Technics RS-646DS-D User manual

“ORDER NO. ARD-7706063C
Service Manual
Cassette Deck
RS-646DS-D
Portable High-Fidelity Stereo Cassette Deck with
Separate Bias/Equalizer and Mic Attenuator
RS-640U MECHANISM SERIES
Specifications (Catalog specifications for sales)
Power
requirement:
AC;
110/220V,
50/60
Hz
Input:
MIC;
sensitivity
0.25
mV/applicable
microphone
Power
consumption;
10
W
impedance
400Q~
10K
DC;
12V,
eight
R-20
size
dry
cell
batteries
INE;
sensitivity
60
mV/input
impedance
47
KQ
Motor:
1-DC
electronical
speed
control
motor
DIN;
sensitivity
16
mV/input
impedance
2.7
KQ
Track
system:
4-track
2-channel
stereo
recording
and
playback
Output:
LINE;
output
level
420
mV/load
impedance
50
K2
Tape
speed:
4.8cm/s
over
Battery
life:
Approx.
32
hours
with
alkaline
batteries
DIN;
output
level
420
mV/output
impedance
1
KQ
Wow
and
flutter:
0.1%
(WRMS),
£0.2%
(DIN)
HEADPHONE
;
output
level
65
mV/load
Frequency
response:
CrOz
tape;
50~14,000Hz
+3dB
impedance
82
45
~
14,000
Hz
(DIN)
Monitor
speaker;
output
power 0.8
W
(monaural)
Normal
tape;
50~14,000Hz
+3dB
Head:
2-head
system
45
~14,000Hz
(DIN)
1-super
permalloy
head
for
record/playback
Signal-to-noise
ratio:
Dalby
NR
in;
66dB
(above
5kHz)
1-doub!
gap
ferrite
head
for
erasure
Dolby
NR
out;
56 dB
Dimentions:
36.3cm(W)
X
10.6
cm(H)
X
28.0
cm(D)
(signal
level
max.
recording
level)
Weight:
5.0kg
(without
batteries)
Fast forward and
rewind time: Approx. 130 seconds with C-60 cassette tape
Specifications are subject to chang without notice.
gees 7 Matsushita Electric Trading Co., Ltd.
Technics
P.O.
Box
288,
Central
Osaka
Japan

LOCATION OF CONTROLS
AND COMPONENTS
DOAO@®D@OOOO@QOY Di
@ Eject button
@ Record button
@ Rewind button
@ Fast forward button
® Playback button
© Stop button
@® Cassette compartment cover
Pause button
Silent-stop button
Tape counter and reset button
Level meter
Level/battery check meter
Built-in speaker
Handle
Level controls lock button
Meter light button
Battery-check button
nput level controls
Tape-end indicator
Tone contro!
Speaker volume control
Equalization selector
Bias selector
Dolby noise-reduction switch
Limiter switch
Input selector
Microphone jacks
Headphones jack
Voltage selector switch
Car battery input jack
AC connection socket
Line output jacks
Record/playback DIN socket
Line input jacks
22 2) Q 19 48
SSSSSSSSSSSOSHSSSSsdQaGesoso@
32) 33) 34
Fig. 1

DISASSEMBLY
INSTRUCTIONS
—
(B)
Fig.
2
Fig.
3
Fig.
4
Fig.
5
—
Procedure
To remove — -.
Pes.
Shown in fig. ——.
1
Top
panel
(A),
(B),
(C),
(D),
4,2,2,2,3,4
2,3,4
a
Brent
natal
(G),
(H)
3,9
:
2,3
:
Mechaniern
(1)
.
:
neinlifier
i
),

MEASUREMENT & ADJUSTMENT
BEFORE ADJUSTMENTS OR REPAIRS ---.--
1. For electrically related adjustments only, each of the variable resistors and connection points for adjustment can be seen when the
bottom cover is removed as shown in fig. 7 below. Make adjustments by referring to each adjustment description.
—Connection
|
: :
-
;
woes
point
®
for
pele
a
ope
.
.
:
Connection
point
<B)
for
L-ch
playback
=
be
|
level
meter
adjustment.
frequency
.
response
adjustment.
2.
When
electrical
parts
of
printed
circuit
board
are
to
be
repaired,
rernove
the
mechanism,
amplifier
and
power
supply
printed
circuit
board
from the
case
as
shown
in fig.
8
below. When each section
is
reconnected
by
connectors,
the operation
of each
section
can
be
confirmed.
Note: 1. Secure the mechanism assembly to the jack angle.
2. Secure the power supply printed circuit board, in the same way, to the headphone jack angle.

