Casio CTK-480 User Manual download pdf (Page 7)

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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

MSM 6755B-06

LSI101

RESET

Reset IC

RE5VA35A

IC102

VDD

Battery Set

TROUBLESHOOTING

Nature of Trouble Faulty Block Cause/Remedy

No power Power supply circuit Faulty IC101. Replace IC101.

Faulty D106 ~ D109. Replace D106 ~

D109.

Faulty Q101 ~ Q104. Replace Q101 ~

Q104.

Power switch Poor contact. Clean the contacts.

Power jack (J101) Open J101 or poor soldering. Replace

J101 or resolder.

No sound at all Power Amp (IC101: LA4596) Open or shorted IC101. Replace IC101.

CPU (LSI101: MSM6755B-06) Faulty LSI101. Replace LSI101.

Oscillator Faulty Q111. Replace Q111.

Open X101. Replace X101.

Certain keys or switches

do not function

Key and switch matrix Open circuit on KO or KI line.

Replace keyboard PCB assembly.

CPU (LSI101: MSM6755B-06) Faulty LSI101. Replace LSI101.

A certain key or switch

does not function

Key and switch matrix Dust on the contact.

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Casio CTK-480 User Manual Page 7