JVC KS-FX621 User manual

SERVICE MANUAL
COPYRIGHT © 2003 VICTOR COMPANY OF JAPAN, LTD. No.49825
2003/03
KS-FX621
CASSETTE RECEIVER
49825200303 KS-FX621
TABLE OF CONTENTS
1 Safety precaution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
2 Disassembly method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
3 Adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17
4 Description of major ICs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
MO D ES
C M
11 R PT
12 RND
1097 8
MO
Area Suffix
U ------ Other Areas

KS-FX621
1-2 (No.49825)
SECTION 1
Safety precaution
CAUTION
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.

KS-FX621
(No.49825)1-3
SECTION 2
Disassembly method
2.1 Main body
2.1.1 Removing the front panel assembly
(See Fig.1)
(1) Press the release button and remove the front panel as-
sembly.
Fig.1
2.1.2 Removing the bottom cover
(See Fig.2)
• Prior to performing the following procedure, remove the front
panel assembly.
(1) Turn the body upside down.
(2) Insert ascrewdriver under the joints to release the two
joints aon the left side, the two joints bon the right side and
the joint con the back of the body, then remove the bottom
cover from the body.
CAUTION:
When releasing the joint cusing a screwdriver, do not damage
the main board.
Fig.2
2.1.3 Removing the front chassis
(See Fig.3)
• Prior to performing the following procedure, remove the front
panel assembly and bottom cover.
(1) Remove the screw Aon each side of the body.
(2) Release the two joints dand the two joints eon the sides,
then remove the front chassis toward the front.
Fig.3
Front panel assembly
Release button
Bottom cover
Joint b
Joint b
Joint a
Joint c
Joint a
Joint dJoint e
Front chassis
Joint d
A
Joint e

KS-FX621
1-4 (No.49825)
2.1.4 Removing the heat sink
(See Fig.4)
• Prior to performing the following procedure, remove the front
panel assembly.
(1) Remove the two screws Band two screws Cattaching the
heat sink on the left side of the body, and remove the heat
sink.
Fig.4
2.1.5 Removing the rear panel
(See Fig.5)
• Prior to performing the following procedure, remove the front
panel assembly and bottom cover.
(1) Remove the two screws D, three screws Eand three
screws Fattaching the rear panel on the back of the body.
Fig.5
2.1.6 Removing the main board
(See Fig.6)
• Prior to performing the following procedure, remove the front
panel assembly, bottom cover, front chassis, heat sink and
rear panel.
(1) Remove the two screws Gattaching the main board on the
top chassis.
(2) Disconnect the connectors CP701 on the main board from
the cassette mechanism assembly.
Fig.6
Heat sink
CB C
ED
EFF
DRear panel
G
Main board assembly
CP701
G

KS-FX621
(No.49825)1-5
2.1.7 Removing the cassette mechanism assembly
(See Fig.7)
• Prior to performing the following procedure, remove the front
panel assembly, bottom cover, front chassis, heat sink, rear
panel and main board.
(1) Remove the four screws Hattaching the cassette mecha-
nism assembly from the top chassis.
Fig.7
2.1.8 Removing the mecha board
(See Fig.8)
• Prior to performing the following procedure, remove the front
panel assembly, bottom cover, front chassis, heat sink, rear
panel, main board and cassette mechanism assembly.
(1) Disconnect the wire from the connectors CN402 and
CN403 on the mecha board.
(2) Remove the screw Jattaching the mecha board.
Fig.8
2.1.9 Removing the front board
(See Figs.9 to 11)
• Prior to performing the following procedure, remove the front
panel assembly.
(1) Remove the four screws Lattaching the rear cover on the
back of the front panel assembly. (See fig.9)
(2) Release the eleven joints f, the front panel and the rear
cover become separate. (See fig.10)
(3) Remove the front board from the front panel assembly.
(See fig.11)
Fig.9
Fig.10
Fig.11
HH
H H
Top chassis
Cassette mechanism assembly
J
CN402
CN401 CN403
K
K K
K
Joint h
Joint h
Joint h
Joint h
Front panel assembly
Rear cover
LCD & Key control board

