Casio CTK-611 Service Manual page 7

Note: Each key has two contacts,
the first conatct (1) and second contact (2).
NOMENCLATURE OF KEYS
C#2 G#2 A#2 C#3
D#2 F#2 D#3
C2 D2 E2 F2 G2 A2 B2 C3 D3
POWER SUPPLY CIRCUIT
The power supply circuit generates five voltages as shown in the following table. VDD voltage is always
generated. The others are controlled by APO signal from the CPU.
Name Voltage
VDD +5 V CPU, Reset IC, DSP, Sound source ROM, Working storage RAM, Effect RAM
DVDD +5 V LCD driver, Power jack, Sustain jack, MIDI jack
AVDD +5 V DAC, Filter
LVDD +5.6 V LCD dirver
VCC +9 V Power amplifier, Pilot lamp
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, and clears the working storage RAM.
When the power switch is pressed, the CPU receives a low pulse of POWER signal. The CPU sends APO
signal to the power supply circuit, also sends a reset signal to the DSP.
Battery set
VDD
Reset IC
IC1
RN5VD40AA
From power switch
MC-Service
F#3 G#3 A#3 C#4 D#4 F#4 G#4 A#4
E3
F3 G3 A3 B3 C4 D4 E4 F4
VDD
RESET PLE
CPU
LSI1
UPD913GF-3BA
SCKO
POWER
NMI
— 5 —
Key
First contact (1)
Second contact (2)
C#5 D#5 F#5 G#5 A#5
G4 A4 B4 C5 D5 E5 F5 G5 A5
For operation of
Reset signal
HG51B277FB-1
APO
To power supply circuit
FI
KC
SI
D#6 F#6 G#6
C#6 A#6
B5 C6 D6 E6 F6 G6 A6 B6 C7
VDD
DSP
LSI2