Casio LK-120 Troubleshooting guide

LK-120
JUL. 2010
LK-120
Ver. 2 : Jan. 2012
ELECTRONIC KEYBOARD

CONTENTS
SPECIFICATIONS........................................................................................... 1
BLOCK AND WIRING DIAGRAM .................................................................. 2
PCB INFORMATION....................................................................................... 3
CIRCUIT DESCRIPTION ................................................................................ 4
PRINTED CIRCUIT BOARDS......................................................................... 5
DISASSEMBLY............................................................................................... 7
DIAGNOSTIC PROGRAM ............................................................................ 16
EXPLODED VIEW......................................................................................... 22
PARTS LIST.................................................................................................. 23
SCHEMATIC DIAGRAMS............................................................................. 26
LK-120

LK-120
– 1 –
SPECIFICATIONS
Keyboard 61 standard-size keys; 5 octaves
Key Light System Can be turned on and off (up to 4 keys can be lit at the same time)
Tones 100 presets
Polyphony 12 notes maximum
3-Step Lesson System Number of simultaneously lit keys; 4
3-Steps
Playback 1 tune repeat playback
Voice Fingering Guide On/Off
Auto-accompaniment
Rhythm Patterns 50 presets
Tempo Adjustable, (216 steps, = 40 to 255), initial value; 120
Chords Two systems; CASIO CHORD, FINGERED
Other Fill-in pattern, Synchro start
Song Bank Tunes 100 tunes
Musical Information Function Tone, Auto Accompaniment, Song Bank numbers and names; tempo,
3 step lesson display, chord name, ngering, timing indicator, key lighting,
voice ngering
Other Functions
Transpose F# to C to F: half-note
Tuning Adjustable A4 = Approx. 440 Hz ± 50 cents,
Initial value: A4 = Approx. 440 Hz
Speakers 10 cm diameter × 2 (Output: 2 W+2 W)
I/O Terminals
Power Supply DC 9.5 V jack
Headphones/Output Stereo standard jack (Output is monaural.)
Output impedance 78 Ω, output voltage: 4 V (RMS) MAX
Power Supply 2-way
Batteries 6 AA-size zinc-carbon batteries or alkaline batteries
Battery Life:
Approximately 4 hours continuous operation on alkaline batteries
Approximately 1 hour continuous operation on zinc-carbon batteries
AC Adaptor AD-E95100L
Auto Power Off Approximately 6 minutes after the last operation
Power Consumption 9.5 V 7.7 W
Dimensions 94.9 × 30.4 × 9.3 cm (37 3/8× 11 15/16 × 3 11/16 inch)
Weight Approximately 3.4 kg (7.5 lbs) (without batteries)

LK-120
– 2 –
BLOCK AND WIRING DIAGRAM
VD5
VE5
VC
RIGHT
SPEAKER
LEFT
SPEAKER
VE5VA5VD5
VD5
VCP
D202
LSP
RSP
VA5 VE5
VD5 VA5 VE5
LCD
VCP
KEYBOARD
PCB
(M800-KYA2)
KEYBOARD LED PCB
(M821-LDA2)
KEYBOARD LED PCB
(CSM446-LD5M)
KEYBOARD LED PCB
(M821-LDA1)
KEYBOARD PCB
(M800-KYA1)
LCD
CONTROLLER
IC3
KEYBOARD LED
CONTROLLER
IC2
POWER
AMPLIFIER
IC201
RESET IC
IC4
POWER SUPPLY
CIRCUIT
Q202, Q203, Q204,
D206, D207,
C225-C229
CN3 (17 pin)
CN201 (17 pin)
CN205
CN206CN207
CN6
CN8
CN204
LSP+
LSP-
CN9
CN7
CN4
CN5
RSP+
RSP-
CN803 (16 pin)
CN801 (13 pin)
CN802 (13 pin)
CN1 (16 pin) CN2 (16 pin)
CN506 (16 pin) CN503 (12 pin)
CN504 (6 pin) CN504 (6 pin)CN505 (6 pin)
JE (6 pin)
KEYBOARD LED PCB
(CSM446-LD4M)
JF (6 pin)
KEYBOARD LED PCB
(CSM446-LD3M)
JG (6 pin)
CN501 (12 pin)
SI1, SI2, SI4~SI6,
KI7S, SO1~SO6
KI0~KI7 KO0~KO7 LY0~LY7, LX0~LX7
KI4S~KI7S,
KO11S
PHONES/OUTPUT
(J202)
9 V
DC IN
(J201)
POWER AMP PCB (M820-PSA1)
MAIN PCB
(M821-MDA1)
BUTTONS VOLUME
(SW202)
POWER
SWITCH
(SW201)
POWER OFF
CIRCUIT
Q201
MPU
IC1
BUTTONS
KI0S~KI7S,
KO8S~KO11S
RESET
RESET
A0~A2
DB0~DB3
DB4~DB7
CN202 (-)
CN203 (+) BATTERY

