Akai 1730-SS User manual

ee
se
iy
ST
Se
ches
90
ree
ox
at
Fae
ens
is
scope
Deeaegnet
ag
Eman
See
ee
ay
Sera
Boies

Zee
xxR Sg <
TABLE OF CONTENTS
SPECIFICATIONS ..0ins cede eg ieee pKa eee wees 2
MEASURING METHODS ................00.-0000- 3
CONTROL LOCATIONS .... 20.0.2... eee eee eee 5
DISMANTLING OF TAPE TRANSPORT UNIT
6c AMPLIPIERS 202s ae oes eae deed sone ee coed darade 6
TRANSPORT MECHANISM ........00...0..2-02000- 8
MECHANISM ADJUSTMENT ............-2..0200005 12
AMPLIFIER ADJUSTMENT ..............2-.-00055 14
MAINTENANCE PROCEDURES ..............2005. 16
TROUBLE SHOOTING CHART ................... 17
COMPOSITE VIEWS OF COMPONENTS ............. 22
SCHEMATIC DIAGRAM
When placing order for parts, please use Separate
PARTS LIST or PRICE LIST FOR PARTS.

I. SPECIFICATIONS
WEIGHT
DIMENSIONS
37.5 Ibs. (17.0 kg)
18"(H) x 16.5’°(W) x 9.5'(D)
(H450 x W420 x D240 mm)
POWER SUPPLY 100 to 240 V AC, 50/60 Hz
RECORDING
SYSTEM In-line 4-track 4-channel stereo and
4-track 2-channel stereo recording
PLAYBACK
SYSTEM In-line 4-track 4-channel stereo and
4-track 2-channel stereo playback
POWER CON-
SUMPTION 80 W (Deck 55 W)
TAPE SPEED 3-3/4, 7-1/2 ips.
TAPE SPEED
DEVIATION Within +1.5% at all speeds.
WOW AND
FLUTTER Less than 0.15% R.M.S. at 7-1/2”
Less than 0.2% R.M.S. at 3-3/4"
FREQUENCY
RESPONSE 30 to 22,000 Hz +3 dB at 7-1/2”
40 to 13,000 Hz +3 dB at 3-3/4”
SIGNAL TO NOISE
RATIO More than 48 dB
DISTORTION (Total
Harmonics) Within 2% at 1,000 Hz OVU
recording (LINE OUTPUT)
Within 3% at 1,000 Hz 5 W (when
terminated with 82) (MAIN OUTPUT)
CROSS-TALK Less than —SO dB (track)
Less than —40 dB (channel)
ERASE RATIO Less than 70 dB
INSULATION
RESISTANCE More than 50 MQ
INSULATION
DURABILITY 1,000 V AC for more than one minute
duration
LINE OUTPUT +4 dB 41.5 dB (1.228 V), at OVU indi-
cation, 250 Hz OVU recorded tape
Required load impedance more than
25K
More than 5 W
Impedance ; 8 2
—6 dB +1.5dB when using a 250 Hz
recorded tape
POWER OUTPUT
DIN OUTPUT
Required load impedance more than
50 KQ
Above 40 mV
Impedance ; 330 KQ
Above 0.4 mV
Impedance ; 30 KQ
Above 20 mV
Impedance ; 100 KQ
LINE INPUT
MIC. INPUT
DIN INPUT
FAST FORWARD &
REWIND TIME
MONITOR SYSTEM
(recording)
MOTOR
HEADS
RECORDING
HEAD
PLAYBACK
HEAD
ERASE HEAD
ERASE HEAD
TRANSITORS &
IC USED
DIODES
REELS
90 seconds 1,200 ft. tape at 50 Hz
70 seconds 1,200 ft. tape at 60 Hz
With Record/Play back Switch at “REC”
The program being recorded can be
monitored by using :
built-in speakers
stereo headphones
external speakers
crystal receiver
Hysteresis synchronous 2 speed motor
Horse Power: 1/100 HP
Power Ratio: 85%
Revolutions : 3,000 to 1,500 R.P.M.
at 50 Hz
3,600 to 1,800 R.P.M.
at 60 Hz
Condenser capacity : 3 uF at 50 Hz
2 pF at 60 Hz
In-line 4-track 4-channel stereo (4-track
2-channel stereo)
Impedance : 125 420% at 1,000 Hz
Gap: 4/1,000 mm
In-line 4-track 4-channel stereo (4-track
2-channel stereo)
Impedance : 1,200 2 +15% at 1,000 Hz
Gap : 2/1,000 mm
In-line 4-track 2-channel stereo
Impedance: 195 2 +10% at 100 KHz
In-line Full track
Impedance : 350 2 +10% at 100 KHz
2SC458LG (C) x 4 | apCURDING
28C871 (E,F) x4 | AMPLIFIER
LD-3141 x 4 }
2SC458LG (C) x 8| PLAYBACK
LD-3141 x 4 | AMPLIFIER
STK-011(A) x2 MAIN AMPLIFIER
2SC971 (2,3) (RED) x2 BIAS OSC.
2SD223 (Y)x 1 POWER AMP.
IN34A x4
VO6B x 4
10DC-1 (BLACK) x 1
RD-24A (M) x 1
7'', 5" reels can be used.

