JVC UX-Z7MDR User manual

SERVICE MANUAL
COPYRIGHT © 2003 VICTOR COMPANY OF JAPAN, LTD. No.22042
2003/02
UX-Z7MDR
MICRO COMPONENT MD SYSTEM
22042200302
UX-Z7MDR
TABLE OF CONTENTS
1 Important Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
2 Disassembly Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
3 Adjustment method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-37
4 Description of major ICs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-44
Area Suffix
E -------- Continental Europe

UX-Z7MDR
1-2 (No.22042)
SECTION 1
Important Safety Precautions
1.1 Safety Precautions
(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 man-
ufacturer. Replacement parts must be identical to those
used in the original circuits. Services should be per-
formed 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 manufacturers 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 characteris-
tics are often not evident from visual inspection nor can the
protection afforded by them necessarily be obtained by us-
ing replacement components rated for higher voltage, watt-
age, etc. Replacement parts which have these special safety
characteristics are identified in the Parts List of Service Manu-
al. Electrical components having such features are iden-
tified by shading on the schematics and by ( ) on the
Parts List in the Service Manual. The use of a substitute re-
placement which does not have the same safety character-
istics as the recommended replacement parts shown in the
Parts List of Service Manual may create shock, fire, or oth-
er 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 reassembling.
(5) Leakage shock hazard testing)
After reassembling 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, particular-
ly any exposed metal part having a return path to the
chassis, to a known good earth ground. Any leakage cur-
rent 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 ohm 10W resistor
paralleled by a 0.15 µF 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 measure 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.).
1.2 Warning
(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.
1.3 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 pre-
forming repair of this system.
1.4 Critical parts for safety
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.
When replacing them, be sure to use the parts of the same type
and rating as specified by the manufacturer. (Except the JC version)

UX-Z7MDR
(No.22042)1-3
1.5 Preventing 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.
1.5.1 Grounding to prevent damage by static electricity
Static electricity in the work area can destroy the optical pickup (laser diode) in devices such as DVD players.
Be careful to use proper grounding in the area where repairs are being performed.
(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) Ground yourself
Use an anti-static wrist strap to release any static electricity built up in your body.
(3) Handling the optical pickup
• 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.)
• 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.
1.6 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 replace-
ment 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) I t is not possible to adjust the semi-fixed resistor that adjusts the laser power. Do not turn it.
1.7 Attention when traverse unit is decomposed
*Please refer to "Disassembly method" in the text for the CD pickup unit.
• Apply solder to the short land before the flexible wire is disconnected from the connector on the CD pickup unit.
(If the flexible wire is disconnected without applying solder, the CDpickup may be destroyed by static electricity.)
• In the assembly, be sure to remove solder from the short land after connecting the flexible wire.
Pickup Solder part b
Main board
Flexible wire
Shorting round
CN601 on
mechanism
P.C. board

UX-Z7MDR
1-4 (No.22042)
1.8 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.
CAUTION
Please use enough caution not to see the beam directly
or touch it in case of anadjustment or operation check.
VARNING
Osynlig laserstrålning är denna del är öppnad och spårren är
urkopplad. Betrakta ej strålen.
VARO
Avattaessa ja suojalukitus ohitettaessa olet alttiina näkymät-
tömälle lasersäteilylle. Älä katso säteeseen.
ADVARSEL
Usynlig laserstråling ved åbning, når sikkerhedsafbrydere er
ude af funktion. Undgå udsasttelse for stråling.
ADVARSEL
Usynlig laserstråling ved åpning, når sikkerhetsbryteren er
avslott. unngå utsettelse for stråling.
REPRODUCTION AND POSITION OF LABELS
WARNING LABEL
DANGER : Invisibie laser radiation
when open and interlock or
defeated.
AVOID DIRECT EXPOSURE TO
BEAM (e)
VARNING : Osynlig laserstrålning är
denna del är öppnad och spårren är
urkopplad. Betrakta ej strålen. (s)
VARO : Avattaessa ja suojalukitus
ohitettaessa olet alttiina
näkymättömälle lasersäteilylle.Älä
katso säteeseen. (d)
ADVARSEL :Usynlig laserstråling
ved åbning , når
sikkerhedsafbrydere er ude af
funktion. Undgå udsættelse for
stråling. (f)
CLASS 1
LASER PRODUCT

