Dokorder 7700 User manual

DOKORDER
rnoder 77OO SERVICE MANUAL
sM, 1004-00
1977.3
sEcroN 1
TECHNICAL DESCRIPTION AND ADJUSTMENT
PROCEDURES
D
bokorder, lnc.
5430 ROSECRANS AVENUE, I-{WNDALE, CALIF. 90260 U.S.A.
r-rE\] Kr <)\JK-YO CO., r--trE).
26.1 1, 3-CHON4E, NISHI-ROKUGO, OTA-KU, TOKYO, JAPAN

TABLE OF CONTENTS
1. GENERAL DESCRIPTION 1
1 1 Amplifier Circuitry g
1-2 Tape Transport Mechanism
1-3 Power Supply Circuitry
2. SERVICE DATA 2
21 Mechanical
2-2 Electrical
3. PARTS LOCATION . 3-4
3-1 Outer Parts
3-2 lnner Parts
4. REMOVAL OF OUTER PARTS 5 r
4-1 Front Panel
4-2 Amp Panel
4-3 Top and Bottom Boards ../
5. ADJUSTMENT -MECHANTCAL- ... . 6-'11
5-1 Auto Shut-off Switch
5-2 Pinch Roller Drive Mechanism
5-3 Reel Motor Torques
5-4 Brake Mechanism
5-5 Tape Speed
5-6 Wow/Flutter g
6. ADJUSTMENT -ELECTRTCAL- .12-20
6-1 Adjustable Parts Location
6-2 Adjustment Procedures
7. MAINTENANCE . 21
7 -1 Cleaning
7-2 Lubrication
7 3 Demagnetizing y)
B. TECHNICAL DESCRIPTION ....22-31
8-1 Solenoid Drive Circuit
8-2 Capstan Drive Circuit
9. SCHEMATIC DIAG RAM
Note
This Service Manual consists of three sections:
Section 1: Descriptions of circuitry, operating procedures, and methods of adjustments
and maintenance, plus technical data.
Section 2: Exploded views, and parts list.
Section 3: Patterns, schematics and parts lists for printed Circuit boards. v