lil. MEASURING METHOD
TAPE SPEED DEVIATION
1. Method involving use of pre-recorded tape
Playback a tape pre-recorded at 1000 Hz (+0.1%) on
recorder to be tested. Connect the appropriate
output to a frequency counter meter in order to
measure the tape speed deviation.
2. Method involving use of timing tape. (designed for
tape speed measurement)
This method utilizes a timing tape marked at
intervals of 7-1/2". The running time of over 60
marked sections of tape is measured in order to
calculate the deviation of the tape speed. In
applying this method, however, it should be kept in
mind that timing tape stretch or contract measure-
ment error is inevitable, so that it is necessary to
measure the total length of the tape in advance.
WOW AND FLUTTER
Playback a 3,000 Hz pre-recorded tape, of which the
wow and flutter level is guaranteed to be smaller than
0.07%, and measure with a wow meter. It is also possible
for a 3,000 Hz sine wave to be recorded and played back
for measurement with a wow meter. In this case,
however, the wow meter will indicate a value as much as
twice that given in the specifications.
SIGNAL TO NOISE RATIO
1730-SS
ae = atv
Set the Equalizer Switch to the “7-1/2 ips” position and
playback a tape containing a 250 Hz sine wave recorded
at “Q’ VU level on a standard recorder. Connect a
V.T.V.M. to the line output jack of the recorder and
measure its output. Next, remove the tape and measure
the noise level under the same conditions. Convert each
of the measured values into decibels.
TOTAL HARMONIC DISTORTION FACTOR
1 KHz
Audio 1730-SS Distortion
Oscillator meter
Connect the measuring instruments as shown above, and
record a 1,000 Hz sine wave at “0” VU. Playback the
resultant signal and measure the overall distortion factor.
Measure the noise level of the tape recorder with the
tape removed ; connect the audio oscillator directly to
the distortion meter for measurement of the distortion
factor of the oscillator.
The resultant distortion factor can be obtained from the
results of the above measurement by using the following
formula :
do = d—d, —d2
where, do = Required
d = Overall distortion factor
d,; = Noise level
d2 = Distortion factor of the oscillator
(Note : New tape of particularly good quality should be
used for measurement of the distortion factor. Fuji L is
recommended).
POWER OUTPUT
Playback a tape containing a sine wave of 250 Hz
recorded at “0” VU ona standard recorder.
Measure
the
Voltage
at
the
output
of
the
recorderto
be
tested
when
terminated
with
8
Q..
Then use the following formula :
By P = Desired output (W)
P= E = Measured Voltage (R.M.S.)
R=8Q2

CROSS TALK
1. Between the tracks (2 Channel)
(TAPE)
ZENG
BKC
Tape direction
As shown in the figure, first record a 1,000 Hz sine wave
on track No.3 at +3 VU level. Next, remove the
1,000 Hz input signal and record under a non-input
condition. Then, playback the tape on tracks 3 and 1
(reversed condition of tape) through the 1,000 Hz B.P.F.
(Band Pass Filter, Sensitivity ... 1: 1) and obtain the
ratio between the two by using the following formula.
C = 20 log? (AB)
2°c= 1
C= Desired cross talk ratio (dB)
Eo = 1,000 Hz signal output level BES
E2 = 1,000 Hz cross talk output level
E, = Non-input signal record level CERRY
2. Between the channels (4 Channel)
Tape direction ©)
As shown in the figure, first record a 1,000 Hz sine wave
on track No.1 at +3 VU level. Next, remove the
1,000 Hz input signal and record under a non-input
condition.
Then, playback the tape on track No.1 and No. 2
through the 1,000 Hz B.P.F. (Band Pass Filter, Sensiti-
vity ... 1:1) and obtain a ratio between the two from
the following formula.
E
C = 20 log = (dB)
2 I
C= Desired cross-talk ratio (dB)
Eo = 1,000 Hz signal output level fest |
E, = 1,000 Hz cross-talk output level CLA
E, = No-input signal record level RES
Tape direction
FREQUENCY RESPONSE
Audio 1730-SS
Oscillator Input Output
Connect the measuring instruments as shown in the
above diagram, and measure the frequency response in
the following sequence :
RECORD :
1) Introduce a sine wave of 1,000 Hz to the Line Input
of the recorder being tested through an attenuator
from an audio frequency generator.
2) Set the Record/Playback Lever to ‘‘Rec” position
and adjust the line input volume so that the VU
meter needle indicates “0” VU.
3) Under the conditions described in (2), lower the
input level 20 dB with the attenuator.
4) Record the spot frequency from the audio fre-
quency generator in the range of 30 to 23,000 Hz.
PLAYBACK :
5) Set the Record/Playback Lever to “Play” position.
6) Connect a V.T.V.M. to the Line Output.
7) Playback the previously recorded tape.
8) Adjust the output level to “0” dBm at 1,000 Hz
(indicated on range selector of V.T.V.M.).
9) Playback the recorded spot frequencies under the
conditions in (8); make a memo of Output Level
and plot the value ona graph.
(Note : New tape of particularly good quality should be
used for measurement of the frequency response. Fuji F
tape is recommended).
In case of trouble, etc. necessitating disassembly, pleas
disassemble in the order shown in photographs. Reas-
semble in reverse order.

