JVC TD-W20A User manual

JVC
TD-W20A/B/C/E/G/J/
36
we!
MODEL
-W20
A/B/C/E/
G/J/U
Contents
Safety precaution 2.0 orb be ee ees
Features so. set Se teas PE des Saale wm Bra es
Specifications.......
Names of Parts and Their Functions..............
Location of Main Parts
Removal of Main Parts
Main Adjustments... .
Block Diagram ......
2 Wiring Connections: <x scsiau sane a eis Rohe oes 1
3 Standard Schematic Diagram of TD-W20......... 14
3 P.W. Board and Parts List ...............000- fe)
4 Exploded View of Enclosure Assembly ........... 2)
5 Exploded View of Mechanism Assembly ......... 22
6 DIMeNSIONS: oes) Si ee ale eee ee 28
8 Packing: ak. ohare ede Meatae Be end & 2h es 29
12 AccessorieéS 2.000. ee eee Back Cover
No. 4256
August 1985

TD-W20A/B/C/E/G/J/U
Safety precaution
1. The design of this product contains special hardware.
Many circuits and components specially for safety
purposes. .
For continued protection, no changes should be made to
the original design unless authorized in writing by the
manufacturer. Replacement parts must be identical to
those used in the original circuits. Service should be per-
formed by qualified personnel only.
2. Alterations of the design or circuitry of the product
should not be made. Any design alterations or additions
will void the manufacturer’s warranty and will further
relieve the manufacturer of responsibility for personal
injury or property damage resulting therefrom.
3. Many electrical and mechanical parts in the product
have special safety-related characteristics. These charac-
teristics are often not evident from visual inspection
nor can the protection afforded by then necessarily be
obtained by using replacement components rated for
higher voltage, wattage, etc. Replacement parts which
have these special safety characteristics are identified in
the parts list of Service manual. Electrical components
having such features are identified by ( Z\) on the
schematics and parts list in Service manual. The use of
a substitutue replacement which does not have the same
safety characterisitics as the recommended replacement
part shown in the parts list in Service manual may
create shock, fire, or other hazards.
4. The leads in the products are routed and dressed with
ties, clamps, tubings barriers and/or the like to be
separated from live parts, high temperature part, mov-
ing parts and/or sharp edges for the prevention of elec-
tric shock and fire hazard.
When service is required, the original lead routing and
dress should be observed, and they should be confirmed
to be returned to normal, after re-assembling.
2 (No. 4256)
5, Leakage current check
(Safety for electrical shock hazard)
After re-assembling the product, always perform an
isolation check on the exposed metal parts of the Pro-
ducts (antenna terminals, knobs, metal cabinet, screw
heads, earphone jack, contro! shafts, etc.) to be sure the
product is safe to operate without danger of electrical
shock.
Do not use a line isolation transformer during this check.
e Plug the AC line cord directly into the AC outlet. Us-
ing a ‘Leakage Current Tester’, measure the leakage
current from each exposed metal part of the cabinet,
particularly any exposed metal part having a return
path to the chassis, to a known good earth ground
(water pipe, etc,). Any leakage current must not ex-
ceed 0.5 mA AC (r.m.s.).
e Alternate check method.
Plug the AC line cord directly into the AC outlet. Use
an AC voltmeter having 1,000 ohms per volt or mroe
sesitivity in the following manner. Connect a 1500 2
10.W resistor paralleled by a 0.15 uF AC-type capaci-
tor between an exposed metal part and a known good
earth ground (water pipe, etc.).
Measure the AC voltage across the resistor with the
AC voltmeter.
Move the resistor connection to each exposed metal
part, particularly any exposed metal part having a
return path to the chassis, and measure the AC volt-
age across the resistor. Now, reverse the plug in the
AC outlet and repeat each measurement. Any voltage
measured musy not exceed 0.75 V AC (r.m.s.).
This corresponds to 0.5 mA AC (r.m.s.).
AC VOLTMETER
(HAVING 1000 2/V OR
MORE SENSITIVITY)
O.1SpF AC- TYPE
1500.
1OW
PLACE
THIS
PROBE
ON
EACH
EXPOSED
METAL
PART
GOOO EARTH GROUND