UX-Z7MDR
(No.22042)1-5
SECTION 2
Disassembly Method
2.1 Main body
2.1.1 Removing the metal cover
(See Fig.1 to 3.)
(1) Remove the six screws Aon the rear part of the main body
that attach the metal cover.
(2) Remove the two screws Bon each side of the main body
that attach the metal cover.
(3) Lift the rear part of the metal cover upward while releasing
the lower sides of the metal cover in the right and left direc-
tion. The metal cover will be removed.
Fig.1
Fig.2
Fig.3
A
A
A
Matal cover
Matal cove
r
B
Matal cover
B

UX-Z7MDR
1-6 (No.22042)
2.1.2 Removing the CD mechanism assembly
(See Fig.4 to 7.)
• Prior to this procedure, remove the metal cover.
(1) Remove the card wire from the connector CN302 on amp
board on the left side of the main body.
(2) Remove the three screws Con top of the body that attach
the CD mechanism assembly.
(3) Lift the CD mechanism assembly upward and move it
backward to remove.
(4) Remove the card wire from CN606 on CD servo board, on
the bottom of the CD mechanism assembly.
Fig.4
Fig.5
Fig.6
Fig.7
CD mechanism ass'y
Amp board
CN302
C
C
C
Amp board
CN302
CD mechanism ass'y
CD mechanism ass'y
CD mechanism ass'y CD servo board
CN606

UX-Z7MDR
(No.22042)1-7
2.1.3 Removing the front panel
(See Fig.8 to11.)
• Prior to this procedure, remove the metal cover and the CD
mechanism assembly.
(1) Remove the card wire from the connector CN705 on micon
board, in the center of the right side of the main body.
(2) Remove the plastic rivet in the right side of the main body
that attaches tuner board.
(3) Remove the card wire from the connector CN301 on amp
board in the center of the left side of the main body.
Remove the card wire from the connector CN704 on micon
board.
Remove the wire from each connector CN703 and CN710
respectively.
(4) Remove the card wire from the connector CN452 on FL
connection board on top of the main body.
(5) Remove the two screws Don the right and left sides of the
main body that attach the front panel assembly.
(6) Remove the two screws Eon the bottom of the main body
that attach the front panel assembly.
(7) Remove the joint "a" on the bottom of the main body and
the joint "b" on the right and left sides respectively by using
a screwdriver. Remove the front panel assembly in the
front direction.
Fig.8
Fig.9
Fig.10
Fig.11
Plastic rivet
Tuner board
Front panel ass'y
D
Micon board
CN705
joint b
D
Micon board
CN704
Front panel ass'y
joint b CN703
CN710
Amp board
CN301
FL connect board
CN452
Front panel ass'
y
Micon board
CN704
CN710
CN703
EE
j
oint a
Front panel ass'
y

UX-Z7MDR
1-8 (No.22042)
2.1.4 Removing the tuner board
(See Fig.12.)
• Prior to this procedure, remove the metal cover.
(1) Remove the card wire on the right side of the main body
from the connector CN1 on the tuner board.
(2) Remove the plastic rivet on the right side of the main body
that attaches the tuner board.
(3) Remove the two screws Fon the rear side of the main body
that attach the tuner board.
Fig.12
2.1.5 Removing the rear cover
(See Fig.13.)
• Prior to this procedure, remove the metal cover and the CD
mechanism assembly.
(1) Remove the two screws Gon the rear side of the main
body that attach the rear cover.
Fig.13
2.1.6 Removing the fan
(See Fig.14 to 16.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, and the rear cover.
(1) Remove the wire from the connector CN603 on the MD
connect board in the right side of the main body.
(2) Remove the four screws Hon the rear side of the main
body that attach the fan.
(3) Move the fan bracket that attaches the fan from inside the
rear panel upward to remove the two fixing points "c". Fan
will be detached at the same time.
Notice
When attaching the fan, attach the two "e" to the two "d" re-
spectively before pressing the fan with fan bracket.
Fig.14
Fig.15
Fig.16
CN1 Tuner doard
Plastic rivet
F
G
G
Rear panel
Rear cover
Fan Rear panel
H
H
MD connect board
CN603
Fan Rear panel
j
oint c
joint
c
Fan blacket
Fan hole e
hole e
hook d
hook d