ADJUSTMENTS
Before
measuring
and
adjusting
“Overall
frequency
response”,
“Overall
distortion”
and
“Overall
S/N
ratio”.
confirm
that
the
characteris-
tics
of
5
items
below
are
within
standard
which
have
much
relation
to
or
influence
on
electrical
performances
above.
1. Head azimuth adjustment. 2. Bias current. 3. Playback gain. 4, Overall gain.
5. Playback frequency response.
I. TEST INSTRUMENTS
1. Prepare test instruments which are equivalent in accuracy to those shown below.
2.
The
test
instruments
should
be
inspected
and
corrected
by
specialists
once
every
6
months,
because
a
long
period
of
use
without
maintenance
may
increase errors in
indication.
3.
Warm-up
the
test
instruments
for
30
minutes
and
the
set
to
be
measured
for
10
minutes
before
taking
the
measurements.
_
If
not,
there
may
arise
an
error
or
difference
between
the
initial
value
and
the
stabilized
value
measured
after
“aging”
4. Specifications of test instruments.
(1) Audio frequency oscillator
a. Oscillation frequency: 5Hz~ 500 kHz (5 ranges)
b. Frequency tolerance: +(3% +1Hz)
c. Sine wave
* Output voltage (at 25°C): 5Vrms £10% (without load)
2.5Vrms +10% (with 6002 load)
* Output frequency response: Within £0.2 dB, 20Hz~20kHz
Within £0.5dB, 5Hz~ 500 kHz
* Distortion factor: Not more than 0.05%, 200 Hz ~ 20kHz
Not more than 0.5%, 5Hz~ 500 kHz
* Output impedance: 6002 unbalanced, within + 15%
* Output attenuator: OdB, 20dB, error; within +0.2dB
d. Temperature in use of set: Temperature = 0 ~ 40°C, humidity = 90% or less
(2) Automatic-stop distortion meter (with vacuum tube voltmeter)
A. Distortion factor measurement
a. Frequency (fundamental wave): = 400Hz, 1kHz +10%
b. Measurement: 0.1~ 100% (6 ranges)
c. Input: 50mV~50V
d. Fundamental wave attenuation: 60 dB or more
B. Level measurement
a. Measurement: mV (—60 dB) ~ 30 V (30 dB) (9 ranges)
b. Frequency response (1kHz basis): 20Hz~100kHz £0.3¢dB
c. Input impedance: 1MQ2 +10%, less than 50 pF
d. Error in indicated value: Within £3% at 1kHz
C. Output terminal
a. Frequency response: OQHz~100kHz +1dB
100kH2~1MHz +3dB
b. Output voltage: 1Vrms + 10% (1kHz sine wave)

(3) Attenuator
a. Input impedance: 6002 unbalanced
b. Maximum attenuation: 121dB
c. Minimum attenuation: 0.1dB
(4) Oscilloscope
a. Cathode ray tube: Effective ranges 88cm
b. Vertical axis
* Input sensitivity : 30mV~30V/cm
* Frequency band: DC ~2MHz
* Transient time: 180ns.
* Input impedance: 1MQ, 35 pF
c. Horizontal axis
* Tuning range: 30 Hz ~ 2 MHz
* Sweep time: lus~ 100ms/cm
* External Sweep: 1Vp-p/cm or more
(5) Digital electronic counter
a. Number of figure: 4 (decimal system)
b. Input sensitivity; 100mVrms
c. Input impedance: 1MQ, 40 pF
d. Frequency measurement range: 10Hz~ 100 kHz
e. Counting time: 0.1s, Is, 10s
(6) Wow meter
a. Measured center frequency range: 3kHz +4%
b. Input level range: 30mV~3V
c. Input impedance: About 50 KQ unbalanced
d. Measurement: 0.01~3% (5 ranges)
e. Indicator error: Maximum error in indicated value +5%
in each range.
f. Frequency response: Contorming to weighting curve
characteristics (WRMS), JIS C5551.
Flat characteristics (RMS)
0.5~200Hz, within ~3 dB (4Hz basis)
g. Meter indication system: Effective value indication, conforming to
JIS C5551.
h. Meter response characteristic: About 5~ 7 sec.
i. Oscillation frequency: 3 frequencies (3kHz, 3kHz +3%)
j. Temperature range: 0~40°C