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1. GENERAL DESCRIPTION
The Dokorder Model 7700 is a -track,2-channel,2-speed tape deck equipped with 3-motor, 3-heacl and sole-
noid operation facility. Designed for high dependability and electrical performance. Their features:
1.1 AMPLIFIER CIRCUITRY
1. The convenience features of the 7700's amplifier circuit such as the Monitor Switch. Mic AMp Circuit, Head-
phone AMP Circuit and Level Meter AMP Circuit built in.
2. 4-separate controls permit subtle input/output level adjustments.
3' 2-stepped Equalizer Switch is equipped to use for the several type of tapes. The relation between the tapes and
the position of the switch is illustrated below.
1-2 TAPE TRANSPORT MECHANISM
1. The convenience features of the 7700's tape transport such as the all-electronic operation buttons, pause con-
trol, tape travel counter are positive, and the mechanisms themselves are rugged and dependable.
2. fhe tape transport offers an Auto Stop convenience, and when the tape reaches its end in any mode (fast for-
ward, rewind, play or record). a solenoid releases the locked operating control (s) to place the deck in the stop
mode.
3. High dependability is proven by using newly improved electronic solenoid control system that reduces the
powerconsumption and heat up in the solenoid and its control transistors.
4. Especially high speecl-accuracy and surprising wow/fluttel characteristics are realized by using most advanced
PLL (Phase-Locked Loop) Servo System in capstan motor drive.
5. Newly designed high-torque outer-rotor eddy-current motor is used for reel drive.
1-3 POWER SUPPLY CIRCUITRY
1. The primary winding of the power transformer is provided two taps 100 V and 54 V. The former is used for
the reel motor drive in the fast winding mode. while the latter is used for the reel motor drive in the rec/play
mode.
2. On the secondary side, the transformer also offers two windinqs for 5.6 V and 14 V x 2. The former is used for
illuminating the pilot lamps, while the latter is rectified and then used to power the amplifiers, solenoid, PLL
circuit and capstan motor.
Equalizer Switch Type of Tape
Normal (button out) Scotch #212 or equivalents
Special (button in) Maxell #UD-35 or equivalents
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2. SERVICE DATA
2-1 MECHANICAL
Record/Playback System 4 track 2 channel stereophonic
Tape Width Standard 1/4 inch tape
Reel Size 7-inch or smaller
Motor Three (one 2 speed PLL DC servomotor for capstan, two 6 pole induction
outer-rotor type for reels)
Head Three (1 erase, 1 rbcord, 1 playback)
Tape Speed !1 .5o/oat 19 cm/sec (7-1 l2ipsl ,!1 .5%at 9.5 cm/sec (3 3/4 ips)
Wow and Flutter Playback (RMS)
0.13o/oat 19 cm/sec (7 112ipsl ,0.20% at 9.5 cm/sec (3-3/4 ips)
Fast Winding Time 100 sec for 7-inch reel (1800-foot tape, 60 Hz)
Motor Torque Hold-back tention (playback) 85 gr 110 gr (255 t30 g.cm)
Take-up torque (playback) 150 gr (450 g.cm)
FFlREW hold-back tention 30 gr ( 90 g.cm)
Brake Torque 600 - 800 gr (1.8 - 2.4 kg.cm)
weight 35 lbs
Dimension 17-314" (H) X 16-718" (W) X 6 3/4" (D)
2-2 ELECTRICAL
al
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Y/
V'
Equalization
Bias Frequency
Frequency Response
(Playback )
Frequency Response
(Overa ll )
One-channel Recording
Signal to Noise Ratio
Crosstalk
Channel Separation
Bias Leakage
Erase Ef{iciency
Distortion (Overall)
Meter Calibration
lnput Mic
L ine
DIN
Output Line
DIN
Circuit Complement
Power Consumption
Power Requirement
Headphone 2mW 8Q
NAB
130 KHz +1 KHz
.19 cm/sec (7 l12ipsl
50 - 100 Hz l! oa, 1o1 Hz - 1 5 KHz 13 dB
o 9.5 cm/sec (3 3/4 ips)
50 Hz - 7.5 KHz 13 dB
o 1 9 cm/sec (1-1 12 ips)
Normal 30 Hz - 20 KHz t3 dB (30 - 100 Hz, 15 - 20 KHz t5 dB)
Special 30 Hz - 20 KHz 13 dB (50 - 100 Hz, 15 - 20 KHz t5 dB)
o 9.5 cm/sec (3-3/4 ips)
Normal 35 Hz- 12KHz t3dB (35 -'1 00 Hz, 1.5- 12 KHz15 dB)
Special 35 Hz - 12 KHz 13 dB (35 - 100 Hz, 7.5 - 12 KHz 15 dB)
TOOHzll dB, 15 KHz+5dB at 19 cm/sec (7'1 /2ipsl
500 Hz 11 dB, 7.5 KHz +5 dB at 9.5 cm/sec (3-314 ips)
Better than 50 dB (Playback) at 0 dB output level
Better than 46 dB (Overall) at 0 dB output level
Better than 50 dB at 1 KHz
Better than 40 dB at 1 KHz
Less than -25 dB
Better than 65 dB at 1 KHz
Less than 3% at 1 KHz 0 dB output level
0 dB at IOOHz 0 dB output level (P.8. VR-Max)
-58 dB 10 KO (load imPedance)
-20 dB 220 K9
30 mV 80 KQ
OdB 47KQ
260 mV 47 KS)
34 transistors, 29 diodes, 5 lC,2 FET ,2 LED, 1 PUT
75W
U.S.A. type 117 V (60 Hz)
Universal type 100 V,117V,125V,20OV,220V,24O V (50/60 Hz)
Specs are subject to change withor-rt notice.
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3. PARTS LOCATION
3-1 OUTER PARTS
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Front View
20 Push Button, Metal, EO, Speed, Monitor, Pause SW
21 Push Button, Red, Rec. SW (556-0009-00)
22 Operate Button, Rec. (556-0038-80)
23 Ope. Button, FF & REW (556-0037-80)
24 Ope. Button, Stop (556-0035-80)
25 Ope. Button, Plav (556-0036-80)
26 Level Meter (141-1004-00)
Back View
1 Panel Ass'y, Deck (880-0017-00)
2 Panel Ass'y, Amp (880-0018-00)
3 Side Board {551-0018-02)
4 Top Board (551-0013-90)
5 Bottorn Board (551-00'10-00)
6 Foot Ass'y (880-0019-00)
7 Head Cover {880-0016-00)
8 Counter (143-31 02-00)
9 Turn Table Ass'y (810-001 1-00)
1O Dressing Washer, Pinch Roller (555-0050-02)
11 Pinch Roller (523-0029-00)
12 Tape Guide(L), Tension Arm (558-0020-00)
13 Tape Guide(R), Tension Arm (558-0021-00)
14 Switch, Push, Power (131-1018-80) or (131-1019-80)
15 Switch. Push, EO. Select (131-1014-00)
16 Switch, Push,2-station Speed & Monitor (131-10i5-00)
17 Switch, Push, 2-station, Rec. (131-1017-00)
18 Switch, Push, Pause {131-1016-00)
19 Push Button, Metal, Power SW (556-0030-02)
(556-0013-83)
fiililfi1
tiilltill
27 Control Knob, Metal (556-0001-00)
28 Jack. Mic (135-5001-00)
29 Jack, Headphone {135-5002-00)
30 Cup Washer (532-0021-00)
60 Back Board (551-0019-03) or (551-0020-00)
61 AC Cord with Plug (162-1001-00)
62 Holder, F use 1135-7001-00)
Fuse, 1.5 A (138-1003-00)
63 Jack, 4-Pin (1 35-5008-00)
64 Terminal, GND (135-1001-00)
65 Socket, DIN (136-6003-00)
ar

3.2 INNER PARTS a
Front View
31 Solenoid, Brake, DC-24V 48 ohm (1 1 6-2002-00)
32 Linkage, Brake (525-0025-00)
33 Stopper, Brake Linkage (528-0008-00)
34 Linkage, Brake Solenoid (525-0027-00)
35 Bracket, Brake (533-0082-00)
36 Guide, Brake Linkage (528-0009-00)
37 Spring, Brake (541-0007-05)
38 Solenoid, Pinch Roller Pressure, DC-24V 15 ohm
(1 1 6-2003-00)
39 Spring, Pressure (541-0010-01 )
40 Arm, Pinch Roller Drive (525-0029-00)
41 Arm, Pinch Roller (525-0032-00)
42 Shaft, Pinch Roller (521-0025-05)
43 Arm, Auto Shut-Off (525-OO24-O4\
44 Switch, Micro, Auto Shut-Of f (131-3001-00)
45 Bearing, Capstan 1522-OO1O-O2)
46 Dressing Plate, Tape Lifter (521-0029-00)
4-l Head Base Ass'y (830-001 1-00)
48 PC Board Ass'y (PCM-365A), Head Connect (831-0004-00)
49 Tension Arm Ass'y (Left) 1840-0016-00)
50 Tension Arm Ass'y (Right) (840-0018-00)
51 Pulley, Motor, No.3 (523-0031-04)
52 Belt, Capstan Drive 1524-OoO7-O2l
53 Belt, Counter Drive (524-0006-00)
54 PC Board Ass'y (PCM-3978), Rec. & Pause (821'0020 00)
55 PC Board Ass'y (PCM-3954), LED (821-0019-00)
56 Switch Ass'y, Operate (820-0016-00)
57 Chassis(A), Amp. (512-001 1-83)
66 Power Transformer (1 1 1-1021-00)
67 Resistor, Wirewound, 1200 ohm 20W \3O2-122O-8O)
Resistor, Wirewound, 600 ohm 15 W {302-6018-90)
68 Resistor, Wirewound, 200 ohm 10 W {302-2018-90)
Resistor, Wirewound, 150 ohm 10 W (302-1518-90)
69 Motor, Reel (113-1002-00)
70 Motor, Capstan (114-5001-00)
71 PC Board Ass'y (PCM-4118), Capstan Motor (861-0003-00)
72 PC Board Ass'y (PCM-361C), Capacitor, Reel Motor
(161-1034-00 )
73 PC Board Ass'y (PCM-417C), Control (851-0008-00)
74 PC Board Ass'y (PCM-4138), Bias OSC (851-0009-00)
75 Arm, Flywheel Support (533-0020-02)
76 Flywheel {523-0030-01 )
77 PC Board Ass'y (PCM416E), Operate SW (821-0021-O0)
78 PC Board Ass'y (PCM4464), Amp. 1871-0012-00)
79 Chassis(A), Power Supply (533-0048'01)
Chassis (B), Power Supply (533-0049-00)
80 Chassis(B), Amp. (512-00'l 2-00)
2-
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2,