LK-120
– 3 –
PCB INFORMATION
M820-PSA1 M800-KYA2M800-KYA1 M821-MDA1
CSM446-LD5
M821-LDA2M821-LDA1
CSM446-LD3 CSM446-LD4
Classifi cation Parts Name PCB Name Components
Main PCB PCB ASSY/MDA1 M821-MDA1
MPU, LCD Controller, Keyboard LED
Controller, Reset IC, Buttons,
Right Speaker Terminal
Power Amp PCB PCB ASSY/PSA1 MX820-PSA1
Power Supply Circuit, Power Amplifi er,
Power Switch, Volume, Buttons,
DC 9.5 V Jack, Left Speaker Terminal,
Phones/Output Jack
Keyboard LED
PCB
PCB ASSY/LDA M821-LDA1
Keyboard LED
M821-LDA2
PCB ASSY/LD3M CSM446-LD3M
PCB ASSY/LD4M CSM446-LD4M
PCB ASSY/LD5M CSM446-LD5M
Keyboard PCB PCB ASSY/KYA M800-KYA1 Keyboard
M800-KYA2

LK-120
– 4 –
CIRCUIT DESCRIPTION
KEY MATRIX

KC0 KC1 KC2 KC3 KC4 KC5 KC6 KC7
KI0 C2 C2# D2 D2# E2 F2 F2# G2
KI1 G2# A2 A2# B2 C3 C3# D3 D3#
KI2 E3 F3 F3# G3 G3# A3 A3# B3
KI3 C4 C4# D4 D4# E4 F4 F4# G4
KI4 G4# A4 A4# B4 C5 C5# D5 D5#
KI5 E5 F5 F5# G5 G5# A5 A5# B5
KI6 C6 C6# D6 D6# E6 F6 F6# G6
KI7 G6# A6 A6# B6 C7
NOMENCLATURE OF KEYS

C2 C3 C4 C5 C6 C7
BUTTON MATRIX

KO8S KO9S KO10S KO11S
KI0S 0 5 TONE STEP 1
KI1S 1 6 RHYTHM STEP 2
KI2S 2 7 SONG BANK STEP 3
KI3S 3 8 PART SELECT SPEAK
KI4S 4 9 ONE KEY PLAY
LEFT
FINGERED
(POWER/MODE)
KI5S START/STOP TEMPO DOWN/
VALUE
ONE KEY PLAY
RIGHT
CASIO CHORD
(POWER/MODE)
KI6S TEMPO UP/
VALUE KEY LIGHT NORMAL (POWER/MODE)
KI7S SYNCHRO/
FILL-IN DEMO OFF (POWER/MODE)

LK-120
– 5 –
PRINTED CIRCUIT BOARDS
Main PCB: M821-MDA1 Sub PCB: M820-PSA1

LK-120
– 6 –
Keyboard PCB: M800-KYA1
Keyboard LED PCB: M821-LDA1
Keyboard LED PCB: M821-LDA1
Keyboard PCB: M800-KYA2

LK-120
– 7 –
DISASSEMBLY
CAUTION

The photos show a prototype. The appearance of the instrument, such as color, may
z
differ from the actual model.
To avoid damages to the instrument and the oor, lay the instrument on a mattress
z
or blanket before starting disassembling.
There are several kinds of screws. Be sure to use the correct type of screws when
z
reassembling. It is advisable to sort the screws as shown below after removing
them.
If a screw cap is attached to a screw, be sure to reattach the screw cap when
z
reassembling.
BEFORE STARTING REPAIR OR SERVICING

Remove the AC adaptor or the AC cord.
z
Remove accessories such as the music stand.
z

LK-120
– 8 –
DISASSEMBLY

PANEL UNITA.
Undo 11 screws on the bottom surface of the main unitA-1.
When replacing the keyboard LED PCBs, undo 16 screws and then remove the L-COVER-A/B/C.A-2.
L-COVER-C L-COVER-B L-COVER-A
<Caution for installing L-COVER-A/B/C>
To install the L-COVER-A/B/C, tighten the screws indicated with arrows engraved on each cover
rst.
L-COVER-C L-COVER-B L-COVER-A

LK-120
– 9 –
Turn over the panel unit.A-3.
Unsolder two battery lead wires.A-4.
Unsolder two FFCs.A-5.
Lead wire (Red)
Lead wire (Black)
FFC (M800-KYA2)FFC (M821-LDA2)
Remove the panel unit.A-6.
M821-MDA1 PCBM820-PSA1 PCB

LK-120
– 10 –
MAIN PCB (M821-MDA1)B.
Unsolder two FFCs.B-1.
FFC (M800-KYA2)FFC (M821-LDA2)
Unsolder two lead wires and one FFC.B-2.
Lead wire (White)
Lead wire (Blue)
FFC (M820-PSA1)
Unsolder two lead wires connected to the right speaker.B-3.
Lead wire (White)
Lead wire (Blue)