UX-Z7MDR
(No.22042)1-9
2.1.7 Removing the rear panel
(See Fig.17 to 20.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, and the rear cover.
(1) Remove the wire from the connector CN603 on MD con-
nect board on the right side of the main body.
(2) Remove the eight screws Fon the rear side of the main
body that attach the rear panel.
(3) Remove the two joint "f" on the right and left bottom of the
rear panel.
Notice
The fan assembly will be kept attached to the rear panel.
Fig.17
Fig.18
Fig.19
Fig.20
Rear panel
MD connect doard
CN603
Rear panel
F
F
F
F
F
Rear panel
joint f
joint f
Rear panel

UX-Z7MDR
1-10 (No.22042)
2.1.8 Removing the MD mechanism assembly
(See Fig.21 and 22.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, and the rear cover.
(1) Remove the card wire from the connector CN601 on the
MD connect board in the rear part of the MD mechanism
assembly.
(2) Remove the four screws Hon the front side and the rear
side that attach the MD mechanism assembly.
Remove the MD mechanism assembly upward.
Fig.21
Fig.22
2.1.9 Removing the headphone board
(See Fig.23 and 24.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, and the rear cover.
(1) Remove the wire from the connector CN101 on the amp
board on the left side of the main body.
(2) Remove the band that fixes the wire to the amp board. Re-
move the wire from the two clamps in the bottom chassis.
(3) Remove the screw Ion the right side of the main body that
attaches the headphone board.
Fig.23
Fig.24
MD connect board
CN601 MD mechanism ass'
y
H
H
MD mechanism ass'y
H
H
Headphone board
clamp
Band
A
mp board
CN101
Headphone board
I

UX-Z7MDR
(No.22042)1-11
2.1.10 Removing the amp board and heat sink
(See Fig.25 and 26.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, the front panel assembly, and the rear cover.
(1) Remove the wire from the connector CN101 and CN102 on
the amp board on the left side of the main body. Remove
the band that fixes the wire. Remove the card wire from the
connector CN303.
(2) Remove the two screws Jthat attach the amp board.
(3) Pull out and remove the connector CN304 and CN305 on
the amp board outward. Remove the two joint "g" that fix
the bottom chassis.
Notice
The heat sink will be kept attached to the amp board. The
heat sink can be removed without removing the amp
board.
(4) Remove the three screws Kthat attach the heat sink.
Fig.25
Fig.26
2.1.11 Removing the MD connect board
(See Fig.27.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, and the rear cover.
(1) Remove the card wire from the connector CN601 on the
MD connect board.
(2) Remove the two screws Lon the rear side of the main body
that attach the MD connect board.
(3) Pull out the connector CN604 on the MD connect board in
the rear direction.
Fig.27
Band
CN102
CN101
joint g
joint g J
J
Heat sink
A
mp board
CN303
CN304
CN305
Amp board
K
K
Heat sink
L
LCN604
MD connect board
CN601

UX-Z7MDR
1-12 (No.22042)
2.1.12 Removing the MD base chassis/the micon board
(See Fig.28 to 30.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, the front panel assembly,
the rear cover, the amp board, and the MD connect board.
Notice
The MD base chassis/the micon board can be removed with-
out removing the MD mechanism assembly.
(1) Remove the wire from the micon board connector CN707
in the center of the right side of the main
body. Remove the card wire from the connector CN708.
(2) Remove the screw Mon top of the main body that attaches
the MD base chassis.
Notice
The MD mechanism assembly will be kept attached to
the MD base chassis.
(3) Remove the two screws Nthat attach the micon board. Re-
move the two joint "h" that fix the MD base chassis. Fig.28
Fig.29
Fig.30
MD mechanism ass'y MD base chassis
Micon board
CN707
CN708
MD mechanism ass'y MD base chassi
s
M
N
Micon board
joint h

