JVC KS-T707, Service Manual

Page: 23 / 147

(No.MA069)1-23
The tuner section is of an adjustment-freedesign. In case the tuner is in trouble, replace the tuner pack.
Item Conditions Adjustment and Confirmation methods S.Values Adjust
1. Head azi-
muth adjust-
ment Test tape:
SCC-1659
VT703 (10kHz) ‹ 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 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.
(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.
Test tape:
VT724 (1kHz)
VT703 (10kHz)
VT721 (315Hz) ‹ 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 lev-
el 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 differ-
ence between channels should be within 1.5dB.
2. Tape speed
and wow flut-
ter confirma-
tion Test tape:
VT712 (3kHz) (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.
Tape speed:
3015Hz to 3045Hz
Wow flutter:
less than 0.35% Built-in volume
resistor
3. Play back
frequency re-
sponse confir-
mation Test tape:
VT724 (1kHz)
VT739 (63Hz /
1kHz / 10kHz) (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.
Speaker out
1kHz / 63Hz: 0 ±3dB
1kHz / 10kHz: -1 ±3dB
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