LK-120
– 11 –
Undo 16 screws and then remove the M821-MDA1 PCB, rubber keys and LCD.B-4.
Rubber keys LCD
<Caution for installing M821-MDA1 PCB>
To install the M821-MDA1 PCB, tighten the screws for
the LCD part in the order shown in the right.
If not tighten correctly, it may cause the LCD display
errors.
4
3
2
1
5
6

LK-120
– 12 –
POWER AMP PCB (M820-PSA1)C.
Unsolder two lead wires and one FFC connected to the M821-MDA1 PCB.C-1.
Lead wire (White)
Lead wire (Blue)
FFC (M820-PSA1)
Unsolder two lead wires connected to the left speaker.C-2.
Lead wire (Blue)
Lead wire (White)
Undo eight screws and then remove the M820-PSA1 PCB, rubber keys and switches.C-3.
Rubber keys Switches

LK-120
– 13 –
KEYBOARDD.
Undo eight screws and then remove the side panels.D-1.
Left side panel Right side panel
Undo 21 screws and then remove the white keys and black keys.D-2.

LK-120
– 14 –
KEYBOARD PCB (M800-KYA1/KYA2)E.
Disengage the hooks and then remove the M800-KYA1/KYA2 PCBs.E-1.
Remove ve rubber contact strips.E-2.
One rubber contact strip differs in length.NOTE:
Rubber contact strips This rubber contact strip differs
from the others in length.
<How to install rubber contact strips>
Lightly insert the tip of a rubber contact strip into the PCB.
Pull the tip from the back of the PCB and install it using
a tool such as tweezers. Do not forcibly pull it.

LK-120
– 15 –
KEYBOARD LED PCB (M821-LDA1/LDA2, CSM446-LD3M/LD4M/LD5M)F.
M821-LDA1 PCB
CSM446-LD3M PCB CSM446-LD4M PCB CSM446-LD5M PCB
M821-LDA2 PCB
Undo 14 screws on the M821-LDA1/LDA2 PCBs.F-1.
Turn over the M821-LDA1/LDA2 PCBs.F-2.
Do not touch the LEDs.NOTE:
Unsolder three FFCs and then remove the M821-LDA1/LDA2 PCBs.F-3.
After repairing, arrange the FFCs again.NOTE:
Undo 12 screws on the CSM446-LD3M/LD4M/LD5M PCBs and then remove the CSM446-LD3M/F-4.
LD4M/LD5M PCBs.
After repairing, arrange the FFCs again.NOTE:
FFC (CSM446-LD3M) FFC (CSM446-LD4M) FFC (CSM446-LD5M)

LK-120
– 16 –
DIAGNOSTIC PROGRAM
INITIAL SETTING

Connect the AC adaptor.(1)
Turn the volume to the maximum.(2)
HOW TO START THE DIAGNOSTIC PROGRAM

Hold down the “0” and “START/STOP” buttons at the same time, to turn the power ON.(1)
Set the mode switch to the “NORMAL”.NOTE:
Be sure to turn off the power when the test is nished.NOTE:
Release the “0” and “START/STOP”(2) buttons.
After the diagnostic program is launched, the test menu appears.(3)
TEST ITEMS

Pushing a test button enables the corresponding test item to be tested.
Test Items Buttons Note
Mode Switch Check ―
Button Check 0
ROM Version Check 1
Keyboard LED Check TONE
LCD Check STEP 1
Auto Power Off Check PART SELECT
This diagnostic program does not test the following items.
Check the functions with regular power-on state.
Test Items Buttons Note
Keyboard Check ―
Headphones Check ―Headphones

LK-120
– 17 –
DIAGNOSTIC PROGRAM

MODE SWITCH CHECKA.
Switch the mode switch and check that the following screen appears on the LCD.A-1.
Mode Switch LCD
FINGERED
CASIO CHORD
NORMAL

LK-120
– 18 –
BUTTON CHECKB.
Press the “0” button to select the “Button Check”.B-1.
Press the keys in the order of the numbers indicated in the illustration below.B-2.
If the button function is OK:
The conrmation chord sounds, and the button number and “OK” appear on the LCD.
If a button function is not operating properly or a button is pressed in a wrong order:
The error tone sounds, and the button number and “NG” appear on the LCD.
You cannot cancel this check procedure mid-way.NOTE:
01 02 05 06 10 11 12 13 24 25 26
03 04 07
23
22
21
20
19
14
15
16
17
18
08 09
When the “SPEAK” button is pressed at the end, the conrmation chord sounds and “SWITCHOK” B-3.
appears on the LCD.
ROM VERSION CHECKC.
Press the “1” button to perform the “ROM Version Check”.C-1.
The ROM version appears on the LCD.
Check that the ROM version is “821VR100”.C-2.