KS-FX621
1-6 (No.49825)
2.2 CD Mechanism Assembly
REFERENCE:
Prior to performing the following procedures, turn the mode
gear on the bottom of the body until the respective part comes
to the EJECT position (Refer to Fig.1).
Fig.1
2.2.1 Removing the cassette guide
(See Fig.2)
(1) Turn the mode gear to set to RVS play or subsequent
mode.
(2) Remove the cassette guide from the main chassis while re-
leasing each two joint tabs ain the direction of the arrow.
Fig.2
2.2.2 Removing the load arm
(See Fig.3)
(1) Remove the E-washer attaching the load arm.
(2) Move the load arm in the direction of the arrow and release
the joint bon the cassette catch.
Fig.3
Mode gea
r
Cassette guide
Tab a
Tab a
Load arm
E-washer
Joint b

KS-FX621
(No.49825)1-7
2.2.3 Removing the cassette hanger assembly / cassette holder
(See Fig.4 to 7)
(1) Check the mode is set to EJECT. Push down the front part
of the cassette holder and move in the direction of the ar-
row to release the joint c.
(2) Move the rear part of the cassette hanger assembly in the
direction of the arrow to release it from the two joint bosses
d.
(3) Release the holder stabilizer spring from the hooks eand
f, then pull out from the cassette hanger assembly.
(4) Bring up the rear side of the cassette hanger assembly to
release the joint gand h.
(5) Pull out the cassette catch from the cassette hanger as-
sembly.
Fig.4
Fig.5
Fig.6
Fig.7
Cassette holder assembly
Side bracket
Joints c
Cassette holder assembly
Cassette hanger
assembly
Boss d
Boss d
Cassette hanger assembly
Cassette stabilizer spring
Hook f
Hook e
Cassette hanger assembl
y
Hook h
Hook g
C
assette holder
a
ssembly
Cassette holder assembly
Cassette hanger assembly
Cassette catch

KS-FX621
1-8 (No.49825)
2.2.4 Removing the side bracket assembly
(See Fig.8 to 10)
(1) Remove the screw Aattaching the side bracket assembly.
(2) Detach the front side of the side bracket assembly upward
and pull out forward to release the joint iand jin the rear.
CAUTION:
When reassembling, make sure that the boss kof the main
chassis is set in the notch of the load rack under the side
bracket assembly. Do not reattach the load rack on the boss k.
CAUTION:
After reattaching the side bracket assembly, confirm opera-
tion.
Fig.8
Fig.9
Fig.10
A
Side bracket assembly
Side bracket assembly Joint i
Joint j
Joint i
Joint j
Side bracket assembly
Boss k
Load rack
Boss k
Load rack

KS-FX621
(No.49825)1-9
2.2.5 Removing the pinch arm (F) assembly
(See Fig.11 and 12)
(1) Remove the polywasher and pull out the pinch arm (F) as-
sembly.
(2) Remove the compulsion spring.
Fig.11
Fig.12
2.2.6 Removing the pinch arm (R) assembly
(See Fig.11 and 13)
(1) Remove the polywasher and pull out the pinch arm (R) as-
sembly.
Fig.13
Fig.14
2.2.7 Removing the slide chassis assembly
(See Fig.14 and 15)
REFERENCE:
It is not necessary to remove the head and the tape guide.
(1) Move the slide chassis assembly in the direction of the ar-
row to release the two joints land remove from the main
chassis.
(2) Remove the rack link.
CAUTION:
When reassembling, first reattach the rack link, and next fit the
boss mand hook nof the slide chassis assembly to the hole
of the main chassis, and engage the two joints l.
Fig.15
Polywashe
r
Polywasher Pinch arm
(F) assembly
Pinch arm
(R) assembly
Polywasher Pinch arm (F) assembly
Compulsion spring
Pinch arm
(R) assembly Polywashe
r
Slide chassis
assembly
Joint l
Joint l
Boss m
Hook
n
Rack link
Head
Tape guide