I. MEASUREMENT CONDITIONS
1, Standard measurement conditions
* Ambient temperature: 10~30°C (50~86°F)
* Ambient humidity: 30 ~90% RH
* Power voltage accuracy: 3%
2. Position of tape recorder
* When measuring, place the unit under test in a horizontal position.
3. Oscillator output voltage adjustment
* Connect the equipments as shown in the following and adjust the oscillator output control knob for 1 V (f=1kHz) through the
attenuator while keeping the attenuator at 0 dB.
* When supplying a signal to the tape recorder amplifier, adjust the input level using the attenuator.
Output control knob
Audio frequency oscillator } Attenuator : Vacuum tbe voltmeter Oscilloscope
f=1kHz
Testers
-
Output
voltage
1V
(OdB)
Il. TEST TAPE
Test tape life
The
more
frequently
the
test
tape
is
used,
the
more
the
tape
characteristics
will
deteriorate
(e.g.
lowering
of
recorded
level,
worsening
of
frequency
response
particularly
in
high-frequency
range,
and
an
increase
in
wow
due
to
tape
elongation)
until
measured
values
be-
come
unreliable.
Even
in
such
a
case
when
a
tape
is
not
used,
but
stored,
for
a
long
period
of
time,
tape
shows
deterioration
in
per-
formance because of self damagenetization due to storage conditions, etc.
Please
refer
to
the
tape
life
specitication
and
use
care
not
to
use
a
tape
longer
than
its
rated
life
when
servicing.
Frequence of use: Not more than 20 times for each tape length.
Storage period: Not more than 6 months.
Test tape
PARTS
NO.
PARTS
NAME
SPECIFICATIONS
REMARKS
Standard
recording
level
5
times
repetitive
recording
and
frequency
response
Tape
speed:
1-7/8ips.
(4.8cm/s)
tape
BS
x
Full
track
(10
min.)
OdB: STANDARD REC. LEVEL (160pWb/mm)
Ti d: 1-7/8ips. (4.
Wow
and
tape
speed
tepe
Tape
Speed:
1-7/8os,
(t.Bom/s
OdB: 250pWb/mm
Tape speed: 1-7/8ips. (4.8cm/s)
Azimuth
tape
6.3kHz
Full
track
(15
min)
OdB: 250pWb/mm
Reference blank tape
(Normal)
Unrecorded
tape
(20
min.)
Reference blank tape
(CrO2) Unrecorded tape (20 min.)

iV. MEASUREMENT & ADJUSTMENT METHOD
NOTE:
1.
. Make sure capstan and pressure roller are clean.
2
3. Judgeable room temperature: 20-+5°C (68+9°F)
4
Make sure heads are clean.
. Bias selector: Low
Pressure of pressure roller
Equipment:
* Tension gauge (max. 500 gr)
5. Dolby NR switch: OUT
7. Output level control: MAX
MEASUREMENT & ADJUSTMENT
Place UNIT into playback mode.
2. Hook the tension gauge to pressure roller lever and pull it in the direc-
tion of the arrow as shown in fig. 9.
. Measure the tension at the moment when the pressure roller moves
away from the capstan.
Standard value: 390+60 gr |
l
Adjustment method
Bend the part (A) of the pressure roller spring in either direction shown
by the arrow until the correct pressure is attained.
6. Equalizer selector: 120.8
REMARKS
* Playback mode
Pressure ~
roller spring
Fig. 9
Takeup tension
Equipment:
* Cassette torque meter
(SRK-CT or RP8063)
1. Mount cassette torque meter on UNIT.
2. Place UNIT into playback mode and read takeup torque.
3. Measure several times and determine the mean value.
Standard value: 55+15gr-cm |
If the measured value is not within standard, firstly clean the rotational
parts of the mechanism with alcohol, and if it still is not within standard,
make the following adjustment.
Adjustment method
Adjust by turning the plate spring attached in the takeup reel table (See
fig. 10).
* Playback mode
Plate spring
Fig. 10
Head azimuth adjustment
Equipment:
* VTVM
* Oscilloscope
* Test tape (azimuth) --- C-AA
Record/playback head adjustment
1. Test equipment connection is shown below.
VTVM
Fig. 11
Test tape Playback mode Oscilloscope
. Play azimuth tape (C-AA, 6.3 kHz).
. Adjust record/playback head angle adjustment screw (8) in fig. 12 so
that output level at LINE OUT becomes maximum.
. Measure both channels, and adjust levels for equal output.
. After adjustment lock head adjustment screw with lacquer.
* Playback mode
R/P Head

