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new member - suddenly silent / hissy MP4....

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  • simezagreb
    Hi All Long time MP4 lover here.. turned it on today after a couple of months storage and it s virtually silent, till I crank the headphones loud and then....
    Message 1 of 8 , Dec 8, 2008
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      Hi All

      Long time MP4 lover here.. turned it on today after a couple of
      months storage and it's virtually silent, till I crank the headphones
      loud and then....

      when I play keys, I can hear at very low level noise like the "gate"
      opening.

      The VCA envelope controls shape the envelope of this low level noise.

      If I twiddle the filter resonance, I can hear the noisy pot, but no
      actual filter resonance.

      If I twiddle the filter cutoff I hear nothing, it doesn't filter the
      noise.

      I can tell the VCO's are receiving trigger because their LED's light up.

      *** SO *** looking a the block diagram, I guess I either have a
      problem in the "mixer" (post VCO's pre VCF) or in the VCF itself???

      Does anyone have an opinion on this??

      Any suggestions graciously accepted,,,,,,

      peace & sine waves
      Simon

      p.s. I never even knew there was an MP4 group....
    • Florian Anwander
      Hi Simon ... if you turn all four parameters of the VCA-Envelope fully counter-clockwise. Playing a key you should hear a klick. - if yes - VCA is good and
      Message 2 of 8 , Dec 8, 2008
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        Hi Simon



        > when I play keys, I can hear at very low level noise like the "gate"
        > opening.
        > The VCA envelope controls shape the envelope of this low level noise.
        if you turn all four parameters of the VCA-Envelope fully
        counter-clockwise. Playing a key you should hear a klick. -> if yes ->
        VCA is good and the output socket is good.

        Then set
        VCA-Envelope to A=0, D=0, S=10, R=10
        VCF-Envelope to A=0, D=0, S=0, R=0
        VCF Cutoff = 5, Resoncance = 10, Envelope amount = 10(+5)
        press a key several times, you should hear a fast resonance
        "Zongggg"-like sound.
        -> if not -> check the VCF-cutoff-modulation input socket. -> many other
        problems tooo... ;-/ (see below)
        -> if yes -> turn the cutoff frequency fully clockwise and turn up noise
        volume: do you hear noise?
        If no ->
        If you are keen enough to open up the monopoly (ATTENTION: live
        endangering electric power inside!) set the keyboard to hold, press four
        notes (or unisono) and check the noise and VCOs signal at pin 1 of
        connector 14 (the connector is at the right hand side of the VCO-pcb
        between the volumes of VCO1 and VCO2). If you do not have an
        socilloscope, the connect the output with an mixer and use the tip of
        another cable, connected to the same mixer as signal search (don't turn
        up the volume too loud, the signals might kill your
        tweeters/headphones/ears).

        If there is still nothing to hear I assume that the powersupply is
        defect. If there is something to hear, either the cable between VCO pcb
        and VCF pcb is broken, or the VCF chip SSM2044 is gone. Sometimes the
        2044 is socketed, then you might check whether the chip is seated ok in
        the socket. But this requires unmounting the pcb from the frontpanel,
        which is not much fun.

        Florian
      • simezagreb
        Hi Florian, Thanks man! I m enjoying this, nerd that I am. Indeed can t get the filter to self oscillate audibly as per your instructions. There is signal
        Message 3 of 8 , Dec 8, 2008
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          Hi Florian, Thanks man!

          I'm enjoying this, nerd that I am.

          Indeed can't get the filter to self oscillate audibly as per your
          instructions.

          There is signal present at connector 14 pin 5 (I seem to have the "new
          production" version).
          Pin 1 of connector 14 is this great distorted version of the VCO's...
          I'll resist the urge to go hotrodding the synth....

          anyway...

          Got the SSM2044 datasheet.

          I have signal at Pin 1 (input) of the SSM2044 - though much lower in
          level, though looking at the schematic theres a 33k resistor in line.

          But no signal at Pin 3 (output) of the 2044 - totally dead - with the
          controls set right.

          I've reseated the 2044 and put a bit of deoxit on the pins and cable
          connectors but no go.

          Seems like the silence at 2044 pin 3 points to a dead filter chip, do
          you think????

          There are some 2044's on ebay, though some of the other numbers on the
          top are different. Do you think that matters????

