Whether you are experienced in electronics repair?
if not, try this simply way:
1: Test whether the power amplifier is still working. See figure 1.
Power OFF,adjust the EQ settings as shown in the picture.
Minimize LEVEL.Switch ON Power. Touch pin 3 at the INPUT socket by using a small screwdriver or piece of wire / cable.
Slowly raise the LEVEL,a little bit only (as the clock showed 7-8) until
sound is heard in speaker. If not heard, slowly raise again LEVEL.
If audio input signal is heard,it can simply be taken to mean
that the amplifier is working.
If LEVEL at 9 o'clock position,and the audio is not heard,
the possibility of the amplifier is damaged.
Switch OFF the power. Take it to a repair place.
2: When the Power LED is lit, but no sound,
There are many possible causes, one of which is:
I have been getting 3 times similar cases, and all are caused by
two Rectifier-Diode (either or both.) damage on the power-supply-unit.
Remove/desolder,measure, if damaged replace it with a new one.
See figure 2-3.
Hope it helps. Regards.
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