Tape speed
Equipment:
* Digital electronic counter or
frequency counter (RP8067)
* Test tape--- C-WAT
MEASUREMENT & ADJUSTMENT
Tape speed accuracy
1. Test equipment connection is shown below.
LINE OUT
Test tape Playback mode Digital electric counter
Fig. 13
2. Play test tape (C-WAT 3,000Hz), and supply playback signal to fre-
quency counter.
3. Measure this frequency.
4. On the basis of 3,000Hz, determine value by following formula:
f—3,000 5
3.000 x 100 (%)
where, f=measured value
5. Take measurement at middle section of tape.
Tape speed accuracy =
Standard value: +1.5% |
Adjustment method
1. Play the test tape (middle).
2. Adjust the tape speed adjustment VR shown on page 18 so that fre
quency becomes 3,000 Hz.
Tape speed fluctuation
Make measurements in same manner as above (beginning, middle and end
of tape), and determine difference between maximum and minimum values
and calculate as follows:
_ fi—fe 6
Tape speed fluctuation = 3.000 x 100 (%)
fi1=maximum value
f2=minimum value
Standard value: 1.5%
REMARKS
* Playback mode
Wow and flutter
Equipment:
+ Wow meter
* Test tape --- C-WAT
1. Test equipment connection is shown below.
LINE OUT
/
Test tape Playback mode Wow meter
Fig. 14
. Use wow test tape (3,000Hz) and measure its playback signal on
wow meter.
.
Wow
and
flutter
is
expressed
in
percentage
and
that
measurement
can
be
weighted
by
JIS
network
(WRMS).
. Measure at middie section of test tape.
I
| Standard value: 0.10% (WRMS)
+ Playback mode

Playback frequency
response
Equipment:
* VTVM
* Oscilloscope
* Test tape --- C-FH
Playback gain
Equipment:
*VTVM
* Oscilloscope
* Test tape--- C-FH
MEASUREMENT & ADJUSTMENT
. Test equipment connection is as same as “Head azimuth adjustment” |
but use the test tape (C-FH) instead of head azimuth tape (See fig.
11).
. Place UNIT into playback mode.
. Play frequency response test tape (C-FH).
. Measure output level at 1OkHz, 8kHz, 4kHz, 1kHz, 125Hz and 63Hz
and compare output level with standard frequency 333Hz, at LINE
OUT.
. Make measurement for both channels.
. Make sure that the measured value is within the range specified in the
frequency response chart.
Playback frequency response chart
150Hz 250Hz 333H2 sobez L ski
Fig. 15
. If measured value is not within standard, adjust the following points:
Change the “Connection points’ of the amplifier pattern, and then
adjust the playback frequency response.
@lf the high range (8~10kHz) decreases about —1~ —1.5aB,
short circuit connection points (@) as shown in fig. 7.
@lf the high range (8~10kHz) decreases about —1.5~ —2qB,
also short circuit connection points (B) as shown in fig. 7.
. Test equipment connection is shown in fig. 11.
Play standard recording level portion on test tape (C-FH 333Hz), and
using VTVM measure the output level at LINE OUT jack.
. Make measurement for both channels.
Standard value: 0.42V (—7dB)
Adjustment method
1. If measured value is not standard, adjust VR1 (L-CH), VR2 (R-CH)
(See fig. 28 on page 17).
2. After adjustment, check “Playback frequency response” again.
REMARKS
* Playback mode
; * Playback mode
Playback S/N ratio
Equipment:
* VTVM
* Oscilloscope
* Test tape---C-FH
* Empty cassette
. Test equipment connection is shown in fig. 11.
put level on VTVM.
Refer to "Playback gain adjustment”.
. Place empty cassette (which has been cut) and play again.
. Measure noise level at this time using VTVM, and determine ratio of
this level to test tape output signal voltage (333 Hz).
Standard value: Greater than 43dB |
An example calculation is shown below.
A: Es=playback output signal voltage of test tape (333 Hz)
B: En=playback output noise level
Es=0.42V (—7dB)
En=0.003 V (—50dB)
S/N ratio= Es _ _0.42V — 140
En 0.003 V
20 log:: 140=43dB
S/N ratio = Es(dB) — En(dB) = —7 —(—50) = 43dB
! * Playback mode
. Play standard recording level test tape (C-FH 333Hz) and read out- :

