Yamaha F-20 User manual

SERVICE MANUAL
HAMAMATSU, JAPAN
1.338K-713 K Printed in Japan 2001.09
011551
GA
CONTENTS
SPECIFICATIONS .............................................................................. 3
PANEL LAYOUT.................................................................................. 3
CIRCUIT BOARD LAYOUT................................................................. 4
BLOCK DIAGRAM .............................................................................. 4
DISASSEMBLY PROCEDURE ........................................................... 5
CIRCUIT BOARDS ............................................................................. 7
IC BLOCK DIAGRAM.......................................................................... 8
INSPECTIONS.................................................................................... 8
PARTS LIST
OVERALL CIRCUIT DIAGRAM
GUITAR AMPLIFIER
This document is printed on chlorine free (ECF) paper with soy ink.

2
F-20
IMPORTANT NOTICE
This manual has been provided for the use of authorized Yamaha Retailers and their service personnel. It has been assumed that
basic service procedures inherent to the industry, and more specifically Yamaha Products, are already known and understood by the
users, and have therefore not been restated.
WARNING: Failure to follow appropriate service and safety procedures when servicing this product may result in per-
sonal injury, destruction of expensive components and failure of the product to per form as specified. For
these reasons, we advise all Yamaha product owners that all service required should be performed by an
authorized Yamaha Retailer or the appointed service representative.
IMPORTANT: This presentation or sale of this manual to any individual or firm does not constitute authorization, certifica-
tion, recognition of any applicable technical capabilities, or establish a principal-agent relationship of any
form.
The data provided is believed to be accurate and applicable to the unit(s) indicated on the cover. The research engineering, and
service departments of Yamaha are continually striving to improve Yamaha products. Modifications are, therefor, inevitable and
changes in specification are subject to change without notice or obligation to retrofit. Should any discrepancy appear to exist, please
contact the distributor's Service Division.
WARNING: Static discharges can destroy expensive components. Discharge any static electricity your body may have
accumulated by grounding yourself to the ground buss in the unit (heavy gauge black wires connect to this
buss).
IMPORTANT: Turn the unit OFF during disassembly and parts replacement. Recheck all work before you apply power to
the unit.
WARNING: CHEMICAL CONTENT NOTICE!
The solder used in the production of this product contains LEAD. In addition, other electrical / electronic and / or plastic (where
applicable) components may also contain traces of chemicals found by the California Health and WelfareAgency (and possibly other
entities) to cause cancer and / or birth defects or other reproductive harm.
DO NOT PLACE SOLDER, ELECTRICAL / ELECTRONIC OR PLASTIC COMPONENTS IN YOUR MOUTH FOR ANY REASON
WHAT SO EVER!
Avoid prolonged, unprotected contact between solder and your skin! When soldering, do not inhale solder fumes or expose eyes to
solder / flux vapor!
If you come in contact with solder or components located inside the enclosure of this product, wash your hands before handling food.
IMPORTANT NOTICE FOR THE UNITED KINGDOM
Connecting the Plug and Cord
WARNING: THIS APPARATUS MUST BE EARTHED
IMPORTANT: The wires in this main lead are coloured in accor-
dance with the following code:
GREEN-AND-YELLOW: EARTH
BLUE: NEUTRAL
BROWN: LIVE
As the colours of the wires in the main lead of this apparatus may not
correspond with the coloured markings identifying the terminals in your
plug, proceed as follows:
The GREEN-and-YELLOW wire must be connected to the terminal in the
plug that is marked with the letter E or the safety earth symbol (or coloured
GREEN or GREEN-and-YELLOW).
The BLUE wire must be connected to the terminal that is marked with the
letter N (or coloured BLACK).
The BROWN wire must be connected to the terminal that is marked with
the letter L (or coloured RED).
This applies only to products distributed by Yamaha Kemble Music (U. K.) Ltd.
WARNING
Components having special characteristics are marked and
must be replaced with parts having specification equal to those
originally installed.

3
F-20
Rated Output Power: 20W
Speaker: 20cm x 1
Controls: VOLUME, GAIN, MASTER VOL., TREBLE, MIDDLE, BASS, CH SELECT switch (A/B)
Input/Output Terminals: INPUT, AUX IN, PHONES
Output Impedance: 100Ω(PHONES)
Power Consumption: 30W/100V (J)
25W/120V (UL,CSA)
25W/230V (E,BS)
Power Requirements: U.S. and Canadian models: 120V, 60Hz
General model: 230V, 50Hz
Dimensions (W x H x D): 357 x 330 x 197mm (14.1" x 13" x 7.8")
Weight: 6.5kg (14 lbs 5 oz)
SPECIFICATIONS
PANEL LAYOUT
 INPUT
 CH SELECT A/B (Channel Select Switch A/B)
A Channel
 VOLUME
* No sound is produced when the VOLUME knob is
set to "0".
B Channel
 GAIN
 MASTER VOL.
* No sound is produced when the MASTER VOL.
knob is set to "0".
         