4. REMO\/AL OF OUTER PARTS
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4.1 FRONT P
1. Referring to Fig. 4-1. withdraw head cover O
and remove head cover posts @ by turning them
counterclockwise with pliers or box driver.
2. Holding pinch roller @ stitl, turn counterclock-
wise screw @ securing pinch roller dressing
washer @ and withdraw the screw together with
the dressing washer. Then extract nylon washer
@ anO the pinch roller from the pinch roller
s h aft.
NOTE: When extracting the pinch roller, take
care not to lose the nYlon washer.
3. Remove four screws @ anA @ securing the
front panel by turning them counterclockwise;
then remove the panel itself by moving it as the
arrow in the illustration shows.
NOTE: When mounting the front panel, reverse
the steps described above. Take note that
cup washer @ should be fitted on the
two screws securing the bottom part of
the front panel. Also, note that conduc-
tive rubber washer @ shoutO be f itted
on the screw securing the right side of the front panel. This is for grounding the front panel.
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4-2 AMP PANEL
1. Withdraw control knobs-RECORD LEVEL CONTROLS and PLAYBACK LEVEL CONTROLS.
2. Remove the two screws (BS-3 X 6) above and (BS-3 X 18) below the level meters by turning them counter-
clockwise. Then, remove the four screws (BS-4 X 15) that secure the amp panel.
NOTE: Take care not to lose the nylon washer when'removing the two screws above and below the level
meters.
3. When mounting the amp panel, reverse the steps described above'
NOTE: Fit and tighten the screws only after checking to see that the record indicator LEDs are correctly
fitted in the holes on the amp panel and that the level meters are also fitted correctly in the amp
panel holes. Take note that the conductive rubber washer should be fitted on the screw that secures
the upper right side of the amp panel (see 4-1. 3 above)'
4.3 TOP AND BOTTOM BOARDS
1. Remove the six black-painted screws (RS-3 X 6) that secure the top board.
2. To remove the botrom board, remove the four screws {RS-3 X i4) securing the two FOOT ASS'YS by turning
them counterclockwise. Then remove the FOOT ASS'YS themselves'
3. With the FOOT ASS,YS dismounted, remove the screw (RS-3 X 8) securing the bottom board at its center by
turning it counterclockwise, then remove the bottom board itself'
4. When mounting the top and bottom boards, take care not to confuse the screws securing the top board with
those securing the bottom board; they are different in size and finish.
(e)
aI
F-a
Fig.4-1
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3-2 INNER PARTS
*T*-
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Front View
Back View
ffiir:t:rj':::.. : :- -:;.. :'. .:.:ii.::':::l:;.=?:@
31 Solenoid, Brake, DC-24V 48 ohm (1 1 6-2002-00)
32 Linkage, Brake (525-0025-00)
33 Stopper, Brake Linkage (528-0008-00)
34 Linkage, Brake Solenoid (525-0027-00)
35 Bracket, Brake (533-0082-00)
36 Guide, Brake Linkage (528-0009-00)
37 Spring, Brake (541-0007-05)
38 Solenoid, Pinch Roller Pressure, DC-24V 15 ohm
(1 1 6-2003-00)
39 Spring, Pressure (541-0010-01 )
40 Arm, Pinch Roller Drive (525-0029-00)
41 Arm, Pinch Roller (525-0032-00)
42 ShaIt, Pinch Roller (521-0025-05)
43 Arm, Auto Shut-Off 825-OO24-O4)
44 Switch, Micro, Auto Shut-Off (131-3001-00)
45 Bearing, Capstan \522-OO1O-O2)
46 Dressing Plate, Tape Lifter (521-0029-00)
4-l Head Base Ass'Y (830-001 1-00)
48 PC Board Ass'y (PCM-365A), Head Connect (831-0004-00)
49 Tension Arm Ass'v (Left) (840-0016-00)
50 Tension Arm Ass'y (Right) (840 0018'00)
51 Pulley, Motor, No.3 (523-0031-04)
52 Belt, Capstan Drive 1524-OOO7-O2)
53 Belt, Counter Drive {524-0006-00)
54 PC Board Ass'y (PCM-3978), Rec. & Pause (821-0020-00)
55 PC Board Ass'v {PCM-395,4), LED (821-00i9-00)
56 Switch Ass'y, Operate {820-0016-00)
57 Chassis(A). Amp. (512-0011-83)
66 Power Transformer (1 1 1-102 1-00)
67 Resistor. Wirewound, 1200 ohm 20 W \3O2-122O-8OI
Resistor, Wirewound, 600 ohm 15 W (302-6018-90)
68 Resistor, Wlrewound, 200 ohm 10 W (302-2018-90)
Resistor. Wirewound, 150 ohm 10 W (302-1518-90)
69 Motor, Reel {1 1 3-1 002-00)
70 Motor, CaPstan (1 14-5001'00)
71 PC Board Ass'y (PCM-4118), Capstan Motor (861-0003-00)
72 PC Board Ass'y (PCM-361C), Capacitor, Reel Motor
(161-1034-00)
73 PC Board Ass'y (PCM'417C), Control {851-0008-00)
74 PC Board Ass'v {PCM-4138), Bias OSC (851-0009-00)
75 Arm, Flywheel Support (533-0020-02)
76 Flywheel (523-0030-0 i )
77 PC Boarcl Ass'y (PCM-416E), Operate SW (821-0021-00)
78 PC Board Ass'v (PCM-446Ai, Amp {871-0012-00)
79 Chassis(A), Power Supplv (533-0048-01)
Chassis (B), Power Supplv (533-0049-00)
8o chassis (B), AmP. (512-0012-oo)
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5. ADJUSTMENT -MEGHANICAL-
5.1 AUTO SHUT.OFF SWITCH
a. Specification
When the auto shut-off urrn @ is pushed upward,
the microswitch @ clicks lswitches on) at the
point of more than 8 mm (0.32 inch) outside of
the tape travel position and clicks again (switches
off) at the point of more than 14 mm (0.56 inch)
outside of the tape travel position.
b. Adjustment
Adjust the mounting position of the microswitch
@
c. Reference
Refer to Fig.5 1 or section 2 on page M-12.
d. Special Tools and/or lnstruments required
N one
e. Preparation
Remove the head cover and front panel.
f. Procedure
(1) Check the on/off position of the microswitch by gently moving the auto shut-off arm by hand.
(2) lf the on/off position does not meet the spec, adjust the position of the microswitch by loosening two
mount screws @.
g. Note
(1) Replace the dismounted parts and check again that the auto shut-off arm moves freely through the hole
in the front panel and does not come into contact with head cover.
(2) Load the tape and set the deck in play mode and check if the tape travels normally. Then take up the tape
completely by setting the deck in FF or REW mode, checking that the auto shut-off arm returns to shut
off the tape travel automatically at the tape end.
5.2 PINCH ROLLER DRIVE MECHANISM
2.1 STROKE ADJUSTN/IENT OF THE PINCH ROLLER PRESSURE SOLENOID
a. Specification
Stroke of plunger 4 - 4.5 mm (0.16 - 0.18 inch).
b. Adjustment
Adjust the stroke adjusting nut @.
c. Reference
Refer to Fig.5-2 or section 2 on page M-20.
d. Special Tools and/or lnstruments required
A open end wrench (4 mm).
e. Preparation
Remove the front panel (including pinch roller and
head cover).
Fix the auto shut-off arm ON by a piece of
sticking tape.
f. Procedure
(1) Push the play and stop buttons alternately several times, mark the position of the solenoid plunger @ as
it pulls and returns.
(2) Adjust the nut @ ro that the operating stroke of the plunger (indicated ur @ ) is from 4 to 4.5 mm
(0.16 - 0.18 inch).
g. Note
a
lvlount(auto shur-011 swirch2Tape Travet Posrtion
\^@r/
61 ;* (up"cu,a" =
qls
Dressing Plate z
?,
a.
@roct< lusting Nut
Pressure Spring
@Pressure Solenoid Pinch Roller Drive Arm
Fis.5-2
b
(i ) Loosen the lock nut @ first and then proceed with step f-(2).
(2) After the stroke has been adjusted. fix the nut @ with the lock nut @, tt.'.n paint-lock it.
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(1) Read the pressure indicated on the spring
balance when the pinch roller loses contact with the capstan and the pinch roller stops revolving
(2) Adjust the pressing force of the pinch roller by turning the nut @ and @, if nec.ssaty.
rY g Note
(1) Use a precision spring balance with a scale of up to 4 kg graduated in steps of 50 g or less.
(2) Loosen lock nut first before attempting step f-(2).
(3) Fix the adjusting nut @ with the lock nut @ and then paint-lock it.
5-3 REEL MOTOR TOROUES
2-2 PINCH ROLLER PRESSURE
a. Specification
1 '5 ks tQ"l Pg
r.t b. Adlustment
Adjust the pressure adjusting nut @.
c. Reference
Refer to Fig. 5-3 or section 2 on page M-20.
d. Special Tools andlor lnstruments required
A open end wrench (4 mm) and spring balance
(4 kql'
e. Preparation
Remove the front panel (including pinch roller
and head cover).
Fix the auto shut-off arm ON by a piece of
stickinq tape.
f. Procedure
a. Speci{ication
y Hold-back Tension 85 gr 110 gr (255 +30 g. cm)
Take-up Torque 150 gr (450 g. cm)
b. Adjustment
Adjust the wirewound resistor R-2 (150 ohm) for
the hold-back tension.
c. Reference
Refer to Fig. 5 4, 5-5 or section 2 on page M-22.
d. Special Tools and/or lnstruments required
A spring balance (200 q) and 7-inch small-hub reel
ry (6 cm in diameter).
e. Preparation
Remove the back and top boards.
Fix the auto shut-off arm ON by a piece of
sticki ng taPe.
f. Procedure
f-i. Hold-back tension (Playback)
(1 ) Mount the 7-inch reel on the left turntable
with a piece of string attached to it, as shown
in Fig. 5-5 (A).
(2) Set the deck in play mode and pull the spring
balance gently in the direction indicated by
the arrow in F ig. 5 5 (A) and read the
indicated figures on the spring balance.
(3) Loosen lock screw @ securing the slide ring
O on the R-2 in Fig. 5-4 and adjust the
position of the slide ring so that the spring
U balance indicates 85 g 110 9 (255 g. cm 130).
f-2. Take-up torque (Playback)
Pinch Roller
Capstan Shaft
Capstan Bearing
Fig.5-3
\Pinch Roller Arm
@stioe ning
@Lock Screw---
lncrease{-- --->Decrease
Fig.5-4 "Moror chasis
/^-\-i
\ t)---< )
, \,fo oo\.,"
q\
4.^/
\\\//
tlo \ /
\\ \ / /
\ L-/ ,,',
F ig.5-5
(1) Mount the 7-inch reel on the right turntable with a piece of string attached to it. as shown in Fig. 5-5 (B).