Bias current
Equipment :
*VTVM
* Oscilloscope
Erase current
Equipment:
* VTVM
* Oscilloscope
* Resistor (12)
MEASUREMENT & ADJUSTMENT
1. Test equipment connection is shown below.
Record mode
R7{L-CH)
VIVM Oscilloscope
Fig. 16
2. Place UNIT into record mode, and bias selector switch to "LOW",
position.
3. Read voltage on VTVM and calculate bias current by following for-
mula:
Value read on VTVM (V)
Bias current (A) = 10 @)
Standard value: 0.3+0.001mA
. Adjust L.5 (L-CH) and L6 (R-CH) (See adjustment part location on
page 17).
. Then changing the bias selector to “HIGH”, confirm that bias current
become greater by 30% than that for normal.
. Connect 12 resistor between ground side terminal of the erase head
ground lead wire removed (See fig. 18).
. Connect VTVM to both ends of 1 resistor.
Erase head
o
VTVM Oscilloscope
Fig. 17
3. Place UNIT into record mode, and measure voltage across the on
resistor.
4. Determine erase current with the following formula:
Voltage across both ends of 1 (Q)
1 (Q)
Erase current (A) =
Standard value:
Bias LOW: 90+20mA
Bias HIGH: 120+30mA
REMARKS
* Record mode
* Be sure the ground end of
the meter is connected to
the ground end of the
resistor.
* When bias current is
adjusted on one channel
only, note that bias current
on the other channel may
vary.
* Record mode
Erase head
BLACK
Fig. 18
10

Overall gain
Equipment:
* AF oscillator
* VTVM
+ ATT
* Oscilloscope
* Test tape
(reference blank tape)
+--+ C-RF for CrO2
«+» C-RA for Normal
MEASUREMENT & ADJUSTMENT
1. Test equipment connection is shown in fig. 19.
VTVM
Fig. 19
2. Place UNIT into record mode, and bias selector to “LOW”, and
selector to “1204S”
3. Supply 1kHz (—24dB) from AF oscillator, through ATT, to signal
LINE IN.
Adjust ATT until monitor level at LINE OUT becomes 0.42 V (—7 dB).
Using test tape (C-RA), make recording.
Playback recorded tape, and make sure the value at LINE OUT on
VTVM becomes 0.42 V.
7. |f measured value is not 0.42 V, adjust VR7 (L-CH), VR8 (R-CH) (See
fig. 28 on page 17).
Repeat from step (2).
For CrO2 bias selector to “HIGH”, and EQ. selector to "70uS” change
test tape to (C-RF), and take the same steps for normal but to adjust,
use VRQ (L-CH) and VR10 (R-CH). (See fig. 28 on page 17).
How to check recording current
Playback mode
Test tape Oscilloscope
EQ.
Hoar
Role)
LINE IN
6000 .
Record mode
R7(L-CH)
AF Oscillator ATT
Oscilloscope VIVM
R/P Head
Fig. 20
1. Test equipment connection is shown in fig. 20.
2. Stop bias oscillation by unsoldering point L302 shown in AMP circuit
board on page 20.
3. Supply 1 kHz signal (— 24 dB) again and adjust ATT until monitor level
at LINE OUT becomes 0.42 V.
4. Measure voltage and then calculate recording current by formura given
below.
Value read on VTVM (V)
Recordi urrent =~ - : ~
ve 10 (Q)
| Standard value: 40+5uA |
5. At this time, set the bias selector to “HIGH”, and EQ. selector to
"70S" and confirm variation of recording current.
| Standard value: 60£5uA |
REMARKS
* Record/playback mode
* LINE IN level control
we MAX
* Standard input level:
—72+4dB
LINE IN --» ~24+4dB

