Re: Audio amp won't stay on.

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

Date: Sun, 28 Nov 2004 17:58:26 -0600

P.S.

Use only the original type 2SD1915F or a 2SC2878. Regular signal types won't
do.

The PDF is on it's way.

Mark Z.

"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:30v1qnF32uadbU1@uni-berlin.de...
> 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
>>>>
>>>
>>>
>>
>>
>
>

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