(2) Set the deck in play mode and pull the spring balance gently in the direction indicated by the arrow in
Fig.5-5 (B) and check that the take-up torque is nearly 150 g (450 g.cm).
N ote
(1) The hold-back tension in both the FF and REW modes are determined by a fixed wire-wound resistor;
therefore, there is no need to adjust, but do check that the hold-back tension is 90 g. cm.
(2) When the adjustment has been completed, paint-lock the Iock t.t.* (E.
5.4 BRAKE MECHANISM
4 1 BRAKE BAND
a. Specification
1 - 1.5 mm (0.04 - 0.06 inch) space between the
brake drum @ and the brake band @.
b. Adjustment
Adjust the set position of the bracket @.
f.
R eferen ce
Refer to Fig.5-6 or section 2 on page M-16.
Special Tools and/or lnstruments required
None
Pre parati on
Remove the front panel (including pinch roller
and head cover).
F ix the auto shut-off arm ON by a piece of
sticking tape.
Proced u re
(1) Push the play and stop buttons alternately
several times and check the movement of the
brake band (4).
'!L
L
c-
d.
e.
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(2\
(3)
Push the play button once again and loosen the two lock_screws @ securing the bracket @ to that the
space between rhe brake band @ and the brake drum @ will be from 1 to 1.5 mm (0.04 - 0'06 inch).
(Moving the bracket in the directin of arrow @ will increases the space @)
Keeping the tape deck in the stop mode, push the brake linkage () downward by hand, check that the
brake band @ contacts the inside of the brake band guide (5) uniformly and that the space between the
brake drum @ anO the brake band @ is also uniform.
g. Note
When the adjustment has been completed, paint-lock the two lock screws @
4-2 STROKE OF BRAKE SOLENOID
a. Specification
Stroke of plunger 1 - 1.5 mm (0.04 - 0.06 inch).
b. Adjustment
Adjust the set position of the brake solenoid O.
c. Reference
Refer to Fig.5 7 or section 2 on page M-16.
d. Special Tools and/or lnstruments required
N one
e. Preparation
Remove the front panel (including pinch roller
and head cover).
Fix the auto shut-off arm ON by a piece oi
sticking tape.
f. Procedure
(1) Push the play and stop buttons alte nately
and check the stroke of the brake solen.id plunger @ {indi"ut.O @ in Fig.5-7).
L
@Lock Screws
F iq.5-7
@
t
+
@
@Brake Drum
Fis.5 6
@ Brake'Linkage
(2) Loosen two lock ,.r.*, @ and adjust the position of the solenoiO @ to that the operating stroke o{
L

