Marantz SR7009/U1B Service Manual page 111

4.2. Power AMP (AMP PCB)
No audio output.
Protection is activated.
YES
Is the power transistor open or short circuit-
ed?
2SB1647/2SD2560
NO
Is the emitter resistor of the power transis-
tor open?
0.47 Ω
NO
Is the base resistor of the power transistor
open?
22 Ω
NO
Is the trimmer potentiometer between the
base of the power transistor open?
1k Ω
NO
Are any other transistors faulty?
NO
Are any other resistors faulty?
NO
Turn on the power and check that the voltage of each part is correct and that there is an idling
current.
YES
Replace the power transistor.
YES
Replace the emitter resistor.
YES
Replace the base resistor.
YES
Replace the trimmer potentiometers.
YES
Replace the transistor.
YES
Replace the resistor.
111