Technics RS-676US User manual

TAPE RECOh.
Technics
Service Manual cee,
HI-Fl STEREO CASSETTE DECK WITH FRONT CONTROLS
AND DOLBY* NOISE REDUCTION SYSTEM
RS-676US MECHANISM SERIES
MODEL RS-676US
SPECIFICATIONS
Power Source: AC: 90~109, 110~125, 200~219, Frequency Response: Normal tape; 20~16,000 Hz
220~250 volts, 50/60 Hz 25~14,000 Hz (DIN)
Power Consumption: 25W. 30~13,000 Hz (+3 dB)
Motors: 2-motor system CrOz2 tape: 20~18,000 Hz
1-Electronic speed contro! motor for 25~15,000 Hz (DIN)
capstan drive 30~14,000 Hz (+3 dB)
1-DC motor for reel table drive Signal to Noise Ratio: Dolby NR out; 52 dB
Transistors: 28C1327 (6), 2SC644(2), (0 VU=250 PWb/mm)
28C828 (28), 2SC1318(3), 2SA719(1), Dolby NR in; 62 dB at 10 kHz
2SC1096Z (3), 2SC1384 (3), Harmonic Distortion: 2.0% (0 VU at 1,000 Hz)
2SD288 (1), 2SA666H(3), 2SC945(2), Inputs: MIC: sensitivity 0.3 mV/applicable
2S8C1407 (2), 2SK30(2) microphone impedance 600Q~
Head: HPF head for rec/playback head 20KQ
Diode & Rectifiers: 1$1211(8), OA90Z(20), OA91 (3), LINE: sensitivity 60 mV/110KQ
MA162(10), RD7A(2), FR202(6), TUNER: sensitivity 100 mV/190 KQ
M21C(2), EQA0119(1), 10DC1 (3), Outputs : LINE: output level 420 mV (max.)
1ODC1R(2) impedance 50 KQ over
Track System: 4-track 2-channel stereo recording HEADPHONE: output level 45 mV/8Q
and playback Rec/PB Connection: 5 P DIN type
Recording System: AC bias (90 kHz), AC erase Fast Forward and Approx. 80 second with C-60 cassette
Tape Speed: 4.8cm/s, (1-7/8 ips.) Rewind Time: tape
Program Time: 1 hour stereo recording with C-60 Dimensions: 410mm(W) x 140mm (H) x 360mm (D)
cassette tape 16-3/8” (W) x 5-1/2” (H) x 14-3/87 (D)
Wow and Flutter: 0.063% (WRMS) ,+0.15% (DIN) Weight: 10.5 Kg, (23-1/8 ips.) :
These specifications are subject to change in order to accommodate improvements in design.
Matsushita Electric Industrial Co.,Ltd. Baga |
MATSUSHITA ELECTRIC TRADING CO., LTD. begga <
P.O. Box 288 Central, Osaka, Japan

LOCATION OF PARTS
®
Q®@
@@OOO®
Q
@ Ejection button Dolby FM calibration controls
@ Cassette cover @ Recording level control
@ Fast forward button @ Tape selector
@ Tape counter and reset button Pause button
® Memory playback button @) Record button
© Dolby NR/MPX Filte @ Stop button
@ Dolby FM switch @ Playback button
Output level contro @ Rewind button
© VU meters @ Remote control jack
Peak-signal check button @) Dolby FM de-emphasis switch
@ Input source selector @) Tuner input jacks
@ Power switch @ Line input jacks
@ Headphones jack @ Record/playback connection socket
Microphone jacks @ Line output jacks
4) Recording balance control Voltage select switch
@) Ground terminal

DISASSEMBLY INSTRUCTIONS
HOW
TO
REMOVE
CASE
COVER,
BOTTOM
PANEL
AND
FRONT
PANEL
Procedure | How to remove-—— | Remove——. PCS.
1 Case cover (A) (4)
2 Bottom panel (B) (11)
3 | Front panel ©,©.© | ©.@, 2)
HOW TO REMOVE FRONT ANGLE AND CASSETTE COVER
Procedure | How to remove-—— -| Remove-—— Pcs. Remarks
1
|
Front
angle
©
(7)
In
this,
condition,
front
angle
car
be
tilted
2
Front
angle
(G)
(2)
in
this
condition,
front
angle
can
be
removed from chassis.
3 Cassette cover (H) (4) ;
NOTE:
Before
tilting
front
angle
(procedure
1),
remove
counter
belt
from
connection
pulley
and
hang
it
on
the
arrow position in
fig.
4.