          Thanks heaps for your assistance Florian, really appreciated.
          Sime



          --- In korg_mono-poly@yahoogroups.com, Florian Anwander
          <fanwander@...> wrote:
          >
          > Hi Simon
          >
          >
          >
          > > when I play keys, I can hear at very low level noise like the "gate"
          > > opening.
          > > The VCA envelope controls shape the envelope of this low level noise.
          > if you turn all four parameters of the VCA-Envelope fully
          > counter-clockwise. Playing a key you should hear a klick. -> if yes ->
          > VCA is good and the output socket is good.
          >
          > Then set
          > VCA-Envelope to A=0, D=0, S=10, R=10
          > VCF-Envelope to A=0, D=0, S=0, R=0
          > VCF Cutoff = 5, Resoncance = 10, Envelope amount = 10(+5)
          > press a key several times, you should hear a fast resonance
          > "Zongggg"-like sound.
          > -> if not -> check the VCF-cutoff-modulation input socket. -> many
          other
          > problems tooo... ;-/ (see below)
          > -> if yes -> turn the cutoff frequency fully clockwise and turn up
          noise
          > volume: do you hear noise?
          > If no ->
          > If you are keen enough to open up the monopoly (ATTENTION: live
          > endangering electric power inside!) set the keyboard to hold, press
          four
          > notes (or unisono) and check the noise and VCOs signal at pin 1 of
          > connector 14 (the connector is at the right hand side of the VCO-pcb
          > between the volumes of VCO1 and VCO2). If you do not have an
          > socilloscope, the connect the output with an mixer and use the tip of
          > another cable, connected to the same mixer as signal search (don't turn
          > up the volume too loud, the signals might kill your
          > tweeters/headphones/ears).
          >
          > If there is still nothing to hear I assume that the powersupply is
          > defect. If there is something to hear, either the cable between VCO pcb
          > and VCF pcb is broken, or the VCF chip SSM2044 is gone. Sometimes the
          > 2044 is socketed, then you might check whether the chip is seated ok in
          > the socket. But this requires unmounting the pcb from the frontpanel,
          > which is not much fun.
          >
          > Florian
          >
        • Florian Anwander
          Hi Simon ... Now, still there is a little hope for the 2044. Check the voltage at pin 15 (offset) and pin 13. If it would be -15 Volts, then the VCF would shut
          Message 4 of 8 , Dec 9, 2008
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            Hi Simon

            > But no signal at Pin 3 (output) of the 2044 - totally dead - with the
            > controls set right. [...]
            > Seems like the silence at 2044 pin 3 points to a dead filter chip, do
            > you think????
            Now, still there is a little hope for the 2044. Check the voltage at pin
            15 (offset) and pin 13. If it would be -15 Volts, then the VCF would
            shut down completely and no other CV would help.

            But in fact I fear a dead 2044 too.

            > There are some 2044's on ebay, though some of the other numbers on the
            > top are different. Do you think that matters????
            No. Single SSMs are available from Senso (http://www.vintageplanet.nl/)
            for around 17 Euros. The seller "technologytransplant" on ebay sells
            good ones as sixpack for 55 Euros!

            Florian
          • simezagreb
            Hi Again ... pin ... Hummm.. do you mean the voltage difference between those two pins? Or the difference between each of them and ground?? thanks and thanks
            Message 5 of 8 , Dec 9, 2008
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              Hi Again


              > Now, still there is a little hope for the 2044. Check the voltage at
              pin
              > 15 (offset) and pin 13. If it would be -15 Volts, then the VCF would
              > shut down completely and no other CV would help.

              Hummm.. do you mean the voltage difference between those two pins?
              Or the difference between each of them and ground??

              thanks and thanks again

              Simon
            • Florian Anwander
              Hi Simon ... I mean difference between each of them and ground. Florian
              Message 6 of 8 , Dec 9, 2008
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                Hi Simon


                >> Check the voltage at pin
                >> 15 (offset) and pin 13. If it would be -15 Volts, then the VCF would
                >> shut down completely and no other CV would help.
                >
                > Hummm.. do you mean the voltage difference between those two pins?
                > Or the difference between each of them and ground??
                I mean difference between each of them and ground.

                Florian
              • simezagreb
                Hi Florian I might of lost something in translation here. This is what I measuring... I am referenceing the 2044 datasheet here:
                Message 7 of 8 , Dec 13, 2008
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                  Hi Florian

                  I might of lost something in translation here. This is what I
                  measuring...