KS-FX621
1-10 (No.49825)
2.2.8 Removing the head / tape guide
(See Fig.16 and 17)
REFERENCE:
It is not necessary to remove the slide chassis assembly.
(1) Remove the band attaching the wire to the head.
(2) Remove the two screws B, the head and the head support
spring.
(3) Remove the pinch arm spring from the tape guide.
(4) Remove the tape guide and the pinch spring arm.
CAUTION:
When reattaching the pinch arm spring, set both end of it to the
pinch spring arm ( remarked o).
CAUTION:
When reattaching the head, set the wires into the groove of the
tape guide (Fig.16).
Fig.16
Fig.17
2.2.9 Removing the flywheel assembly (F) & (R)
(See Fig.18 and 19)
REFERENCE:
It is not necessary to remove the slide chassis assembly.
(1) Remove the belt at the bottom.
(2) Remove the two polywashers on the upper side.
(3) Pull out each flywheel assembly downward.
Fig.18
Fig.19
B
Slide chassis assembly
Head Tape guide
BPinch arm spring
Head
Head support spring
Tape guide
Pinch spring arm
Slid chassis assembly
o
o
Flywheel assembly (F)
Flywheel assembly (R)
Belt
Polywasher
Polywasher
Flywheel assembly (F)
Flywheel assembly (R)

KS-FX621
(No.49825)1-11
2.2.10 Disassembling the flywheel assembly (F)
(See Fig.20 and 21)
(1) Push and turn counterclockwise the spring holder (F) to re-
lease the three joints pon the bottom of the flywheel.
(2) The spring holder (F), the TU spring and the friction gear
play come off.
(3) Remove the polywasher and felt.
Fig.20
Fig.21
2.2.11 Disassembling the flywheel assembly (R)
(See Fig.20 and 22)
(1) Push and turn clockwise the spring holder (R) to release
the three joints qon the bottom of the flywheel.
(2) The spring holder (R), the FF spring and the friction gear
FF come off.
(3) Remove the polywasher and the felt.
Fig.22
Fig.23
2.2.12 Removing the reel board
(See Fig.23 and 24)
(1) Remove the two screws Cattaching the reel board.
(2) Move the reel board in the direction of the arrow to release
the joint r.
(3) Unsolder the wires if necessary.
CAUTION:
When reattaching, confirm operation of the MODE switch and
the ST-BY switch.
The mode position between EJECT and ST-BY is optimum for
reattaching.
Connect the card wire extending from the reel board to the
FFC pad before reattaching the reel board.
Fig.24
Flywheel assembly (F) Flywheel assembly (R)
Joints p
Joint p
Joints q
Joint q
Polywasher
Spring holder (F)
TU spring
Friction gear play
Flywheel assembly (F)
Felt
Polywasher
Spring holder (R)
FF spring
Friction gear FF
Flywheel assembly (R)
Felt
FFC pad
Joint
r
Reel board
C
C
FFC pad
CT-1 switch
ST-BY switch
Soldering
MODE switch

KS-FX621
1-12 (No.49825)
2.2.13 Removing the gear base arm / gear base link assembly
(See Fig.25 to 27)
(1) Move the gear base arm in the direction of the arrow.
(2) Insert a slotted screwdriver to the gear base spring under
the gear base arm, and release the gear base arm upward
from the boss on the gear base assembly.
(3) Remove the gear base arm from the main chassis while re-
leasing the two joints s.
(4) Move the gear base link assemby in the direction of the ar-
row to release the two joints t.
REFERENCE:
When reattaching the gear base arm, make sure that the boss
on the gear base assembly is inside the gear base spring.
Fig.25
Fig.26
2.2.14 Removing the FFC pad
(See Fig.27 and 29)
(1) Push each joint hook uof the FFC pad and remove toward
the bottom.
Fig.27
Gear base
link assembly
Gear base arm
FFC pad
Joint t
Joint t
Joints s
Hook u
Hook u
Gear base arm
Screwdriver
Gear base spring
FFC pad
Gear base link assembly Gear base arm

