink
Heat sink
Amp. board
FCW3
JCW2
RCW1
JCW1
HCW3
PCW1
Heat sink
Power transformer
Power IC solder point
Main board
RCW1
PCW1
Amp. board
(reverse side)
Bottom chassis

MX-K50R
1-10
Disconnect the card wire from the connector UCW3,
UCW4, UCW5 and UCW6 on the front board.
Remove the six screws Battaching the front board.
Disconnect the card wire from the connector UCW2
on the front board.
1.
2.
3.
Removing the front board (See Fig.1)
Disconnect the card wire from the connector UCW1
on the switch board.
Remove the five screws Aattaching the CD switch
board.
1.
2.
Prior to performing the following procedure, remove
the metal cover, the CD changer unit and the front
panel assembly.
Removing the CD switch board
(See Fig.1)
Prior to performing the following procedure, remove
the front board.
Pull out the sound mode knob, volume knob and
active bass ex. level knob from front side.
Remove the twelve screws C attaching the front key
board.
Remove the front board releasing the two tabs.
Disconnect the card wire from the connector UCW7
on the front key baord, if needed.
1.
2.
3.
4.
Removing the front key board
(See Fig.2 and 3)
<Front panel assembly>
Prior to performing the following procedure remove
the front board.
You can pull out the headphone jack board.
1.
Removing the headphone jack board
(See Fig.3)
Disconnect the card wire from the connector on the
mecha. board.
Remove the six screws Dattaching the cassette
mechanism assembly.
1.
2.
Removing the cassette mechanism
assembly (See Fig.3)
Fig.1
Fig.2
Fig.3
Headphone
jack board
Mecha.
board
Cassette mechanism
assembly
A
B
B
C
C
D
D
CD switch board
Front panel assembly (inner side)
Front panel assembly (inner side)
Front board
Front key board
Active bass ex. level knob
UCW1
UCW3
UCW4
UCW7
Tab
Tab
Connector
UCW5
UCW6
UCW2
D
(fixing the earth wire)
Sound mode knob
Volume knob

1-11
MX-K50R
Turn the black loading pulley gear on the under side
of the CD changer unit in the direction of the arrow
and draw the CD tray toward the front until it stops.
Disconnect the card wire from connector CW103 on
the CD board.
Push down the two tray stoppers marked aand pull
out the CD tray.
1.
2.
3.
Align the gear-cam with the gear-tray as shown fig.3,
then mount the CD tray.
When assembling the CD tray, take extreme care not
engage with gear - synchro.
1.
2.
Prior to performing the following procedure, remove
the CD changer unit.
Removing the CD tray (See Fig.1 and 2)
Reinstall the CD tray (See Fig.3 and 4)
<CD changer unit>
Fig.2
Fig.1
Fig.3 Fig.4
Loading pulley
gear
CD changer uint (reverse side)
CD board
CD tray
CW103
CD tray
Gear-convert
Gear-convert
Gear-cam
Gear-tray
Gear-synchro
Gear-tray
Gear-tray
Gear-cam
timing point
CD tray
CW103
(on the CD board)
a
(Tray stopper)
a (Tray stopper)

MX-K50R
1-12
Prior to performing the following procedure, remove
the CD tray.
Remove the screw A attaching the sensor board on
the CD tray.
Remove the sensor board releasing the two tabs a.
Disconnect the harness from the connector CW1 on
the sensor board.
1.
2.
3.
Removing the sensor board (See Fig.5)
Prior to performing the following procedure, remove
the CD tray and sensor board.
Remove the screw Battaching the turn tray. Detach
the turn tray from the base tray.
Pull outward the tab battaching the turn tray motor
on the base tray and detach the turn tray motor.
1.
2.
Removing the turn tray motor
(See Fig.6 and 7)
Introductory notes:
Base tray + Turn tray = CD tray
Fig.7
Fig.6
Tab a
Tab b
Sensor board
CW1
Turn tray
Base tray
CD tray (reverse side)
Base tray (upper side)
B
Turn tray motor
A
Fig.5