Features
1. Two logic-control deck mechanisms
¢ Double-speed dubbing function reduces tape editing
time by half.
. Dolby* B & C noise reduction systems
e Built-in MPX filter
. 2-color 6-LED peak level indicator
. Synchro-start dubbing
. Metal tape compatibility
. Auto tape select mechanism (deck A)
Nn
Oo nh Ww
Dolby Laboratories Licensing Corporation.
Dolby Laboratories Licensing Corporation.
Specifications
Type : Stereo double cassette deck
Track system : 4-track, 2-channel
Tape speed : 1-7/8 inch/sec (4.8 cm/sec)
Frequency response
O dB recording : Metal tape; 40—11,000 Hz (+3 dB)
Chrome tape; 40—8,000 Hz (+3 dB)
Normal tape; 40—8,000 Hz (+3 dB)
—20dB recording: Metal tape; 30—16,000 Hz
40—15,000 Hz (+3 dB)
Chrome tape; 30—16,000 Hz
40—15,000 Hz (+3 dB)
Normal tape; 30—15,000 Hz
40—14,000 Hz (+3 dB)
:58dB (S =1kHz, K3=3%, N=A-
weighted, Metal tape)
The S/N is improved by about 15 dB
at 500 Hz and by max. 20dB at
1kHz—10 kHz with Dolby C NR on
and improved by 5 dB at 1 kHz and
by 10 dB at above 5 kHz with Dolby
BNR on.
Improvement of MOL: 4dB at 10 kHz with Dolby C NR on
Wow and flutter : 0.08 % (WRMS)
0.20 % (DIN 45 500)
Crosstalk : 60 dB (1 kHz)
Harmonic distortion : K3 ;0.5 %, THD ;1.0%
(metal tape, 1 kHz, 0 dB)
: Deck A; METAPERM head for play-
back
S/N ratio
Heads
Deck B; METAPERM head for record-
ing/play back,
2-gap ferrite head for erasure
Noise reduction system manufactured under license from
“Doiby”” and the double-D symbol are trademarks of
TD-W20A/B/C/E/G/J/4
: Electronic governed DC motor for
capstan/reel x 1 (for both decks A
and B)
Motors
Fast forward/
Rewind time
Input terminals
Mic jack x 2
: Approx. 100 sec with C-60 cassette
: Max. sensitivity; 0.4 mV (-68 dB V)
Matching impedance; 600 2 — 10kQ
: Max. input level; 80 mV
imput impedance; 50 kQ
Input jack x 2
Output terminals
Output jack x 2. : Output level; 300 mV
Output impedance; 5 kQ
: AC 240 V, 50/60 Hz (TD-W20A)
AC 120 V, 60 Hz (TD-W20C/J)
AC 240/220/115 V, 50/60 Hz .
(TD-W20U)
Power requirement
Power consumption : With power on; 14 W
With power switch standby; 0.8 W
Dimensions : 17-1/8" (135 mm) W
4-11/16” (118 mm) H
9-1/8" (230mm) D
Weight : 8.8 Ibs (4.0 kg)
Accessories : Pin plug cord x 2
Design and specifications are subject to change without notice.
(No. 4256) 3

TD-W20A/B/C/E/G/J/U |
Names
of
Parts
and
Their
Functions
Qe)
POWER switch
Cassette holder (deck A)
Indicators
@ DUBBING
This
lights
to
indicate
that
the
unit
is
in
the
dub-
bing mode.
® HIGH SPEED
This lights when in the double-speed dubbing mode.
® RECORDING
Lights
when
deck
B
is
in
the
recording
and
record
pause mode.
MULTI PEAK INDICATOR
These
indicate
the
recording
level
during
recording
and
output
level
during
playback.
The
LED
indication
varies
with
the
signal
strength
during
recording
and
playback.
Cassette holder (deck B)
TAPE
COUNTER
and
RESET
button
MIC jacks (L [eft] , R [ight] )
Connect
microphones
(with
an
impedance
of
600
22
to 10 kQ) to these jacks.
With
microphones
connected
to
these
jacks,
the
in-
put
to
the
LINE
IN
(REC)
terminals
is
cut
off
auto-
matically.
SYNCHRO PLAY button
Press
this
button
when
performing
synchro-dubbing.
Do
not
press
this
button
other
than
for
this
purpose.
(See page 14.)
Cassette
operation
buttons
(deck
A)
>» (play) button:
Press to play the tape.
<< (rewind) button:
Press to rewind the tape.
p> (fast forward) button:
Press to fast forward the tape.
a /4 (stop/eject) button:
Press
to
stop
the
tape.
Pressing
this
button
after
the
tape
stops
opens
the
cassette
holder.
(The
tape
automatically
stops
when
it
reaches
the
end.)
4 (No. 4256)
@)
@
NR SYSTEM switches
The
left
switch
switches
on
and
off
the
noise
reduc-
tion circuits and the right switch selects which noise
reduction
system
(Dolby
B
NR
or
Dolby
C
NR)
is
to
be used.
DUBBING switch
Set
to
ON
(
mm
)
when
dubbing
from
deck
A
to
deck
B.
INPUT LEVEL control
Adjust the recording level with this control.
SPEED switch
Used to switch the tape speed when dubbing.
( = ) HIGH : For double-speed dubbing
(
a
)
NORM:
For
normal-speed
dubbing.
Moreover,
this is required when recording from the LINE
IN input or MIC jacks. Set to this position ex-
cept during double-speed dubbing.
TAPE switches (deck B)
When recording or playing back on deck B, select the
correct setting according to the type of tape used.
Cassette operation buttons (deck B)
© (record) button:
Press to record the tape.
il (pause) button:
Press to temporarily stop the tape in the record or
playback mode. Press it again to release the”
pause mode and restart the tape.
The other operations of the buttons are the same
as those of deck A.

