JVC KS-FX490 Service Manual page 22

Item Conditions
1. Head Test tape:
azimuth SCC-1659
adjustment VT703 (10kHz)
Test tape:
VT724 (1kHz)
VT703 (10kHz)
VT721 (315Hz)
2. Tape speed Test tape:
and wow VT712 (3kHz)
flutter
confirmation
3. Play back Test tape:
frequency VT724 (1kHz)
response VT739 (63Hz /
confirmation 1kHz / 10kHz)
The tuner section is of an adjustment-freedesign. In case the tuner is in trouble, replace the tuner pack.
1-22 (No.49845)
Adjustment and Confirmation methods
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.
(1) Load the SCC-1659 mirror tape. Adjust with
height adjustment screw A
adjustment screw B so that line A of the mirror
tape runs in the center between Lch and Rch in
the reverse play mode.
(2) 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.)
(3) 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.
Head azimuth adjustment
(1) Load VT724 (1kHz) and play it back in the reverse
play mode. Set the Rch output level to max.
(2) 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 .
(3) Engage the reverse mode and adjust the output
level to max, with azimuth adjustment screw
C.(The phase difference should be 45 or more.)
(4) When switching between forward and reverse
modes, the difference between channels should
be within 3dB. (Between FWD L and R, REV L and
R.)
(5) When VT721 (315Hz) is played back, the level dif-
ference between channels should be within
1.5dB.
(1) 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).
(2) In case of out of specification, adjust the motor with
a built-in volume resistor.
(1) Play test tape VT724, and set the volume position at
2V.
(2) Play test tape VT739 and confirm.1kHz / 10kHz: -1
±3dB,1kHz / 63Hz: 0 ±3dB,
(3) When 10kHz is out of specification, it will be neces-
sary to read adjust the azimuth.
S.Values
Head shield
The head is at low position
during.
and azimuth
Head shield
The head is at High position
during REV.
Output
level:
Maximum
PBHead
FWD Adj B
REV Adj C
(0 )
Tape speed:
3015Hz to 3045Hz
Wow flutter:
less than 0.35%
Speaker out
1kHz / 63Hz: 0 ±3dB
1kHz / 10kHz: -1 ±3dB
Adjust
A line
B line
HEIGHT Adj A
phase
(45 )
Built-in volume
resistor