KS-FX621
(No.49825)1-13
2.2.15 Removing the mode gear
(See Fig.28 and 31)
(1) Remove the polywasher on the bottom and pull out the
mode gear.
2.2.16 Removing the mode switch actuator
(See Fig.28, 29 and 31)
(1) Pull out the mode switch actuator at the bottom.
REFERENCE:
When reattaching the mode switch actuator to the main chas-
sis, make sure to set on the shaft and insert vinto the slot w.
2.2.17 Removing the direction link / direction plate
(See Fig.29 to 31)
(1) Remove the polywasher attaching the direction link.
(2) Bring up the direction link to release the three joints x, y
and zat a time.
(3) Move the direction plate in the direction of the arrow to re-
lease the two joints a'.
REFERENCE:
When reattaching the direction plate, engage the two joints a'
and move in the direction of the arrow (Refer to Fig.30).
REFERENCE:
When reattaching the direction link, move the direction plate in
the direction of the arrow and engage the three joint x, yand
zat a time (Refer to Fig.31).
2.2.18 Removing the mode rack assembly
(See Fig.29 and 30)
(1) Move the mode rack assembly in the direction of the arrow
to release the two joints b' and the joint c'.
REFERENCE:
When reattaching, set the two b' Eon the bottom of the mode
rack assembly into the slots of the main chassis and move in
the direction of the arrow (See Fig.30).
Fig.28
Fig.29
Fig.30
Fig.31
Polywashe
r
Mode switch actuator Mode gear
Direction plate Direction link
Mode rack assembly
Slot w
Direction plate
Joints a'
Joint z
Direction link Polywasher
Joint y Joint x
Direction plate Mode rack assembly
Joint c'
Joint b'
Joint b'
Joints a'
Polywasher
Mode gea
r
Mode switch actuator
Direction link
Direction plate
Mode rack assembly
v

KS-FX621
1-14 (No.49825)
2.2.19 Removing the gear base assembly / take up gear / reflector gear
(See Fig.32 to 34)
(1) Push in the pin d' of the gear base assembly on the upper
side of the body and move the reflector gear toward the
bottom, then pull out.
(2) Remove the polywasher on the bottom and pull out the
take up gear.
(3) Move the gear base assembly in the direction of the arrow
to release it from the two slots e' of the main chassis.
REFERENCE:
The parts are damaged when removed. Please replace with
new ones.
Fig.32
Fig.33
2.2.20 Removing the reel driver / reel spindle
(See Fig.34)
(1) Draw out the reel driver from the shaft on the main chassis
and remove the reel driver spring and the reel spindle re-
spectively.
CAUTION:
The reel driver is damaged when removed. Please replace
with a new one.
Fig.34
Gear base assembly
Pin d'
Slot e'
Slot e'
Polywasher
Reflector gear
Take up gear
Reel driver spring
Reel driver spring
Reel driver
Reel driver
Reel spindle
Reel spindle
Gear base assembly
Slots e
Main chassis
Reflector gear
Polywasher
Take up gear