UX-Z7MDR
(No.22042)1-13
2.1.13 Removing the power trans assembly
(See Fig.31 and 32.)
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, the front panel assembly, the rear cover, the
amp board, and the MD base chassis.
(1) Move the power cord stopper upward from the rear part of
the main body to remove. Remove the power supply cord
from the connector CN901 on the power trans board.
Notice
The power cord can be removed without removing the
power trans assembly.
(2) Remove the four screws Oon top of the main body that at-
tach the power trans assembly. Remove the wire from the
two clamps on the bottom chassis.
Fig.31
Fig.32
2.2 Front panel assembly
• Prior to this procedure, remove the metal cover, the CD mech-
anism assembly, and the front panel assembly.
2.2.1 Removing the cassette mechanism assembly
(See Fig.33 and 34.)
(1) Remove the spring that is attached to the cassette door
from inside the front panel.
(2) Remove the four screws Pthat attach the cassette mecha-
nism assembly.
Fig.33
Fig.34
Power trans assembly
Power trans board
CN901 cord stopper
Power cord
clamp
Bottom chassis
OO
O
Power trans
assembly
P
P
P
Cassette mechanism assembl
y
Spring
Cassette door
Spring

UX-Z7MDR
1-14 (No.22042)
2.2.2 Removing the key board
(See Fig.35 to 37.)
• Prior to this procedure, remove the cassette mechanism as-
sembly.
(1) Pull out the volume knob in the front side of the front panel
to remove.
(2) Remove the five screws Qthat attach the bracket (1) from
inside the front panel.
(3) Remove the ten screws Rthat attach the key board.
Fig.35
Fig.36
Fig.37
Front panel assembly
Volume knob
Bracket(1) Q
Q
Q
Front panel
R
R
R
R
Key boad

UX-Z7MDR
(No.22042)1-15
2.2.3 Removing the FM connection board
(See Fig.38 to 40.)
(1) Remove the three screws Sand the screw Tthat attach the
bracket (2) from inside the front panel.
(2) Remove the card wire from the connector CN451 on the FL
connection board.
(3) Press the tab in the front panel and the one in joint "i"
downward to remove. Pull out the FL connection board to
remove.
2.2.4 Removing the drive motor assembly
(See Fig.38, 39, and 41.)
(1) Remove the three screws Sand the screw Tthat attach the
bracket (2) from inside the front panel.
(2) Remove the screw Uthat attaches the drive motor assem-
bly. Remove the tab in joint "j" that fixes the front panel. Pull
out the drive motor assembly to remove.
Fig.38
Fig.39
Fig.40
Fig.41
S
S
FL connect board
CN451 Front panel
Bracket(2)
Bracket(2) Front panel
Drive motor
T
joint i
joint i
FL connect board
CN451
U
joint j
Drive motor

UX-Z7MDR
1-16 (No.22042)
2.2.5 Removing the belt/drive motor
(See Fig.42.)
• Prior to this procedure, remove the drive motor assembly.
(1) Remove the belt from the pulley.
(2) Remove the two screws Vthat attach the drive motor.
Fig.42
2.2.6 Removing the switch board
(See Fig.43 and 44.)
• Prior to this procedure, remove the bracket (2) / the drive motor
assembly.
(1) Remove the card wire from the connector CN451 on FL
connection board.
(2) Remove the joint "k" by releasing it outward. And then, re-
move the joint "l" in the same way.
(3) Remove the screw Wthat attaches the switch board. Re-
move the tab on the joint "m" that fixes the front panel.
Fig.43
Fig.44
Belt
Drive motor
V
FL connect board
CN451
j
oint l
joint k
Switch board
Shift gear
Switch board
W
joint m