lil. CONTROL LOCATIONS
RESET BUTTON
INDEX COUNTER
TAKE-UP REEL TABLE
REEL RETAINER
——~~— AUTOMATIC SHUT-OFF LEVER
PLAY/RECORD LEVER
~—-REWIND/FAST FORWARD LEVER
PAUSE LEVER
SUPPLY REEL TABLE
REEL RETAINER
PINCH WHEEL
CAPSTAN
CYCLE CONVERSION SWITCH {A}
HEAD COVER
HEADPHONE JACK ‘Front?
HEADPHONE ‘JACK ‘Rear’
RECORD SAFETY BUTTON
VU METER (Right)
VU METER (Left}
TAPE SPEED SELECTOR
RECORDING LEVEL CONTROL (Left)
RECORDING LEVEL CONTROL(Right)
MICROPHONE JACK (Left)
MICROPHONE JACK (Right)
MONITOR SWITCHES
AUTOMATIC SHUT-OFF SWITCH
POWER SWITCH
RECORDING LEVEL CONTROL {Left}
RECORDING LEVEL CONTROL (Right)
SPEAKER VOLUME CONTROL
STEREO SELECTOR
MICROPHONE JACK (Right)
MICROPHONE JACK (Left)
VU METER [Right)
VU METER (Left)
AC CORD
VOLTAGE SELECTOR PLUG
FUSE POST
CYCLE CONVERSION SWITCH (B)
SPEAKER SWITCH
LINE OUTPUT JACK (Right)
DIN JACK (Front)
LINE OUTPUT JACK (Left)
LINE INPUT JACK (Left)
LINE INPUT JACK (Right)
SPEAKER JACKS (Left. Right)
LINE OUTPUT JACK (Left)
LINE OUTPUT JACK (Right)
LINE INPUT JACK (Right)
DIN JACK (Rear!
LINE INPUT JACK (Left)

IV. DISMANTLING OF TAPE TRANSPORT
UNIT & AMPLIFIERS
In case of trouble, etc, necessitating disassembly, please
disassemble in the order shown in photographs. Reas-
semble in reverse order.
EAY, REC.-LE'
Le RWOMLEVER >
"MECH.
AMP. BLOCK
| CASE BLOCK