1-13
MX-K50R
Prior to performing the following procedure, remove
the CD tray.
Detach the belt from the pulley on the upper side of
the CD changer unit (Do not stain the belt with
grease).
Disconnect the card wire from the pickup unit
connector on the under side of the CD changer unit.
Attention : Solder is put up before the card wire is
removed from the pick-up unit
connector on the CD mechanism
assembly.
(When the card wire is removed without
putting up solder, the CD pick-up unit
assembly might destroy.)
Disconnect the motor wire harness from connector
on the CD board.
Remove the screw Cattaching the switch board and
release the two tabs eattaching the switch board
outward and detach the switch board.
Remove the two screws Dattaching the CD board.
First release the two tabs fand two tabs gattaching
the motor, then release the CD board.
If the tabs fand gare hard to release, it is
recommendable to unsolder the two soldered parts
on the motor terminal of the CD board.
1.
2.
3.
4.
5.
Removing the belt, the CD board and the
switch board (See Fig.8 and 9)
Soldering
Card wire
Picup unit
connector
Fig.9
Fig.8
Belt
CD changer unit
DCD board
Tabs g
Tabs f
Soldered parts
Motor
Switch board
C
CW3
Tabs e
CD mechanism board
motor connecter
Pickup unit connector

MX-K50R
1-14
Disconnect the harness from connector on the CD
mechanism board in the CD mechanism assembly
on the under side of the CD changer unit. Disconnect
the card wire from the pickup unit connector.
Attention : Solder is put up before the card wire is
removed from the pick-up unit
connector on the CD mechanism
assembly. (Refer to Fig.9)
(When the card wire is removed without
putting up solder, the CD pick-up unit
assembly might destroy.)
Remove the screw Eattaching the shaft on the right
side of the CD mechanism holder assembly. Pull
outward the stopper fixing the shaft on the left side
and remove the CD mechanism holder assembly
from behind in the direction of the arrow y.
Turn the CD mechanism holder assembly half
around the lift up slide shaft hof the CD mechanism
holder assembly until the turn table is reversed, and
pull out the CD mechanism holder assembly.
1.
2.
3.
Removing the CD mechanism holder
assembly (mechanism included)
(See Fig.10 to 13)
Fig.10
Fig.11
Fig.12
Fig.13
Motor connecter
CD mechanism holder assembly
CD changer unit
Pickup unit connector
E
CD mechanism holder assembly Stopper
CD mechanism holder assembly
Lift up slide shaft n
Lift up slide shaft
CD mechanism holder assembly
y

1-15
MX-K50R
<CD mechanism section>
•Removing the CD mechanism holder from the CD
chager unit.
(Refer to "Removing the CD mechanism holder
assembly" )
Removing the pickup unit (See Fig.1)
1. Removing the cut washer on the feed gear
sleeve and pull out the feed gear.
2. Remove the two screws Afixing the pickup
shaft.
3. Removing the pickup unit.
Removing the feed motor (See Fig.1)
Remove the two motor fixing screws at Band
removing the feed motor.
Removing the spindle motor
Removing the motor board (See Fig.2)
1. Unsolder the motor terminal on the motor board.
2. Remove the moter board.
The spindle motor cannot be removed as a single
unit.
When removing the spindle motor, change the chasis
and turntable together as aunit.
Fig.2
Fig.1
Cut washer
Unsolder
A
A
B
Shaft
Feed Gear
Shutter
Pickup unit
Motor board Unsolder Feed motor
Spindle motor
< Speaker section >
It is exchange in a unit.
Please do not decompose.

MX-K50R
1-16
<Cassette mechanism section>
Removing the record/playback mechanism.
Removing the R/P head.
1. Remove the screw Aon the right side of the
R/P head.(Fig.1, Fig.2)
2. Remove the screw Bon the left side of the
R/P head.(Fig.1, Fig.2)
Remove the erase head.
Remove the screw Cfixing the erase head.(Fig.1)
Removing the pinch roller.
1. Pull out the pinch roller by opening the pinch
roller stopper outward to unlock .(Fig.3)
2. When reassembling the pinch roller, refer to
fig. 4 to hook up the spring.
Fig.1
Fig.2
Fig.3
Fig.4
R/P Head
R/P Head
E. Head
Spring
Stoppsr
Pinch roller
assembly
A
A
B
B
C
Pinch roller Pinch roller
stopper
Pinch roller Pinch roller spring
Return spring
Return spring
Return spring