Level meter
Equipment:
+ VTVM
* Oscilloscope
* AF oscillator
+ ATT
Overall distortion
Equipment:
* Distortion meter
* AF oscillator
* ATT
* Oscilloscope
* Test tape---C-RA
(reference blank tape)
MEASUREMENT & ADJUSTMENT
When standard recording level is supplied
1. Test equipment connection is shown in fig. 21.
Bw
AF Oscillator
LINE IN LINE OUT
ATT Record mode
Fig. 21
.
Set
the
bias
selector
to
“LOW”
and
the
EQ.
selector
to
"120uS".
.
Supply
1kHz
signal
(~24dB)
from
AF
oscillator,
through
ATT,
to
LINE IN (L-CH) jack.
. Adjust ATT until monitor level at LINE QUT (L-CH) jack becomes
0.42 V (—7 dB) and confirm that the level meter indicates 0 VU posi-
tion.
. If in the above condition, the level meter doesn’t indicate OVU posi-
tion, change the “Connection points” of the amplifier pattern, and make
the adjustment.
D
If
the
indication
of
the
left
channel
meter
is
below
—1.5dB,
short
circuit connection point © as shown in fig. 7.
@
If
the
indication
is
still
insufticient
by
shorting
connection
point
©,
short
circuit
connection
point
©
also
as
shown
in
fig.
7.
.
Adjust
VR11
so
that
the
right
meter
will
indicate
the
same
value
as
the left meter. (See fig. 28 on page 17).
REMARKS
* Record mode
. Test equipment connection is shown in fig, 22.
co
ATT 6002 Record
mode
LINE OUT
law 3
oscillat
AF
oscillator
Test
tape
R/P head
Playback mode Disto Higa?
meter
Fig. 22
Supply 1 kHz signal to LINE IN and adjust ATT so that output jevel
at LINE OUT indicates 0.42 V (—7dB).
Make recording.
Playback and measure distortion factor of output signal.
When the distortion factor does not satisfy the standard, check the
bias current. When the bias current is lower than standard, distor-
tion will increase.
Care should be exercised in the adjustment because the bias current
also has an influence on the overall frequency response. Refer to
"The overall frequency response” and "The bias current adjustment”
Test tape
Standard value: |
Less than 3.0% (Normal) |
Less than 3.5% (CrO2) |
* LINE IN level contro!
* Bias selector ++++++++- LOW
*EQ
selector
+--+
1
(for
Normal
tape)
| * Bias selector «+--+
*EQ selector -.+..+++
(for CrOz tape)
20uS
12

13
Overall frequency response
Equipment:
* VIVM
* AF oscillator
+ ATT
* Test tape
(reference blank tape)
+++ C-RA for Normal
+++ C-RF for CrOz
Overall frequency response
(As a standard for adjustment)
MEASUREMENT & ADJUSTMENT
Note:
Before measuring, and adjusting, make sure of the playback frequency
response (For the method of measurement, please refer to the playback
frequency response).
1. Test equipment connection is shown in fig. 19.
2. Load reference blank test tape and place UNIT into record mode.
3. Supply 1 kHz signal from AF oscillator through ATT to LINE IN.
4. Adjust ATT so that input level is —20dB below standard recording
level (standard recording level = 0 VU).
. At this time, LINE OUT level indicates 0.042 V.
. Record each frequency 40 Hz, 100 Hz, 200 Hz, 500 Hz, 1 kHz, 2 kHz,
3kHz, 10kHz, 12kHz and 13kHz at the same level.
. Playback and express in dB the difference between playback output
level of each frequency based on playback output level of 1 kHz.
. Make sure that the measured value is within the range specified in
the overall frequency response chart.
. Set the bias selector to “HIGH”, and the EQ. selector to “70S”.
. Measure as same as manner above.
. Make sure that the measured value is within the range specified in
the overall frequency response chart (See fig. 23).
Overall frequency response chart (Normal & CrO2)
A.SKHz 2KHz
12KHH 7.948
Adjustment 1—Using bias current
1. When the frequency response between the middle- and high-frequency
range becomes higher than the standard value, as shown by the solid
line in fig. 24 increase the bias current by turning L5 (-CH), L6 (R-
CH).
. When it becomes lower, as shown by dotted line, reduce the bias cur-
rent by turning L5 (L-CH), L6 (R-CH). (See fig. 28 on page 17).
oe
~ 4
Me
GLA
1KHz2 1 .5KHz 2KHz 4K
Frequency (Hz)
Fig. 24
REMARKS
* Record/playback mode
* Record level control
..» MAX
LOW
120uS
* Bias selector
* EQ. selector
(for Normal tape)
* Bias selector
* EQ. selector
(for CrOz tape)

