JVC CD-1920 User Manual

Mechanical Adjustment
1. Replacement and adjustment of the head
2.
(See @ ®@ © O in Fig. 7 of page 6)
If either of the record/playback head and the erase head
shown low performance because of wear, broken wire or
excessive magnetization, it should be replaced.
Screws to be removed
REC/PB head
E head
REC/PB head
After replacement, adjust the head for azimuth.
1. Insert the cord plug into the LINE OUT jack (or
REC/PB), and connect the other end of the cord to a
V.T.V.M. (vacuum tube voltmeter).
2. Play the azimuth adjustment test tape (e.g. JVC’s
VTT-653, 10kHz).
3. Turn the azimuth screw so that the output will
become maximum.
If the azimuth adjustment test tape is not available,
play a music cassette.
When treble response becomes optimum, set the
adjustment screw (@).
4. After this adjustment, the screw @) should be locked
with a bond.
If necessary, adjust playback sensitivity,
current, REC signal current and bias trap.
REC _ bias
Erasing head
After replacement, adjust the head for height position.
1. Play the test tape (C-120).
2. Turn the adjustment screw © so that the test tape
move running to no touch the tape guide tip (up or
under side).
If checking is difficult, cut front upper side of the
cassette of C-120 by a cutter knife, etc., then can easy
check it.
REC/PB HEAD
Adjusting the motor speed
1) Play back reference tape (3000Hz), and adjust the
semi-VR in the motor that it’s speed in 3000Hz+2%
(2970Hz~ 3060Hz).
2) CD-1920 need not to change cycle, whether the
commercial frequency in your area is 50 or 60Hz.
CD-1920/A/B/C/E/U
No. 4142
Trouble Shooting Guide
[ELECTRICAL CIRCUIT]
1. Playback tone quality is poor.
1. Check the record/playback head for dust.
2. Check the record/playback head for wear.
If worn excessively, the loss of treble response will
result.
3. Check wiring for a short-circuit.
Check each transistor for condition.
2. Recording tone quality is poor.
The playback tone quality of a recorded tape such as the
audition tape is good, but the recording by this unit
produces poor tone quality. In this case, the unit should
be checked in the following manner. ‘
1. By monitoring a music while recording, check the
tone quality. |
2. If found poor, check the wiring of the recording
system for a broken wire and short-circuit.
3. If no irregularity is found, check the recording bias
current. Also check the oscillation circuit.
3. For other failures, check the unit in the same manner as
other amplifiers.
a a
3. Standard torque
70 gr-cm or more
70 gr-cm or more
35~ 70 gr-cm
Fast forward torque
Rewinding torque
Take-up torque
4. Door opening speed adjustment
(See in Fig. 7 of page 6)
Door opening is opened slowly by screw E is loosened
and move the bracket position to back side. (The spring
tension varies strong)
[MECHANISM SECTION] (wow and flutter)
If wow and flutter increase, check the following points.
If there is defect in revolving parts, the wow and flutter
generated will increase in proportion to the number of
revolutions.
es
Capstan and
flywheel
Pinch roller
Take-up idler arm
[MECHANICAL REPAIRS]
Take-up idler arm Standard take-up torque not available.
Play a 3000Hz test tape, and defective part can be detected
from the sound.
Capstan shaft has excessive run-out.
Flywheel turns heavily.
(shaft seisure, thrust play, etc.)
Replace flywheel.
Adjust plastic screw with flywheel holder.
Clean the capstan shaft and the groove in the
flywheel.
Apply oil to the metal position.
Replace the capstan assembly.
Rough rotation (Deformation
scratches, or dust).
The angular position of the pinch
roller is not correct.
The pinch roller pressure is not correct.
Replace pinch roller.
Clean the pinch roller or apply oil to the rotary
shaft.
Adjust the pinch roller so that it-is parallel with
the capstan shaft.
Adjust the pinch roller spring.
Clean the belt or remove the distortion.
Replace the belt.
Belt has undue run-out. ;
Belt is dirty or slippery.
Back tension is irregular, or back
tension is too strong.
Replace supply disc.
Replace back tension spring (under supply disc),
or apply silicon grease.
Motor shaft has undue run-out.
Motor pulley is oily and dusty.
Replace motor.
Clean motor pulley.
Pulley has deflection.
Pulley is stuck.
Replace take-up idler arm.
Replace take-up idler arm.
Replace take-up idler arm pressure spring.
Clean or replace capstan belt.
Clean rubber rim of the right reel.
Reel disc and idler Fast-forward torque not available. Clean rubber rim of the right reel or replace reel
disc assembly.
Clean or replace fast-forward idler.
Clean rubber rim of the left reel or repalce reel
disc assembly.
Clean rewind idler tire.
Door brake Door does not open fully. Apply a small quantity of silicon grease to the
inside surface of the brake pipe.
(SHIN ETSU KAGAKU KS-64 or equivalent)
Braking not sufficient. Replace brake pipe or rubber O-ring.
Check slide lever and solenoid iron core for
smooth movement.
Check if the locking and sliding parts of the
operation button cam are well coated with
molybdenum.
Auto-stop
mechanism
Auto-stop not operating.

JVC CD-1920 Specifications

General

Brand	JVC
Model	CD-1920
Category	Cassette Player
Language	English