J
the solenoid plunger @ will be from 1 to 1.5 mm (0.04 - 0.06 inch).
g. Note
After the stroke has been adjusted, paint-lock the two lock screws @.
4 3 STROKE OF BRAKE LINKAGE STOPPER
a. Specification
1 mm (0.04 inch) space between the rubber
damper @ and the brake linkage@.
b. Adjustment
Adjust the set position of the brake linkage stoppers
@
c. Reference
Refer to Fig. 5-8 or section 2 on page M-16.
d. Special Tools and/or lnstruments required
A thickness gauge.
e. Preparation
Remove the front panel (including pinch roller
and head cover).
F ix the auto shut-off arm ON by a piece of
sticking tape.
f. Procedure
(1) Push the play and stop buttons alternately and check that the brake linkage e moves up and down
properly.
(2) Push the play button once again. loosen the two lock r.ru*r @ and adjust the position of the brake
linkage guides so that the space between the rubber damper @ and the brake linkage O .uU be 1 mm
(0.04 in ch ) .
g. Note
After the adjustment has been completed, paint-lock the two lock screws @.
44 BRAKE TOROUE
a. Specification b. Adjustment c. Reference
600 - 800 S (1.8 - 2.4 kg. cm) Adjust the brake linkage stoppers@. Refer to Fig. 5-5 on page 7.
d. Special Tools and/or lnstruments required
A spring balance (1 kg) and 7-inch small-hub reel (6 cm in diSmeter).
e. Preparation
Remove the f ront panel (including pinch roller and head cover).
Fix the auto shut-off arm ON by a piece of sticking tape.
{. Procedure
(1) Mount the 7-inch reel on the left turntable with a piece of string to it, as shown in Fig. 5 5 (A).
(2) Push the stop button, hook a spring balance to the string attached above reel, pull the balance gently in
the direction indicated by the arrow in Fig. 5 5 (A), and read the pressure indicated by the balance when
the left turntable begins to turn.
{3) The reading (brake torque) on the spring balance should indicate pressure from 600 to 800 g as a brake
torque (1 .8 - 2.4 kg. cm).
(4) Repeat the steps (2) and (3) for the right turntable. lf you discover a considerable difference between the
brake torques for the left and right turntable, refer to adjustment chart.
When Torque is
Greater than
800 grams
Refer to Fig. 5-8 in 4-3 "STROKE OF BRAKE LINKAGE STOPPERl'and set
the distance between the rubber damper @ and the brake linkage @ to
less than 1 mm (0.04 inch).
Less than
600 grams
Refer to Fig. 5-8 in 4-3 "STROKE OF BRAKE LINKAGE STOPPER" and set
the distance between the rubber damper @ and the brake linkaqe C to
more than 1 mm (0.04 inch).
Brake Solenoid
F is.5 8
J
J
J
J

