Casio WK-1800 Service Manual

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POWER SUPPLY CIRCUIT
The power supply circuit provides various voltages as shown below.
The voltage VDD (+5 V) is provided as long as batteries or AC adaptor is set.
Other voltages are controlled by APO (Auto Power Off) signal from CPU.
The regulator IC BA9700A generates square waveform from pin 5 as PWM (Pulse Wide Modulation).
The LC filter makes stable output voltage (+5 V) for each circuit as shown above.
LC Filter
(To digital)
(To analog)
(To FDD)
(To LCD)
CPU
HD6433048SA89F
LSI9
PA 7
NMI
PW/SW
APO
NMI
PW/ON
APO

Casio WK-1800 Specifications

General

Number of Keys	76
MIDI	Yes
Display	LCD
Effects	Reverb, Chorus
Weight	8.5 kg
Polyphony	32
Speakers	Yes
Power Supply	AC adapter or batteries
Floppy Disk Drive	Yes
Connections	Headphones, MIDI In/Out, Sustain pedal
Sequencer	6 tracks