JVC CD-1920 User Manual

Adjustments
Electrical Adjustment
Equipment and measuring instruments used for 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 (QP-12, C521V) — normal tape
TS-2 (TP-18, C401R) — chrome tape
5. Reference tapes for playback
VTT-664 (1kHz 16mM)
VTT-666 (400Hz 22mM)
6. Resistors
1002 (for measurement of the bias current)
AUDIO Freq. OSC
6002 (for attenuator matching) Fig. 8
. Set the deck in the record mode, and
set INPUT SELECT switch at LINE
IN.
2. Input 1kHz signals (about 10dBs)
from LINE IN jacks and adjust
volume control so that test points
and are -3dBs.
3. Adjust semi-fixed resistors VR103
and 203 in this condition it obtain
zero VU meter reading.
Peak level 1. Set as same mode at step(1) and (Peak level
adjust semi-fixed resistor VR703 so C. board
that the 0” indicator is lighting and TAA305306)
no lighting at -1dB from step(1) with VR703
attenuator.
2. Adjust semi-fixed resistor VR704 so VR704
that the ‘’-5” indicator is lighting at
-5dB from step(1) with attenuator.
3. Adjust semi-fixed resistor VR705 so VR705
that the ‘’-10” indicator is lighting
at -10dB from step(1) with attenuator
and no lighting at -11dB from step(1)
with attenuator.
4. Adjust semi-fixed resistor VR702 so
that the “+3” indicator is lighting at
+3dB from step(1) and no lighting at
+2dB from step(1) with attenuator.
5. Adjust semi-fixed resistor VR701 so
that the +6” indicator is lighting at
+5dB from step(1) with attenuator.
1. Level meter
deflection
(Main amp
C. board
TAA305204)
The angle of meter deflec-
tion has been factory-
adjusted, but should be
adjusted when parts are
replaced.
VR103,203 When adjust the level meter,
don’t use a headphone.
Playback 1. Set equalizer switch at normal and (Main amp 1. Adjust playback sensi-
sensitivity playback reference tape VTT-664. C. board tivity when heads are
Adjust semi-fixed resistors VR101(L) VR101,201 replaced.
and VR201(R) so that test points
and are —3dBs, then level
meters indicate zero VU (about
0.3V at LINE OUT).
2. Playback reference tape VTT-666 and
check that the VU meter indicate
CAL.
2. Make this adjustment
after making sure level
meter deflection angle is
correct.
No. Item
4. | Bias
current
Recording
signal
current
ANRS
circuit
(DC bias)
. Set the deck in the record mode.
. Input the 1kHz signals to LINE IN
Procedure
. Insert a 1009 resistor into the ground
side wiring of the head and connect
the V.T.V.M. across the resistor, and
set the BIAS SW at chrome or normal.
Set the deck in record mode.
Input signals to LINE IN jacks and
adjust the recording level control so
that the test points and are
-13dBs.
First adjust for chrome tape, then for
normal tape.
. After the deck correct the head wires,
input the standard level of 1kHz sig-
nals to use reference tape, and measu-
re REC/PB frequency response at
10kHz.
. Adjust semi-fixed resistors VR502,504
(chrome) 501, 503(normal) so that
the 10kHz frequency response does
become +10dBs
Repeat the recording and playback so
that 10kHz signals become correct fre-
quency response.
Level over at 10kKHz compared
with 1kHz — bias current less
Level less at 1OkKHz compared
with 1kHz — bias current over
jacks and adjust the recording level
control so that the test points and
are -13dBs, make recording in
such a way.
. Adjust the semi-fixed resistors VR104,
204 (chrome), VR105,205(normal) so
that the test points are -13dBs.
. Disconnect +B of bias circuit so that
oscillator does not operate.
(Desolder the BIAS CUT in main amp
circuit board)
. Set the deck in the record mode.
. Apply signal of 1kHz to LINE IN and
adjust volume control so that test
points [12] and [62] (in main amp
circuit board) are OdBs.
. Then, connect the V.T.V.M. to test
points (h) G) in main amp circuit
board and adjust below steps.
. Apply signal of 1kKHz, —40dB to LINE
IN and adjust R401,401 so that LINE
OUT is -34.3dB with ANRS ON.
. Apply signal of 5kHz +40dBs to LINE
IN and adjust R302,402 so that LINE
OUT is -17.5dBs with ANRS ON.
. When apply signal of 1kHz to LINE
IN and output is OdB, adjust steps (5)
through (6) so that level does not
change when ANRS is turned on and
off (£5dB less).
. Playback reference tape VTT-664 and
check LINE OUT level so that it’s
compare are +1dB less with ANRS SW
on to off.
. Connect +B of bias circuit (Solder the
printed in main amp circuit board for
connect +B).
(re | Ree [Remar
1. Adjust bias current when
heads or other parts are
replaced.
2. Use the highclass V.T.V.M.
for high frequency re-
sponse.
3. After the bias current
adjustment, check the fre-
quency response at 10kHz
signals.
chrome
VR502,504
normal
VR501,503
(Main amp
C. board)
. This adjustment is necessa-
ry when heads are replaced.
2. Make this adjustment after
adjusting steps (1) through
(4).
3. Check the frequency re-
chrome sponse at 10kHz after this
VR104,204 adjustment.
normal 4. Set EO and BIAS switches
VR105,205 according to type of tape
used,
1. See figure of ANRS
circuit.
2. Repeat steps (5) through
(6).
Step (5) is 5.7dB up.
Step (6) is 2.5dB up.
CD-1920/A/B/C/E/U
No. 4142

JVC CD-1920 Specifications

General

Brand	JVC
Model	CD-1920
Category	Cassette Player
Language	English