(ei)
4
we) WI)
£
12
RETAINING PLATE

V. TRANSPORT MECHANISM
Fig. 1
Braked Rotation
1. CAPSTAN DRIVE
Figure 1.
(A) Motor
(B) Drive Belt (flat belt)
(C) Capstan
(D) Flywheei
High-speed rotation of Motor (A) is transmitted by Drive
Belt (B) to Capstan (C); which is connected to a
flywheel that provides necessary inertia. This flywheel
maintains the rated rotation and absorbs minor rotation
variations of the motor.
Capstan Rotation :
606 R.P.M. at 7-1/2” (19 cm) per sec.
303 R.P.M. at 3-3/4” (9.5 cm) per sec.
151.5 R.P.M. at 1-7/8" (4.75 cm) per sec.
Motor Rotation :
3,000 to 1,500 R.P.M. at 50 Hz
3,600 to 1,800 R.P.M. at 60 Hz
2. PINCH WHEEL DRIVE
The pressure of the pinch wheel as it pushes against
capstan, transports tape between rotating capstan and
pinch wheel at the rated speed. The proper pinch wheel
pressure is between 1,000 to 1,150 grams at the tape
speed of 7-1/2’ (19 cm) per second.
3. RECORD AND PLAYBACK MECHANISM
Turning the RECORD/PLAYBACK LEVER (A) to
“PLAY” position causes the pinch wheel to press against
the capstan and move the tape at the rated speed. At the
same time, Idler (B) moves between Motor Bushing (C)
and the Take-Up Reel Spindle (D) to transmit the motor
rotation to (D) so that the tape is moved and wound on
the take-up reel. The Take-up Reel Spindle Base,
composed of two plastic wheels (discs) (1 and 2) witha
felt clutch between, is rotated from below by the idler.
Tape-winding friction is adjusted by the slipping of the
felt and maintains rated winding of the tape. The Supply
Reel Spindle (H) hasa Brake Roller (E) contacting plastic
wheel (disc) (4) from below which provides appropriate
back tension by the slipping of the felt clutch to the
rotation of the Pulley (3) above. To prevent accidental
erasure, the Record Safety Button (F) must be depressed
before the RECORD/PLAYBACK LEVER can _ be
moved to the “REC” position. Safety device (G) is
depressed to operate the recording mechanism.
(See figure 2)

4. FAST-FORWARD MECHANISM
Turning the FAST FWD-REWIND LEVER (A) to
“FAST FWD” position, causes cam (B) under the knob
to push up Lever (C). Idler (D) moves into the space
between Plastic Roller (F) above the Take-Up Reel
Spindle and the upper part of the rotating motor drive
bushing to transmit the motor rotation to the take-up
reel spindle. At the same time, Brake Rollers (H) and (I)
come off the reel spindle to free Supply Reel Spindles
(G) and (F), thereby allowing fast winding of the tape
onto the take-up reel.
(See figure 3)
5. REWIND MECHANISM
nee
Turning
the
FAST
FWD-REWIND
knob
(A)
to
“REWIND” position, causes cam (B) under the knob to
push up Lever (C). Idler (D) moves into the space
between the upper part of the rotating Motor drive
bushing (E) and the Intermediate Pulley (F) to transmit
the high-speed rotation of the motor through the
intermediate pulley to Supply Reel Spindle (G). At the
same time, Brake Rollers (H) and (I) come off the reel
spindle to free take-up reel spindles (J) and (G), thereby
rewinding the tape onto the supply reel at a fast speed.
(See figure 4)
6. STOP CONTROL
Turning the stop lever to “STOP” position, causes Brake
Rollers (A) and (B) to depress the reel spindles andstop
rotation.
ie ~P take-up Reel Sendie’
Ba
ier
Ax
/F7w
°
As
the
brake
rubbers
depress
the
plastic
rollers
below
the
a
‘
reel
spindles,
no
friction
is
applied
to
the
tape.
(See figure 5)
=
Pinch | ake-up | Rewind | Take-up | Swp ly
Modes
of
Operation
Wheel
Idler
Idler
side
ide
Wheel Wheel Brake Buk €
=
aie
STOP
x
x
£
Guide
Roller
caemas
‘
:
:
a
t + t +
(b)
FAST-FOR
WARD
x
oO
x
x
if
{c)
REWIND
x
x
a
x
i
+ +
RECORDING os O
‘)
PLAYBACK
cs
.
x
*
L i —
NOTES : X-marks indicates “open” and
“)-marks “engaged”

TR40!
280223 (Y)
TO OSC. J20 P20
7. RECORD/PLAYBACK CHANGING
MECHANISM
When the Rec/Playback Lever is switched from playback
to recording position, the driving rotary switch is set to
recording mode and voltage is applied to the recording
amp as well as to the transmitting circuit.

8. 4¢CHANNEL SURROUND STEREO SYSTEM
(1) Head Construction
| ‘
Recording / Playback Head
(4CH) (2CH)
Ch | —»> | FRONT LEFT LEFT
ane So aoa rece
Ch 2 —» | REAR LEFT
Ch 3 —> | FRONT RIGHT = RIGHT
ch 4 A] —> | REAR RIGHT
(2) ORDER OF HEADS
UU UU
Full Tr/4-Ch 4-Tr/2-Ch 4-Tr/4-Ch 4-Tr/4-Ch
ERASE ERASE RECORDING PLAYBACK
(3) BLOCK DIAGRAM WHEN SWITCHED
FROM 2-CH TO 4-CH
1. During 2-Ch operation, the internal main amp serves
tracks ] and 3.
2. When switched to 4-Ch operation, the internal main
amp is connected to serve channels 2 and 4 (Left
Rear and Right Rear).
3. During 4-Ch operation, it is necessary for the
external main amp to be connected for Front
Channel operation (tracks 1 and 3).
EXTERNAL SPEAKER
PRE-AMP MAIN AMP
a1 =°3 (rom er
INTERNAL
— aN AMP
~~ ©
| ourrur os "3 C REAR LEFT
Ee = we rg iv (2Ch LEFT)
| | sweor
4ch
°3 C] ror
LO ————
+ [ap +--+ ee ae
6 on (2.Ch RIGHT)
Ch3
1]