ITEM
MEASUREMENT & ADJUSTMENT
Note:
1.
For adjustment when the bias current is lower than the standard value
0.29mA, the bias current beyond this point may worsen the distortion
factor.
For the method of bias current measurement, refer to “Bias current
adjustment” on page 10.
REMARKS
Overall S/N ratio
Equipment:
* VTVM
* AF oscillator
+ ATT
* Oscilloscope
* Test tape---C-RA
(reference blank tape)
. Test equipment connection is shown in fig. 19.
. Supply 1kHz signal to LINE IN and adjust ATT so that output level
at LINE OUT indicates 0.42 V (—7 dB).
. Make recording.
Make another recording without supplying signal (disconnect input
plug to LINE IN).
Rewind to recorded part and playback.
Measure output signal level and no signal level (noise), and determine
the ratio in decibels (dB).
. The value is difference between “Playback S/N and overall S/N”, but
for decibel calculation refer to “Playback S/N measurement” on page
9.
Standard value: Greater than 40dB
(without NAB filter)
ij
* Record/playback mode
* LINE IN level control
ve MAX
* Erase the tape with a bulk
tape eraser.
| * Bias selector ----+-++- LOW
* EQ selector
Dolby NR circuit
Equipment:
* VTVM
* AF oscillator
* ATT
* Oscilloscope
DaRw
N
Place UNIT into record mode, set the Dolby NR switch to OUT posi-
tion and supply to LINE IN to obtain —34.5dB at TP1(L-CH), TP2
(R-CH) (frequency 5 kHz).
Confirm that the value at IN position is 8dB greater than the value at
OUT position of Dolby NR switch.
When it is not in condition above, adjust as follows.
Set VR3 (L-CH), VR4 (R-CH) to maximum.
Set the Dolby NR switch to IN position.
At this time adjust VR5 (L-CH), VR6 (R-CH) so that the reading of
VTVM become 10dB greater than the value in step (1) above.
Adjusting VR3 (L-CH), VR4 (R-CH), make the reading of VTVM be-
come 2dB smaller than the value obtainted through the adjustment
in step (6) above. (See adjustment parts location on page 17).
* Record mode
* LINE IN level control
..» MAX
* Stop the bias oscillation by
unsoldering point L302
shown in circuit board
on page 20
14

MEASUREMENT & ADJUSTMENT REMARKS
Battery meter . Place UNIT into record and playback mode. * Playback mode
. Set the VR604 (S12) power amplifier volume to the OFF position. * Record/playback mode
. Apply DC 9.1V to the DC IN jack.
. Set the S6 battery check switch to the IN position.
. Adjust the VR12 battery meter adjustment VR, aqjusting so that the
meter indication needle moves to the position shown in fig. 25 below.
(See fig. 28 on page 17).
(saad within this range
Equipment :
* DC voltage supply
Fig. 25
Setting of power amplifier . Set the VR604 (S12) power amplifier volume to the ON position.
intermediate potential . Connect the measuring instrument between the test point (TP3) and
Equipment: earth, and contirm that an intermediate voltage of 7V (+0.5V, —OV)
« Tester iS present.
. If intermediate voltage does not reach 7V, short circuit connection
point ©) as shown in fig. 28, and adjust so that the value is within the
standard.
Adjustment of leaf switch . Adjust the playback leaf switch so that its clearance will be 0.2~0.4
for playback mm, as shown in the figure below, when, in the condition that the acci-
dental-erase-prevention lever is locked (the record button is not locked),
the record button is pushed.
2. After adjustment, secure by locking the screw.
| Note:
Be sure that the playback leaf switch adjustment is made only after first
securing the stopper.
Stopper
Playback rod 0.2 ~0.4mm
Fig. 26