                  I am referenceing the 2044 datasheet here:
                  http://www.synthdiy.com/show/?id=86

                  Setting the multimeter to DC and a range of 20v this is what I have

                  2044
                  pin 16 +V = +15
                  pin 15 SIG IN- = -0.09
                  pin 1 SIG IN+ = -0.06
                  pin 9 -V = -15
                  pin 13 freq ctrl = -0.10 filter knob fully open
                  = 0.09 filter knob fully closed


                  Two things confuse me here... the voltage for the signal seems very
                  low.. and also the Fc ctrl voltage seems low, and yet it responds
                  correctly to Fc knob, envelope etc.

                  Looking at the specs, the range is supposed to be 0.6 to 1.5.

                  However, I don't really know what I'm talking about here. Do you know
                  ??? :)))

                  thanks again
                  pot.

                  --- In korg_mono-poly@yahoogroups.com, Florian Anwander
                  <fanwander@...> wrote:
                  >
                  > Hi Simon
                  >
                  > > But no signal at Pin 3 (output) of the 2044 - totally dead - with the
                  > > controls set right. [...]
                  > > Seems like the silence at 2044 pin 3 points to a dead filter chip, do
                  > > you think????
                  > Now, still there is a little hope for the 2044. Check the voltage at
                  pin
                  > 15 (offset) and pin 13. If it would be -15 Volts, then the VCF would
                  > shut down completely and no other CV would help.
                  >
                  > But in fact I fear a dead 2044 too.
                  >
                  > > There are some 2044's on ebay, though some of the other numbers on the
                  > > top are different. Do you think that matters????
                  > No. Single SSMs are available from Senso (http://www.vintageplanet.nl/)
                  > for around 17 Euros. The seller "technologytransplant" on ebay sells
                  > good ones as sixpack for 55 Euros!
                  >
                  > Florian
                  >
                • simezagreb
                  Hi Florian Happy to report that my new SSM2044 arrived from vintage planet in the Netherlands in record time. Popped it in and all is well. The synth sounds
                  Message 8 of 8 , Dec 22, 2008
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                    Hi Florian

                    Happy to report that my new SSM2044 arrived from vintage planet in the
                    Netherlands in record time. Popped it in and all is well. The synth
                    sounds "new". Really happy.

                    Thanks heaps for your research and advice, much appreciated!!

                    Another MP4 lives to squelch another day....

                    Sime

                    --- In korg_mono-poly@yahoogroups.com, Florian Anwander
                    <fanwander@...> wrote:
                    >
                    > Hi Simon
                    >
                    >
                    >
                    > > when I play keys, I can hear at very low level noise like the "gate"
                    > > opening.
                    > > The VCA envelope controls shape the envelope of this low level noise.
                    > if you turn all four parameters of the VCA-Envelope fully
                    > counter-clockwise. Playing a key you should hear a klick. -> if yes ->
                    > VCA is good and the output socket is good.
                    >
                    > Then set
                    > VCA-Envelope to A=0, D=0, S=10, R=10
                    > VCF-Envelope to A=0, D=0, S=0, R=0
                    > VCF Cutoff = 5, Resoncance = 10, Envelope amount = 10(+5)
                    > press a key several times, you should hear a fast resonance
                    > "Zongggg"-like sound.
                    > -> if not -> check the VCF-cutoff-modulation input socket. -> many
                    other
                    > problems tooo... ;-/ (see below)
                    > -> if yes -> turn the cutoff frequency fully clockwise and turn up
                    noise
                    > volume: do you hear noise?
                    > If no ->
                    > If you are keen enough to open up the monopoly (ATTENTION: live
                    > endangering electric power inside!) set the keyboard to hold, press
                    four
                    > notes (or unisono) and check the noise and VCOs signal at pin 1 of
                    > connector 14 (the connector is at the right hand side of the VCO-pcb
                    > between the volumes of VCO1 and VCO2). If you do not have an
                    > socilloscope, the connect the output with an mixer and use the tip of
                    > another cable, connected to the same mixer as signal search (don't turn
                    > up the volume too loud, the signals might kill your
                    > tweeters/headphones/ears).
                    >
                    > If there is still nothing to hear I assume that the powersupply is
                    > defect. If there is something to hear, either the cable between VCO pcb
                    > and VCF pcb is broken, or the VCF chip SSM2044 is gone. Sometimes the
                    > 2044 is socketed, then you might check whether the chip is seated ok in
                    > the socket. But this requires unmounting the pcb from the frontpanel,
                    > which is not much fun.
                    >
                    > Florian
                    >
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