CASIO CTK-495 ELECTRONIC KEYBOARD Repair Manual

GM SOUND KEYBOARD CTK-495 JULY.1999 CTK-495 START/ STOP ACCOMP VOLUME TEMPO MAIN VOLUME POWER / MODE FINGERED 100 SONG BANK KEYBOARD MUSICAL INFOMATION SYSTEM SYNCHRO / FILL-IN CASIO CHORD NORMAL ON OFF SONG BANK CONTROLLER TRANSPOSE / TUNE CHORD BOOK M LEFT ON/OFF REW FF STOP SONG BANK CONTROLLER RIGHT ON/OFF PLAY/ PAUSE m 7 7 8 9 4 5 6 1 0 2 3 M7 dim aug sus4 CLEAR -5 add9 MUSICAL INFORMATION SYSTEM TONE RHYTHM SONG BANK STATUS TEMPO MAIN VOLUME FINGERING/PART LEFT/ ACCOMP RIGHT/ MELODY L R :1 OCTAVE UP :PEDAL(SUSTAIN)

— 1 — CONTENTS Page Specifications ---------------------------------------------------------------------------------------------- 2 Block Diagram --------------------------------------------------------------------------------------------- 3 Circuit Description --------------------------------------------------------------------------------------- 4 Troubleshooting ------------------------------------------------------------------------------------------- 8 Adjustment -------------------------------------------------------------------------------------------------- 9 Printed Circuit Boards -------------------------------------------------------------------------------- 10 Schematic Diagrams ------------------------------------------------------------------------------------11 Exploded View ------------------------------------------------------------------------------------------- 13 Parts List --------------------------------------------------------------------------------------------------- 14

— 2 — ELECTRICAL Current drain with 9 V DC: No sound output 91 mA ± 20 % Maximum volume 675 mA ± 20 % with white keys C1 to B1 pressed in Synth-Lead 1 Volume: maximum. Speaker output level (Vrms with 4 Ω load): with key F1 pressed in Synth-Lead 1 1,600 mV ± 20% Phone output level (Vrms with 8 Ω load each channel): with key C5 pressed in Synth-Lead 1 110 mV ± 20% SPECIFICATIONS GENERAL Model: CTK-495 Keyboard: 61 standard-size keys, 5 octaves Tones: 100 Polyphony: 12 notes maximum Auto accompaniment Rhythm Patterns: 100 Tempo: Variable (236 steps, = 20 to 255) Chords: 2 fingering methods (CASIO CHORD, FINGERED) Rhythm controller: START/STOP, SYNCHRO/FILL-IN Song Bank Tunes: 100 Controllers: PLAY/PAUSE, STOP, LEFT (ON/OFF), RIGHT (ON/OFF), REWIND, FF Multi function display Name display: TONE, RHYTHM, SONG BANK name/number Tempo: Tempo value, metronome, synchro standby, beat indicator Other functions Transpose: F # to C to F Tuning: Variable (A4 = approximately 440 Hz ± 50 cents) Volume: 0 to 9 (10 steps) Terminals Phones/output terminal: ø6.3mm Stereo standard jack Output Impedance: 78 Ω Output Voltage: 4.0 V (RMS) MAX Power supply terminal: 9 V DC Power supply: Dual power supply system Batteries: 6 AA-size batteries Battery life: Approximately 2 hours (SUM-3/R6P)/4 hours (AM3/LR6) AC adaptor: AD-5 Auto power off: Turns power off approximately 6 minutes after last key operation. Enabled under battery power only, can be disabled manually. Speaker output: 2.0 W + 2.0 W Power consumption: 9 V . . . 7.7 W Dimensions (HWD): 92.9 × 32.9 × 10.8 cm (36 5/8 × 12 15/16 × 4 1/4 inches) Weight: Approximately 4.0 kg (8.8 lbs) (without batteries)