HOW
TO
REMOVE
JACK
BASE
PLATE
AND
PRINTED
CIRCUIT
BOARD
(AMP
&
CONTROL)
Procedure How to remove—— Remove——
| Pcs.
1 Jack base plate O.O.® | ©.0.@
2
Printed
circuit
board
(CONTROL)
(L)
eee
ee ee
3 Printed circuit board (AMP) — wm | © (6)
HOW TO REMOVE HEAD COVER
1.
Pushing
the
head
cover
as
shown
in
Tig.
7,
and
lift
it
up
as
shown
in
fig.
8.
2. Then head cover can be removed.

ADJUSTMENTS
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 stablized
value measured after “Warming up”. :
4. Specifications of Test Instruments.
(1) Audio Frequency Oscillator
a. Oscillation Frequency
5 Hz~500 kHz (5 ranges)
b. Frequency Tolerance
+(3% +1 Hz)
c. Sine Wave
* Output Voltage 5 Vrms+10% (open)
(at 25°C) 2.5 Vrms +10% (600Q load) f
* Output Frequency Response Within +0.2dB 20Hz~20 kHz
Within +0.5dB 5Hz~500 kHz
* Distortion Factor Not more than 0.05% 200 Hz~20 kHz
Not more than 0.5% 5Hz, 500 kHz
* Output Impedance 600Q Unbalanced Within +15%
* Output Attenuator 0,20dB Error: Within +0.2 cB
d. Temperature in Use of Set
Temperature=O0~40°C: Humidity=90% or less
(2) Automatic-spot Distortion Meter (with Vacuum Tube Voltmeter)

A. Distortion Factor Measurement
a. Frequency (Fundamental wave)
b. Measurement
c. Input
d. Fundamental Wave Attenuation
B. Level Measurement
a. Measurement
b. Frequency Response (1 kHz basis)
c. Input Impedance
d. Error in Indicated Value
C. Output Terminal
a. Frequency Response
b. Output Voltage
(3
Ww
Attenuator
400 Hz 1 kKHZz+10%
0.1~100% (6 range)
50mV~50V
— 60 dB or more
1 mV (—60 dB) ~30 V (30 cB) 9 range
20 Hz~100 kHz+0.3 dB
1MQ+10% Less than 50 pF
With in +3% at 1 kHz
10 Hz~100 kHz+1 dB
100 kHz~1 MHz+3 cB
1 Vrms+10 % (1 KHz Sine Wave)
a. Input Impedance
b. Maximum Attenuation
c. Minimum Attenuation
(4) Oscilloscope
Ba
600Q Unbalanced
“121 dB
0.1 dB

a.
Cathode
Ray
Tube
Effective
Range
8x
8cm
b. Vertical Axis
e
Input
Sensitivity:
30
mV~30
V/cm
e
Frequency
Band:
DC~2
MHz
e Transient Time: 180 ns
«
Input
Impedance:
TMQ,
35
pF
c. Horizontal Axis
«
Tuning
Range:
30
Hz~2
MHz
«
Sweep
Time:
lus~100
ms/cm
°
External
Sweep:
1
Vp-p/cm
or
more
(5) Digital Electronic Counter
a. Number of Figures: 4 (decimal system)
b. Inout Sensitivity: 100 mV rms
c. Input Impedance: 1 MQ, 40 pF
d. Frequency Measurement Range: 10 Hz~100 kHz
e. Counting Time: 0.1,1,10s
(6) Wow Meter

. Measured Center Frequency Range: 3 kHZz+4%
a
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:
Conforming
to
Weighting
Curve
Characteristic
(WRMS),
JIS
C5551.
Flat Characterstic (RMS)
0.5~200 Hz, Within —3 dB (4 Hz basis)
. Meter Indication System: Effective Value Indication, conforming to JIS C5551
g
h. Meter Response Characteristic: About 5~7 sec.
i. Oscillation Frequency: 3 Frequencies (3 kHz, 3 kHz+3%)
j. Temperatur Range: O~40°C ;
lH. MEASUREMENT CONDITIONS
1. Standard Measurement Conditions
* Ambient Temperature: 10°~30°C (50°~86°F)
* Ambient Humidity : 30~90% RH
* Power Voltage: Rated Voltage=120 V+5%
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 contro! knob for 1 V
(f=1 kHz) through the attenuator while keeping the attenuator at O aB.
* When supplying a signal to the tape recorder amplifier, adjust the input level using the attenuator.
Connection of Test Equipments.
Oscilloscope
é
ae
oo
.
a
‘
f
?
‘
Attenuator
=
#
Vacuum
Tube
Audio
Frequency
j
f
Voltmeter
~
Oscillator
.
é
f=1kHz Output Voltage=1 V (0 dB)

