4.2. Power AMP (AMP PCB)
No audio output.
Protection is activated.
Is the power transistor open or short circuited?
2SB1560 / 2SD2390
Is the emitter resistor of the power transistor
open?
0.47 Ω
Is the base resistor of the power transistor open?
4.7 Ω
Is the trimmer potentiometer between the base
of the power transistor open?
1 k Ω
Are any other transistors faulty?
Are any other resistors faulty?
Turn on the power and, check that the voltage of each part is correct and that there is an idling cur-
rent.
Replace the power transistor.
Replace the transistor.
Replace the resistor.
Replace the emitter resistor.
Replace the base resistor.
Replace the trimmer potentiometers.
NO
NO
NO
NO
NO
NO
YES
Check the CPU.
4.3. Analog audio
No audio output.
Is a voltage of ± 12 V supplied to DIGITAL PCB
CN823?
Is there an audio signal in DIGITAL PCB CN822?
Reconnect the connectors correctly.
If the malfunctioning channel and function can be identified, check the corresponding signal path.
Repair the ± 12 V power supply.
Repair the power amplifier.
Is the serial data for electronic volume sent to
the IC821 of DIGITAL PCB?
YES
NO
YES
YES
YES
YES
YES
YES
NO
YES
NO
YES
66
Caution in
servicing
Electrical
Mechanical
Repair Information
Updating