TD-W20A/B/C/E/G/J/
Location of Main Parts
Power Cord N.R.P.W.B
Power Transformer
Pin Jack Rear Panel
Deck
A
Main
P.W.B
Deck
B
Front Panel
Power
Switch
Rec/P.
B.
Switch
Fig. 2
(No. 4256) 5

TD-W20A/B/C/E/G/J/U
Removal of Main Parts
Enclosure Section
» Removal of Top Cover
1.
Remove
six
screws
retaining
the
both
sides
of
the
top cover.
2.
Remove
two
screws
retaining
the
back
side
of
the
top cover.
= Removal of Bottom Cover
1.
Remove
three
screws
retaining
the
front
side
of
the bottorn cover.
2.
Remove
three
screws
retaining
the
rear
side
of
the bottom cover.
s Removal of Rear Panel
1.
Remove
three
screws
retaining
the
pin
jack
and
chassis to the rear panel.
2.
Remove
four
screws
retaining
the
Power
Trans.
3.
Remove
two
plastic
rivet
retaining
the
DIN
jack
to
from the rear panel. (TD-W20G)
= Removal of Front Panel
1. Remove three screws M,@ and 2) retaining
the Front Panel.
2. Remove one screw 8) retaining the earth wire
with the mechanism ass’y.
3. Pull out input level knobs.
2 Removal of Mechanism Ass‘y
(Deck B)
1. Remove the counter belt.
2. Remove four screws (4) and 6) retaining the
Deck B.
3. Open the cassette lid by depressing the STOP/
EJECT button.
4. Remove the cassette holder from the mechanism
ass’y by disengaging its fulcrums on the both sides.
(See Fig. 5-B.)
Note:When reassembling the cassette holder, set the
holder spring in the right foot of the holder prior
to reassembly.
(Deck A)
1. Remove four screws 6) and ®D retaining the
Deck A.
2. Open the cassette lid by depressing the STOP/
EJECT button.
3. Remove the cassette holder from the mechanism
ass'y by disengaging its fulcrums on the both sides.
(See Fig. 5-B.)
Note:When reassembling the cassette holder, set the
holder spring in the right foot of the holder prior
to reassembly.
# LED Indicator
Disengage five Pawls a) retaining the indicator
board ass’y.
6 (No. 4256)
G@ 41 “eS
DeckA/B Cassette
Holder
Rear View
Fig. 6

_| TD-W20A/B/C/E/G/J
= Removal of Power Switch (See Fig. 5)
1. Push the switch knob outward to remove it.
2. Push the switch ass’y in the direction of the arrow
to remove it.
Note : When reinstalling the switch ass’‘y :
1) Set the switch to its ON position.
2) Fix it as shown in the right figure.
3) Set the knob to the switch.
Removal figure
reinstement figure
Fig. 7
Mechanical parts
@ Rec./PB head (Deck B) PB head (Deck A)
1) Remove two screws 6) for the button assembly.
2) Remove a screw :
3) Loosen a screw for adjustment.
@ Erase head (Deck B) Dumy head (Deck A)
1) Remove a screw
2) Remove a screw for adjustment.
@ Pinch roller arm assembly
1) Remove a stopper holding its assembly, and
pull it off from the shaft.
©@ Supply reel disc assembly
1) Pull out the E ring 67) and remove its disc from
the shaft.
@ Take-up ree! disc
1)
Pull
out
the
E
ring
and
remove
it
from
the
shaft.
@ Motor
1) Remove three screws 2 and fastening
the FM bracket. (When removing the FM bracket 42),
remove with the main belt and the RF belt
44) .)
2) Remove three screws 45) fastening the motor.
3) Pull out the motor pulley from the motor shaft.
Fig. 9
Note: Be careful not to stain the main belt and RF belt.
(When assembling the motor pulley, adjust the
pulley position as next figure.)
10.5mm Fig. 10
MOTOR Fig. 8
@ Flywheel assembly
Pull out the flywheel from the capstan metal.
(No. 4256) 7

