Power Amplifier (LA4598)
The power amplifier is a
The following table shows the pin functions of the power amplifier.
Pin No. | Terminal | In/Out | Functiion | ||||
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1 | Power GND |
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| Ground (0 V) source |
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2 | Ch1 B.S. |
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| Out | Terminal for a bootstrap capacitor | ||
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3 | Ch1 OUT |
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| In | Channel1 output | ||
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4 | VCC |
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| In | +9 V source. Connected to the power source directly. | ||
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5 | Ch1 N.F. |
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| In | Negative feedback input | ||
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6 | Ch1 IN |
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| In | Channel1 input | ||
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7 | D.C. |
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| Terminal for a decoupling capacitor |
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8 | Pre GND |
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| In | Ground (0 V) source | ||
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9 | Standby |
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| In | Power control signal input. 0 V: OFF, +9 V: ON | ||
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10 | Ch2 IN |
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| In | Channel2 input | ||
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11 | Ch2 N.F. |
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| In | Negative feedback input | ||
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12 | Ch2 OUT |
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| Out | Channel2 output | ||
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13 | Ch2 B.S. |
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| Terminal for a bootstrap capacitor |
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14 | NC |
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| Not used. |
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TROUBLESHOOTING
Nature of Trouble | Faulty Block | Checkpoint |
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No power | Power Supply Circuit | Emitter of T2 should provide +5.5 V. |
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| Base of T2 should receive +6 V. |
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| Power Jack | Jack contact. |
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No sound at all | Power Amp. (LA4598) | Pin 9 should receive +9 V when the |
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| power switch is turned on. |
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| Check output signals of pins 3 and 12. |
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| CPU | Pins 21 ~ 30 should provide pulses. |
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| Pin 5 should have a sound signal when |
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| keys are pressed. |
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| Oscillator | Pins 8 and 9 of the CPU should receive |
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| an ocsillation signal. |
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A certain key or switch | Key and Switch Matrix | Dust on the contact. |
does not function |
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Certain keys or switches | Key and Switch Matrix | Open circuit on KC or KI line. |
do not function |
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— 5 —