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Re: [Electronics_101] Yamaha AVX-20 stereo receiver problems

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  • jon
    ... The cone was damaged by too much movement. ... The volume was moderate , not anywhere near cranked. ... No ... With a DVM in diode mode. Checked
    Message 1 of 13 , Apr 1, 2002
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      >How did the woofer blow?
      The cone was damaged by too much movement.

      >Was the amp cranked?
      The volume was "moderate", not anywhere near cranked.

      >Do you have a low filter?
      No

      > How did you check the output transistors?
      With a DVM in diode mode. Checked BE,EB,etc.

      Every now and then, the amp will come on without cycling the protection
      relay.

      Looked at the 50V power rails on a scope, and there was a little bit of
      ripple. Don't know if it was an acceptable amount.

      This may be something as simple as power supply capacitors.

      Any thoughts on a source of schematics?

      Jon
    • SexyBrian1979@aol.com
      Your 50v supply has ripple? Hmm. Wether this is acceptable or not, really depends on wether the 50V rail is a stabalized rail or if it s unstabalized. If it s
      Message 2 of 13 , Apr 1, 2002
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        Your 50v supply has ripple? Hmm. Wether this is acceptable or not, really
        depends on wether the 50V rail is a stabalized rail or if it's unstabalized.
        If it's stabalized, it should be a fairly straight, if not dead straight DC
        line. If you suspect this is your problem, then change a few of the high
        capacitance Electrolytics on the 50V rail

        Brian
      • Gary
        I have been in car stereos in the past and can tell you only two things I have ever seen will cause this.. 1. Too much power in the wrong enclosure i.e.: open
        Message 3 of 13 , Apr 1, 2002
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          I have been in car stereos in the past and can tell you only two things I
          have ever seen will cause this.. 1. Too much power in the wrong enclosure
          i.e.: open air or port too large 2. DC current.
          ----- Original Message -----
          From: jon <jon@...>
          To: <Electronics_101@yahoogroups.com>
          Sent: Monday, April 01, 2002 3:16 PM
          Subject: Re: [Electronics_101] Yamaha AVX-20 stereo receiver problems


          >
          > >How did the woofer blow?
          > The cone was damaged by too much movement.
          >
          > >Was the amp cranked?
          > The volume was "moderate", not anywhere near cranked.
          >
          > >Do you have a low filter?
          > No
          >
          > > How did you check the output transistors?
          > With a DVM in diode mode. Checked BE,EB,etc.
          >
          > Every now and then, the amp will come on without cycling the protection
          > relay.
          >
          > Looked at the 50V power rails on a scope, and there was a little bit of
          > ripple. Don't know if it was an acceptable amount.
          >
          > This may be something as simple as power supply capacitors.
          >
          > Any thoughts on a source of schematics?
          >
          > Jon
          >
          >
          >
          > To unsubscribe from this group, send an email to:
          > Electronics_101-unsubscribe@yahoogroups.com
          >
          >
          >
          > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
          >
          >
        • Robert Graf
          ... From: jon To: Sent: Monday, April 01, 2002 3:16 PM Subject: Re: [Electronics_101] Yamaha AVX-20
          Message 4 of 13 , Apr 1, 2002
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            ----- Original Message -----
            From: "jon" <jon@...>
            To: <Electronics_101@yahoogroups.com>
            Sent: Monday, April 01, 2002 3:16 PM
            Subject: Re: [Electronics_101] Yamaha AVX-20 stereo receiver problems


            >
            > >How did the woofer blow?
            > The cone was damaged by too much movement.
            >
            > >Was the amp cranked?
            > The volume was "moderate", not anywhere near cranked.
            >
            Was the voice coil thrown out of the gap? When you said that the woofer was
            blown, I figured you meant that the voice coil was burned. I don't
            understand how too much cone excursion could happen if the amp was not
            turned up. Low frequency transients can cause this. How long are the speaker
            wires? I've seen some huge cone movements caused by people waing across the
            floor where the speaker wires were. The low filter took care of this. What
            is the impedance of the speaker? Are the spaekers matched to the amp? A 2 or
            4 ohm speaker hooked up to an output rated for 8 ohm speakers will put out
            full power even when the volume control is not turned up all the way. Also,
            if the input source has a high enough level, full output (or greater) will
            occur even if the volume control is not full up. What was the signal source
            that caused the woofer failure?

            > >Do you have a low filter?
            > No
            >
            > > How did you check the output transistors?
            > With a DVM in diode mode. Checked BE,EB,etc.
            >
            > Every now and then, the amp will come on without cycling the protection
            > relay.
            >
            So, the amp does work, just intermittently? Unfortunately, these problems
            are the toughest to figure out. If the amp does work periodically, the
            transisor check was probably unnecessary. You'll need to see what the
            proection circuit monitors and check those sources out. It should look for
            dc on the output and overpower conditions at the least. It might also be
            used to prevent turn-on/turn-off transients, but plenty of amps don't
            require that.

            > Looked at the 50V power rails on a scope, and there was a little bit of
            > ripple. Don't know if it was an acceptable amount.

            Probably nomal. If you're not getting hum, then it's probably ok.

            >
            > This may be something as simple as power supply capacitors.

            If you observed the power supply rails with a scope and didn't see anything
            but ripple, I doubt that a ps cap would be the culprit. If you measured the
            ripple with a dvm, you don't know what you have. You could be getting some
            short duration spikes don't register much on the dvm.
            >
            > Any thoughts on a source of schematics?

            How about the manual? Have you tried the Yamaha site?

            >
            > Jon
            >
            >
          • Robert Graf
            ... From: To: Sent: Monday, April 01, 2002 4:16 PM Subject: Re: [Electronics_101] Yamaha AVX-20
            Message 5 of 13 , Apr 1, 2002
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              ----- Original Message -----
              From: <SexyBrian1979@...>
              To: <Electronics_101@yahoogroups.com>
              Sent: Monday, April 01, 2002 4:16 PM
              Subject: Re: [Electronics_101] Yamaha AVX-20 stereo receiver problems


              > Your 50v supply has ripple? Hmm. Wether this is acceptable or not, really
              > depends on wether the 50V rail is a stabalized rail or if it's
              unstabalized.
              > If it's stabalized, it should be a fairly straight, if not dead straight
              DC
              > line. If you suspect this is your problem, then change a few of the high
              > capacitance Electrolytics on the 50V rail
              >
              > Brian
              >
              I'm not sure if stabilized refers to filtered or regulated, but a typical
              stereo amplifier would not have a regulated supply for the power amp. If it
              did, the output voltage would either be correct or zero volts. I suppose it
              could be cycling on and off if the protection circuit was intermittent. The
              50v rails are probably only filtered and some ripple is normal as the output
              stage is most likely common collector which is pretty gain independent with
              regard to collector-emitter voltage variation. I don't think changing any of
              the filter caps will do anything. If one of the caps opened, there would be
              a lot of ripple as very few amps use multiple filter caps on any power rail.
              If the cap shorted, tere wouldn't be any voltage on that rail.
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