Casio LK-127 Troubleshooting guide

LK-127
MAR. 2013

LK-127
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............................................................................. 27

LK-127
– 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, 2= 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-127
– 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)
DC 9 V
(J201)
POWER & AMP PCB (M820-PSA1)
MAIN PCB
(M821-MDA1)
BUTTONS VOLUME
POWER
SWITCH
POWER OFF
CIRCUIT
Q201
MPU
IC1
BUTTONS
KI0S~KI7S,
KO8S~KO11S
RESET
RESET
A0~A2
DB0~DB3
DB4~DB7
CN202 (-)
CN203 (+) BATTERY

LK-127
– 3 –
PCB INFORMATION
M820-PSA1 M800-KYA2M800-KYA1 M821-MDA1
CSM446-LD5M
M821-LDA2M821-LDA1
CSM446-LD3M CSM446-LD4M
Parts Name PCB Name Functions
MAIN PCB
PCB UNIT/MAIN M821-MDA1 MPU, LCD controller, Keyboard LED controller, Reset IC,
Buttons, Right speaker
POWER & AMP PCB
PCB UNIT/
POWER & AMP MX820-PSA1 Power supply circuit, Power ampli er, Power switch, Volume, Buttons, DC 9.5 V jack, Left speaker, PHONES/OUTPUT jack
KEYBOARD PCB
PCB UNIT/KYA M800-KYA1 Keyboard
M800-KYA2
KEYBOARD LED PCB
PCB UNIT/LDA M821-LDA1
Keyboard LED
M821-LDA2
PCB UNIT/LD3 CSM446-LD3M
PCB UNIT/LD4 CSM446-LD4M
PCB UNIT/LD5 CSM446-LD5M

LK-127
– 4 –
CIRCUIT DESCRIPTION
 Nomenclature of Keys
C2 C3 C4 C5 C6 C7
 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
 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-127
– 5 –
PRINTED CIRCUIT BOARDS
MAIN PCB: M821-MDA1 POWER & AMP PCB: M820-PSA1

LK-127
– 6 –
KEYBOARD PCB: M800-KYA1
KEYBOARD PCB: M800-KYA2
KEYBOARD LED PCB: M821-LDA1
KEYBOARD LED PCB: M821-LDA2

LK-127
– 7 –
DISASSEMBLY
 About Repair
• The photos show a prototype. The appearance of the instrument, such as color, may differ
from the actual model.
• Toavoiddamagestotheinstrumentandoor,laytheinstrumentonamattressorblanket
beforestartingdisassembling.
• Thereareseveralkindsofscrews.Besuretousethecorrecttypeofscrewswhen
reassembling.Itisadvisabletosortthescrewsasshownbelowafterremovingthem.
• Ifascrewcapisattachedtothescrew,removeit.Besuretoreattachthescrewcapwhen
assembling.
• Checkhowcablesarewiredbeforeremovingcables.Besuretowirethecablesinthesame
mannerastheywerebeforedisassembly.
• Incasecablesaresecuredwithcableties,securingbands,clips,ortapes,removethemrst.
Besuretosecurethecablesinplaceinthesamemannerastheywerebeforedisassembly.
 Before Starting Repair or Servicing
• RemovetheACadaptor,ACcordorbatteries.
• Remove accessories such as the music stand.
 Flowchart
B. PCB UNIT/MAIN
C. PCB UNIT/POWER & AMP
A. Panel Unit
Assembled Product
D. SPEAKER
E. KEY
F. PCB UNIT/KYA
G. PCB UNIT/LDA
PCB UNIT/LD3
PCB UNIT/LD4
PCB UNIT/LD5

LK-127
– 8 –
 Disassembly Procedure
A. Remove the Panel Unit
A-1. Undo 11 screws on the bottom surface of the main unit
A-2. When replacing the keyboard LED PCB, undo 16 screws and then remove the LOWER COVER.
LOWER COVER/C LOWER COVER/B LOWER COVER/A
<Notes on Assembly>
• To install the LOWER COVER, tighten the screws indicated with arrows engraved on each
cover rst.
LOWER COVER/C LOWER COVER/B LOWER COVER/A

LK-127
– 9 –
A-3. Turn over the panel unit.
A-4. Unsolder two battery lead wires and two ribbon cables.
Lead wire (Red)
Lead wire (Black) Ribbon cable (KYA2 PCB)Ribbon cable (LDA2 PCB)
A-5. Remove the panel unit.
PCB UNIT/MAINPCB UNIT/POWER & AMP

