JVC KD-21 - Page 8

<—
mc
/3$/U
Main Adjustments
{!] Equipment and measuring instruments used for
adjustment.
1. Electrical adjustment
1) V.T.V.M. (measuring AC in millivolt)
2) Audio frequency oscillator
(range;50~20kHz and output OdB with impedance
6002)
3) Attenuator
4) Reference tapes for REC/PB
TS-1 (OQP-12, C521V) — normal tape
TS-2 (TP-18, C401R) — chrome tape
5) Reference tapes for playback (JVC Test Tape)
VTT-658 (for head azimuth adj.)
VTT-656 (for motor speed, wow flutter adj.)
VTT-664 (for Reference level 1kHz)
VTT-675N (for playback frequency responce)
6) Resistors
100Q
(for
measurement
of
the
bias
current)
Fig.
8
6002
(for
attenuator
matching)
;
AUDIO Freq. OSC V.T.VM
ATTENUATOR
0058,
t0"
OUTPUT
=|
OUTPUT
2. Mechanical adjustment
1) Gaze for checking the head position
2) Torque gaze
3) Blank tape (C-120) for tape runing checker
[11] Procedure for adjustments
When
you
adjust
following
items,
we
recommend
to
you
to
keep
doing
step
No.
1 Take up Measure by the torque measure cassette or
torque the torque gaze tool, at the playback.
(If not)
1. Clean the main belt, rubber
rim of idler, and rubber rim
of the right reed disc.
2. Replace the idler arm of
take-up and spring.
Fast forward | Measure as same way at FF mode or at 70 gr-cm | (If not)
torque REW mode. or more | 1. Clean the main belt, rubber
Rewinding rim of the idler, motor pully,
torque rim of the flywheel, and
rubber rim of the reel disc
for REW.
. Replace the reel disc.
0.7mm
or less
. Check with your own eyes.
2. If not, high frequency
range or, erase ratio will
be down.
. Checker tape (C-120).
Check the head position by the gaze.
The clearance is 0.7mm or less between
the head and the gaze.
2 Head posi-
tion check
No
touch
the tape
guide
Adjustment
screw
1. Playback the reference tape C-120
(front cutted cassette) and turn the ad-
justment screw (spring side) so that the
tape may run in the center of the guide.
2. \f incorrect adjustment does not, make
the tape run correctly as the following
illustration
tape guide
~<— (upper side)
3 Tape runn-
ing check
O70
°
cuting
Fig. 10
2. Adjustment screw
tape
tape
ill tape guide
(under side) Fig. 9
ee Adj. screw
Fig. 11
No. 4150 Zs gee