Re: Audio amp won't stay on.

From: Mark D. Zacharias (mzacharias_at_yis.us)
Date: 11/28/04 

Date: Sun, 28 Nov 2004 16:29:48 -0600

Look to see which amp channnel spikes negative at the instant that channel
should "unmute". The muting transistor associated with that channel is
faulty.

Mark Z.

"io" <francescolorenzalorena@virgilio.it> wrote in message
news:P0oqd.419002$35.18477957@news4.tin.it...
>I injected an sine wave on both channels and with the oscilloscope I was
>able to see the output.
> Since the power amplifier works,I'm not sure about the behaviour of the
> microcontroller witch drives the POWER ON relay.
> I need to know from witch components it receives the data.
>
> Frank.
>
> "Mark D. Zacharias" <mzacharias@yis.us> ha scritto nel messaggio
> news:30r8k8F3274g0U1@uni-berlin.de...
>> Assuming an amp channel isn't "blown" which would likely give an instant
>> shut-down, the most likely scenario is a bad muting transistor. At the
>> precise moment the speaker relay should come on, a negative bias is
>> applied to shut off the muting transistor. If the transistor is leaky, it
>> passes the DC to the input of the power amp, and this triggers the
>> shut-down. One of Yamaha's "red-flag" repairs, quite common. It might be
>> a surface-mount type transistor.
>>
>> Are you a technician or otherwise able to read a schematic?
>>
>> Mark Z.
>>
>>
>> "io" <francescolorenzalorena@virgilio.it> wrote in message
>> news:wCHpd.221201$b5.10837140@news3.tin.it...
>>> 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
>>>
>>
>>
>
>

Quantcast