Denon AVR-591 Service Manual page 44

4.2. Power AMP (7CH AMP B'D)
No sound is output.
The protector operates.
YES
Is the power transistor open or short circuit?
2SB1560/2SD2390
NO
Is the emitter resistance of the power
transistor open?
0.47Ω
NO
Is the base resistance of the power
transistor open?
22Ω
NO
Is trimmer potentiometer between the base
of the power transistor open?
1kΩ
NO
Is the zener diode and diode which are
connected with the base of a power
transistor short-circuited?
MTZJ3.3B
1SS133
NO
Is other transistor trouble?
NO
Is other resistance trouble?
Turn on power, check that voltage of the section is normal and that idling electric current is flowing.
YES
Replace the power transistor.
YES
Replace the emitter resistance.
YES
Replace the base resistance.
YES
Replace the trimmer potentiometers.
YES
Replace the Zener diode and the diode.
YES
Replace the transistor.
YES
Replace the resistance.
44