Tone Controls
 TREBLE
 MIDDLE
 BASS
 AUX IN
* Use the volume control on the audio device to
control its volume level.
 PHONES
* The speaker produces no sound when a pair of
headphones is connected to this jack.
 POWER

4
F-20
CIRCUIT BOARD LAYOUT
MAIN 1/2
MAIN 1/2
MAIN 1/2
AC Cord
Power Transformer
MAIN 2/2
MAIN 2/2
BLOCK DIAGRAM
+B
+12V
-12V
-B
OPAMP
IC1
31
OPAMP
IC2
31
OPAMP
IC1
57
OPAMP
IC2
57
POWER
AMP
IC3
14
INPUT
CH. SELECT SW
CH. A
CLEAN
IC1. IC2
CH. A
CLEAN
CH. B
DRIVE
CH. B
DRIVE
+B
VOLUME
GAIN
MASTER
FUSE
FZ1
INDICATOR
BASS MIDDLE TREBLE
PASSIVE TYPE
TONE CONTROL
POWER SUPPLY CIRCUIT
POWER TRANSFORMER
VR1
VR2
VR3
VR4 VR5 VR6
4ΩSpeaker
PHONES
AUX IN
CN2 4P
CN1 2P
CN3 3P
CN4 5P CN5 5P
POWER SWITCH
SW1
SW2
T2
T1
T4
T1
T2
G
U, C, S, BS
MAIN 1/2
MAIN 2/2
T3
+12V
-12V
+12V
-12V
+12V
-12V
+12V
-12V
+B
-B
JK3
JK2
JK1
V695450
Top View Side View
Front View

5
F-20
DISASSEMBLY PROCEDURE
[30] x 4 Speaker
[B]
Pre-Main UnitPre-Main Unit
[A] Back Board
1. Pre-Main Unit (Time required: about 1 min)
1-1 Remove the speaker wires.
1-2 Remove the four (4) screws marked [30]. The pre-main unit can then be removed by sliding it backward. (Fig.1)
2. Speaker (Time required: about 1 min)
2-1 Remove the four (4) screws marked [A]. The back board can then be removed. (Fig.1)
2-2 Remove the four (4) screws marked [B]. The speaker can then be removed. (Fig.1)
3. MAIN 1/2 Circuit Board (Time required: about 3 min)
3-1 Remove the pre-main unit. (See procedure 1)
3-2 Remove the six (6) knobs marked [P100] and the six (6) hexagonal nuts marked [C]. (Fig.5)
3-3 Remove the hexagonal nuts marked [A120] and the hexagonal nuts marked [A140]. (Fig.5)
3-4 Push the hooks of the spacer support (at the arrow symbol area of illustration) with a needle-nose plier to unlock.
The Main 1/2 circuit board can then be removed. (Fig.2)
[30]: Truss Head Screw 4.0X25 MFZN2BL (VN347600)
(Fig. 1)
MAIN1/2 Circuit Board
MAIN1/2 Circuit Board
Needle Nose Plier
Needle Nose Plier
MAIN1/2 Circuit Board
[P40]
[P40]
[P40]
Needle Nose Plier
(Fig. 2)
[A]: Bind Head Tapping Screw 4.0X25 FCRM3-BL (EI340256)
[B]: Bind Head Screw 4.0X20 ZMC2BL (VB403600)