VI. MECHANISM ADJUSTMENT
1. PINCH WHEEL ADJUSTMENT
It is important that the pinch wheel shaft be kept in
perfect alignment with the capstan shaft. Proper pinch
wheel pressure is between 1,000 and 1,150 grams when
the unit is operated at the tape speed of 7-1/2 ips. Any
deviation will result in wow and flutter. Check pinch
wheel pressure with a spring scale, and if necessary,
adjust the pinch wheel load spring.
2. TAKE-UP IDLER WHEEL ADJUSTMENT
The take-up idler wheel must be kept in perfect
alignment with the take-up reel shaft. In fast forward
operation, the idler wheel contacts the upper knurled
wheel of the take-up reel shaft assembly, and conversely
contacts the lower knurled wheel during record or play
operation. Adjust idler wheel load spring so that the
idler wheel pressure is kept between 50 and 80 grams.
The idler wheel wears rapidly if the pressure is excessive.
Slippage occurs if the pressure is less than specified.
Sit ings cece
reel shaft ring -——— ~~
reel spring ~—
reel retainer
i
3R O ring
mibber plate, reel table - -~
reel shaft B
reel table B, w/shaft A~-@
rubber ring
ss take-up roller A
rewind drive putley-———
spring G-2—~
})—~-—- take-up roller D
Reel
table
spring
plate
A
———aS
72
washer ——————~<25>
thrust washer
washer —
reel
table
thrust
retaining
pin
———~ES>
washer ————--—-->
washer
aD
i
Cz ae
XR
reel
bearing
plate
———
So
washer —— |
“ES ring -——_——--.—
spring
F-4
—-—--
-.
F
ft -—_—— washer
washer
BAY
a
reel
table
spring
plate
C
€————___washer
= —- retaining pin
set sleeve B — == - i
ae)
Set
Serewen-—
+
ge
;
reel
table
pultey
i
|
{
Be
wh
screw
Fig. 1
3. REWIND IDLER WHEEL ADJUSTMENT
The rewind idler wheel must be kept in perfect alignment
with the rewind reel shaft. The amount of pressure on
the knurled motor bushing should be about 50 grams
during rewind operation. Adjust both the idler load
spring and rewind roller.
4. INTERMEDIATE WHEEL ADJUSTMENT
The intermediate wheel is located between the rewind
idler wheel and the rubber ring which is used on the
upper part of the supply reel shaft assembly. In rewind
mode, it contacts these parts while simultaneously
transmitting motor torque. An adequate pressure is 50
grams. Adjust the load spring of the intermediate wheel
if the pressure is not sufficient.
5. TAKE-UP REEL SHAFT ASSEMBLY
ADJUSTMENT
A felt clutch is attached to the bottom side of the reel
table base plate so that recording tape will not stretch
due to excessive tension during fast forward operation.
To check the amount of friction on this part, install a
5-inch ree] with a 60 mm diameter tape and gently pull
the end of the tape upward with a spring scale. Adjust
the conical spring so that the amount of tension on this
part is between 350 to 450 grams. Another felt clutch is
attached to the take-up drive wheel to provide proper
slippage during record or play mode. The procedure for
checking friction of this part is the same as the foregoing,
and between 150 and 200 grams of friction provides the
best results. Adjust the star-shaped spring just under the
take-up drive wheel. During rewind operation, the
amount of friction of this part will decrease to 10 to 15
grams. Check to see whether this is satisfactory. If not,
readjust the star-shaped brake spring and the pressure of
the spring retainer washer accordingly.
6. SUPPLY REEL SHAFT ASSEMBLY
ADJUSTMENT
A felt clutch is used between the lower side of the reel
table base plate and the rewind rubber ring to protect
the recording tape from excessive tension during record-
ing. To check the amount of friction on this part, install
a 5-inch reel with a 60 mm diameter tape, and gently
pull the end of tape upward with a spring scale. Adjust
the conical spring so the tension is between 350 and 450
grams. Another felt clutch is attached to the rewind
drive wheel to provide proper slipping operation during
record or play mode. The procedure for checking
friction on this part is the same as the foregoing, and
between 110 and 130 grams of friction gives best results.
In fast forward operation, the amount of friction will
decrease to 10 to 15 grams.
Check to see whether this is correct. If not, readjust coil
spring and spring retainer washer. (See figure 1 (a) at
left).
re py
12