Il. TEST TAPE
«x 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
become
unreliable.
Even
in
such
a
case
where
a
tape
is
not
used,
but
stored,
for
a
Jong
period
of
time,
the
tape
shows
deterioration
in
performance
because
of
self
demagnet-
ization
due
to
storage
conditions,
etc.
Please
refer
to
the
tape
life
specification
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.
3% Test Tape
PARTS
NO.
PARTS
NAME
SPECIFICATIONS
REMARKS
5 TIMES REPETITIVE RECORDING
TAPE SPEED:
1-7/8 IPS (4.8CM/S),
FULL TRACK (10 MIN.)
STANDARD REC.
LEVEL & FREQ.
RESPONSE TAPE
0 dB: STANDARD REC ‘LEVEL (160 PWb/mm)
FULL TRACK (45 MIN.)
-10 dB
eee
pe
3
kHz
TAPE
SPEED:
1-7/8 IPS (4.8 CM/S).
0 dB: 250P Wb/mm)
em
FULL TRACK (15 MIN.)
AZIMUTH
TAPE
6.3
kH
TAPE
SPEED:
;
z
1-7/8
IPS
(4.8
CM/S).
0 dB: 250PWb/mm
REFERENCE BLANK
TAPE
NORMAL
UNRECORDED
TAPE
(20
MIN.)
REFERENCE BLANK
TAPE
CrOz
UNRECORDED
TAPE
(20
MIN.)

iV. MEASUREMENT & ADJUSTMENT METHOD
NOTE:
1. Make sure heads are clean.
2. Make sure capstan and pressure roller are clean.
3. Judgeable room temperature: 20+5°C (68+9°F)
4.
Source Selector:
ITEM
LINE IN 8. Dolby FM Switch: OUT
MEASUREMENT & ADJUSTMENT
5. Output Level Control: MAX.
6. Tape Select Switch: NORMAL
7. Dolby NR/MPX Filter Switch: OUT
REMARKS
Pressure of Pressure Roller
Equipment:
* Cassette Type Tension
Gauge (max. 500 gr)
\
Q
1. Place UNIT into playback mode.
2. Hook tension gauge to pressure roller shaft top (A), and
pull gauge in direction opposite to pressure of pressure
roller against capstan (See fig. 10).
3. Read pressure indicated on gauge immediately when pres-
sure roller moves away from capstan and stops rotating.
Standard Value: 400+50 gr
Adjustment method
Adjust by bending the (B) part of the pressure roller spring
(See fig. 10).
* Playback Mode
Takeup Tension
Equipment:
* Cassette Torque Meter
(RP-8063N)
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+15 gr-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. 11).
Plate Spring
Fig. 11
Head Azimuth Adjustment
Equipments:
* VTVM
* Oscilloscope -
* Test Tape (Azimuth)
.C-AA
«x Tape Path Viewer
. RT-8133
Record/playback head adjustment
1. Test equipments connection is shown below.
LINE OUT
(av)
(Test Tape) (Playback Mode)
Fig. 12
2. Play azimuth tape (C-AA 6.3 kHz).
3. Adjust record/playback head angle adjustment screw (C).
in fig. 13 so that output level at LINE OUT becomes maxi-
mum. ;
4. Measure both channels, and the level difference between
channels shoud be minimised by adjusting.
5. After adjustment lock head adjustment screw with lacquer.
(Oscilloscope)
Erase head adjustment
1. Test equipments connection is the same above but use the
tape path viewer (RT-8133) in stead of test tape (C-AA).
2. Play this tape.
3. Adjust screw (D) shown in fig. 14 so that the tape may
not get curled or malformed by tape guide of the erase
head.
4. After adjustment lock head adjust screw with lacquer.
* Playback Mode
Fig. 13
Erase Head