6
F-20
MAIN 1/2
MAIN 2/2
[P100], [C][A120]
[P60][P70][C80]
[A140]
[P70][P60][P40] [P40]
Power Transformer
4. MAIN 2/2 Circuit Board (Time required: about 3 min)
4-1 Remove the pre-main unit. (See procedure 1)
4-2 Remove the screw marked [C80]. The MAIN 2/2 circuit board can then be removed. (Fig.5)
5. Power Transformer (Time required: about 4 min)
5-1 Remove the pre-main unit. (See procedure 1)
5-2 While pushing down the nut marked [P70] with a spanner, remove the two (2) screws marked [P60]. The power
transformer can then be removed. (Fig.4)
[A120]: Hexagonal Nut 9.0 12X2 MFNI33 (LX200060)
[A140]: Hexagonal Nut 12.0 14X2 MFNI33 (ES200210)
[C80]: Bind Head Tapping Screw-1 3.0X16 MFZN2BL (EP030310)
[P70]: Hexagonal Nut #1 4.0 MFZN2Y (VB837300)
[P60]: Pan Head Screw 4.0X10 MFZN2BL (V7018000)
[P100]: Knob (V6955100)
(Fig. 5)
[P60][P70] [P60][P70]
Power Transformer
ransformer
Power Transformer
(Fig. 4)
[C80][C80]
MAIN1/2 Circuit Board
MAIN2/2 Circuit Board
MAIN1/2 Circuit Board
MAIN2/2 Circuit Board
(Fig. 3)

7
F-20
A
INPUT CH SELECT
A/B VOLUME GAIN MASTER VOLUME TREBLE A'
A
MIDDLE BASS AUX IN PHONES
A'
to Speaker
from Power Cord
to Power Transformer
to Main 2/2 CN5
from Power Transformer
MAIN1/2 Circuit Board
CIRCUIT BOARDS
MAIN 1/2 (J, U): CNA-V733720
1
MAIN 1/2 (H, B): CNA-V733730
MAIN 2/2 (J, U): CNA-V733720
MAIN 2/2 (H, B): CNA-V733730
to MAIN 1/2 CN4
MAIN 2/2 Circuit Board
Component Side
Component Side
VERSION FUSE
RATE INDICATION
J, U 250V 500mA
E, BS 250V T160mAL
Must be
erased
Must be
erased

8
F-20
INSPECTIONS
1. Preparation
To inspect the main unit, the following jigs are required.
CD player
Headphones
Before turning the power on, set all the knobs on the panel to "0".
Raise the CH SELECT switch to select channel A.
2. Power supply
Connect the power cord to the suitable power supply socket for each version.
(UC - 120V, E&BS - 220V)
3. Inspection procedure
3-1 Input the audio signal of CD player to the AUX-IN jack.
3-2 Make sure that the sound becomes gradually larger (or smaller) according as you turn the VOLUME knob to the
right (or left).
3-3 Make sure that the high frequency is gradually emphasized (or eliminated) as you turn the TREBLE knob to the
right (or left).
3-4 Make sure that the middle frequency is gradually emphasized (or eliminated) as you turn the MIDDLE knob to
the right (or left).
3-5 Make sure that the low frequency is gradually emphasized (or eliminated) as you turn the BASS knob to the right
(or left).
3-6 Make sure that the sound becomes larger when you depress the CH SELECT switch to select channel B.
Besides, make sure that the sound becomes gradually distorted according as you turn the GAIN knob to the right.
3-7 Make sure that the sound becomes gradually larger (or smaller) according as you turn the MASTER VOLUME
knob to the right (or left).
3-8 Raise the CH SELECT switch to select channel A and make sure that the audio signal sounds over the speaker.
3-9 Connect headphones to the PHONES jack. Make sure that the speaker does not produce any sound and audio
signal sounds over the headphones.
3-10 Set all the knobs on the panel to "0" and finish the inspection.
IC BLOCK DIAGRAM
BA4558 (XO078A00)
Dual Operational Amplifier
1
2
3
4-V
8
7
6
5
Output A +V
Non-Inverting
Input A
-DC Voltage Supply
+DC Voltage
Supply
Output B
Inverting
Input B
Non-Inverting
Input B
Inverting
Input A
+-
+-
MAIN: IC2,IC3

F-20
1
PARTS LIST
GUITAR AMPLIFIER
CONTENTS
OVERALLASSEMBLY ..................................................................................2
PRE-MAIN UNIT ............................................................................................4
ELECTRICAL PARTS ....................................................................................6
WARNING
Components having special characteristics are marked and must be replaced with parts having
specifications equal to those originally installed.
The numbers in “QTY” shows quantities for each unit.
The parts with “--” in “Part No.” are not available as spare parts.
The second letter of the shaded ( ) part number is I, not one.
The second letter of the shaded ( ) part number is O, not zero.