— 3 — BLOCK DIAGRAM LSI-SYY ML6755-02 LSI301 Keyboard Buttons LCD LCD Driver SED1278F2A LSI201 Reset IC IC401 Power Switch Oscillator X301 Power Supply Circuit Q201 ~ Q203, Q401, D205 Power Amp. LA4598 IC201 Filter Q204 Phones/Output Speaker (L) Speaker (R) VC VCC DVDD AVDD APO DC + 9 V IN DB4 ~ DB7 COM1 ~ COM16 SEG1 ~ SEG40 RS R/W E KO8 ~ KO12 KI0 ~ KI6 KI0 ~ KI7 KO0 ~ KO7

— 4 — CIRCUIT DESCRIPTION KEY MATRIX NOMENCLATURE OF KEYS One Key One Key Demo KI0 KI1 KI2 KI3 KI4 KI5 KI6 KI7 KO0 C2 G#2 E3 C4 G#4 E5 C6 G#6 KO1 C#2 A2 F3 C#4 A4 F5 C#6 A6 KO2 D2 A#2 F#3 D4 A#4 F#5 D6 A#6 KO3 D#2 B2 G3 D#4 B4 G5 D#6 B6 KO4 E2 C3 G#3 E4 C5 G#5 E6 C7 KO5 F2 C#3 A3 F4 C#5 A5 F6 KO6 F#2 D3 A#3 F#4 D5 A#5 F#6 KO7 G2 D#3 B3 G4 D#5 B5 G6 KO8 0 1 2 3 4 Start/ Stop Volume Up Tempo Up KO9 5 6 7 8 9 Volume Down Tempo Down Synchro/ Fill-In KO10 Tone Rhythm Light Song Bank Part Select KO11 Step-1 Step-2 Step-3 Fingered Casio Chord Normal Off F#3 G#3 A#3 C#4 D#4 F#4 G#4 A#4 C#5 D#5 F#5 G#5 A#5 F3 G3 A3 B3 C4 D4 E4 F4 G4 A4 B4 C5 D5 E5 F5 G5 A5 B5 C6 D#3 C2 D2 E2 F2 G2 A2 B2 C3 D3 E3 B6 A6 G6 F6 E6 D6 C7 C#3 A#2 G#2 F#2 D#2 C#2 A#6 G#6 F#6 D#6 C#6

— 5 — CPU (LSI301: ML6756-02) The CPU reads sound data from the ROM in accordance with the pressed key and the selected tone; the CPU can read rhythm data simultaneously when a rhythm pattern is selected. Then it provides the left and the right channels’ waveforms separately, by converting the data into the waveforms with two built-in DACs. The CPU also controls key and button input. The following table shows the pin functions of LSI301. Pin No. Terminal In/Out Function 1 PD6/RXD/SYNC In MIDI signal input 2 PD7/TXD Out MIDI signal output 3 ~ 10 PB0 ~ PB7 In Terminals for key/button input signal 11 ~18 PA0 ~ PA7 Out Terminals for key scan signal 19 DGND In Groynd (0 V) source 20 DVCC In +5 V source 21, 22 XTLO, XTLI In/Out 20 MHz clock input/output 23 AGND In Ground (0 V) source 24,26 VREF, AVCC In Power source and reference voltage for internal A/D, D/A 25 DAO Out Channel sound waveform output 27 RSTB In Reset signal input 28, 29, 30 MOD2, MOD1, MOD0 In Mode selection terminal. Connected to ground 31~38 PC0 ~ PC7 In/Out Terminals for button input signal. 39 ~ 42 PD0 ~ PD3 In/Out Data bus for the LCD driver 43 PD4 In AC adaptor detection terminal 44 PD5 In/Out APO (Auto Power Off) signal output