LK-127
– 10 –
B. Remove the PCB UNIT/MAIN
B-1. Unsolder two ribbon cables.
Ribbon cable (LDA2 PCB)Ribbon cable (KYA2 PCB)
B-2. Unsolder two lead wires and one ribbon cable.
Lead wire (White)
Lead wire (Blue)
Ribbon cable (PSA1 PCB)
B-3. Unsolder two lead wires from the right speaker.
Lead wire (White)
Lead wire (Blue)
B-4. Undo 16 screws and then remove the PCB UNIT/MAIN, four RUBBER KEY, and LCD components.
RUBBER KEY LCD components

LK-127
– 11 –
<Notes on Assembly>
• To install the 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
6MDA1 PCB
C. Remove the PCB UNIT/POWER & AMP
C-1. Unsolder two lead wires and one ribbon cable from the MDA1 PCB.
Lead wire (White)
Lead wire (Blue)
Ribbon cable (PSA1 PCB)
C-2. Unsolder two lead wires from the left speaker.
Lead wire (Blue)
Lead wire (White)

LK-127
– 12 –
C-3. Undo eight screws and then remove the PCB UNIT/POWER & AMP, two RUBBER KEY, and two
CONTACT/SLIDE SWITCH.
RUBBER KEY CONTACT/SLIDE SWITCH
D. Remove the SPEAKER
D-1. Unsolder two lead wires.
D-2. Undo four screws and then remove the SPEAKER.
<Left speaker> <Right speaker>
Lead wire (Blue)
Lead wire (White)
Lead wire (White)
Lead wire (Blue)

LK-127
– 13 –
E. KEY
E-1. Undo eight screws and then remove two SIDE PANEL.
SIDE PANEL/LEFT SIDE PANEL/RIGHT
E-2. Undo 21 screws and then remove the KEY.

LK-127
– 14 –
F. Remove the PCB UNIT/KYA
F-1. Disengage the hooks and then remove the PCB UNIT/KYA.
F-2. Remove ve RUBBER CONTACT.
NOTE: The RUBBER CONTACT/CS differs from the others in length.
RUBBER CONTACT/CSRUBBER CONTACT/CB
<How to Install RUBBER CONTACT>
• Lightly insert the tip of a RUBBER CONTACT 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-127
– 15 –
G. Remove the PCB UNIT/LDA, PCB UNIT/LD3, LD4, and LD5
PCB UNIT/LD3 PCB UNIT/LD4 PCB UNIT/LD5
PCB UNIT/LDALDA1 PCB LDA2 PCB
G-1. Undo 14 screws on the LDA1 and LDA2 PCB.
G-2. Turn over the PCB UNIT/LDA.
NOTE: Do not touch the LEDs.
NOTE: After repairing, arrange the ribbon cables again.
G-3. Unsolder three ribbon cables from the LDA1 and LDA2 PCB.
G-4. Undo 12 screws on the LD3, LD4, and LD5 PCB and then remove the PCB UNIT/LDA, PCB UNIT/
LD3, LD4, and LD5.
NOTE: After repairing, arrange the ribbon cables again.
Ribbon cable (LD3 PCB) Ribbon cable (LD4 PCB) Ribbon cable (LD5 PCB)

LK-127
– 16 –
DIAGNOSTIC PROGRAM
 Preparation
(1) Connect the AC adaptor.
NOTE: The AC adaptor (AD-E95100L) is sold separately and does not come with the product. If
you do not have the AC adaptor, use six AA-size dry batteries with enough capacity.
(2) Adjust the main volume so that it is at about 1/3 of the full volume.
 How to Start the Diagnostic Program
(1) Hold down the “0” and “START/STOP” buttons at the same time, to turn the power ON.
NOTE: Set the mode switch to the “NORMAL”.
NOTE: Be sure to turn OFF the power when the test is nished.
(2) Release the “0” and “START/STOP” buttons.
After the diagnostic program is launched, the test menu screen appears.

LK-127
– 17 –
 Test Items
Pressing a test button enables the corresponding test item to be tested.
Test Items Buttons Note
A. Mode Switch Check
B. Button Check 0
C. ROM Version Check 1
D. Keyboard LED Check TONE
E. LCD Check STEP 1
F. 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
G. Key Check
H. Headphones Check Headphones

LK-127
– 18 –
 Test Procedure
A. Mode Switch Check
A-1. Switch the mode switch and then check that the following screen appears.
Mode Switch LCD
FINGERED
CASIO CHORD
NORMAL