F-20
2
OVERALL ASSEMBLY
60
20
10
C40
C60
C50
C60
C50
C30
C30
B
A
C20
C70
C90
C80
50
30
C120
C100
C110
OVERALL CABINET ASSEMBLY
Pre-Main Unit
[A]
Speaker
Back Board
Pre-Main Unit
(See P. 4)

F-20
3
REF NO.PART NO. DESCRIPTION REMARKS QTY RANK
RANK: Japan only*New parts
*
*
*
*
*
*
*
*
*
10
20
20
20
20
30
50
60
60
60
C10
C20
C30
C40
C50
C60
C70
C80
C90
C100
C110
C120
A
B
--
--
--
--
V6954600
--
--
--
--
VN347600
ET500040
--
--
--
V6954600
--
V5969000
21770200
V6327200
V6327300
V8480700
V6327400
EP030310
03765580
V7363300
VN729100
XO175A00
EI340256
VB403600
OVERALLASSEMBLY
Overall Assembly
Overall Assembly
Overall Assembly
Overall Assembly
Overall Assembly
Pre-Main unit
Pre-Main unit
Pre-Main unit
Pre-Main unit
Truss Head Screw
Flat Washer
Label
Label
Label
OVERALL CABINETASSEMBLY
Overall Cabinet Assembly
Cabinet Assembly
Corner Protector
Oval Head Screw
Handle
Handle Holder
Oval Head Screw
Foot
Bind Head Tapping Screw-1
Flat Washer
Name Plate
Bind Head Tapping Screw-1
Speaker Unit
Bind Head Tapping Screw
Bind Head Screw
4.0X25 MFZN2BL
GA-10
3.0X12 MFZN2BL
KPBO KAH1D-205
KPBO KAH3D400-A
4.0X30 MFZN2BL
KPBO KRRU19
3.0X16 MFZN2BL
3.0X8X0.5 MFZN2BL
F-20
3.0X10 MFZN2BL
4ohm 30W
4.0 X 25 FCRM3-BL
4.0 X 20 ZMC2BL
F20 (V695390)
(V736090)
(V736100)
(V736110)
J (V695450)
U (V736130)
H (V736140)
B (V736150)
J (V695470)
U (V736160)
H,B (V736170)
F20
(V695500)
4
4
6
12
2
2
4
4
4
2
4
4
01
01
01
01
01
01
01
01

F-20
4
A10
A70
A60
A40
A10
A30 A80
A90
A20
P60 P40
P60
P30
P75
P70
P50
P10
P20
P90
P80
A50
P100
P120 P110
A100
A110
A130
A140
A120
PRE-MAIN UNIT

F-20
5
REF NO.PART NO. DESCRIPTION REMARKS QTY RANK
RANK: Japan only*New parts
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
P10
P20
P30
P30
P30
P30
P40
P50
P60
P70
P75
P80
P90
P100
P110
P120
A10
A10
A20
A30
A40
A50
A50
A50
A60
A70
A70
A70
A70
A80
A90
A100
A110
A120
A130
A140
--
--
--
--
V6954800
V6954900
--
--
--
--
V7511400
V7017600
V7018000
VB837300
VB501900
V7018100
V7554300
V6955100
ET900050
--
--
--
--
--
V7337200
V7337300
VV849300
V7356900
V7054700
XZ805A00
XZ806A00
XZ807A00
VV104600
V6286700
V6286900
V6287000
V6287100
V7356700
V7356800
ET800150
VL802300
LX200060
VB508700
ES200210
PRE-MAIN UNIT
Pre-Main unit
Pre-Main unit
Pre-Main unit
Pre-Main unit
Chassis
Panel Sheet
Amp Kit
Amp Kit
Amp Kit
Amp Kit
Spacer Support
Heat Sink
Pan Head Screw
Hexagonal Nut
Spring Washer
Pan Head Screw
Button
Knob
Toothed Lock Washer-B
Earth Mark
Amp Kit
Amp Kit
Amp Kit
Amp Kit
Circuit Board
Circuit Board
Insulation Sheet
Sleeve
Power SW
Transformer
Transformer
Transformer
Cord Holder
Cord
Cord
Cord
Cord
Cord Strain Relief
Cord Strain Relief
Toothed Lock Washer-A
Flat Washer
Hexagonal Nut
Flat Washer
Hexagonal Nut
PINGOOD LCC-10
4.0X10 MFZN2BL
#1 4.0 MFZN2Y
4.0 MFZN2Y
3.0X10 MFZN2BL
GA-RED
4.0 MFZN2BL
BFG-20AD 19X24
12SWS0220
SDDJE1-A-2
CV-100
J VCTF
UC 3 SJT 18/3
E 3 HO5VV-F
UK 3 HO5VV-F
KR-61 KITAGAWA
KF-41 KITAGAWA
9.0 MFZN2Y
9X14 0.5 FNM3
9.0 12X2 MFNI33
18X12.5 0.6 MFZN2
12.0 14X2 MFNI33
F20
J (V695450)
U (V736130)
H (V736140)
B (V736150)
J (V733660)
U (V733670)
H (V733680)
B (V733690)
CH SELECTA/B
VOL,GAIN,MASTER VOLUME
TREBLE,MID,BASS
(CA06069)
J (V733660)
U (V733670)
H (V733680)
B (V733690)
J,U
H,B
POWER SW
J
U
H,B
J
U
H
B
2
2
2
2
2
6
2
01
01
01
01
01
01
01
01