1-17
MX-K50R
Removing the motor.
1. Remove the two screws Dfixing the motor.
Be careful to grease's splash when the
drive belt comes off.(Fig.5, Fig.6)
2. Unsolder the motor terminal.(Fig.5)
Removing the mechanism board.
1. Unsolder the four parts aon the solenoid
coil terminal.(Fig.5)
2. Remove the two screws Efixing the board.(Fig.5)
3. Unhook the three parts bfrom the board.(Fig.5)
4. Remove the mechanism board.(Fig.5)
Removing the flywheel.
Remove the cut-washers at c and dfrom the
capstan shaft, then remove the flywheel.
When reassembling the flywheel,
be sure to use new washers as they
cannot be reused.(Fig.8, Fig.9)
Fig.5
Drive belt
Drive belt
Drive belt (Flat)
D
D
EE
abb
a
Motor
Motor
terminal
Motor
c
d
FR belt
FR belt
Washer
Capstan
washer
Flywheel
Flywheel
Flywheel
Capstan
washer
Mecha.
board
Fig.6
Fig.7
Fig.8
Fig.9
Sleeve
Sleeve

MX-K50R
1-18
09
0
2
92
0
09
90
9
0
9
0009
9
9
882
000
0
0
2
22
8
8
999
909
0
0
2
2
90
9
0
0
9
09
CON01
FCW3
JCW2 JCW1
RCW6 OCW
FCW1
FCW2
HCW3
RW1 RW2
HCW2
CD board
UCW1
UCW7
UCW2
UCW3
UCW4
UCW6
UCW5
CW3 CW101
CW104
CW102 CW103
CW106 CW105
CW2 CW1
CW3
AAN1
CD mechanism
RCW1
RFS2
RFS5 RFS6 RFS7 RFS8
PCW1
ACW1 ACW2
Front board
3809-001184 3809-001228
AH39-20002D
AH39-00022A
3809-001185
3809-001224
3809-001315
3809-001121
AH38-12001A
3809-001034
Amp. board
CD switch board
Front key board
Tuner board
Main board
Headphone J.board
Color codes are shown below.
1 Brown
2 Red
3 Orange
4 Yellow
5 Green
6 Blue
7 Violet
8 Gray
9 White
0 Black
Wiring connection
3809-001223
0
92
CW107
02
9
ECW1
ECO board
PJ2
SUB
P/T
PJ3
RCW5
Power transformer 9
0
9
0

1-19
MX-K50R
TESTER
MAIN
PCB VT GND
Fig.1 OSC Voltage
Adjustment method
1. Tuner
* Adjustment Location of Tuner PCB
AM(MW) OSC
Adjustment
Output 1~7.0V
Received FREQ.
Adjustment
point
522~1629 KHz
MO
AM(MW) RF
Adjustment
ITEAM
594 KHz
MA
Maximum
Output(Fig.1)
LW OSC
Adjustment
144~288 KHz
LO
2~7.0V
LW RF
Adjustment
150 KHz
LA
Maximum
Output(Fig.1)

MX-K50R
1-20
FM THD Adjustment
Output
Output 28 dB( 2dB)
60 dB
Minumum Distortion (0.4% below)
(Fig.2)
SSG FREQ.
Adjustment
point
(FM DET)
98 MHz
FM DETECTOR COIL
FM Search Level Adjustment
Adjust SVR1 so that "TUNED" of FLT
is lighted (Fig.3)
Fig.3 FM Auto Search Level Adjustment
*Adjust FM S.S.G level to 28dB
Fig.2 IF CENTER and THD Adjustment
SSG FREQ.
Adjustment
point
(SVR1)
98 MHz
BEACON
SENSITIVITY
SEMI-VR(20K )
FM S.S.G GND
28 dB
FM S.S.G
Output
GND
Speaker
Terminal
FM
Antenna
Terminal
Distortion Meter
Input
SET
Input
output
Oscilloscope
FM IN
FM Antenna
SET
20 k
OUTPUT
AM SSG
450KHZ
INPUT
AM ANT
IN
Speaker Terminal
60cm
AM IF
VTVM Oscilloscope
AM(MW) I.F Adjustment
Maximum output (Fig.4)
SSG FREQ.
Frequency
Adjustment
point
450 kHz
522 kHz
AM IF
Fig.4 AM I.F Adjustment
OUTPUT