KS-FX621
(No.49825)1-15
2.2.21 Removing the side bracket assembly
(See Fig.35 to 39)
(1) Remove the eject cam plate spring.
(2) Push the joint f' through the slot to remove the load rack
downward.
(3) Move the eject cam limiter in the direction of the arrow to
release it from the boss g'of the side bracket assembly and
from the two joints h'.
(4) Move the eject cam plate in the direction of the arrow to re-
lease the joint i'.
CAUTION:
When reassembling, confirm operation of each part before re-
attaching the eject cam plate spring.
Fig.35
Fig.36
Fig.37
Fig.38
Fig.39
Joint f'
Load rack
Eject cam plate spring
Eject cam limiter
Side bracket assembly
Boss g'
Joint h'
Load rack
Joint f'
Joint h'
Boss g'Eject cam limiter
Side bracket
assembly
Joint h' Joint h'
Eject cam plate
Side bracket assembly
Boss g'
Joint i'
Eject cam plate
Side bracket assembly
Eject cam plate
Joint i’

KS-FX621
1-16 (No.49825)
2.2.22 Removing the main motor assembly / sub motor assembly
(See Fig.40 to 42)
(1) Remove the belt at the bottom.
(2) Remove the polywasher and pull out the mode gear.
(3) Pull out the reduction gear (B).
(4) Remove the polywasher and pull out the reduction gear
(A).
(5) Remove the two screws Dattaching the main motor as-
sembly.
(6) Remove the two screws Eattaching the sub motor assem-
bly.
(7) Unsolder the wires on the reel board if necessary.
CAUTION:
When reassembling, adjust the length of the wires extending
from the sub motor asswmbly by attaching them to the side of
the sub motor assembly with the wires extending from the
main motor assembly using a spacer.
Fig.40
Fig.41
Fig.42
Belt
Polywasher
Polywashe
r
Mode gear
Reduction
gear (A)
Main motor
assembly
D
Sub motor
assembly
E
Reduction gear (B)
Polywasher
Reduction gear (B)
Reduction gear (A)
ED
Main motor assembly
Sub motor assembly
Spacer
Spacer
Sub motor assembly
Main motor assembly

KS-FX621
(No.49825)1-17
SECTION 3
Adjustment
3.1 Adjustment method
AM mode 999kHz/62dB, INT/400Hz, 30%
modulation signal on recieving.
FM mono mode 97.9MHz/66dB, INT/400Hz, 22.5kHz
deviation pilot off mono
Test instruments reqired for adjustment Standard volume position
Measuring conditions(Amplifier section)
Frequency band
1. Digital oscilloscoe(100MHz)
2.Frequency counter meter
3.Electric voltmeter
4.Wow & flutter meter
5.Test tapes
6.Torque gauge...................Cassette type for CTG-N
(Mechanism adjustment)
VT724.......................for DOLBY level measurement
VT739............For playback frequency measurement
VT712....For wow flutter & tape speed measurement
VT703.....................For head azimuth measurement
Balance and Bass, Treble volume, Fader
: Center(Indication"0")
Loudness, Dolby NR, Sound, Cruise : Off
Volume position is about 2V at speaker output with
following conditions, Playback the test tape VT721.
Power supply voltage.............. DC14.4V(11V to 16V allowance)
Load impedance............ 4 (4 to 8 allowance)
Line out level/Impedance..............1.0V/20k load (250 nWb/m)
FM stereo mode 1kHz, 67.5kHz dev.pilot 7.5kHz dev
Output level 0dB (1 V,50 /open terminal)
87.5 MHz to 108.0MHz
522 kHz to 1620 kHz
144 kHz to 279 kHz
Band FM
AM MW
LW

KS-FX621
1-18 (No.49825)
Front panel assembly
Extension cord
EXTKSRT002-18P
Main board
Cassette mechanism
EXTKSRT002-18P
To
Main board
To
Cassette mechanism
D i sasse m bl y m e t hod
1. Remove the front panel assembly.
2. Remove the bottom cover.
3. Remove the front chassis.
4. Remove the rear panel.
5. Remove the heat sink.
6. Remove the main board.
7. Reattach the heat sink with two screw B. (Refer to Disassembly method.)
8. Install the front chassis and front panel assmbly.
9. Confirm that current is being carried by connecting an extension cord jig.
Note
Available to connect to the CJ701 connector when installing the front panel.
CAUTION :
Be sure to attach a heat sink on the power amplifier IC of a main board when supplying the power.
If voltage is applied without attaching the heat sink, the power amplifier IC will be destroyed by heat.
1. We're advancing efforts to make our extension cords common for all car audio products.
Please use this type of extension cord as follows.
2. As a U-shape type top cover is employed, this type of extension cord is needed to check operation of the
mechanism assembly after disassembly.
3. Extension cord : EXTKSRT002-18P ( 18 pin extension cord ) For connection between mechanism assembly
and main board.
4. Check for mechanism driving section such as motor ,etc.
Information for using a car audio service jig