5-5 TAPE SPEED
a. Specif ication
19 cm/sec (l'112 iPsl !1-5% (2955
3 KHz test tape).
9.5 cm/sec (3-3/4 iPs) !1.5% (2955
3 KHz test tape).
b. Adjustment
Adjust the semi-fixed resistor VR-901 on the
C.P.M. control PC Board Ass'Y.
c. Reference
Refer to Fig. 5-9.
d. Special Tools and/or lnstruments required
Test tape DTT-5114 (19 cm/sec) , DTT 3114
(9.5 cm/sec) or equivalents and frequency counter'
e. Preparation
Remove the back board'
f. Procedure
(1) Set to the tape speed switch to the 19 cm/sec
the line outPut jack.
-Component Slde-
C.P.lvl. Control PC Board
(PCN1 41 7)
$-l
q_J
##
F ig.5-9
test tape (DTT 51 14) on the deck and push the play
control PC Board (PCM-417), so that the frequency
- 3045 Hz bY
- 3045 Hz bY
(-
(7-1 12 ips\ position. then connect the frequency counter to
(2) After the above connection are completed, load the
button to enter the PlaYback mode'
(3) Adjust the semi-fixed resistor VR-901 on the C'P'M'
counter reading may be 2955 to 3045 Hz' position, then check that the line output signal
(4) Change the tape speed switch to the 9'5 cm/sec (3 3/4 ips)
frequencY is 2955 to 3045 Hz'
q' Note r:..^.-^^+ ,^,i^a nraen r de and all other parts that touch the tape,
Before starting the adjustment, wipe clean the pinch roller' tape gul
andalsocheckifthepinchrollerpressureandwowarewithinspecifications'
5-6 WOW/FLUTTER
L
t
L
a. Specification
19 cm/sec (7 l12iPs]r 0'13% RMS
9.5 cm/sec (3-3/4 iPs) 0.20% RMS
b. Adjustment
Adiust the motor torque, pinch pressure' alignment of tape path'
c. Reference
RefertoS-1,5.2,5.3,5-4and5-5describedaboveformechanicaladiUstment.
d. Special Tools and/or lnstruments required
TesttapeDTT-s114(1gcm/sec),DTT-3114(9.5cm/sec)oritsequivalents,wow/fluttermeter,frequency
counter and tools described in the mechanical adjustment above'
e. Preparation
Remove the head cover and clean the heads, pinch roller, tape guide and all other parts that touch the tape'
f. Procedure
(1) Deterioration of wow/flutter may be avoided by attending to the following problems:
l.Partsalongthetapepath(thepinchroller,heads,tapeguides'capstanshaft)mavbestainedwithoxide
particles, etc., scraped from tape surfaces'
2.Reel-motortorque.pinchrolIerpressureandtapepathalignmentmaybeneeded.
3. capstan drive assembly (the capstan belt, flywheel. motor pulley) may be fouled'
4. Rotational parts (such as the pinch roller metal, pinch roller shaft, capstan bearing' capstan shaft and
motor shaft) may need lubrication'
5. Tape drive mechanism (such as the reel motors, capstan motor' guides' counter mechanism and
solenoids) maY need rePlacement'
6. other causes might include cases where lead cables running along the tape drive mechanism are worn
by friction, or where the disengaging action of the brake mechanism is faulty'
10
L

(2) Adjustments should be undertaken in the most efficient manner, as suggested below:
'l . Use test tapes and measuring apparatus that are new (if possible) and well calibrated.
2. Check first that the tape transport mechanism is in order.
J t :i'.,""t,|ff:il:tffi",XT;:11"J;'fiflT;':fi;,', metar parts, pinch rorer shart. capstan shart, capstan
bearing, etc.
b) Clean the belts, flywheel, motor pulley, etc., and check for rubbing parts or marred surfaces.
4. Measure the wow; if it exceeds the specification, measure and adjust the reel motor torque.
5. ln most cases, the measured wow/flutter should meet the specification by the time you reach the 3rd
or 4th step above. lf not, a faulty pinch roller, capstan or belt may be the cause. and replacement is
called for.
Usually replacement of a motor should not be considered; should the motor be suspect, first apply oil
to its shaft and keep it running for two or three hours, and check it again. lnspecting the reel motor
capacitor may also reveal the solution.
11

6. ADJUSTMENT -ELECTRICAL-
rL-
PRECAUTION
1. Before actually adjusting the parts, be sure to first clean the heads' pinch rollerand othertape-scraping parts
aswellasthebelts,idlersandothertape-drivetorquetransmissionpartswithalcohol.Lubricate,foo,if
necessary' Such procedures may bring back the performance to Within tolerable specifications, eliminating any
need for part replacements or torque re-adjustments'
Thepositionofthethruststopper,ifImproperlyset,maydeterioratethewow/flutter.Soitisadvisableto
remove the belt and then turn the flywheel with your fingers to see if it turns smoothlv'
2. For an efficient adiustment of record/playback level and frequency response' follow the order of preferences
forthedifferentadjustingprocedures.Forinstance,ifyouadjusttherecordlevelbeforeadjustingtheplay-
back level or without checking it, you'll have to re-adjust the record level same after you have adiusted the
, fili::t:},::ll,,ln ,n. overarr response, it may sometimes become necessarv to fine-adjust the previousrv-adjusted
parts.lnsuchacase,makesurethatthefine.adjustmentsarestillWithintolerableratings,beforeproceeding
a 1,".T:?::::0.r." if of the same brand and type, show identicar recordins responses, especiatv in the hish-
frequencyrange'Thusifyouswitchtapesduringadjustments,youmayhavetore-adjustthepartsyouhave
alreadyadjusted.lfyouareusingatapeforttretlrsttime,it.softenadvisabletocheckitsresponsebefore-
hand, to know how different it is in response from the previous tape'
NOTES
L
L
L
TheproceduresinthissectionapplytotheamplifiercircuitsoftheModelTT00.
ln adjusting the amplifier "i.cuits following the instructions in this section, the tapes belowlisted should be used.
1. When adiusting the playback circuits:
lt gffit|,Jjl:110 dB) or equivarents {Adiustment or Plavback Level & Frequencv Response)
DTT-5113 (15 KHz -10 dB) or equivalents (Aiiustment of Head Almuth & Playback Frequency Response)
DTT-5102 (50 Hz-10 dB) or equivalents (Adjustment of Playback Frequency Response)
9.5 cm/sec (3 3/4 iPs)
DTT-3106 (500 UtllOdB) or equivalents (Adiustment of Playback. Frequency Response)
DTT-3110 (7.5 KHz -10 dB) or equivalents (Adiustment of Playback Frequency Response)
DTT-3102 (50 Hz -10 dB) or equivalents (Adiustment of Playback Frequency Response)
(orothertypesofatignmenttapeWiththelevelsasarerecordedontheabovetapes.)
, H::: llil':il.g ff"ff;H:i:t'..",d bias and the record equarizer can be used independentrv of each other,
thereareseveraltypesoftapetobeused,foradiustmentsuchasthoselistedbelow.Foradjustmentofrecord
frequency response, the Scotch #212 and Maxell UD-35'
ADJUSTMENT
For the rocation of parts for adiustment on each of the amprifier circuit pc board (pcM-446), refer to the section
,,ADJUSTABLE PARTS LOCATION."
Adiustment TaPe
Tape Select Mode
Equalizer Switch
Scotch 212 or equivalents
NORMAL
Maxell UD-35 or equivalents
SPECIAL
I
12