(oral
|
SAME WIDTH
y oll
(ABOUT
0.4
mm)
Li
es
7. HEAD ADJUSTMENT
(A) Adjustment of Head Height (See Fig. 2 and 3)
a.
Erase Head (2-Ch)
Adjust the Erase Head Height by turning head
height screws (a) (a’) so that the upper edge of
the tape as it passes the erase head is 0 (—0,
+0.1) mm top edge of the CH-1 erase head core.
Erase Head (4-Ch)
With height control screws (b) (b’), adjust so
that the width of the head protruding from
both sides of the tape is exactly the same
(about 0.4 mm at both top and bottom).
Recording Head
With height control screws (c) (c’), adjust so
that the width between the upper edge of track
1 head core and the upper edge of the tape is
equal to the width between the lower edge of
track 4 head core and the lower edge of the
tape (about 0.5 mm).
Playback Head
With height control screws (d) (d’), adjust so
that the width between the upper edge of track
1 head core and the upper edge of the tape is
0 (-0,+0.1) mm
d’
Fig. 2
SAME
WIDTH
(ABOUT
0.05mm)
Fig. 3
equal to the width between the lower edge of
track 4 head core and th lower edge of the
tape (about 0.05 mm).
(B) Adjustment of Vertical Azimuth of the Head
Adjust the vertical azimuth of each head (Record
and playback) by turning head height screws (¢) (c’)
and (d) (d’) until the tape comes in conplete
contact with each head.
(C) Adjustment of Head Alignment
a.
Playback Head
Playback an Ampex Alignment tape (8,00) Hz)
at 3-3/4 ips and turn alignment control screw
(f) until the output level of both channels
reaches maximum.
Recording Head
At recording position, supply a 8,000 H: sine
wave at a —10dB recording level fron an
Audio Frequency Oscillator to the Line In put
of the 1730-SS, and set the SOURCE/IAPE
Monitor Switch to “TAPE” position.
Then turn alignment control screw unt! the
out-put level of both channels reaches maxinuim.

Vil. AMPLIFIER ADJUSTMENT
<i Oscillator Circuit
Recording Head
O ©
OSCILLOSCOPE
AUDIO
FREQUENCY
OSCILLATOR
Fig. 1
ROTARY SWITCH
° ©@EQOLEe --__3-—_--
»
<
<4
<
=
——-4
}
=SmS 5
bene]
450Px4
L501
1502
1503
L504
5.6mH*4
(J)
~ L 505 ‘
2 =>, 8 STS TST c505 OT-204 2eeon (oS H
R.R. HA Oo (S] oO
as te
REC ; 7
hean 7 So Ea
F.R FI Ay,
— 4
L
Feb
a5
2
ERASE | 27CH ys 3
HEAD
~~
'
L4-CH . :
a,
2S¢971(2.3)
BIAS OSCILLATOR 5
1. RECORDING BIAS FREQUENCY 2. RECORDING BIAS VOLTAGE
ADJUSTMENT (Fig. 1) ADJUSTMENT (Fig. 2)
a. Install a resistor of 10 or 50 Ohms in series with the Connect a V.T.V.M. to point (A) to (D) and adjust the
Recording Head and connect the Vertical Input recording bias voltage by turning Variable Capacitor
Terminal of the Oscilloscope to points (a) and (b). C505, 6, 7, 8 (50 to 70 PF) until it reads between AC 15
b. Feed ina sine wave signal from an Audio Frequency and 20 Volts. (The voltage of tracks 3-2 should be very
Oscillator to the Horizontal Input of the Oscil- slightly higher than that of tracks 1-4).
loscope and tune the Dial of the Audio Frequency Note: There is no way of adjusting the erasing bias
Oscillator until the Oscilloscope displays a circular voltage, but the correct bias voltage is between AC
or linear pattern. 63 and 66 Volts.
c. <A reading of 100 KHz +5 KHz (4-Ch operation),
indicates that the Recording Bias Frequency is
correct.
d. If incorrect, it can be adjusted by inserting another
condenser (C509) value 5600PF.
14