Micro-switch (S10)
mounting method
MEASUREMENT & ADJUSTMENT
1. Lock the record button and playback button.
2. As shown in the figure below, attach the micro-switch holding plate so
that, with the detection lever assembly and detection rod engaged, the
clearance between the detection rod and the actuator of the micro-
switch is 0.5£0.2mm.
Note:
The micro-switch can be attached by pushing the actuator with a finger,
illuminating the light-emitting diode, and then resetting the actuator gently
and attaching the micro-switch by stopping at the point where the light:
emitting diode extinguishes.
0.5£0.2mm
Screw 2.6 X6
Micro switch (S10)
Detecting rod
Detecting lever-A
REMARKS
16

ADJUSTMENT PARTS LOCATION
VR2
VR4 VR6 L6
VR7 VR1i0
VR1
17
VR2
VR3VR5 L6~ Ld
|
|
point ©) for |
power amp.
voltage |
adjustment. |
|
|
|
|

ELECTRICAL PARTS LOCATION
18
E56
E55
E55
eS
E15
E14
Tape speed adjustment VR. £55
E12

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NOTE:
1 Sli -Slda Record/playback select switch (shown in playback position), 18. VR7. 8 Record level adjustment VR for NORMAL tape.
2 $21 $24 Input select switch (shown in LINE position) 19. VRQ, 10 -s+-+--Record level adjustment VR for CrO2 tape.
ioe
3
$3.1-$3-4.
-+.-EQ
select
switch
(shown
in
"120s"
position)
20,
VRID
v0
-+-Level
meter
adjustment
VR
for
Rech
MAISOLF
4
$41,542
Limiter
ON/OFF
switch
(shown
in
OFF
position)
21,
VR12
soo-Battery
level
adjustment
VR
i
:
8.
S51
S52
Dofby
IN/OUT
switch
(shown
in
OUT
position)
22.
VRGQ1,
602
----Record
input
level
control
11202
288324
7201
2801383
UM-1x8
6
SE
Battery
check
switch
(shown
in
OFF
position)
23,
VR603.---
Tone
volume
7. 37 Bias Low/HIGH select switch (shown in Low position? 24. VRE04-----0---Speaker volume with speaker ON/OFF switch
TERMINATIONS
(BOTTOM
VIEW)
r
8
os
Mets
light
ich
(shown
in
OFF
position)
25.
Resistor
values
are
in
ohms
(11),
1/4
watt
unless
specified
otherwise
280828
,
2SA584
2801568
,
2801847
288324
ibd
;
ee
Micro:
Rasitots
astises.
2SK30AD
2SA886
t
SM102.F
10
a
Motor
ON/OFF:
Micro-switci
t
Resistors
indicatea
thickly
show
printed
type
resistor,
|
I
e5
LL
SH
-
AC/DC
select
switch
26.
Capacitor
values
are
in
microfarads
(uF)
unless
specified
otherwise
310
|
Tr301
12.
$12
Power
arnplifier
IN/OUT
switen
P=Picofarads
|
fom
do
2SC1568
13.
$13
Piay
switcn,
27.
The
mark
(¥)
shows
test
point.
e.g.
¥=Test
point
|
|
aK
|
14,
$14
1,
$14.2.--Muting
switch
{off
at
REC/PLAY
poston)
28.
All
voltage
vaiues
shown
in
circuitry
are
under
no
signal
condition
with
volume
Lo
be
|
15.
S15
2
voltage
selector
switen
control
at
minimum
position
16. VR1, 2 Playback tevel adjustment VR For measurement, use VIVM
17 VR3. 4.5, 6 ---Doiby NR adjustment VR. 29. For parts which are shaded (sis). only parts specified by the manufacturer
OE
ee
f
should
be
used
for
replacement
sn
critical
circurt
19