6-1 ADJUSTABLE PARTS LOCATION
ArvrP P.c.B. (PCM 4464)
BrAS OSC P.C.B. (PCM-4138)
REC & PAUSE P.C.B. (PCM 3978)
1gcm^(7-112 ips)
IP7 TP8
oo
oo o
L-401 o
BIAS OSC ADJ.- TP-4 O
TP-s O
L601
oL$03
SL-602
S
c$06
Mc-604
ffi
oFis.6 1
BIAS TRIMMER
13

6.2 ADJUSTMENT PROCEDURES
2-1 HEAD AZIMUTH (P.8. Head)
a. Specification
Max. output level under the signal in- phase
cond ition.
b. Adjustment
Adjust the azimuth screw.
c. Reference
Refer to Fig.6-2, Fig.6-5 or section 2 on page
M-20.
d. Test tape, special tools and instruments required
DTT-5113 (15 KHz -10 dB) or equivalents.
VTVM and oscilloscope.
e. Test point
Connect the VTVM and oscilloscope to the line
output jacks.
f . Mode of switch
(1) Tape speed SW-19 cm/s (button out), Monitor SW-TAPE (button out).
(2) Playback level controls-MAx, Record level controls-MlN.
g. Procedure
(1) After the above connections are completed, load the test tape (DTT-5113) on the deck and push the play
button to enter the playback mode.
(2) Adjust the head azimuth by turning azimuth screw, so that the line. output level becomes maximum and
phase shift between both channels becomes minimum by observing the lissajous figure on the oscilloscope
as shown Fig.6-5 on page20.
(3) When the azimuth adjustment is completed, paint-lock the azimuth screw'
h. Note
Since head azimuth is,already adjusted before the deck leaves our Dokorder factory, normally azimuth adjust-
ment is unnecessary; it is necessary only when heads are replaced.
2-2 PLAYBACK
a. Specification
-1 0 dB r0.5 dB of the line output iacks.
b. Adjustment
Adjust the semi-fixed resistors VR-106 (L-ch) and VR-206 (R-ch)'
c. Reference
Refer to Fiq. 6-1.
d. Test tape, special tools and instruments required
DTT-s106 (700 Hz -10 dB) or equivalents and VTVM.
e. Test point
Connect the VTVM to the line output jacks.
f . Mode of switch
(1 ) Tape speed SW-19 cm/s, Monitor SW-TAPE'
(2) P.B. level controls-MAX, Record level controls-M lN.
g. Procedure
(1) After the above connection is completed, load the test tape (DTT-5106) on the deck and push the play
button to enter the PlaYback mode'
(2) Adjust the semi-fixed resistors VR-106 and VR-206 on the AMP PC Board (PCM-446), so that the line
output levels of the deck are -10 dB 10.5 dB on the VTVM.
q-.
ADJUSTING SCREWS
(E o,. ,r S r"i.h @ 2""
Q..o*-
c
Be.ord tsead P;,b.Lr Hp.d
F iq.6-2 t*
v
14