UX-Z7MDR
(No.22042)1-17
2.2.7 Removing the FL display
(See Fig.45 to 50.)
(1) Remove the four screws Xon the front side of the front pan-
el that attach the case cover.
(2) Pull out the FL panel from the bosses of the four joint "n"
on the FL display cover.
(3) Remove the four screws Ythat attach the FL display cover.
Remove the card wire from the connector CN671 and CN
672 on the FL connect board inside the FL display cover.
Fig.45
Fig.46
Fig.47
Fig.48
X
X
Case cove
r
FL panel
j
oint n
joint n
YY
FL cover
FL connect board
CN671 CN672
FL cover

UX-Z7MDR
1-18 (No.22042)
(4) Remove the two screws Zon the front side of the FL dis-
play cover that attach the FL display.
(5) FL board and lens will be detached from the FL display.
Fig.49
Fig.50
2.2.8 Removing the FL connect board
(See Fig.51.)
• Prior to this procedure, remove the FL display cover.
(1) Remove the card wire from the connector CN673 on the FL
connect board.
(2) Remove the two screws Z’ that attach the FL connect
board.
Fig.51
FL FL cover
ZZ
FL
FL board
Lens
FL connect board
CN673
Z'Z'

UX-Z7MDR
(No.22042)1-19
2.3 CD Mechanism Assembly
2.3.1 Removing the CL. Base Assembly and Tray
(Refer to Figs. 1 to 5.)
(1) Remove the two screws Afastening the CL. base assembly
from the top of the CD mechanism assembly.
(2) Move the CL. base assembly diagonally upwards as in-
dicated by the arrow to release it from the two hooks a.
(3) Turn the idle gear in the arrow-marked direction from the
upper side of the CD mechanism assembly. Accordingly,
the TRAMECHA assembly moves downwards.
Note:
When drawing out the tray, shift down the TRAMECHA
assembly to the position where the tray does not contact
the T-T assembly of the TRAMECHA assembly.
(4) Draw out the tray frontwards for removing it.
Note:
When reinstalling the tray:
• Turn the idle gear so that the part bof the tray gear is
positioned in the part cshown in Fig. 4. (Eject position)
• Engage the right and left hooks dand eof the tray with
the right and left grooves of the TRAMECHA assembly
respectively for retaining the tray.
Fig.1
Fig.2
Fig.3
Fig.4
Fig.5
ACL. base assembly
A
Hook a
Hook a
Idle gea
r
TRAMECHA
assembly
Tray
TRAMECHA assembly
Idle gear
Tray
Tray gear
Part c
Part b
Idle gea
r
Tray gear
Hook d
Hook d
Tray

UX-Z7MDR
1-20 (No.22042)
2.3.2 Removing the TRAMECHA Assembly
(Refer to Figs. 6 to 9.)
• Remove the CL. base assembly and tray.
Reference:
The TRAMECHA assembly can be removed without removal
of the mechanism P.C. board.
(1) If the TRAMECHA assembly is lowered and it is located out
of the PLAY position, turn the idle gear in the arrow-marked
direction so that the hole in the part f of the tray gear meets
the hole on the CL. base assembly. (Set the TRAMECHA
assembly at the PLAY position.)
(2) Remove the three screws Bfastening the
TRAMECHA assembly and then remove the
TRAMECHA assembly upwards from the front side.
(3) At the same time, remove the spring from the groove of the
CH. base assembly in the part gof the TRAMECHA as-
sembly.
Note:
When reinstalling the TRAMECHA assembly:
• Check to see if the spring is properly engaged with
groove of the CH. base assembly in the part gof the
TRAMECHA assembly.
• After making sure that the three insulators of the
TRAMECHA assembly are properly set on the boss-
es of the L. base assembly's guide, fasten them
with the screws.
Fig.6
Fig.7
Fig.8
Fig.9
BB
Idle gear
TRAMECHA
assembly
B
Tray gea
r
Part g
Tray gea
r
Part f
L. base assembly
Spring
Part g
Spring
Groove of CH. base assembly