‘D-W20A/B/C/E/G/J/U
Main Adjustments
1.
Equipment
and
measuring
instruments
used
for
adjustments
1) Electronic voltmeter
2)
Audio
frequency
oscillator
(range;
50-20
kHz
and
output
0 dB with impedance of 600 22)
3)
Attenuator
(impedance;
600
£2)
4)
Standard
tapes
for
REC/PB
Maxell UD — Normal (SF) tape —
TDKSA
—
Chrome
(SA)
tape
—or
equivalent
JVC ME — Metal tape
5)
Reference
tape
for
playback
(ve.
Test
Tape)
TMT6451
(or
VTT656A)
(for
tape
speed,
wow
flut-
VTT64
VTT73
ter adj.)
4 (or VTT724) (for playback level)
9 (for playback frequency response)
TMT7008 (14 kHz) (for head azimuth adj.)
2. Mecha
Adjusting
motor speed
Checking
wow and
flutter
torque
Checking
fast forward
torque
| Checking re-
wind torque
nism adjustment proceder
6) Resistor 600 Q (for attenuator matching)
7) Distortion meter (bandpass filter)
8) Torque testing cassette gauge, CGT-N
9) Wow flutter meter
10) Frequency counter
* Adjustment
1, Connect a frequency counter to the
LINE OUT terminals.
2. Play back the TMT6451 (or VTT-
655A) test tape.
3. Adjust for deck{A]:
Adjust VRMO3 for normal speed at
3000 Hz, and VRMO1 for high speed
at 6000 Hz.
Adjust for deck([B]:
Adjust VRM04 for normal! speed at
3000Hz, and VRMO2 for high speed
at 6000 Hz.
Connect a wow and flutter meter to
LINE OUT terminals. Play back the
TMT6451 (or VTT656A) test tape.
Check to see if the reading of the
eter is within 0.08% (WRMS)
m .
Checking Employ a torque testing cassette tape
playback for the checking, or remove the cas-
sette cover and use a torque gauge.
Remarks
For adjusting high speed, HI-SPEED
test point should be grounded.
Adjust high speed after perform
normal speed.
If the reading becomes moving value
even if confirming to the standard, a
re-claim may be raised. Repairs are
necessary.
If the standard torque is not obtained,
replace the take-up disk assembly.
Measure the torque in the fast forward
mode in the same manner as in the
above.
Measure the torque in the rewind mode
in the same manner as in the above.
fis
8 (No. 4256)
Adjusting Standard
point value
Deck[A]: | Normal speed:
Normal; Deck [Al;
VRMO3 3000 Hz
High; Deck|B];
VRMO1 3000 Hz
Deck(B]: | High speed:
Normal; Deck|A|;
VRMO4 6000 Hz
High; Deck({B/;
VRMO2 6000 Hz
0.08% (WRMS)
0.2%
(DIN 45500)
35-75 gr-cm
More than
70 gr-cm
More than
70 gr-cm
If the standard torque is not obtained,
perform the following.
1. Clean the capstan belt, the idler cir-
cumference, the motor pulley, the
take-up reel disk circumference, the
flywheel circumference, etc.
2. Replace the belt and idler.
If the standard torque is not obtained,
clean the capstan belt, idler, motor pul-
ley, flywheel circumference, rewinding
idler circumference, left reel disk cir-
cumference, etc.