KS-FX621
(No.49825)1-19
Head section view
Cassette mechanism
(Surface)
Arrangement of adjusting & test points
Azimuth screw
A
(Forward)
Playback head
Tape speed adjust
Motor assembly
Azimuth screw B
(Reverse)
Azimuth screw A
(Forward)
Playback head
Azimuth screw B
(Reverse)

KS-FX621
1-20 (No.49825)
Item Conditions Adjustment and Confirmation methods S.Values Adjust
Head
azimuth
adjustment
Head height adjustment
Adjust the azimuth directly. When you
adjust the height using a mirror tape,
remove the cassette housing from the
mechanism chassis. After installing the
cassette housing, perform the azimuth
adjustment.
Load the SCC-1659 mirror tape. Adjust with
height adjustment screw A and azimuth
adjustment screw B so that line A of the
mirror tape runs in the center between Lch
and Rch in the reverse play mode.
After switching from REV to FWD then to
REV, check that the head position set in
procedure 1 is not changed. (If the position
has shifted, adjust again and check.)
Adjust with azimuth adjustment screw B so
that line B of the mirror tape runs in the
center between Lch and Rch in the forward
play mode.
Test tape:
SCC-1659
VT703(10kHz)
Test tape: VT712
(3kHz)
Test tape: VT724
(1kHz)
VT739
(63Hz / 1kHz / 10kHz)
1.
Tape speed
and wow
flutter
confirmation
2.
Play back
frequency
response
confiramation
3.
1.
2.
3.
Check to see if the reading of the F, counter /
wow flutter meter is within 3015Hz to 3045Hz
(FWD/ REV), and less than 0.35% (JIS RMS).
In case of out of specification, adjust the
motor with a built-in volume resistor.
1.
2.
Play test tape VT724, and set the volume
position at 2V.
Play test tape VT739 and confirm.
1kHz / 10kHz: -1 3dB,
1kHz / 63Hz: 0 3dB,
When 10kHz is out of specification, it will be
necessary to read adjust the azimuth.
1.
2.
3.
Load VT724 (1kHz) and play it back in
the reverse play mode.
Set the Rch output level to max.
Load VT703 (10kHz) and play it back in
the forward play mode. Adjust the Rch
and Lch output levels to max, with
azimuth adjustment screw B. In this case,
the phase difference should be within 45 .
Engage the reverse mode and adjust the
output level to max, with azimuth
adjustment screw C.
(The phase difference should be 45 or
more.)
When switching between forward and
reverse modes, the difference between
channels should be within 3dB. (Between
FWD L and R, REV L and R.)
When VT721 (315Hz) is played back,
the level difference between channels
should be within 1.5dB.
1.
2.
3.
4.
5.
Head azimuth adjustment
Tape speed:
3015Hz
to 3045Hz
Wow
flutter: less
than 0.35%
Speaker out
1kHz / 63Hz
: 0 3db
1kHz / 10kHz
: -1 3db
Built-in volume
resistor
The tuner section is of an adjustment-freedesign. In case the tuner is in trouble, replace the tuner pack.
A line
B line
Head shield
PBHead
FWD Adj B
REV Adj C HEIGHT Adj A
phase
(0 ) (45 )
Head shield
The head is at low position
during.
The head is at High position
during REV.
Output
level:
Maximum