I just replaced the transistor with the same type but the amplifier does not
work at all.
The voltage readings at base emitter and collector are the same.(around
19V).
Do you have any ideas?
Frank.
"Mark D. Zacharias" ha scritto nel messaggio
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19,xx volts on all the three pin.
Not at all sure what this means.
Nineteen volts at the base doesn't sound right, and there should be no
voltage at the emitter or collector. -2.5 is specified to "unmute" and
full-on muting would run about .7 volts, I would think.
Mark Z.
"io" wrote in message
news
Hi Mark.
I'm waiting for the spare parts.In the meantime I did some voltage
measurement.
When I give power to the amplifier, on both transistors (Q503 and Q504)
the voltage goes to 19,xx volts on all the three pin.
What does it mean?
Bye.
"io" ha scritto nel messaggio
...
OK, I will purchase and replace those transistors.
Stay tuned.
Thanks a lot.
Frank.
"Mark D. Zacharias" ha scritto nel messaggio
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On the main amp board, on the side of the board nearest the front of
the unit, there are two signal sized transistors on either side of
connector W501, a 7-pin connector. The transistors are Q503 and Q504.
They can both be replaced cheaply enough, ever though only one is
likely bad.
Mark Z.
"io" wrote in message
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Can you tell me number of the transistor on the PCB?
It's impossible to find it simply following the copper tracks on the
board.
Frank.
"Mark D. Zacharias" ha scritto nel messaggio
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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" wrote in message
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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" wrote in message
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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
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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