REF NO.PART NO. DESCRIPTION REMARKS QTY RANK
F-20
6
RANK: Japan only
*New parts
ELECTRICAL PARTS
*
*
*
*
*
*
*
*
C01
C02
C03
C04
C05
C06
C07
C08
C09
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
C32
C33
C34
C35
C36
C37
CN1
CN2
CN3
D01
D02
DB1
FZ1
FZ1
IC1
IC2
IC3
JK1
JK2
JK3
LD1
LD2
R01
R02
R03
R04
R05
R06
R07
R08
R09
V7337200
V7337300
V7337200
V7337300
V6609900
VV291400
VV062800
VZ353500
UR866100
VZ353500
VZ353500
VV321100
UR847100
UR847100
UA654470
VZ353500
VV062800
UR847100
UR847100
VZ353500
VZ353500
UA653270
UR866100
UR865470
UR847100
VZ353500
UR866100
VZ353500
UR847100
UR847100
FG613100
UR837470
VV062800
VV062800
UR847100
UR847100
V7355000
VZ354600
VZ354600
UR749220
UR749220
UR847100
UR847100
VG879900
LB932040
LB918030
VD631600
VD631600
VP344100
V7630900
V7630800
X0078A00
X0078A00
XZ311A00
V3633400
V6176500
V7447000
VV620800
VV620800
HF456220
HF459100
HF457100
HF457330
HF457330
HF456220
HF459100
HF458100
HF457100
ELECTRICAL PARTS
Circuit Board
Circuit Board
Circuit Board
Circuit Board
Fuse Holder
Jumper Wire
Mylar Capacitor
Ceramic Capacitor-SL
Electrolytic Cap.
Ceramic Capacitor-SL
Ceramic Capacitor-SL
Monolithic Mylar Capacitor
Electrolytic Cap.
Electrolytic Cap.
Mylar Capacitor
Ceramic Capacitor-SL
Mylar Capacitor
Electrolytic Cap.
Electrolytic Cap.
Ceramic Capacitor-SL
Ceramic Capacitor-SL
Mylar Capacitor
Electrolytic Cap.
Electrolytic Cap.
Electrolytic Cap.
Ceramic Capacitor-SL
Electrolytic Cap.
Ceramic Capacitor-SL
Electrolytic Cap.
Electrolytic Cap.
Ceramic Capacitor-B
Electrolytic Cap.
Mylar Capacitor
Mylar Capacitor
Electrolytic Cap.
Electrolytic Cap.
Capacitor
Monolithic Ceramic Cap.
Monolithic Ceramic Cap.
Electrolytic Cap.
Electrolytic Cap.
Electrolytic Cap.
Electrolytic Cap.
Base Post Connector
Base Post Connector
Base Post Connector
Diode
Diode
Diode Stack
Fuse
Fuse
IC
IC
IC
Phone Jack
Phone Jack
Phone Jack
LED
LED
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
WH-007
0.60
0.1 50V J
100P 50V J
1.00 50.0V
100P 50V J
100P 50V J
0.22 50V J
10.00 25.0V
10.00 25.0V
0.0470 50V J
100P 50V J
0.1 50V J
10.00 25.0V
10.00 25.0V
100P 50V J
100P 50V J
2700P 50V J
1.00 50.0V
0.47 50.0V
10.00 25.0V
100P 50V J
1.00 50.0V
100P 50V J
10.00 25.0V
10.00 25.0V
1000P 50V K
47.00 16.0V
0.1 50V J
0.1 50V J
10.00 25.0V
10.00 25.0V
4700P 250V J.U.C.S
0.10 50V Z
0.10 50V Z
2200 25.0V
2200 25.0V
10.00 25.0V
10.00 25.0V
VA- 2P TE
VH- 4P TE
XH 3P TE
1SS133,176,HSS104
1SS133,176,HSS104
D2SBA20 1.5A 200V
500 mA JU
315 mA E
BA4558
BA4558
TDA2030A
HTJ-064-12I
HTJ-064-05B
ST HTJ-035-09ABT
LT311G-41-C13 RED
LT311G-41-C13 RED
2.2K 1/4 J
1.0M 1/4 J
10.0K 1/4 J
33.0K 1/4 J
33.0K 1/4 J
2.2K 1/4 J
1.0M 1/4 J
100.0K 1/4 J
10.0K 1/4 J
F20
J,U (XZ804B0)
H,B (XZ804B0)
J,U (XZ804B0)
H,B (XZ804B0)
DIP OPAMP
DIP OPAMP
HIFI AMP
INPUT
PHONES
AUX IN
DRIVE
CLEAN
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
03
03
01
01
01
01
01
01
01
03
01
01
01
01
01
01
01
01
01
01
01
01

