I injected an sine wave on both channels and with the oscilloscope I was
able to see the output.
Since the power amplifier works,I'm not sure about the behaviour of the
microcontroller witch drives the POWER ON relay.
I need to know from witch components it receives the data.

Frank.

"Mark D. Zacharias" ha scritto nel messaggio
...
Assuming an amp channel isn't "blown" which would likely give an instant
shut-down, the most likely scenario is a bad muting transistor. At the
precise moment the speaker relay should come on, a negative bias is
applied to shut off the muting transistor. If the transistor is leaky, it
passes the DC to the input of the power amp, and this triggers the
shut-down. One of Yamaha's "red-flag" repairs, quite common. It might be a
surface-mount type transistor.

Are you a technician or otherwise able to read a schematic?

Mark Z.


"io" wrote in message
...
Hi all.

I have a problem on a Yamaha AX-496 amplifier.
When I press the POWER ON button, it will turn on but only for 3-4
seconds.
I already checked the fuses and all the voltages +/-55 +/-12 +/-5 V are
OK
what can I do?

thanks.

Frank