LINE OUT
Fig. 3
RIO74.7K
tw
C107 10/16
C213 10/16
a LINE OUT
8 bs —_
iC-201 ES
LD-314I '
Cc
ian 10/725
9 8 t
ic-liol = & My
LD-3141 | Fz
REC LEVEL 1ORA
CONTROL
y.
7,
MONITOR
SW2
Fig. 4
3. ADJUSTMENT OF LINE OUTPUT LEVEL
1. Playback (See Fig. 3) Tape 2. Recording and Playback (See Fig. 4)
a. Set the Source/Tape Monitor Switch to “TAPE” a. Connect V.T.V.M. to the Line Output Jack.
position. b. Set the Source/Tape Monitor Switch to
b. Connect a V.T.V.M. (use one with Milli-Volt “SOURCE” position.
scale) to the Line Output Jack. c. Load a Scotch-150 blank tape and set the
c. Playback a test tape (250 Hz “0” VU recorded) Record/Playback Knob to recording position.
at 7-1/2 ips. tape speed and turn the volume d. Feed in a 1,000 Hz sine wave signal from an
VR-201 (10 KB) until the Line Output level Audio Frequency Oscillator to the Line Input
reaches “0” VU 1.228 V (+4 dB). of the 1730-SS and turn the Recording Level
Volume Control VR1 to 4 (10 KA) unti the
Line Output Level reaches “O” VU 1.228 V
(+4 dB).
e. Set the Source/Tape Monitor Switck to
“TAPE” position and turn the Recording level
Volume Control VR1 to 4 (10 KA) again antil
the Line Output Level reaches “O” VU.
f. Set the Source/Tape Monitor Switch to
“SOURCE” position again and turn the
Volume Control VR-101 (2 KB) until the Line
Output Level reaches “0” VU.
g. Repeat twice in the same way as indicaticl in
items e. and f. above.

VII. MAINTENANCE PROCEDURE
i
ie
FLYWHEEL @ | drop MOTOR
1. LUBRICATION INSTRUCTIONS
For maximum service life and optimum performance,
lubricate the following parts after each 500 hours of
operation. Use only light machine oil of good quality.
Motor
Flywheel Assembly
Rewind Idler Whee! and Wind Take-Up Idler 1 drop
Intermediate Idler 1 drop
Pinch Wheel 1 drop
Also apply a liberal film of light machine grease to
each roller surface of all levers and cams.
CAUTION: DO NOT OVER-LUBRICATE. WIPE OFF
EXCESS OIL WITH A COTTON SWAB SOAKED
IN ALCOHOL. OTHERWISE, EXCESS LUBRI-
CANT MAY BE SCATTERED DURING OPE-
RATION AND THE RUBBER COMPONENTS
WILLDETERIORATE.
2. CLEANING TAPE HEADS AND OTHER
PARTS
Wipe surface of tape heads, guide roller bearing, capstan
bushing and pinch wheel periodically with a soft cloth
soaked in alcohol.
16

IX.
TROUBLE
SHOOTING
CHART
SECTION “‘A’’ TROUBLE WITH AMPLIFIER
1. Playback Problems (unit set to play position)
Symptom
No sound from Line-Out jack
Trouble
(No B(+) voltage supply) 1. Silicon diode (1ODC—1 BLK) defective
2. R402 (18 Q 3 W) or TR401 (2SD223) defective
(B(+) voltage supply) 1. Check transistor TR201 and TR202
2. Check IC—201 (LD~3141)
3. Playback head coil open or lead wire loose.
No sound from speaker
(No B(+) voltage supply) 1. Silicon diode D401 ~ 404 (VO68) defective
2. Fuse (0.7 A) defective
3. Check source/Tape monitor switch
(B(+) voltage supply) 1. IC—301 (STK—011) defective
Sound, but volume insufficient
(B(+) voltage low) 1. Silicon diode D405 (10DC—1 BLK) defective
2. R402 (18 2 3 W) or TR401 (2SD223) defective
(B(+) voltage normal) Dirty head
2. Check transistor (TR—201, 202)
Loud hum
(Hum is decreased if playback
head is grounded)
(No change even when playback
3. Check IC—201 (LD—3141)
Playback head shield or insulation defective
. Ground wire loose
head is grounded) 2. C401, 402 (220/50) defective
Loud hum
(Inductive pick-up) Ground the recorder
2. Change the set position of the recorder
Irregular scratching or crackling noise 1. Transistor TR201, 202 defective
2. IC—201 (LD—3141) defective
3. Check playback card (LF—5022)
Squeaking noise Dirty head
2. Tape itself defective
Hissing noise
(Noise present when playing
1. Head is magnetized
tape) 2. Tape itself defective
(Not caused by tape’ 1. Transistor TR—201, 202 defective
Lack
of
treble
1.
Poor
contact
between
head
and
tape
(Dirty
head
or
back
tension
weak)
2. Head angle incorrect
3. Head worn-out
4. Tape itself defective
Sound distorted 1. Dirty head
2. Defective transistor TR—201, 202
3. Head worn out
17