— 6 — LCD DRIVER (LSI201: SED1278F2A) The LCD driver can drive a dot matrix LCD having 40 segment and 16 common lines. The LSI contains 240 graphic symbols in the built-in character generator ROM, and stores 80 characters in the built-in display data RAM. In accordance with command from the CPU, the LSI is capable of displaying up to 16 characters simultaneously. The following table shows the pin functions of LSI201. Pin No. Terminal In/Out Function 1 ~ 22, 63 ~ 80 23 VSS — GND (0 V) source Terminals for the built-in clock pulse generator. The external resistor connected determines the oscillation frequency. LCD drive voltage input. 26 ~ 30 V1 ~ V5 In Those voltages are used for generating the stepped pulse of the LCD drive signals. 31, 32 LP, XSCL — Not used 33 VDD In DVDD (+5 V) source 34, 35 FR, DO — Not used Data/command determination terminal. High: data, Low: command 37 R/W In Read/Write terminal. High: read, Low: write Chip enable signal. 38 E In High: enable, the writing is done at fall edge. Low: disenable 39 ~ 42 DB0 ~ DB3 — Not used. Connected to GND (0 V) 43 ~ 46 DB4 ~ DB7 In/Out Data bus 47 ~ 62 COM1 ~ COM16 Out Common signal/output SEG1 ~ SEG40 Out Segment signal output 24, 25 OSC1, OSC2 In/Out 36 RS In

— 7 — FILTER BLOCK Since the sound signals from the CPU is stepped waveforms, the filter block is added to smooth the waveforms. Amp. LA4598 Filter Block CPU ML6756-02 INITIAL RESET CIRCUIT When batteries are set or an AC adapter is connected, the reset IC provides a low pulse to the CPU. The CPU then initializes its internal circuit. CPU ML6756-02 LSI301 RESET Reset IC PST591D-2 IC401 VDD Battery Set POWER AMPLIFIER (IC201: LA4598) The power amplifier is a two-channel amplifier with standby switch. The following table shows the pin function of IC201. Pin No. Terminal In/Out Function 1 Power GND In Ground (0 V) source 2 Ch1 B.S. — Terminal for a bootstrap capacitor 3 Ch1 OUT Out Channel 1 output 4 VCC In +9 V source 5 Ch1 N.F. In Negative feedback input 6 Ch1 IN In Channel 1 input 7 D.C. — Terminal for a decoupling capacitor 8 Pre GND In Ground (0 V) source 9 Stand by In Power control signal input. 0 V: Off, +9 V: On 10 Ch2 IN In Channel 2 input 11 Ch2 N.F. In Negative feedback input 12 Ch2 OUT Out Channel 2 output 13 Ch2 B.S. — Terminal for a bootstrap capacitor 14 NC — Not used

— 8 — TROUBLESHOOTING Nature of Trouble No power No sound at all Certain keys or switches do not function A certain key or switch does not function Faulty Block Power supply circuit Power switch Power jack (J202) Power Amp (IC201: LA4596) CPU (LSI301: ML6755-02) Oscillator Key and switch matrix CPU (LSI301: ML6755-02) Key and switch matrix Cause/Remedy Faulty IC201. Replace IC201. Faulty D204, D205, D401. Replace D204, D205, D401. Faulty Q201 ~ Q203, Q401. Replace Q201 ~ Q203, Q401. Poor contact. Clean the contacts. Open J202 or poor soldering. Replace J202 or resolder. Open or shorted IC201. Replace IC201. Faulty LSI301. Replace LSI301. Open X301. Replace X301. Open circuit on KO or KI line.Replace keyboard PCB assembly. Faulty LSI301. Replace LSI301. Dust on the contact.

— 9 — 3) Equipment connection/Procedure ADJUSTMENT MAIN PCB 1) Items to be adjusted: 2) Adjustment and Test Point Locations Item Measuring Instrument Vop voltage setting Voltmeter Vop voltage setting Watching the LCD at a 39.09° angle to the horizontal, adjust Vop voltage so that unenergized segments are seen dimly. Output Set Voltmeter TP2 Input Connection Input Point Input Signal Adjust Output Connection Output Point Adjust for VR201 Voltmeter LVDD - VOL Adjust for 4.2 ~ 4.3 V reading on voltmeter under the tem- perature 20 ~ 25 °C. Make fine adjustment accord- ing to the following instruc- tion. VR201 LVDD - VOL 39.09 LCD Eye

CASIO CTK-495 ELECTRONIC KEYBOARD Repair Manual

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