F-20
7
REF NO.PART NO. DESCRIPTION REMARKS QTY RANK
RANK: Japan only*New parts
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
-27
R28
R29
R30
R31
R32
R33
SW2
TR1
VR1
VR2
VR3
VR4
VR5
VR6
ZD1
ZD2
CN45
T1T2
T3T4
HF456330
HF456100
HF456100
HF458100
HF456100
HF457330
HF456220
HF456100
HF458100
HF457100
HF456100
HF458220
HF457100
HF457470
HF457100
HF457470
HF457470
HF455470
HF457330
VC740100
VC745000
HF455820
HF455820
VR140800
IC174070
V7054800
V6607700
V7054800
V6607700
V7054900
V6607700
VG440200
VG440200
--
--
--
XO175A00
V7054700
XZ805A00
XZ806A00
XZ807A00
V6286700
V6286900
V6287000
V6287100
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Carbon Resistor
Metal Oxide Film Resistor
Metal Oxide Film Resistor
Carbon Resistor
Carbon Resistor
Push Switch
Transistor
Rotary Variable Resistor
Rotary Variable Resistor
Rotary Variable Resistor
Rotary Variable Resistor
Rotary Variable Resistor
Rotary Variable Resistor
Zener Diode
Zener Diode
Connector Assembly
Connector Assembly
Connector Assembly
Speaker Unit
Power SW
Transformer
Transformer
Transformer
Cord
Cord
Cord
Cord
3.3K 1/4 J
1.0K 1/4 J
1.0K 1/4 J
100.0K 1/4 J
1.0K 1/4 J
33.0K 1/4 J
2.2K 1/4 J
1.0K 1/4 J
100.0K 1/4 J
10.0K 1/4 J
1.0K 1/4 J
220.0K 1/4 J
10.0K 1/4 J
47.0K 1/4 J
10.0K 1/4 J
47.0K 1/4 J
47.0K 1/4 J
470.0 1/4 J
33.0K 1/4 J
1.0 1W J
100.0 1W J
820.0 1/4 J
820.0 1/4 J
2SC1740S R,S
16mm 10KA
16mm 25KA
16mm 10KA
16mm 25KA
16mm 1KA
16mm 25KA
MTZ J 12.0B 12.0V
MTZ J 12.0B 12.0V
B&B #26 5P L 100
#18 2P L 60
#18 2P L 300
4ohm 30W
SDDJE1-A-2
J VCTF
UC 3 SJT 18/3
E 3 HO5VV-F
UK 3 HO5VV-F
CH SELECTA/B
VOL
GAIN
MASTER VOLUME
TREBLE
MID
BASS
(V735970)
(V660880)
(V744980)
POWER SW
J
U
H,B
J
U
H
B
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
01
03
01
01
01

ABCDEFGH
1
2
3
4
5
F-20
F-20
F-20
<P.1>
OVERALL CIRCUIT DIAGRAM
Note: See parts list for details of circuit board component parts.
TRANS
FORMER
MAIN 1/2
MAIN 2/2
VOLUME
GAIN
MASTER
CH SELECTA/B
POWER ON/OFF
INPUT
MIDDLE
BASS
TREBLE
AUX IN
PHONES
4ΩSPEAKER
OP AMP
OP AMP OP AMP
OP AMP
OP AMP
OP AMP
HIFI AMP
KEC-54230
KEC-54230
1
1
J, U, C S, BS
250V 500mA 250V T160mA L
D2SBA20 (VP344100)
DIODE STACK 1.5A 200V
DB1
WARNING
Components having special characteristics are maked and
must be replaced with parts having specification equal to those originally installed.