t}
2-3 PLAYBACK FREOUENCY RESPONSE (19 cm/s & 9.5 cm/s)
a. Specification
-10 dB 1',t.0 dB (15 KHz, 19 cm/s), -10 dB l? Oe (SO Hz, 19 cm/s)
-10 dB 11.0 dB (7.5 KHz, 9.5 cm/s), -1 0 dB t3 dB (50 Hz, 9.5 cm/s)
b. Adjustment
(1) Adjust the semi-f ixed resistors VR-105 and VR-205 (19 cm/s).
(2) Adjust the semi-fixed resistors VR 104 and VR-204 (9.5 cm/s).
c. Reference
Refer to Fig.6-1.
d. Test tape, special tools and instruments required
DTT-S106 (700 Hz -10 dB), DTT-5113 (15 KHz -10 dB), DTT-5102 (50 Hz -10 dB), DTT-3106 (500 Hz
-10 dB), DTT 3110 (7.5 KHz -10 dB), DTT 3102 (5O Hz -10 dB) or equivalents, and VTVM.
e. Test point
Connect the VTVM to the line output jacks.
f . Mode of switch
(1 ) Tape speed SW-19 cm/s, Monitor SW-TAPE.
(2) P.B. level controls-MAX, Record Ievel controls-MlN.
g. Procedure
(1) After tlre above connection is completed, load the test tape (DTT-S113) on the deck and push the play
button to enter the playback mode.
(2) Adjust the semi-fixed resistors VR 105 and VR-205 on the AMP PC Board (PCM-446), so that the line
gutput levels may be -10 dB 11.0 dB in reference to the level (700 Hz -10 dB).
(3) When the step (2) is completed, play the test tape (DTT-5102) and check the output level is within the
range of -10 dB +3 dB -5 dB in reference to the level (700 Hz -10 dB).
(4) Change the tape speed switch to the 9.5 cm/s position, then play the test tape (DTT-3110) and adjust the
semi-fixed resistors VR-104 and VR-204 on the AMP PC Board, so that the line output levels may be
-10 dB 11.0 dB in reference to the level (500 Hz -10 dB).
(5) When the step (4) is completed, play the test tape (DTT-3102) and check the output level is within the
range of -10 dB t3dB in reference to the level (500 Hz-1 0 dB).
2.4 SOURCE MONITOR LEVEL
a. Specification
0 dB i0.5 dB of the line output iacks.
- b. Adiustment
3 Adjust the semi-fixed resistors VR-103 and VR-203.
c. Reference
Refer to F ig. 6-1.
cl. Test tape, special tools and instruments required
Signal generator and VTVM.
e. Test point
Connect the VTVM to the line output jacks.
f . Mode of switch
(1f Monitor SW SOURCE (button in).
(2) P.B. level controls MAX, Record level controls MAX.
g. Procedure
(l ) Connect the signal generator to the line input iacks, and apply a 700 Hz signal of -20 dB to the line
r n puts.
(2) After the above connection is completed, adjust the semi-fixed resistors VR 103 and VR-203 on the AMP
PC Board (PCM-446), so that the line output level may be 0 dB 10.5 dB on the VTVM.
ry
t(
3
15

2-5 LEVEL METER CALIBRATION
a. Specification
0 dB of the level meter scale.
b. Adjustment
Adjust the semi-fixed resistors VR-108 and VR-208'
c. Reference
Refer to Fig.6-1.
d. Test tape, special tools and instruments required
Signal generator and VTVM.
e. Test point
Connect the VTVM to the line output jacks.
f . Mode of switch
(1) Monitor SW-SOU RCE.
(2) P.B. level controls-MAx, Record level controls-MAX'
g. Procedure
(1) Connect the signal generator to the line input jacks, and apply a 7OO Hz signal of -20 dB to the line
i n puts.
(2) After the above connection is completed, adjust the semi-fixed resistors VR-108 and VR-208 on the AMP
pC Board (pCM-446), so that, when the line output level is 0 dB 10.5 dB, the level meter mav indicate
0 dB.
h. Note
Since the level meter may give an incorrect reading when the tape deck is placed horizontally or in a slanted
position, be sure to undertake the adjustment with the tape deck placed vertically'
2.6 BIAS FREOUENCY
Specif ication
130 KHz 11 KHz
Adjustment
Adjust the oscillator coil L-40'l (1139).
Reference
Refer to Fig. 6 1.
d. Test tape, special tools and instruments required
Frequency counter
e. Test point
Connect the frequency counter across the test points TP-4 and TP-5'
f . Mode of switch
(1) Record SW-ON (button in).
(2) P.B. level controls-MlN, Record level controls-MlN'
g. Procedure
( 1 ) After the above connection is completed, load the blank tape on the deck and push the record button and
play button simultaneously to enter the record mode, then push the pause button to stop tape travel'
(2) Adjust the bias oscillator coil L-401 on the Bias PC Board (PCM-413), so that the bias oscillator frequency
may be 130 KHz 11 KHz.
h. Note
Connect the O lead of the frequency counter to the test point TP-4, and its O lead to the test point TP-S.
b
b
a.
16

2-7 BIAS TRAP (REC.Arp)
a. Specification
\t Minimum.
b. Adjustment
Adjust the bias trap coils L-601 (L-ch) and L-602 (R ch).
c. Reference
Refer to Fig. 6-1.
d. Test tape. special tools and instruments required
Blank tape and VTVM.
e. Test point
Connect the VTVM across the test points TP-7 & TP-6. and also across TP-8 & TP-6 on the AMP PC Board.
f . Mode of switch
(1) Record SW-ON
(2) P.B. level controls-M lN, Record level controls-M lN.
g. Procedure
(1) Aftertheaboveconnectioniscompleted,loadtheblanktapeonthedeckandpushtherecordbuttonand
play button simultaneously to enter the record mode, then push the pause button to stop the tape travel.
(2) Adjust the bias trap coils L-601 and L-602 on the REC switch PC Board (PCM-397), so that the bias
leakage may be minimum by reading on the VTVM.
\t,
2-8 BIAS TRAP 2 (P.B. Amp)
a. Specif ication
Less than -30 dB
b. Adjustment
Adjust the bias trap coils L-1O2 and L-2O2.
c. Reference
Refer to Fig. 6 1 .
d. Test tape, special tools and instruments required
Blank tape and VTVM.
e. Test point
Connect the VTVM to the line output jacks.
f . Mode of switch
(1) Monitor SW-TAPE, Record SW-ON.
(21 P.B.level controls MAX, Record level controls-MlN.
g. Procedure
('1 ) Aftertheaboveconnectioniscompleted, loadtheblanktapeonthedeckandpushtherecordbuttonand
play button simultaneously to enter the record mode, then push the pause button to stop the tape travel.
(2) AdjustthebiastrapcoilsL-102andL-202ontheAMPPCBoard(PCM-446),sothatthebiasleakagemay
be less than -30 dB on the VTVM.
(3) Change the record switch over to OFF position and check that the bias leakage is less than -30 dB.
2.9 BIAS SETTING & RECORDING LEVEL
a. Specification
+0.3 dB (Over bias)
0 dB (Recording level)
b. Adjustment
(1) Adjust the bias trimmer capacitors C-604 (L-ch) and C-606 (R-ch).
(2) Adjust the semi-fixed resistors VR 102 (L-ch) and VR-202 (R-ch).
c. Reference
Refer to Fig. 6-1 .
I
17