Trouble
Symptom
Considerable difference between left and 1. Playback level out of adjustment
right levels during playback
2. Recording Problems (Unit plays back pre-recorded tapes satisfactorily but recording unsatisfactory).
Symptom Trouble
Does not record (4 ch or 2 ch)
(No VU meter indication) 1. VU meter itself or lead wire defective
2. Defective input jack
3. Transistor TR—101 defective
4. IC—101 (LD—3141) defective
(VU meter indication normal) 1. Rec/play chenge switch (SW 10) defective
2. Components of oscillator circuit or oscillator coil defective
Recording head defective
Sound distorted
(VU meters function normally. Recording 1. Faulty recording bias circuit
monitor through headphones also normal). 2. Fautly recording equalization circuit
Dirty head
(VU meter function normally, 1. Over-recording input
but recording monitor through headphones 2. Defective input equipment
abnormal) 3. Check recording amp card (LF—5023)
Fautly erasing (4 ch or 2 ch)
(Does not erase at all) 1. Erase head defective
2. Disconnected erase head wire. Excessive amount of dust adhering
to head surface
(Incomplete erasure) 1. Erasing bias voltage low
(TR-—501, 502 ; oscillator coil or Erase Head defective)
Erasing noise
(Popping noise) 1. Defective recording tape
2. Transistor TR-501, 502 defective
3. Head magnetized
Recording sensitivity low
(VU meter functions normally) 1. Dirty head
2. Bias voltage out of adjustment
3. Transistor TR—501, 502 defective
4. Tape itself defective
(UV meter does not indicater properly) 1. Loose input jack connection
2. VU meter sensitivity low
3. Recording level out of adjustment
Sound fades or drops out . Dust adhering to the head surface
. Tape itself dirty
Back tension too weak
Recording bias voltage too low
nA PWN . Head worn
_
Considerable difference between left and . Large deviation from line VR (RV1 ~4) curve
Tight levels when recording 2. Recording level out of adjustment
18

Symptom
Capstan does not rotate
SECTION ‘‘B"" TAPE TRANSPORT MECHANISM TROUBLES
Trouble
(Trouble with motor) 1. Broken field coil
2. Defective motor starting capacitor (C2)
3. Rotor shaft dragging due to lack of oil
4. Foreign matter between rotor and stator
(Trouble with power transmission 1. Broken copstan drive belt
mechanism) 2. Capstan drive belt off of driving position
3. Motor bushing slipping on motor shaft
4. Oil adhering to motor bushing and/or flywheel
Capstan rotates in stop position, but 1. Decreased motor torque
tape does not advance when switched to 2. Defective C2
play position. 3. Motor bushing slipping on motor shaft
(Trouble with motor)
Trouble with power transmission 1. Capstan drive belt stretched
mechanism 2. Oil adhering to motor bushing and/or flywheel
3. Capstan bushing slipping on flywheel shaft
4. Excessive tension in Take-up/Supply reel assembly
5. Oil adhering to capstan and/or pinch wheel
6. Insufficient pinch wheel pressure
Capstan advances tape, but take-up reel 1. Reel shaft dragging due to Lack of oil
does not take up tape 2. Take-up idler wheel does not operate properly
3. Oil adhering to ilder wheel and roller on take-up reel shaft assembly
4. Take-up idler wheel poor contact
Take-up function normal, but tape
speed slower than regular speed
(Trouble with motor) 1. Rotor shaft dragging due to lock of oil or defective motor starting
capacitor (C2)
(Fluctuation in power supply) 1. Check line voltage and cycle use voltage regulator if line voltage
is lower than standard
(Trouble with power transmission 1. Capstan drive belt stretched and slipping on motor bushing
mechanism) 2. Capstan drive belt not in correct driving position
3. Oil adhering to motor bushing and/or flywheel
Wow/Flutter (Irregular tape movement)
(Trouble with motor) . Decreased motor torque
2. Defective motor starting capacitor (C2)
(Trouble with power transmission 1. Take-up, supply reel shaft dragging or excessive tension
mechanism) 2. Capstan drive belt stretched and slipping
3. Unbalanced flywheel rotation
4. Rubber on pinch wheel deteriorated
5. Pinch wheel or tape guide does not rotate smoothly
6. Dirty head surfaces
7. Insufficient pinch wheel pressure
8. Capstan bushing slipping on flywheel shaft
9. Worn-out idler wheel or no oil
19