| TD-W20A/B/C/E/G/J;
Standard
value
Play mode:
within 3 sec
FF/REW mode:
within 5 sec
Adjusting
point
Checking Play back the tape. In playback mode,
auto-stop check that the tape run stops within 3
opeartion sec at the end of the tape. In fastfor-
ward or rewind mode, check that the
tape stops within 5 sec at the tape end.
If the head is worn, disconnected or
exceedingly magnetized so as not to
Screw A
(left side)
1. Connect an electronic voltmeter to
the LINE OUT terminals.
Adjusting
REC/PB
head azimuth| 2. Play back the TMT 7008 test tape. each provide the necessary characteristics,
3.
Adjust
the
head
angle
with
the
|
Deck
replace
it
with
a
new
one.
screw
A
until
the
reading
of
the
peck
a
After
replacement,
the
head
position
electronic voltmeter becomes maxi-
mum for both channels.
4. After adjusting, set the screw with
screw bond.
adjustment as well as the playback level
adjustment, the bias current adjust-
ment and the recording level adjust-
ment are all necessary.
If the output difference between the
left and right channels exceeds 3—4dB,
the head is defective. Replace it with
a new one.
3. Electrical adjustments location
@ Main Amp P. W. Board (parts assembly side view)
(Turning in the direction of the arrow increases the level.)
VRIOL INPUT VR
u
“
o ?
é = o z
S S Pa S|
r 8
4
=
9
°
=
g
BIAS
F
Adj
< - a z Lao!
u 2 rs 3
= 6 be 4
a o = a
Qs
rec cever vate C)) BIAS Ad.
| caterer ene era |
Rch Lich
VRMO3
VRMO4
[J SPEED Ads
NORM
i)
| Radi To RIO, P.B EQ
| ras F203 f i oo
HIGH
_ REC -- PB VRMOI
VRM02
HISPEED
CHECK
G3 SPEED Adj
00
Reh
(A) P. 8. GAIN Ag)
Fig. 11
(No. 4256) 9

‘D-W20A/B/C/E/G/J/U
4, Electrical circuit adjustment procedure
Perform
the
tape
transport
checks
and
head
azimuth
adjustment
before
following
checks
and
adjustments.
Adjustment
should
be
performed
in
the
order
of
alignment
steps.
In the steps marked with an asterisk (*), adjustment should be performed after replacing the heads.
Perform this adjustment with the NR switch set to OFF.
Check and Adjustment
Signal input: LINE IN 1 kHz, Cal. —40 dB +5.7dB+1dB
DOLBY B
(Rec)
Sel [Cal evel: 400 Hz, 68s
(BIAS, CUT) |Output terminal: NR. TP
DOLBY c
P Adjusting Standard
Step Item Adjustment point value Remarks
*2 |Confirming | Play back VTT644 (or VTT724), then |DeckA When the head is replaced, adjust
confirm that the level at LINE OUT is [L:R153,R154/Bi|-8+ 1.5dB
(Al—7dBs+1.5dB,{B]—8dBs+1.5dB alerlee
eC
| playback gain playback gain level.
Deck A
L:R153 cut by +1dB
R154 cut by —1dB
R:R253 cut by +1dB
R254 cut by —1dB
Deck B
L: R122 cut by +1dB
R125 cut by —1dB
R:R222 cut by +1dB
R225 cut by —1dB
bias
frequency
10 (No..4256)
C925,Lead through a 1.2 MQQ resistor,
then adjust L901 so that the counter
reads 95 kHz.
*3. | Playback Deck A: Play back VTT739, then con- B72 cut by —1dB
frequency firm that the level of 1 kHz and IL: B73 cut by —2dB
response 10 kHz signals is 0.5 + 2 dB. R:VR203 | Deck B: B75 cut by —1dB
Deck B: Before adjustment, disconnect |DeckB 0+2dB B76 cut by —2dB
B72, B73 (L-ch) and B75, B76 L:872,873
(R-ch) so that the outputs of 1 KHz |L:B75,B76
and 10 kHz signals are flat.
a
Adjusting Connect the frequency counter to the | L901 95 kHz METAL Position
+ 10%
=
kHz outputs satisfy the standard
values with respect to 1 kHz output.
Response (dB)
a
Decrease in high frequencies
QO 50 Hz 1 kHz
ode
Increase in high frequencies Low bias current
Appropriate bias current
High bias current
12.5 kHz Frequencies
*5
|Recording
|
1)
NR
switch:
OFF
For
With
respect
|
CrO2
frequency
2)
Record
a
1kHz
signal
at
an
input
;
Normal
to
1
kHz
50Hz
Q+3dB
response
reference
level
of
—20dB,
then
|
tape:
reference:
12.5kHz
O+4dB
record
50
Hz
and
12.5
kHz
signals
|}
L:
VR102;}
At
50
Hz,
Metal
and
play
them
back.
At
this
time,
|
R:VR202}
0+3
dB;
50Hz
0+3dB
adjust
VR102
and
VR202
so
that
At
12.5
kHz,
12.5kHz+1+4dB
the
deviation
of
50Hz
and
12.5
0+3dB